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I thought it would be good to start a new topic on how to convert your Dometic AC units to Houghton - Recpro because there is lots of information all over the forum but this can be a one stop shop for all the info needed to convert them.  Thanks to everyone that contributed especially Ken and Tom.

The pdf contains all the details of the conversion.  In my case I had one original 19 year old Duotherm 13.5k with Heat pump and one 8 year old Dometic Penguin 13.5k BTU.  The original owner at some point bought a new Dometic CCC 5 button thermostat.

First, I will explain my reasoning behind purchasing the Houghton – Recpro AC units.  I went with two 13.5k A3501 units because I do not need a heat pump.  If you need a heat pump spend the extra $300 USD and get 15k A3800.  Both are the same size and have large condenser and evaporator coils, dual motors, and the thermostats that are built into the unit are controlled with an IR remote control.  This integrated thermostat /remote control feature allows me to use a different a brand of AC units and still keep my Dometic thermostat, remote temp sensors, and furnaces.  If you are only replacing one AC unit you can still use your old Dometic CCC thermostat and system for the other AC unit.

I bought my units from O’Çonnor RV in Chilliwack, BC and the parts lady (AmandaH@oconnorgroup.com) gave me a better than normal deal because they want to get more out in the area.  You can get them at any RV dealer though, they are distributed through Atlas Trailer Coach Products and have 4 warehouses throughout Canada. In the US, RecPro is probably the easiest way to purchase them at great prices.  Ask your local RV dealer and show them their prices, you will probably get them for the same rate.

Second, the price.  I do not like the Dometic units.  They are fairly complicated and prone to different failures (not saying that other brands don’t fail because they are all RV grade AC units).  The other problem is the price.  In today’s inflationary economy, the dealers were quoting me anywhere from $2000 to $3400 CAD per 13.5k AC unit.  To me that is not acceptable.  O’Connor RV gave me a pretty good quote and I was able to get both of my 13.5K units for $2600 CAD.  I am now getting what I think is a better AC unit for half the price.  At this time, I also bought, a spare remote, AC unit covers, extra filters and they were all very reasonably priced.

Third, you do not need to run extra thermostat wiring along your walls and in your roof.  I looked at converting to Coleman and other brands but I did not want to complete the cable routing portion of the project.  The Dometic CCC (Comfort Control Center) system uses 4 wire RJ11 cable (similar to phone cables) to control every component on a data link.  Every other brand uses 5 to 9 wires (5 being the household standard) to control their thermostat.  There is a lot of work involved in cable routing through the ceiling and walls if you go with another brand and you will also need a new thermostat (or two) for your new AC units. 

To keep everything on your old system online you must keep your old Dometic AC unit control boards (13.5k is in the plenum, 15k is up top in the AC unit) to keep your CCC system communicating.  If your AC unit died because of a bad board, you will need to buy a new one to have your, thermostat, temp sensors (if equipped), furnaces, and other AC unit (if only replacing one) online.  If you have a CCC 4 and 5 button thermostat you may want to look at converting the system to the newer CCC 10 button or Micro Air Easy Touch thermostats because they are obsolete.  I chose to roll the dice and keep using my CCC 5 button with my two old furnaces and remote temp sensors.

If you want to get rid of your Dometic thermostat completely you can run your furnaces on a simple mechanical thermostat or battery powered digital thermostat and just switch the blue furnace wires to call on your furnace individually.  You can feed the two blue wires from the AC unit plenum to a location of your liking.

Forth, you can control your new Houghton – Recpro with a Switchbot Hub 2 from your phone from wherever you are as long as it is connected to WiFi.  I like the ability to monitor the AC air temp and control it for my dogs when we are away and it is too hot for them to be outside.  Yes, spoiled pups…

And lastly, the Houghton – Recpro AC units have temperature specs that are better than other brands when customers have tested the performance of the cold air (and hot air for heat pump) coming out of the vents.  They are also extremely quiet performing as good as AC units with silencer kits installed.

There are a lot of people that are using these newer style Houghton – Recpros and from what I read they are quite happy with them.  I will see in the long run the durability but as for know they are everything that you need in a replacement AC unit. As for right now I have had mine for about a month and they were a good investment.

See the attached pdf on the details on how to convert your system over from Dometic to Houghton AC.

