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DMARTIN7 · 11-27-2022, 01:53 PM

2018 Allegro Bus40AP. My Aquahot 450 is connected to (2) separate heating zones for the "furnace" baseboard heat exchangers. When I turn the temp setting up on my front zone so that the zone comes on, it runs as it should until it reaches set point and the shuts off as it should. Then shortly thereafter it begins cycling on for 20-30 seconds, then off, then on again, over and over. My bedroon zone does not do this, it works as it should with quite some time between off and on.
My question is how does the spider control sense the room temperature to turn the zone heat on? Is there a thermistor similar to the ac sensors in the ceiling? Don't know where to start to diagnose problem. Any help is much appreciated.

FIX-IT-BOB · 11-28-2022, 01:07 PM

Good Day, before you chase down that the thermostat control in the coach is the issue.....
Verify that the AQUAHOT is " keeping up with the heat demand " Use the diesel burner to verify as it will keep up with all demand .....

If that is not the cycling issue... The temp probes are always a tricky find as they normally aren't in the best location either they work well for AC and not HEAT or vice versa .

I found by covering the PROBE ( thermistor) with a plastic tube stopped the cycling..... and kept the coach just right

Cheers

DRM901 · 11-28-2022, 07:46 PM

On our 2014 Allegro Bus 37AP, the same ceiling sensors control both AC, heat pump, & furnace.

I suggest you check the lights on the unit. See attached troubleshooting guide. You could have an overload on the pump.

I agree you should have the system on diesel burner, but ours won't cycle like that if the electric can't keep up. It just shuts down until the electric has caught up, which is longer than 20-30 seconds. Aqua-Hot Electronic Controller.pdf

Sent from my SM-G973U using iRV2 - RV Forum mobile app

DRM901 · 11-29-2022, 07:11 AM

Their app messed the attachment. Trying again.
Attachment 381710

jkorn · 11-29-2022, 07:54 AM

Question

Do you have the diesel burner on? Electric will not be enough to keep the system on. It will cause it to cycle on and off while it reheats the glycol fluid.

Also, be aware that if you run a faucet or shower this will override the cabin heating system. Hot water takes precedence over cabin heating. Jeff

DMARTIN7 · 12-01-2022, 02:46 PM

Diesel burner is on, it keeps up and cycles as it should. The problem is with whatever tells the baseboard heat exchanger fan to cycle on and off. Time to call Tiffin or Aquahot or Spyder.

DMARTIN7 · 12-01-2022, 02:50 PM

Jkorn, this is happening with diesel on, obviously in colder weather hence the need for furnace heat. The cycling problem is happening with nothing else being used, no water faucets or shower in use. Just heat. The hot water is at full temp so I know the glycol is hot. And the rear heating zone works fine. Problem confined to the front zone. I need to find out how the temperature is sensed in that zone. Thanks for the reply.

DMARTIN7 · 12-01-2022, 02:53 PM

DRM901 thank you. I will read through that. I bought new ceiling thermistors while at Red Bay in August. Changing those is simple enough. Will also solder the connections.

jkorn · 12-06-2022, 07:45 PM

While the ceiling sensors could be an issue, one in the unit could also be an issue. Or a bad pump. Now that that I’m writing this the hot water at the shower would go hot then cold in our 2014. I believe it was a bad stir pump. A tech that specialized in AH fixed it.

So many parts. Jeff