Aqua Hot new boiler install

[vito.a]

I'm in the middle of installing a new boiler in our Aqua Hot 100-02S .  The new boilers are quite a bit different.  They do not have a radiator cap, the copper coils are on the inside (which is much better) of the boiler tank, the limit thermostats are a new design, the exhaust opening is 1 1/2" pipe vs 1 1/4" pipe threads, and the tank sits 5/8" more forward in the cabinet.  This last difference forces cutting the copper tubing to the cabinet exit point by 5/8" and re-soldering.  And you can't just move the boiler back because you have to center it on the exhaust opening.  The fresh water lines use braided steel hose but the engine coolant and house heating loops are copper tubing.  Lots of soldering practice!

I have it mostly back together, but I'm currently having trouble.  The diesel burner is not firing and I think it's not getting fuel.  Our resident double E (k7jv) is helping me but the wiring diagrams are incomplete. 

I checked the DC control and high limit thermostats and they have continuity when the boiler temperature is below the cutoff temperature.  I've made sure the fuel supply and return lines didn't get swapped.  I removed the diesel burner and checked the electrode gaps are correct.  It appeared dry on the inside with no sign of fuel.  

I'm thinking of removing the diesel burner again and using jumper wires to check diesel solenoid activation.  After that I'm down to checking wires again and maybe having the controller checked.  

If anyone has any ideas I could use the help?

[Bill C]

Boy, you’re a lot more ambitious than I am: swapping it out on your own. I’m afraid I’m not much help but I sure wish you luck. I hope somebody can help you.

[timaz996]

I will follow this incase I ever have to do this. I have the same model. I wish you all the luck figuring it out.

[96 EVO]

Are you using your old Webasto, or did you get a new one?

[pwhittle]

You can check the pressure by replacing the nozzle with a pressure gauge and turning it on. I took an old nozzle and drilled/tapped it with NPT and then some adapters to a pressure gauge.

Good luck with the project!

Paul

 

[vito.a]

The boiler tank and all the tank contol thermostats are new. The firewall bulkhead and overflow tank are also new. Everything else is original.

At this point, I'm also thinking I should have waited for warmer weather and taken it to Colorado for service.  

I'll post more pictures and details after I get it sorted out. 

[Jdw12345]

Did you get a new float switch or did you use the old one or does that model even need that switch!

 I’m not sure how different the 02 is compared to my 04.

 Did the boiler burn out or spring a leak?

 Sorry for all the questions, how many hours on your unit?

 Don’t rule out a bad new sensor.

Edited March 24, 2023 by Jdw12345

[vito.a]

I don't think this system has a float switch.  If it does, I can't find it in the schematic.  It also doesn't have an hour meter or LED diagnostic board.  

But these are great basic heat and hot water systems.  I've owned a newer 450D and this older 100-02.  This older system has a stainless steel enclosure and all copper pipe.  No plastic connectors or heater hose.  The pumps on these older systems are high quality USA made.  The relays are Dayton made in the USA.  Even the electronic controller is rebuildable where the newer systems are not.  

Yes, the fresh water loop had a slow leak.  One of the outside copper pipe coils rubbed through near the bottom.  That's the weak point on these systems manufactured in 2003 and earlier.  I had to keep water turned off to the system.  

 

[Ivan K]

I have the same original unit. Wonder what the 2 unused black thingies on you new tank are for. And I agree that you would need to remove the burner again to check power and function of the solenoid. I like Paul W's idea about drilling out an old nozzle, that way you could check all the burner functions without risk of igniting it.

Are these just plugs for an additional element and maybe a float at the top? At first they looked like plastic to me but I guess not.

Edited March 24, 2023 by Ivan K

[96 EVO]

5 minutes ago, Ivan K said:

I have the same original unit. Wonder what the 2 unused black thingies on you new tank are for. 

Second electric element 🤔?

[vito.a]

Yes, Ben is correct.  The large pipe plug on the left is for a 2nd 120v element.  The picture is turned sideways.  

The plug at the top may be for a float or level sensor. 

The picture below is the unit disconnected and slid forward into the next compartment.  This took me 1 1/2 days to accomplish.  Lots of hoses and lots of wires.  And the exhaust is tough to disconnect.  I used cardboard to make it easier to slide.  Then slid it out onto a furniture dolly.  

The amount of wiring and plumbing is incredible.  There are two engine heater hoses, two fuel hoses, and two fresh water pex hoses along the bottom.  And there are six more large boiler fluid hoses for the house heat exchangers along the top.  

[vito.a]

Picture of all the boiler fluid copper plumbing.  You can see the fresh water mixing valve under the crescent wrench and the engine loop pump on the far side.  Again, picture turned sideways.    

[vito.a]

After removing all the copper tubing, you drill out the 1/8" rivets holding down the rear stainless-steel enclosure.  Then drill out the 3/16 rivets holding down the old boiler and remove it.  This point is a big deal as now you are halfway! 

After wrapping the new boiler in fiberglass, fit it into the base.  Then turn it all upside down and layout & drill new mounting holes.  You must center the exhaust opening on the opening in the base, then layout and center the new hole pattern.  The holes in the new tank base are 14 3/8" width, and 12 1/2" front to back.  It uses four 3/16" dia x 1/2" grip length rivets. 

Then install the new firewall with 1/8" rivets.  

Edited March 24, 2023 by vito.a

[vito.a]

You need to adapt the new 12v boiler thermostats to the old wiring.  I used this picture to connect the new to old wires.  

Somewhere about this time I discovered that the new boiler sits 5/8" closer to the exit bulkhead.  That meant I had to shorten the two boiler fluid pipe nipples to the fluid pumps as well as all the copper tubing.  I also had to modify the mixing valve copper tubing to adapt the stainless steel fresh water hose.  Lots of copper pipe soldering.  