Houghton Recpro AC Unit for Dometic.pdf Houghton A3501 13.5k BTU Manual.pdf

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21 minutes ago, Brad Loehr said:

I thought it would be good to start a new topic on how to convert your Dometic AC units to Houghton - Recpro because there is lots of information all over the forum but this can be a one stop shop for all the info needed to convert them.  Thanks to everyone that contributed especially Ken and Tom.

The pdf contains all the details of the conversion.  In my case I had one original 19 year old Duotherm 13.5k with Heat pump and one 8 year old Dometic Penguin 13.5k BTU.  The original owner at some point bought a new Dometic CCC 5 button thermostat.

First, I will explain my reasoning behind purchasing the Houghton – Recpro AC units.  I went with two 13.5k A3501 units because I do not need a heat pump.  If you need a heat pump spend the extra $300 USD and get 15k A3800.  Both are the same size and have large condenser and evaporator coils, dual motors, and the thermostats that are built into the unit are controlled with an IR remote control.  This integrated thermostat /remote control feature allows me to use a different a brand of AC units and still keep my Dometic thermostat, remote temp sensors, and furnaces.  If you are only replacing one AC unit you can still use your old Dometic CCC thermostat and system for the other AC unit.

I bought my units from O’Çonnor RV in Chilliwack, BC and the parts lady (AmandaH@oconnorgroup.com) gave me a better than normal deal because they want to get more out in the area.  You can get them at any RV dealer though, they are distributed through Atlas Trailer Coach Products and have 4 warehouses throughout Canada. In the US, RecPro is probably the easiest way to purchase them at great prices.  Ask your local RV dealer and show them their prices, you will probably get them for the same rate.

Second, the price.  I do not like the Dometic units.  They are fairly complicated and prone to different failures (not saying that other brands don’t fail because they are all RV grade AC units).  The other problem is the price.  In today’s inflationary economy, the dealers were quoting me anywhere from $2000 to $3400 CAD per 13.5k AC unit.  To me that is not acceptable.  O’Connor RV gave me a pretty good quote and I was able to get both of my 13.5K units for $2600 CAD.  I am now getting what I think is a better AC unit for half the price.  At this time, I also bought, a spare remote, AC unit covers, extra filters and they were all very reasonably priced.

Third, you do not need to run extra thermostat wiring along your walls and in your roof.  I looked at converting to Coleman and other brands but I did not want to complete the cable routing portion of the project.  The Dometic CCC (Comfort Control Center) system uses 4 wire RJ11 cable (similar to phone cables) to control every component on a data link.  Every other brand uses 5 to 9 wires (5 being the household standard) to control their thermostat.  There is a lot of work involved in cable routing through the ceiling and walls if you go with another brand and you will also need a new thermostat (or two) for your new AC units. 

To keep everything on your old system online you must keep your old Dometic AC unit control boards (13.5k is in the plenum, 15k is up top in the AC unit) to keep your CCC system communicating.  If your AC unit died because of a bad board, you will need to buy a new one to have your, thermostat, temp sensors (if equipped), furnaces, and other AC unit (if only replacing one) online.  If you have a CCC 4 and 5 button thermostat you may want to look at converting the system to the newer CCC 10 button or Micro Air Easy Touch thermostats because they are obsolete.  I chose to roll the dice and keep using my CCC 5 button with my two old furnaces and remote temp sensors.

If you want to get rid of your Dometic thermostat completely you can run your furnaces on a simple mechanical thermostat or battery powered digital thermostat and just switch the blue furnace wires to call on your furnace individually.  You can feed the two blue wires from the AC unit plenum to a location of your liking.

Forth, you can control your new Houghton – Recpro with a Switchbot Hub 2 from your phone from wherever you are as long as it is connected to WiFi.  I like the ability to monitor the AC air temp and control it for my dogs when we are away and it is too hot for them to be outside.  Yes, spoiled pups…

And lastly, the Houghton – Recpro AC units have temperature specs that are better than other brands when customers have tested the performance of the cold air (and hot air for heat pump) coming out of the vents.  They are also extremely quiet performing as good as AC units with silencer kits installed.

There are a lot of people that are using these newer style Houghton – Recpros and from what I read they are quite happy with them.  I will see in the long run the durability but as for know they are everything that you need in a replacement AC unit. As for right now I have had mine for about a month and they were a good investment.

See the attached pdf on the details on how to convert your system over from Dometic to Houghton AC.

