You are not logged in or registered. Please login or register to use the full functionality of this board...
Newell Gurus
Tore out the Aqua hot - Printable Version

+- Newell Gurus (
+-- Forum: Technical Discussions (
+--- Forum: Heating Systems (
+--- Thread: Tore out the Aqua hot (/showthread.php?tid=5266)

Pages: 1 2 3 4 5

RE: Tore out the Aqua hot - RegaNewell - 11-23-2019


Jeff will get you that info today.  

He wants your thoughts on something also...Jeff is thinking about wrapping the tank and coils with 1" thick ceramic wool blanket good for 2,200 degrees.  This will completely encapsulate the entire tank and coils where no heat will be able to escape.  Do you for-see any issues with keeping the heat contained so efficient?

Jeff's hand is under the ceramic blanket on top of the coils.  That is a map gas torch that he is using, he will hold it there as long as you want him to. He loves showing this off. LOL

RE: Tore out the Aqua hot - RegaNewell - 11-23-2019


The best I am able to measure at this time is tank diameter is approximately 16.552", I have measured the circumference around tank and tubing @ 53.125" thus assuming tank would be 52.125". The copper tubing OD is .500", and there are 31 complete coils, plus approx 36" of copper tubing (cold line) before coil wraps start and 16" that go from last coil (hot line) to mixing valve. This roughly equates to 139' of 1/2" copper tubing, I may be all wrong on this, please correct me if I am.

"I am scheming on ways to make the hot water last longer."

Please let me know what you are "scheming" before I completely rebuild this and put it back in the coach. I am in a rough spot here, PAM wants to take a HOT shower in her coach! We just came back from a week in West Virginia, she did not appreciate using the camp showers. LOL

Some of the things I am doing.
Completely redoing all the pluming on the AH system and bay.
Adding shut off ball values on both sides of all 4 pumps.
Replacing and moving both gate values on tank to ball values.
Will be using blue and red Pex, and replacing every 90 degree fitting, with sweeping 90's.
Relocate mixing value to an easily accessible place.
The hot water coil has passed pressure test.
The coach heating coil has passed pressure test.
The Tank has passed pressure test. (the radiator cap starting leaking past at 11psi, replaced with new 13psi cap and pressure held fine. I am going to read the manuals and make sure this is correct cap pressure.)
In process of testing engine preheat coil.


RE: Tore out the Aqua hot - Richard - 11-23-2019

You can insulate the tank more, it won’t hurt anything. But I personally don’t think that is the problem.

There is a known problem where the water in that outside loop can freeze and expand the copper in that loop. When it does, it pulls the loop away from the heat transfer mastic ever so slightly, but it wreaks havoc with the heat transfer. I suspect this has happened in my coach. I need to run the test of measuring incoming water temps, shower temps, and flow rates to see if the unit meets the AH specs which I think, don’t trust my memory, of 40 degree rise in temp at 1.5 gpm.

One more thing to be aware of, and this is a huge difference between using the AH for showers on electric vs diesel. On diesel, the bathroom loop pump is activated when the burner is running. The effect is to circulate the coolant inside the tank which tremendously improves the heat transfer to the hot water loop outside the tank. On electric, the coolant inside the tank is stagnant, and does not transfer heat nearly as well once the hot water starts flowing.

I have three concepts I am thinking about. The first is to add an additional coil to the hot water loop. It would require heat transfer mastic, and obviously the space inside the cover would have to have enough clearance.

The second is to simply fab a squarish tank to sit on top of the AH cover. The cold water would enter the tank first, and then into the hot water coil. The purpose of the tank would be to preheat the water.

The third idea is to add a insulated hot water tank to the bay. That idea would require a circulation pump and controller to make it work.

There are two things that make a big difference with the existing setup with regard to length of showers. First, measure you water output at the shower. If it is more that 1.5 gym, you will have really short showers. The second is to use water from the fresh water tank instead of 50ish degree ground water.

Based on your measurements, the hot water coils around the tank contain less than 2 gallons of water. What this tells me is that heat transfer is the key. The AH is NOT storing hot water of any significance.

