Well Sir, I am as frustrated as you are. Newell may have the best idea of your situation. I have never dealt with the line from the heater never being hot for at least a little while.
Roger mentioned the outside sprayer. In the utility bay on the driver's side, my coach has a water faucet like in the sink. If the hot and cold water valves are left on the water would flow out on the ground. BUT, one of my clients had a hand held sprayer the would cut the water flow off with out turning off the hot and cold valves. This sprayer, like on a home kitchen sink, will kill the hot water to the coach. It allows a easy loop for the hot water to circulate round and round.
Took me nearly an hour to ask about the sprayer. Five seconds to turn valves off and fix the problem of no hot water.
Rudy Legett
2003 Foretravel U320 4010
ISM11 450 hp Allison 4000R
Factory Authorized Aqua Hot Repair Center
Southeast Texas Area
Rudy is there a check valve anywhere in the system that could be stuck open?
It definately sounds like there is something that is common to hot and cold water.
Bill- is the water pressure the same when the temp cools off?
The water pressure seems to start off a little higher and then drop with the temperature. It never tries to "run dry". In other words, at the kitchen sink if I put on only hot water, it still has a pretty good (not great) flow.
My brother just read the maintenance manual and said that the water / antifreeze mix should be 50%. The book said that if you have too much antifreeze, it will affect domestic hot water production. As far as I know, the cap has not been off the unit since I have had it. I have the Aquahot cooling down right now and will open it in the AM. That way I can verify the level of the water and what the mix of water to antifreeze is.
Well, I just pulled the radiator cap. The water was at least a gallon low...and...the radiator cap was totally shot. The rubber gaskets just fell off when I removed it. I added clear water to bring the level back up. Will test the mix next.
Bill,
Might be a good time to replace the overflow hose that goes between the fill neck and the surge tank. It that hose doesn't stay air tight it screws the system up.
Rudy aka trainer, told me the same thing that the hose if it sucks air will mess up the system. Mine didn't have a hose clamp on it but does now. I may even replace the hose and cap just to be sure.
We're all anxiously waiting to see if that fixes your problem.
Might even buy a couple caps in case there is a run on them.
I first turned on the diesel heat AND the electric heat. The Aquahot meter read 207F. I set the shower handle on 100F and measured the water with my laser thermometer. Exactly 100F in shower. Water in my kitchen sink on full hot was 125F. That means that the mixer in shower was working AND the mixer in the water bay was working. The outside temperature is around 45F here but I have tankage heat set on 70F.
During the shower the diesel burner came on when the temp dropped to around 170F and turned off again when the temp got up to 185F.
After the shower I checked the sink temp and it was 131F.
All of this is EXACTLY the way that I think it is supposed to work.
SOLUTION
My problem was that there was not enough water / antifreeze in my Aquahot. The solution was to add water.
I think the reason that I was low on water is that the tube that goes from the radiator cap on top of the Aquahot to the overflow tank was leaking on both ends. It was yellowed and brittle. I replaced with new vinyl tubing from Home Depot. (Will watch to see if it is robust enough to stand the heat). Also, I replaced the radiator cap with a new one from the auto parts store. Just ask them to find a standard cap that has 13LBS stamped on the top. While I had the cap off, I tested the water using a standard antifreeze tester thingy. It tells you the temperature that you are protected down to. Mine said -65F. That means that I was almost all antifreeze. You want a 50/50 mix of antifreeze and water and that will read -35F. According to Rudy / Roger Burke too much antifreeze will adversely affect the hot water performance of the aqua hot. When I tested the overflow tank it went off the scale. (Pure antifreeze). I drained the overflow tank and added pure water.
TROUBLESHOOTING
This thread documents all the things that I tried, but there were two key things that pointed to the solution:
1) The pipe going to the tempering valve (under the burner) was NOT hot. The tempering valve mixes cold water from your fresh water tank with hot water coming out the Aquahot boiler to produce warm water that you use for domestic hot water. Since mine was only warm coming out of the Aquahot boiler there was some problem inside the stainless box.
2) The level in the overflow tank never changed. This was a sure giveaway that I had a vent / radiator cap issue. If you turn your aquahot off and let it cool. (By setting inside switch to AC and leaving diesel switch off), the level in tank should drop to the bottom third. After you turn it on and it heats up, the level should rise to the 2/3 level. Mine always stayed on the upper mark. In essence it was a standalone tank that was not connected to the Aquahot unit since the vent tube was leaking at both ends.
I think what happened is that the vent tube got a leak and then when water / antifreeze was supposed to flow into the overflow tank, it simply leaked down around the radiator cap opening and disappeared below the boiler. That allowed the water / antifreeze level to drop in the tank causing a severe drop in heat transfer to the external coils that are used for domestic hot water. (See Steve's picture).
By making sure that the vent pipe was sealed, it allowed the expansion tank to work properly. Since there was now more water (and a better mix of water / antifreeze) the heat transfer went up and I had a lot more hot water.
I think that checking / replacing the tube and cap should be done as part of yearly maintenance. In my case I have been through two annual maintenance routines but this issue was not found. Also, If you buy a used coach, it would be good to cool off the tank and check the mixture of antifreeze / water. (be careful!)
This has been quite the journey and I am not sure it is finally fixed, but it is much, much better.
Thanks to all you guys for the help and advice. I will report on Roger Burkes site in a few days after I am sure that this is the fix.
Cheers,
bill
ps. I will see whether running on just electric / and just diesel affects this answer.