Houghton Recpro AC Unit for Dometic.pdf 674.34 kB · 3 downloads Houghton A3501 13.5k BTU Manual.pdf 9.83 MB · 0 downloads

Excellent write up.  We have had, based on my UNOFFICIAL polling or tally, less than a 50% success rate.  One member went through the process successfully as you did.  But, we often get MANY “what do I do now?” posts…..outnumbering the OK….works great.  The reasons vary…

Decided to DIY.  Totally gutted the unit.  Pitched it out.  Attached the 12 VDC and 120 VAC.  AC works like a champ.  BUT MY FURNACE (once in a while AH) doesn’t work.

Unfortunately many members have read glowing reports on IRV2.  But they lack the understanding of the Dometic MPX system and then, they have already thrown away the unit….and then want a magic bullet fix. OR….the MPX is so mystical in that they have never dealt with the “critter”….

Myself and other staff and members have posted comments both prior to the project and afterwards….and unfortunately, reading and understanding and then analyzing….and also finding the elusive blue wires…which in many cases are the Dometic side and the ones axtually running from the rooftop to the furnace are “unmarked” and some do not have the skill set to use a DVOM and a piece of hookup wire and sniff or ping out and find the two leads.

This is an excellent writeup.  We really appreciate it. You asked for a comment….so, as a moderator as well as a helping member….my additions would be this.

Copy your post as a preamble or background.  It is excellent….

Add one or two items for clarity.  I understand fully what you wrote….but others might not.

1. The two wires that go to the furnace or Aquahot are only “non powered” switch legs.  They need to be connected or joined to make a circuit.  Think using a paperclip to jumper two terminals.  The Dometic controller does that.  Thermostat calls for heat.  The controller is like a light switch….it closes.  That fires or turns on the furnace or Aquahot.

2.  YES…salvage the original 5 button thermostat.  If you properly install one RecPro and the salvaged controller, the 5 button thermostat will control heat (furnace or AH) for that zone….as well as the other zone(s) with the Dometics. BUT…if either fails….then a new thermostat (Dometic or Microair) will be needed as well as replacing the control module.  The older 5 button is the original CCC system.  The new Dometic’s are CCC2… The decision to replace the 5 button with the more expensive Microair should be made with the realization that there is a high likelihood that the CCC controller will eventually fail.  Right not, you can buy them….and they are not cheap.  Thus upgrading to CCC2 when one fails might be a more cost effective solution.

3. The other brands, for example, Coleman work like a residential.  There is no direct replacement for the 5 button.  Folks have tried a Coleman and ran wires.  OPPS…they sent 12 VDC to the Furnace…it doesn’t work.  The furnace or AH in a Monaco needs dry wires. The mechanical thermostat, or the “line voltage style” must also have an OFF position.  Yes….that is the only way to turn OFF the heat.  

If you have some time, it would be great to add your summary with the above comments….the PDF looked great….really great.  But the number one reason for the failure rate here has been a lack, sometimes total, of how the existing MPX works….and also not being prepared or understanding the need to isolate the inputs snd outputs of the controller and how to properly rewire and salvage.

You can PM this to myself ( @Tom Cherry ) and Frank ( @Frank McElroy ).  We will then get it into the files.

Thanks again for this.  Sometimes members think that there is a bias against conversion.  No, properly executed….along with KNOWING how it will work! AHEAD OF TIME, it works fine and many members are happy.  But lack of understanding and not planning and then not identifying components and wiring is the main reason for all the “How do I fix it”…..which, as you know, is a nightmare and impossible to post every troubleshooting technique…

Thanks again…..

 

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Hey Tom,

The conversion seems a bit daunting but it in itself is very simple when you understand how the system works and what needs to be done.  For the people that want a change from Dometic (both price and quality) just read the document and order the materials needed to complete the job.  You are basically removing the 6 pin connector from output side of the control board to the AC unit and the freeze control.  I bet if you had an AC unit that failed and it took out the relays or AC portion of the board you would still be able to use the board to complete the data link loop and have your CCC and furnaces function.  If not I guess you would have to find a control board dependent on your CCC thermostat you use.  Which still is not that big of a deal.

You either need two things to make your furnaces or other AC unit (if leaving one Dometic AC unit in the system) work after the Houghton - RecPro AC unit install and that is:

1.  Have the control boards in the system and connected for each zone to monitor temperature and CCC thermostat function for the AC unit and furnaces OR

2. If you have to, remove the Dometic CCC system entirely.  You have to replace both AC units in this case because the Dometic AC system that is left over will not function.  However for the furnaces you can wire in a mechanical mercury switch thermostat (like a Honeywell CT410A or Suburban 161154) or a battery powered digital thermostat that simply switches the blue wires for closed for continuity when you want to call on the furnace for heat. 