RE: Tore out the Aqua hot - Trainer - 11-23-2019

Richard, the fresh water heating spec is 55 degree temp rise at a flow rate of 1.5 gal/min.

Through contact of the fresh water coils with the heat transfer mastic is essential to hot water heating for showers. Enabling the diesel burner to allow the zone 2 pump to stir the tank assures a long hot shower.

Sure is a lot of work to accomplish the replacement of the guts of the tempering valve that I do in less than 30 minutes. This has solved loss of hot water many times.

The diagnostic test is to feel the hot water line coming out of the tank to the tempering valve and the hot water line to the coach from the tempering valve. Good hot temps on the line to the valve with loss of temp on the line to the coach equals replace the tempering valve guts.

If the coils are separated from the mastic, then then opening the heater to repair is needed.

But the enhanced maintanence of the heater with new cutoff valves is most helpful the few times they need to be used. Can never have to much insulation under the stainless cover.

Be sure to service the burner before installing in the heater, new nozzle correctly installed, clean combustion chamber, clean U-channels in burn chamber, clean flame sensor, ignitor point gap correct. All the best in finishing this maintenance.

RE: Tore out the Aqua hot - Richard - 11-24-2019


Thanks for the official numbers!

RE: Tore out the Aqua hot - RegaNewell - 11-24-2019

Richard and Rudy,

Thank you for all your help with the information. Jeff could have just replaced the mixing valve, but wanted to go through it to make sure everything is/will work correctly.

What mastic do you guys recommend?


RE: Tore out the Aqua hot - Richard - 11-24-2019

I have not reapplied the mastic. Here is an informative site.

And read this thread, last post on page 1.

RE: Tore out the Aqua hot - folivier - 11-24-2019

This post describes where he replaced the tubing around the tank, and he uses Chemtrax for the mastic.

RE: Tore out the Aqua hot - RegaNewell - 11-24-2019


I have decided I am going to add 100' of .500 OD copper tubing to the outside of the original coil wrapped around the tank. I will use the suggested mastic to bed everything in, and still cover the coils and tank with the ceramic wool. I am thinking of incoming water going through the outside coil first and then through the original coil next to the tank second. I would appreciate your thoughts on going from second to first or would you go from first (original) coil to second? I have been around and used the ceramic wool for over thirty years, it will completely hold the heat and not allow it to transfer to the ambient air. I appreciate both yours, and Rudy's experience, and I have no problem with either of you smacking me upside the head, and steering me straight. Yes, we had the diesel burner running, temp gauge showing 200 degrees, and still only getting warm water when in West Virginia. We always use water from the holding tank whether summer or winter trip. I even had the bay heaters on to try and pre-warm the water in the holding tank.


RE: Tore out the Aqua hot - Richard - 11-25-2019

This is my opinion, and I have not laid eyes on your specific tank. First, you definitely want the incoming water to be on the outside loop. Second, I think that a complete encapsulation of the mastic around the original coils and the new coils will work better than the original concept which was to use the mastic only where the coil touched the tank.

I have read the mastic is runny until it sets. I would think about using something to act as a "form" to keep the mastic from dripping away from the coils while it sets. The key will be to get complete contact of the entire coil with the mastic. Something like heavy duty aluminum may work. Fine weave fiberglas cloth would work, but would remain in place when the mastic cures.

I have gotten really excited about the use of a double walled flat plate heat exchanger to augment the existing hot water loop. I know those things are amazing when it comes to heat transfer. The double wall design is made for domestic hot water heating so you have some protection against glycol contamination of the drinking water. I don't know that I would do it exactly the same way that the guy did in the link I posted. I would mount the FPHE on top of the AH cover. I also would rob the electrical circuitry associated with the engine preheat pump to power the circulation pump for the FPHE. I never use the preheat. If the concept works, then I would figure out something to have it come on when showering. The reason I don't want to use the burner on as a trigger for the pump, is that it commits you to use the diesel for showering.