I also learned that the new boiler exhaust is 1 1/2" pipe and the old one was 1 1/4" pipe thread.  You could make up an entire new exhaust system but mine was in excellent condition, so I used a pipe reducer and 1" shorter pipe nipple with a new elbow into the original Aqua Hot exhaust pipe adapter.  Make sure you have two very large pipe wrenches and a cheater handle.  PB Blaster to loosen threads also helps.  

Edited March 24, 2023 by vito.a

[vito.a]

After the unit was assembled a friend helped me slide it back into the coach forward compartment, then though the divider and back into place.   Then I cut and crimped the two short pieces of Pex water lines (blue in and red out).  After that I reconnected the heater hoses from the engine, and the two fuel lines.  I had removed the three brass elbows at the top of the zone pumps, so I reinstalled them.  Then I connected the six house boiler fluid hoses. 

When taking it apart I used these plugs to keep the fluid from running everywhere.  Amazon.com: 40 Pc 1/16" to 3/4" High Temp Silicone Rubber Tapered Plug Kit - Powder Coating Custom Painting Supplies : Automotive

I spent hours reconnecting all the wires.  The terminal screws are mostly Phillips except the ones below the fuses are T-15 Torx.  Most of the ground wires go to one long bolt.  I also reinstalled the 120v wires.  

The new 120v heat element is much better than before. 

This boiler only has a 90 degree brass hose bib on the top.  No radiator cap.  I installed the new overflow tank in the next compartment forward.  The overflow tank must be 4" above the boiler.  I routed the 5/8" heater hose from the tank up through the plywood basement ceiling cover and then back to the new boiler.  

I order 95% propylene glycol from Chemworld.  You will need at least 8 gallons plus 8 gallons of distilled water.  I used a hand transfer pump to fill the boiler. 

But I'm working on the diesel burner not lighting.  With Paul's advice I ordered a pressure gauge and some fittings.  I'm going to tap an old spray nozzle and make a fuel pressure tester.  

Edited March 24, 2023 by vito.a

[tubsy1]

Great photos and details!  We have taken our aquahot (same model as yours) out of the 2004 Dynasty and have pondered either replacing/updating the tank or purchasing a rebuilt unit.  May I ask where you purchased your tank?  Thank you, Keith

 

[Guest Ray Davis]

I read on one of these forums of someone that sent their boiler to John Carrillo and he rebuilt it.   Might be worth checking into.   I don't know John but have heard good things about him.  Here is a link.

https://www.heatmyrv.com/

[vito.a]

Yes.  I purchased the new boiler assembly from John Carrillo.  A few years ago when my ignition coil failed, he was very helpful.  However, he has been less than helpful this time. 

John Carrillo- Heat My RV

7800 Miller Dr Unit C, Frederick, CO 80504

Phone: (970) 518-3085

 

[vito.a]

The heat/sound insulation mat under our Aqua Hot cabinet was in bad shape.  I used this mat as a replacement.  

Car Heat Sound Deadening Insulation Mat, - 197 Mil 10.8 Sqft Automobile Sound Deadening & Heat Insulation Material for Auto Hood Engine Roof Door and Trunk,40 Inch x 40 Inch, Aluminum Foil Finish (amazon.com)

I used the standard fiberglass hot water heater insulation kit from Home Depot to cover the new boiler.  

Frost King Fiberglass Water Heater Insulation Blanket SP57/11C - The Home Depot

Along with this alum tape.

Nashua Tape 1.89 in. x 30 yd. Water Heater Installation Air Duct Tape 1529787 - The Home Depot

[pwhittle]

I love your posts Vito!

So much information for the other members to benefit from.

Thx Mate.

Paul

Edited March 26, 2023 by pwhittle

[vito.a]

I took Paul's advice and made up a pressure gauge connected to a fuel nozzle.  I thought I was drilling a soft brass nozzle, but they have a hard stainless steel insert.  I ended up drilling it from the back side and pushing the stainless insert out the back.  Then I drilled and tapped it to 1/8" NPT.  

I installed the pressure gauge with nozzle adapter on the diesel pump and ran the system with the pump laying in the tray.  About 20 seconds after tuning it on I saw 1 spark and the fuel pressure rose to 140-145psi.  I tried it twice with the same result.  

I removed the gauge and reinstalled the standard nozzle and pump into the system.  This time when I ran the system, I again had 1 spark (you can here it) and good fuel flow.  but no ignition.  

This morning I again removed the pump and disconnected and checked the resistance of the photo cell flame sensor. Regardless of whether the sensor was covered or uncovered, it measured about 60 ohms.  

I'm going to replace the flame sensor and try again.  

[96 EVO]

I've never had a problem with mine firing (knock on wood).

Are they supposed to spark multiple times?

[Ivan K]

I had to replace the AH igniter once. As I remember, the coil is supposed to repeatedly spark until a flame is detected or the flame detection times out. That, outside of a typical RV upcharge, makes it more expensive than home heating AC coils because it needs electronics to simulate a trigger. Not as simple as some automotive coils. Still way too expensive. Like $300 vs $45 in my shop heater last time I replaced both of mine.

[96 EVO]

Thanks Ivan!

That's what I expected happens.

[Ivan K]

Vito, I agree that the photo sensor needs replacing but there is likely more to it. Yes, the sensor needs to change resistance very very noticeably but it does not have a role in preventing initial firing. When mine was bad, the burner would fire but shutdown shortly after. 

Now thinking about it, my sensor was stuck at over 1k ohm while the new one dropped way down with just day light. Just a crazy idea but maybe your low reading fools the controller into thinking that the flame is present and to stop ignition... Curious what you find out.

Edited March 28, 2023 by Ivan K