Think of it this way, (see wiring diagram below) the furnace through pin 2 blue wire gets power from the circuit breaker when the furnace on/off switch is on and sends a small signal 12 VDC to the AC unit control board at pin 2.  From there the AC unit control board switches the blue wires to close (or have continuity) between both blue wires to turn on furnace based on the CCC thermostat settings and air temperature when you need your furnace to turn on.  The furnace control VDC signal at pin 3 goes back down to the furnace to pin 5 blue wire and activates the relay as long as your furnace on/off switch at the furnace is on and your sail and limit switches function properly to call the other side of the relay on. 

For the new "dumb" thermostat  You can either use the blue wires pin 2 and 3 at the AC unit 6 pin connector and feed them to a location for your new thermostat location or you can use the blue wires pin 2 and 5 at the furnace and feed them to a location for the thermostat that works the best.  All you need to do is have your new thermostat close the circuit between the two blue wires when your ambient air temperature calls for heat.

As for the blue wires they are do change color from the AC unit into the RV harnessing.  In my 2005 HR Endeavor 40DST I have an Atwood 8525-IV so I will speak to this setup but most others will be similar.  From the AC unit pin 2 and 3 are both blue wires for furnace.  Pin 2 turns into a black wire and pin 3 turns into a yellow wire as it goes into the roof headliner. These wires go to the furnace and become again two blue wires at the furnace on pin 2 and pin 5.  This is possibly where some of the confusion comes in when trying to find the correct wires.

Here is some info for you to understand "dry contact" signal wiring for HVAC systems

https://worthtraining.ca/what-are-dry-contacts/

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As for my setup, after installation of what I had done in the pdf my furnaces and remote temperature sensors work properly with the CCC 5 button.  If my CCC 5 button fails at some point I will go with a Micro Air Easy Touch.  The CCC thermostat only controls the furnaces which I don't use very often.  My new Houghton AC units work great and are extremely quiet.  These AC units have an internal thermostat and are controlled with the IR remote control.

All in all you do not need to know how the details on how the Dometic MPX data link system works.  You only need to know that you have to all the nodes in the data link connected with the cables as listed in the pdf for the CCC thermostat to still talk to the control boards, remote temperature sensors, and then finally to the furnace for each zone.  We are just eliminating the output side of the control board to each AC unit. 

Data links can be hard for people to get their heads wrapped around and honestly this Dometic system is pretty archaic compared to J1939 and machine specific data links used in todays automotive and equipment industries.  For the MPX there is a 12 VDC, a ground, and two signal wires on the RJ11 cables.  I never researched how it works but I am assuming it is similar to a CAN J1939 data link where the one signal wire is high and the other signal wire is low.  There is varying pulses on the wires for the modules to communicate with each other digitally.  You can only see what is happening on the signal wires with an oscilloscope.   It was smart as a business decision for Dometic to have their components set up this way because once the system is installed the majority of people will buy Dometic products again to make their system work.  There is no other option because the MPX data link is proprietary to their HVAC setup and no other systems use the same components.

If you have trouble with the conversion reply to this message or DM me.  I will try to respond as soon as I can.

If you need any clarification on something I will help out as best as I can.  Having to replace your AC units and seeing an upcoming bill of $5000 to $6000 CDN plus labor can bring on some anxiety. With this conversion you can get a better AC unit and pay a bit more than 1/2 that bill.

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WOW. Congratulations.  You have put me and some of my “overwhelming technical” posts to shame.  LOL….  

Seriously, It is always great to have real information and explanations.  We do have many members and also staff members who fully understand how the Dometic MPX systems work and we, combined, have helped over 100 (lost count) members troubleshoot and fix or repair theirs.  In addition, I personally am up to about 5 members, on and offline, troubleshoot and then “fix” their Houghton RecPro installations.  Several more either quit posting or whatever and we never got any followup.

I’ll send you a PM as to what we need to finish your “This is HOW TO” PDF and so it can be  added it to the files.  

Since you have gone into great detail here….we’ll add a “clickable hyperlink” to the file or a footnote on the description so that they can come here for the details..

Thanks again..

Will send you a PM later.

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I think the only caveat to this is, these don't work well in a ducted air coach. Monaco put the ducts in a not quite standard location that it seems only the pengion accomodates. I ran into this last year looking for an alternative to a $1900 penguin.

