Need help in understanding 2003 HVAC and how to protect from freezing without Winterizing.

[Just Jim]

Finally, getting back to some maintenance items and dropped the decorative cover to clean the HVAC filters.  The filters/screens were attached with a sheet rock screw at the corners which allowed the filters to hang down with fairly large gaps on the sides.  So, 1st question (this does not appear to be how they were originally installed...) how should they be put back in so that they actually filter the incoming air?  2nd question, are they actually needed?  I saw where some said they had removed them to increase air flow.  

I read my manual and it says that the heat pump would work down to 30 degrees or so then switch to Aux heat which would be the aqua hot.  I tried that yesterday... turned on the heat pump and it ran and was providing heat... however the aqua hot ran continuously (left it on for about 40 minutes) but no heat coming from the exchangers as it was set on heat pump.  The manual indicates that the aqua hot button has to be on for aux heat to work.  I assume the aqua hot would only light when it needed to provide heat???  Anyone have experience with this?  I don't mind living the heat pumps on with the temp set at 50 or so... and having the aqua hot come on to provide heat when outside temps drop below 30... but having the aqua hot running constantly is not acceptable.

I have drained the water tank.  I assume it is ok to run the aqua hot with no potable water in the plumbing lines?

Hopefully, I'll eventually get this stuff figured out...  Thanks

[jacwjames]

I do not have an Aquahot (wish I did) but from what I've read it is better to use the RV anitfreeze on the aquahot to make sure there is no water trapped that could freeze and cause big problems.  Hopefully someone will chime in. 

 

[Frank Bergamo]

I believe your thermostat has to be set for heat pump or furnace, one or the other, not both. As far as winterizing, it is imperative that you run antifreeze through the Aqua Hot or you will have serious problems later. Blowing out with air does not adequately evacuate the water, must run the pink stuff. Also, you can run Aqua Hot for heating purposes when winterized. Hope this helps.

Edited December 18, 2023 by Frank Bergamo

[96 EVO]

2 hours ago, Just Jim said:

 

I read my manual and it says that the heat pump would work down to 30 degrees or so then switch to Aux heat which would be the aqua hot.  I tried that yesterday... turned on the heat pump and it ran and was providing heat... however the aqua hot ran continuously (left it on for about 40 minutes) but no heat coming from the exchangers as it was set on heat pump.  

Well, good luck with that!

I've experimented with my system as well. Thermostat never switched over to 'Furnace' mode on it's own!

Believe it works fine with propane furnaces, but I've never read anyone say it has definitely switched itself over to Aqua Hot heat!

[Tom Cherry]

11 hours ago, Just Jim said:

Finally, getting back to some maintenance items and dropped the decorative cover to clean the HVAC filters.  The filters/screens were attached with a sheet rock screw at the corners which allowed the filters to hang down with fairly large gaps on the sides.  So, 1st question (this does not appear to be how they were originally installed...) how should they be put back in so that they actually filter the incoming air?  2nd question, are they actually needed?  I saw where some said they had removed them to increase air flow.  

I read my manual and it says that the heat pump would work down to 30 degrees or so then switch to Aux heat which would be the aqua hot.  I tried that yesterday... turned on the heat pump and it ran and was providing heat... however the aqua hot ran continuously (left it on for about 40 minutes) but no heat coming from the exchangers as it was set on heat pump.  The manual indicates that the aqua hot button has to be on for aux heat to work.  I assume the aqua hot would only light when it needed to provide heat???  Anyone have experience with this?  I don't mind living the heat pumps on with the temp set at 50 or so... and having the aqua hot come on to provide heat when outside temps drop below 30... but having the aqua hot running constantly is not acceptable.

I have drained the water tank.  I assume it is ok to run the aqua hot with no potable water in the plumbing lines?

Hopefully, I'll eventually get this stuff figured out...  Thanks

FWIW, not doing a full winterization is DANGEROUS.  OK, many say NO.  As my attorney tells me to say…IT DEPENDS.

First…how LOW will it get?  What will be the HIGHS during the cold snap.  I have always winterized.  Several years ago, i had a small water leak after flushing the RV Pink OUT.  Say WHAT?  Was in the toilet flush valve.  Talked to Dometic.  Not the only one.  I DID, religiously, get s good steady stream from the flush wand and the Prefill and the Flush FULL draining. Dometic says the passages and clearances are tight and even if you do use pure RVAntifreeze, some cold snaps will cause issues.

We live in Raleigh.  Not Duluth.  We had a few days of maybe mid to low 20’s and nighttime down to almost zero.  The fact that the day time was below freezing set uo a “Cold Sink”, so the internal temps went super low.

I don’t trust the “furnace” to switch over from HP.  When I have the rig at hime and not winterized, I run the AH on Diesel around 55 - 60 DF.  The AH systems are totally different from year to year.  Mine will come on, with Diesel Burner ON…but NOT require a Furnace Zone to be on. Some of the later Dynasty’s had to have on the rear (bedroom) furnace zone to work.

