Strange Aqua Hot Issue

[boomersooner]

Woke up this morning and coach was in lower 50's. Had furnace on 73 and had not had a problem all week. When I got up at 5am the coach was cold, furnace was running (Aqua Hot 250d), but the flames on the Spyder Control were blue. I could hear the AH start up and turn off periodically. When I got up at 7:30 I wanted to ensure that I had enough fuel so put the key in turned the key to the right, enough to see the dash cluster, but not start the engine. A few minutes later I looked at the Spyder control and the flames were blue and I had hot air coming from all the vents. The temps are now in the upper 50's and climbing. I had both the Electric and the Gas buttons on the Spyder control were lit.

Any ideas why my heat cut off and then turned on after turning the ignition key?

I am concerned because we will be home on Monday and then will be heading to Oklahoma next Sunday where the lows will be in the 30's (from what I can tell from the 10 day weather forecast).

Thanks in advance for all replies!!

[TampaDave]

I don't know what the blue flames signify, I'm all analogue.

First, I listen. The blower is easy to hear, harder to tell if the thing sparks up.

Also I listen and feel to see if the fans are running inside. If they are, and cold air is coming out, could be check valve or bad pump. Keep em from getting stuck by using the unit frequently and keeping antifreeze at the right concentration.

Assuming the fans weren't coming on, which they don't when the unit is below operating temp, I would have gone outside to check the indicator panel and in particular would have been looking at the low temp cutoff light, if off I would wonder if somebody had water running, or if one of the thermostats were getting weird on me. Also look at the zone lights to see if thermostat signal is getting down there. Check fluid level while I'm out there. And the date on the fuel filter to see if annual maintenance is due; waiting too long causes any number of burner faults. Although I don't think the blower comes on if you have a burner fault, it just sits there with the status light off (upstairs and downstairs) until you cycle the switch.

Electric doesn't do much. Does more on newer units than older ones like mine, still it doesn't come on till unit is below operating temp and takes hours to get to operating temp, if it gets there at all. With my unit, if it's cold enough to need the aquahot, it's too cold for the electric element to keep up.

Otherwise, I guess these things get discombobulated sometimes. (Usually at 3am, when it's freezing.) Supposedly cycling 12v recombobulates it. Maybe that's what happened.

[boomersooner]

Originally Posted by TampaDave

I don't know what the blue flames signify, I'm all analogue.

First, I listen. The blower is easy to hear, harder to tell if the thing sparks up.

Also I listen and feel to see if the fans are running inside. If they are, and cold air is coming out, could be check valve or bad pump. Keep em from getting stuck by using the unit frequently and keeping antifreeze at the right concentration.

Assuming the fans weren't coming on, which they don't when the unit is below operating temp, I would have gone outside to check the indicator panel and in particular would have been looking at the low temp cutoff light, if off I would wonder if somebody had water running, or if one of the thermostats were getting weird on me. Also look at the zone lights to see if thermostat signal is getting down there. Check fluid level while I'm out there. And the date on the fuel filter to see if annual maintenance is due; waiting too long causes any number of burner faults. Although I don't think the blower comes on if you have a burner fault, it just sits there with the status light off (upstairs and downstairs) until you cycle the switch.

Electric doesn't do much. Does more on newer units than older ones like mine, still it doesn't come on till unit is below operating temp and takes hours to get to operating temp, if it gets there at all. With my unit, if it's cold enough to need the aquahot, it's too cold for the electric element to keep up.

Otherwise, I guess these things get discombobulated sometimes. (Usually at 3am, when it's freezing.) Supposedly cycling 12v recombobulates it. Maybe that's what happened.

The blue flame indicates the furnace is on, but not actively generating heat, when the heat is on the flame is red. It was blowing cold air and I would hear the AH turning on. The water was hot so I knew it was working, just not generating heat. I had the annual service done in November and the thermostat replaced in December. We were OK when we went to bed, but at 5am my wife said it was cold and when I got up to go to the bathroom was very cold (50 throughout the coach), and hot water was coming out of the faucet so I knew it was only heat and not the AH overall operations. When I turned the key to see if we had enough enough diesel it seemed to work immediately after that and got up to 70 in the coach within about an hour. Very strange, but the turning on the dash to check fuel level seemed to be the trick. Fluid level in the AH is normal, I checked that as well. Seems to be OK so far, will see tonight.

Thanks for responding.

[TampaDave]

Well, I don't claim to know what Aquahot is thinking at any given moment, and have no confidence that I do, but I *think* if the fans are blowing cold air inside the rig, it's a circulation problem. So in other words the unit is at operating temp (maybe that's why the flames are blue, their work is done) but the green stuff isn't going around. You can feel the pipes coming out the top of the unit to confirm, if they are cold then you aren't pumping.

I've heard this is usually due to check valves sticking, you can tap on em to get them unstuck. Haven't had to do this myself so not sure exactly where to tap. Prevent this by running the unit regularly and keep antifreeze mixture in the specified range (too concentrated gums up up apparently)

Other thing would be a bad pump. You can check the board for a fault but I *think* that only red-lights if there's a short circuit as opposed to say the impeller disintegrating.

Maybe it was the check valves, perhaps they finally decided to open. Which is pretty awesome. My feeling is, the thing is like a golden retriever, needs to be run frequently otherwise it goes bonkers

[boomersooner]

Originally Posted by TampaDave

Well, I don't claim to know what Aquahot is thinking at any given moment, and have no confidence that I do, but I *think* if the fans are blowing cold air inside the rig, it's a circulation problem. So in other words the unit is at operating temp (maybe that's why the flames are blue, their work is done) but the green stuff isn't going around. You can feel the pipes coming out the top of the unit to confirm, if they are cold then you aren't pumping.

I've heard this is usually due to check valves sticking, you can tap on em to get them unstuck. Haven't had to do this myself so not sure exactly where to tap. Prevent this by running the unit regularly and keep antifreeze mixture in the specified range (too concentrated gums up up apparently)

Other thing would be a bad pump. You can check the board for a fault but I *think* that only red-lights if there's a short circuit as opposed to say the impeller disintegrating.

Maybe it was the check valves, perhaps they finally decided to open. Which is pretty awesome. My feeling is, the thing is like a golden retriever, needs to be run frequently otherwise it goes bonkers

After that issue it ran flawlessly for the rest of our trip. Did not use the RV for two months prior and did run the AH heat for 4 days during freezing weather. Everything seems fine now. Got the RV parked in the driveway (got home yesterday) and heading out on Sunday to Oklahoma for our longest trip of 14 months ownership. Luckily it is going to be above freezing each night we are there (but below 40 so will be using AH heat in lieu of heat pumps).

I got on an AH forum and the expert who runs the web site (and forum) did not know why my issue occurred either.