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7 hours ago, CMillet86 said:

I think the only caveat to this is, these don't work well in a ducted air coach. Monaco put the ducts in a not quite standard location that it seems only the pengion accomodates. I ran into this last year looking for an alternative to a $1900 penguin.

The Houghton - RecPro AC units I installed work great in my H ducted roof.  There is lots of CFM and it is very quiet.  Compared to the Penguin or DuoTherm it is a substantial noise decrease and CFM increase based on the how the plenum is set up inside the Houghton Rec-Pro.  Having two separate motors for evaporator and condenser and using them on automatic setting allows the AC unit to run as efficient as it can based on the temperatures of the system and demanded coach temperature. 

Also if you don't want to use your ducts and you want maximum flow you can close up the Monaco circular vents and open up the two vents that blow straight down from the AC unit.  

Not sure what you mean by only a Penguin can accommodate the ducts.  Taking apart and both and installing them I would say the plenum is not as efficient on the Dometic.  Using your ducts in any circumstance will cause resistance to flow, but I am not sure how you think the Dometic would be better for a location.

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44 minutes ago, Brad Loehr said:

The Houghton - RecPro AC units I installed work great in my H ducted roof.  There is lots of CFM and it is very quiet.  Compared to the Penguin or DuoTherm it is a substantial noise decrease and CFM increase based on the how the plenum is set up inside the Houghton Rec-Pro.  Having two separate motors for evaporator and condenser and using them on automatic setting allows the AC unit to run as efficient as it can based on the temperatures of the system and demanded coach temperature. 

Also if you don't want to use your ducts and you want maximum flow you can close up the Monaco circular vents and open up the two vents that blow straight down from the AC unit.  

Not sure what you mean by only a Penguin can accommodate the ducts.  Taking apart and both and installing them I would say the plenum is not as efficient on the Dometic.  Using your ducts in any circumstance will cause resistance to flow, but I am not sure how you think the Dometic would be better for a location.

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The ductwork in my dynasty wouldn’t line up with any of the other a/c units. I had my rear unit fail and purchased one locally and there was no way to make the duct work. Looking at pictures of the rec pro it may work. But there was another thread where someone had a similar issue and basically said it wasn’t worth the extra work to make the rec pro work. 

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Edited by CMillet86
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The Houghton will work where a Dometic was. You may have to extend the dam some between the intake and discharge to get a good seal. I have had one for 2 years and it kicks the domestics butt in coolness, quietness and the heat pump is much better also.

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3 hours ago, CMillet86 said:

The ductwork in my dynasty wouldn’t line up with any of the other a/c units. I had my rear unit fail and purchased one locally and there was no way to make the duct work. Looking at pictures of the rec pro it may work. But there was another thread where someone had a similar issue and basically said it wasn’t worth the extra work to make the rec pro work. 

I have the H ducting in my coach and I was unsure what you were talking about.  I guess with that central duct you could extend the foam plenum dam down and around the ductwork and seal it up with HVAC aluminum tape. 

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On the H ducting it is wide open in the center.  Then the plenum gets installed and the air flow goes through the sides marked with red arrows.

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I would contact Rec-Pro and ask them what they have for that style of center ducting. I see on their website they have duct extension tubes for their 2800 and 3400 series AC units.  I cant tell you how this would work out on your coach...

Worse case scenario is that you remove the center duct and portion and block them off.  Then use the plenum and diverters on the Rec-Pro AC unit.  There is one on the front and one on the back and they can be positioned straight down or almost 90 degrees front and back.  The ones on the sides are return air.

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https://www.recpro.com/rv-air-conditioner-15k-quiet-ac-heat-pump-with-condensate-pump-remote-control/

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WE, the STAFF, interrupt the normal banter and discourse for a comment….

Dometic tech support spent a lot of time helping me, a typical Engineer, understand why certain things happen on a Monaco.  I had done a series of early morning  measurements on both the rear 15K and front 15K units.  There was a 10 to maybe 30 Delta T on various parts of the system.  The rear, which was in heat pump mode, ran much hotter.

DUH would have been a good response, but the tech told me to do them again mid day and called me back and spent a lot of time explaining (back in the days when they could do such). I also had an anemometer and he told me to take some CFM and temp readings. 