There is only ONE way to test.  First.  Turn on AH and leave it on.  Get heat from all zones.  Then use the MODE button and kill the Furnace. NOW….pull your prints.  Look at the HVAC with the AH control panel.  There will be a thermostat in the bay.  See which terminals it is wired to….the ZONES in the AH panel do NOT match up with the HVAC…thus the need for the print.  Pull the  cover off.  Use an alligator clip jumper and jumper between the Thermostat terminals.  That’s all the HVAC does…you want heat…when Furnace zone is selected and the thermostat calls for heat….the control module in the AC system closes the contacts.  SIMPLE

NOW…go back to the wet bay. Is the air handler fans running?  Is there heat?  AS IN THE Pump is circulating the Boiler Antifreeze.  Of find the Thermostat.  It probably has a capillary tube bulb.  Fill a glass with cold water and some ice cubes….bend the probe and out it in the glass…BING…

NOW, IF  the registers did NOT blow….then turn on the rear thermostat for Furnace.  Did that fix it?  If not, try all the furnace zones….one at a time.

BTW….there is a great myth.  The AH only uses maybe 1/2 GPM if running full time.  So, it ain’t like flushing a commode.

 

 

[amphi_sc]

Just my 2 cents and your mileage may vary since your climate and coach are different.

We use our coach a lot so not worried about it when we are traveling & living in it and the temp is in teens or high single digits.  There are some times when it may be parked at the home S&B in the DFW TX area and we are out of it.  It can get cold in DFW with single digits on rare occasions but I treat the stored RV just as I do the "stored" S&B house.  The RV would be in unheated uninsulated metal building with electricity.  Most times it is above freezing but it does dip below.  I don't drain the water out of my house when we leave for the winter and I set the old house thermostats to 45.  Two years ago replaced the 30 year old house systems and new thermostats that don't go any lower than 55 so I live with that higher setting. If we happen to be home around Christmas and out of the RV, I just leave the RV thermostats set to 45, Aqua Hot on electric, heat pumps automatically switch over to Aqua hot baseboard heat when the temp / humidity reaches a point when the units can't deliver heat. (In the AZ desert they've delivered heat as low a 27 outside before automatically switching to AH "furnace" but on DFW rainy days they may cycle to AH around 40.) As an additional heat source (if we are in the RV or not) I use a couple of small tractor supply heaters set on low with their thermostats set just below the main RV thermostat settings so they'd come on if the Aqua Hot can't keep up. Those little heaters consume about 6 amps each when running. As the RV is inside unheated storage and plugged in I do NOT use the diesel setting on the AH as on my unit the diesel and electric come on simultaneously and NOT electric first and then if needed diesel.  Some AH units had two independent boiler thermostats but not mine.  My AH is located in the wet bay so it's boiler gives some parasitic heat in addition to the hot water thermostatically controlled radiator mounted there. I do leave the AGS set for the generator in the rare case ice knocks out the regional electric grid and accept the trade-off diesel exhaust vs no juice.  I've never experienced a problem, even with the little plastic ice maker line hanging out in the cold in the electric channel going to the fridge in the slide.  I may turn off that water line at the manifold but never had a freeze induced leak.  One year we were going to be home during the two coldest months so I did blow out the water lines but did not pump in antifreeze as the AH was left on.  My situation & use pattern will be different than yours, but this is what has worked for me over the years. I do know that occasionally water in my unheated storage building will freeze as one year the engine block casting plugs popped out on the 460 engine in my boat.  After that year I did pour antifreeze into the boat engine block as it was impossible to drain the fresh water completely out of the block.

From all my ramblings a couple of points (1) my heat pump system automatically switches to hot water heat as needed, and (2) I leave my aqua hot electric "on" to keep the boiler warm which should keep the little internal heat exchange tubes from freezing even if water settles there from blown out water lines as it is designed to cycle for domestic hot water regardless of furnace settings based on boiler antifreeze temperature ... i.e. it can keep the boiler warm regardless if the fresh water system has water or not, (3) the fridge ice maker line appears to be able to expand enough to absorb ice forming in the part that hangs out in the cold outside air although I've NOT experienced a "no water" situation from the fridge door dispenser, and (4) note that I'm not in a climate that experiences weeks of constantly below freezing temperatures.

Just relating my experiences with my particular coach and usage pattern. To be safest, full winterizing with RV antifreeze is best but I don't want to be flushing out pink water when we are ready leave and it's still freezing where we are but warm where we are headed.

[96 EVO]

30 minutes ago, amphi_sc said:

  heat pumps automatically switch over to Aqua hot baseboard heat when the temp / humidity reaches a point when the units can't deliver heat.  

Well, good to hear it works for somebody 👍!