Bottom line.  My 40 ft floor plan has a continuous duct run from front to rear on the driver side.  But on the passenger, the rear bedroom duct is blocked at the wall.  Reason….shower skylight on that side.  Then it starts again and runs into the front.  SO, per his explanation, the rear Dometic, if you do internal components measurements will always run “Hotter”….so my “what is going on and what do I do to fix it…. ?” question has been asked many times before.   Its a Monaco and it ain’t broke.  Good for HP mode as you will get more heat…not good for AC….but the 15K is OK for the rear.

Now, this “discussion” of duct work and openings and such is not new.  If one does a search, my memory says at least 3 or more times since we switched to the new platform and shut down Yahoo.  And much debate….

Also, FWIW….there are major differences in how Monaco built or constructed the ceilings between the upper ends and the lowers.  Many Dynasty members have had to “do some duct tape” work to patch or correct air leaks.  My Camelot has a totally different design for attaching the outlets.

Bottom line….when talking about duct and cutouts and such…be aware…Monaco was changing construction designs and due to floor plans, there is (not MAY) be many different “configurations” when one pulls out an HVAC unit.  Just don’t get, as has happened, HUNG UP and declare that “MY MONACO is this way and YOURS  will be that way.  

Now back to our regularly scheduled banter…..er, discussion….LOL

 

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Here is the AC system drawing from the binder that came with the coach.  Good reference to see how the basic system is connected.  I would not rely on the color coding and the lack of some of the components such as second furnace, rear AC P2 termination, etc.

image.thumb.jpeg.e85d70163a122eab7faf8664011a0863.jpeg

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I think that if I would consider replacing the Penguin with another brand I'd look at using one of the Air Distribution boxes that just fasten to the ceiling and distributes the air in 4 directions and/or straight down, the vents can be adjusted or even closed.  The fresh air is pulled up throught the bottom.  There is a partition in the middle that keeps cold and return air separated. 

I installed one of these in the Ford Transit van I outfitted for my wife.  One benefit is that there is no head loss due to the ducting, the small slip joint that Penguin uses to mate the AC to the duct work is a BIG restriction.  It seemed to be much quieter and made quick work of cooling the van even in full sun. 

https://www.dometic.com/en-us/outdoor/rv-and-van/rv-air-conditioners/air-conditioner-accessories/dometic-universal-air-distribution-box-non-ducted-application-49997

I actually found one of these NOS on Ebay for $54, brand new

 

 

Test fit of AC shroud.jpg

walls and ceiliing done.jpg

Edited by jacwjames
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  • 3 weeks later...

Is there any reason you can't just drop in a Recpro ducted unit that runs off the remote control and not use any of the Dometic or Microair thermostat wiring?  Would the furnace not operate properly then?  I just don't care about having two zones or being able to remotely set the bedroom a/c.  I'm fine with a remote in the bedroom and a unit that runs independently of the front.  Heck, I don't even care about it being ducted as long as it blows cold! 😁

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Yes you can drop in a Houghton - Recpro and have it run independently from the Dometic thermostat.  That is the benefit of this AC unit as the thermostat and controls are all internal and it has a simple remote to operate.

I prefer to not run my cold AC air through my H ducting.  I rather have the AC blow straight down.  The reason being is it has less resistance to air flow going straight down and out and I dont have to cool the entire roof off before I get all the AC cold air through the vents.

No your furnace will not operate properly.   Read all the information in this post and the attached documents on the reasons why.

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8 hours ago, Brad Loehr said:

Yes you can drop in a Houghton - Recpro and have it run independently from the Dometic thermostat.  That is the benefit of this AC unit as the thermostat and controls are all internal and it has a simple remote to operate.

I prefer to not run my cold AC air through my H ducting.  I rather have the AC blow straight down.  The reason being is it has less resistance to air flow going straight down and out and I dont have to cool the entire roof off before I get all the AC cold air through the vents.

No your furnace will not operate properly.   Read all the information in this post and the attached documents on the reasons why.

Brad is correct.  The FURNACE (Atwood or Aquahot) Function is the most "Mystical and Misunderstood" issue when folks read about how EASY it is and how WONDERFUL it is.

The Dometic Controller for the entire HVAC unit (Penguin or Penguin II) does several things.  It also has a pair of wires (called Blue....often erronously as Monaco ran plain old white #12 stranded). They ran from the Controller (outside on a 15K and in the plenum of a 13.5K).  to each furnace or in the Aquahot, there were a pair for every zone that the Aquahot supplied.  THREE zones....three set of wires.

The RecPro does NOT have any such controller.  It works strictly from the Thermostat (Maybe they have added a remote....don't know) in the HVAC UNIT.  There is NO PROVISION (and we have asked MANY TIMES, or I have....that a FURNACE option or HEAT option be added)....  but that would ONLY be for the Dometic MPX (4 or 5 or 10 Button Thermostats....OR the Microair equivalent).

SO...it is not a complete PLUG and PLAY.  An additional Thermostat for each zone will be required.... Folk have been creative in getting the HARD WIRED (2 lines) to the Thermostat (on a wall or under a cabinet) and back to the furnace(s) of the Aquahot.

MAYBE there is a electronic Thermostat...similar to the "Home Automation" devices that will have a Wireless (or BT) wall mounted thermostat.  All that would be needed would be to have a REMOTE OPERATING DEVICE that could be put next to the Furnace(s) or Aquahot. They would be paired or maybe have ONE remote that got coded signals from each thermostat.  BUT, there has to be an individual OUTPUT or Contacts as in THREE SEPARATE Relays...one for EACH ZONE.

 

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On 6/13/2024 at 3:45 PM, CMillet86 said:

The ductwork in my dynasty wouldn’t line up with any of the other a/c units. I had my rear unit fail and purchased one locally and there was no way to make the duct work. Looking at pictures of the rec pro it may work. But there was another thread where someone had a similar issue and basically said it wasn’t worth the extra work to make the rec pro work. 

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I just installed a recpro on my 2000 dynasty and have this exact same ducting.  I'm not getting much air out of it and the thing seems to cycle all the time.  I'm going to build a duct to connect the unit to the ducting to see if that helps.  I open the frt and back vents on the plenum there isn't much air coming our of them either.  I'm kinds stumped....  This is the one over the bedroom.  And like a moron I did not read up and my frt duotherm wont turn on because of the 4 button thermostat issue.  I will replace the frt one with a recpro I i can get the back one to work properly.

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20 minutes ago, jraynor said:

I just installed a recpro on my 2000 dynasty and have this exact same ducting.  I'm not getting much air out of it and the thing seems to cycle all the time.  I'm going to build a duct to connect the unit to the ducting to see if that helps.  I open the frt and back vents on the plenum there isn't much air coming our of them either.  I'm kinds stumped....  This is the one over the bedroom.  And like a moron I did not read up and my frt duotherm wont turn on because of the 4 button thermostat issue.  I will replace the frt one with a recpro I i can get the back one to work properly.

So if you didn't connect it to the ducting how did you do it? My first thought is if you didn't cut the ducting out of the way most of the air is probably recirculating causing it to short cycle? 

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1 minute ago, CMillet86 said:

So if you didn't connect it to the ducting how did you do it? My first thought is if you didn't cut the ducting out of the way most of the air is probably recirculating causing it to short cycle? 

I called the tech line and was advised to center it over the duct and that should work.  Yes I personally think that is bad info.  The ducting off the old one is just like yours and the outlet on the recpro is bigger.  I did have the "baffle" in backwards it points to the frt of the unit not the back.  That helped some but still not much airflow coming out.  I agree with your diagnosis about the short circuit cycling .  There seems to be few of us who have this issue.  

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As for the Dometic side and furnaces, just follow the documents in the beginning of the forum thread.  Make sure to keep your control boards from your AC units.  If the old Dometic AC units and furnaces worked with your 4 button thermostat they will still work after you complete the set up in the documents. Worse case if the old AC boards didn't work or you pitched them; you have to run individual mechanical furnace thermostats with the blue furnace wiring that are mentioned in this thread.  Run the wiring from the furnace or the AC unit furnace controls.  Not a big deal...

As for your ducting.  You can try and set up some ducting to connect to your central duct.  In my opinion, I would cut back the old duct work and seal off.  Then just use the Houghton-Rec Pro units ducting to vent the AC directly down with the louvers fully open on the AC unit.  Make sure to HVAC aluminum tape the inside air plenum and separate the return air and cold AC air (pictures are in this thread).  Lots of people don't do this on every brand and don't realize that a little bit of air leakage can make a huge cold air loss.  My original Dometic Duotherm installed from factory lost so much efficiency because of the carelessness or lack of knowledge from initial installation.  $5 worth of HVAC aluminum tape in the right spots can make the install last for many years.

There is another benefit to directly porting your AC down from the AC unit.  You have all the cold air going from the evaporator directly into the living area of the coach.  When running the cold air through your roof ducting you have to cool your roof area and ducts before cooling your coach.  The roof can be extremely hot throughout on hot days especially with direct sun.  I have both front and rear 13.5k 3501 Houghton's and I prefer to use downward venting rather than my roof H ducts. The coach cools off faster and the AC units are more efficient at cooling off the coach .

 

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There is a ducted and a non ducted model.  I have only seen what I installed in my coach and that is the ducted model.  The ducted model has diverter controls inside the Houghton plenum.  Select open to have air flow directly down and out the Houghton vents or close them and have the air flow through the H ducts.

H duct entrances are on the side (smaller thin rectangles) shown here with the plenum removed

image.png.e9e20ea56f6c29506e07e7485e2dcce0.png

 

The non-ducted possibly has an air sock that is needed if your roof is extra thick?  Can't confirm this though as I have never seen a non-ducted model.

https://www.recpro.com/rv-air-conditioners/?page=1

Even with the ducted version you should be able to seal off the entire 14 x 14 inch roof area and mount the plenum in and just have the Houghton vents open for it to vent the cold air straight down.  As long as you have the plenum in the correct direction and you have the return air and cold air sides sealed off from each other...

I can remove my inside over and take a few pictures if you need.

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33 minutes ago, Brad Loehr said:

As for the Dometic side and furnaces, just follow the documents in the beginning of the forum thread.  Make sure to keep your control boards from your AC units.  If the old Dometic AC units and furnaces worked with your 4 button thermostat they will still work after you complete the set up in the documents. Worse case if the old AC boards didn't work or you pitched them; you have to run individual mechanical furnace thermostats with the blue furnace wiring that are mentioned in this thread.  Run the wiring from the furnace or the AC unit furnace controls.  Not a big deal...

As for your ducting.  You can try and set up some ducting to connect to your central duct.  In my opinion, I would cut back the old duct work and seal off.  Then just use the Houghton-Rec Pro units ducting to vent the AC directly down with the louvers fully open on the AC unit.  Make sure to HVAC aluminum tape the inside air plenum and separate the return air and cold AC air (pictures are in this thread).  Lots of people don't do this on every brand and don't realize that a little bit of air leakage can make a huge cold air loss.  My original Dometic Duotherm installed from factory lost so much efficiency because of the carelessness or lack of knowledge from initial installation.  $5 worth of HVAC aluminum tape in the right spots can make the install last for many years.

There is another benefit to directly porting your AC down from the AC unit.  You have all the cold air going from the evaporator directly into the living area of the coach.  When running the cold air through your roof ducting you have to cool your roof area and ducts before cooling your coach.  The roof can be extremely hot throughout on hot days especially with direct sun.  I have both front and rear 13.5k 3501 Houghton's and I prefer to use downward venting rather than my roof H ducts. The coach cools off faster and the AC units are more efficient at cooling off the coach .

 

Thank you

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55 minutes ago, Brad Loehr said:

There is a ducted and a non ducted model.  I have only seen what I installed in my coach and that is the ducted model.  The ducted model has diverter controls inside the Houghton plenum.  Select open to have air flow directly down and out the Houghton vents or close them and have the air flow through the H ducts.

H duct entrances are on the side (smaller thin rectangles) shown here with the plenum removed

image.png.e9e20ea56f6c29506e07e7485e2dcce0.png

 

The non-ducted possibly has an air sock that is needed if your roof is extra thick?  Can't confirm this though as I have never seen a non-ducted model.

https://www.recpro.com/rv-air-conditioners/?page=1

Even with the ducted version you should be able to seal off the entire 14 x 14 inch roof area and mount the plenum in and just have the Houghton vents open for it to vent the cold air straight down.  As long as you have the plenum in the correct direction and you have the return air and cold air sides sealed off from each other...

I can remove my inside over and take a few pictures if you need.

I had the plenum and baffle backwards.  The tech had me turn it around so the foam baffle faced forwards putting the slider controls to the back.  That helped with air flow.  That was a week ago I'm going to build a duct to seal the unit to my ducting.  

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9 minutes ago, jraynor said:

I had the plenum and baffle backwards.  The tech had me turn it around so the foam baffle faced forwards putting the slider controls to the back.  That helped with air flow.  That was a week ago I'm going to build a duct to seal the unit to my ducting.  

Yes that is correct.  The vent slider controls for open/close are to the rear of coach.  I would cut back the coach duct and seal up the 14 x 14 square area like the pictures above.  Seal up the return air from the cold air in the plenum 100% and then vent cold air directly down.  Hope that helps...

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