Thermal cut-off switch in Alde system?

DIYerTAB320 · December 3

My Alde system switches off and then back on even though the cabin temperature has not reached the set point. Is there a thermal cut-off somewhere in the system, and if so, then implies that my system is malfunctioning in some way?

I'm considering adding a 12v computer fan into the radiator compartment in the center rear in hopes of heating the cabin faster. But I want to understand why it's cycling on and off first.

AnOldUR · December 3

Can't help much with the temperature not being reached. Although the temperature that the control panel displays is not too accurate, it does cycle the furnace to match whatever is displayed.

As for the fan, I added one to force air up behind the gap at the rear of our 320. My first attempt had it wired to the furnace so that when the thermostat called for heat and the circulation pump went on it would also activate the fan. That did not work great. It would start blowing before the convectors got hot, blowing cold air. Then when the circulation pump stopped the fan would stop even though there was heat that could have been distributed. I ended up wiring an independent on/off switch.

MuttonChops · December 3

DIYerTAB320 said:
. . . Alde system switches off and then back on even though the cabin temperature has not reached the set point. Is there a thermal cut-off somewhere in the system,

There is not a specific Thermal Cut-Off Switch** in the Alde unit.

Do expect the Main Circuit Board Control Logic monitors various system sensors and can/does cycle heating sources / pump off & on.

** There is a thermal-fuse on the Main PCB. It is to protect the PCB & full system
and not part of the heat-cycle-control.

Adle Service Manual notes:

Since the Control Panel is in a common location on all trailers of the same model and others have not reported your issue - - Adle cycling on/off when cabin is still cold - -

Suggest you look for:
1) Is anything blocking air circulation around the Control Panel?
2) Is a 'fan' or other owner-installed item causing variable air circulation in cabin?
3) Are floor vents for Alde clear, are cabinet spaces behind vents obstructed?

If 1) - 3) are okay; consider running Alde on 120VAC only, then Propane only to see if the odd cycling stops/changes. One of the heat sources could be causing the issue . . . not controlling it's output level. {just a guess}

DIYerTAB320 · December 3

Since the mattress pad seals off the back gap even though I try to position the mattress clear of the gap, I just now drilled a series of holes in the top of the back panel above the table mount. I dunno if those holes will work against natural convection from the bottom slot however. Could be I made a mistake.... we'll see.

Funny your first attempt was a fan in the furnace compartment. I just put a fan in there myself, not hard wired but simply set in there while I'm playing around trying to figure it out. My instincts tell me to mount a 12V computer fan into the back panel wall with a switch on the underside of the above cabinet.

In your explanation above (and thank you), why would the circulation pump stop if the cabin was not up to temperature? What controls the circulation pump? Obviously I have much still to learn.

AnOldUR · December 3

DIYerTAB320 said:

... why would the circulation pump stop if the cabin was not up to temperature? What controls the circulation pump?

The thermostat on the wall is what controls the circulation pump. The pump turns off when the thermostat reaches whatever temperature you've set. The problem is that the temperature probe is not located in a great spot, so it doesn't accurately correlate to the cabin temperature.

Can you post a picture of how your mattress is blocking the gap?

Here's where I mounted the fan.
(note that I've moved the convector lower)

Image: https://us.v-cdn.net/5021717/uploads/editor/9y/0u9ggc8qua8p.jpg

DIYerTAB320 · December 3

MuttonChops - thank you. I'm sure there is nothing blocking air circulation anywhere, so that's not the problem. I have been playing with 120V versus propane and so far it seems to behave similarly. However it's possible I don't yet understand the system well enough for proper diagnostics. I'll keep reading on this forum and playing with it. This forum ROCKS! My thanks to all of you.

pthomas745 · December 3

There are a couple of other things that can be adjusted. The thermostat for the Alde is in a nice, warm, comfy spot on the circuit board inside the Control panel. If the light on the control panel is on, that can influence the temperature the Alde thinks the cabin of the trailer is. What you are hearing (the Alde turning on and off) is normal behavior. You might have asked for "70 degrees" for a cabin temp. The Alde thermostat gets to 70 degrees before the cabin does, and shuts off.

What the Alde has to help with this situation is the "Thermostat Offset" procedure in the manual. You will need to have a separate thermometer that you can compare the temps in the cabin to what the temperature the Alde thinks the cabin is.

There is such a thing as an Alde "Discrete Temperature Sensor" that gives you more control of where the temperature is measured, which, in theory, will help quite a lot. Most of these parts are available in Europe from suppliers. In the USA, Alde...not so much.

This one comes from Ebay, , from England, so they do exist.

https://www.ebay.com/itm/283847191248

ScottG · December 3

I would expect the boiler (i.e., heat source, whether propane or electric) to cycle on and off around a predetermined glycol temperature. However, the circulator pump should run continuously until the cabin reaches temp.

Is the circulator pump actually shutting off as well as the boiler? That was unclear from the OP, but was implied in later comments.

DIYerTAB320 · December 4

I can definitely hear the boiler turning off and then back on. I was able to tune my ear to the sound of the pump by switching on the control panel from Therm to Continuous and back. It's still a bit difficult for me to hear or feel if the pump is running.

Thanks for the tip to turn off the display light on the control panel for a more accurate temperature reading. Makes sense, and I wouldn't have thought of that.

Another question: the radiator under the passenger side bench is exposed for the last 3" on the end to the rear which I find hard to believe is by design. It's too easy for something stored in that compartment to move during transport, come in contact with the radiator and melt or possibly catch fire. I'm thinking this trailer I recently bought used was simply built wrong, and I should correct that.

I've also wondered why the ends of the box around the radiator is open. I read one person on this forum closed off the ends of the radiator enclosure box and found this did increase the heat flow out the upper slot.

pthomas745 · December 4

Can you tell us what year your trailer is? On my 2017 320, the radiator (Alde calls them "convectors") under the passenger side bench are covered with a simple wooden L-shaped wood structure. You will find the convectors and hoses at the far end of the "glycol loop" do not get very hot, at least not hot enough to burn anything. The convectors do have thin aluminum "vanes" that can get bent pretty easily. And, some of these "vanes" have pretty sharp edges.

So, tell us what year your trailer is. And, a picture will help if you can get to it.

Maxcamp · December 5

No clue to the cycling, sorry.

Here's another take on heat circulating fans. It made a huge difference in both comfort and making the thermostat action reliable. We set glycol pump to Continuous not Therm.

https://tab-rv.vanillacommunity.com/discussion/comment/207162/#Comment_207162

Grumpy_G · December 5

To answer the original question, yes there is an overheating protection sensor at the boiler itself, however it only causes a shut down if the regular sensor fails. Otherwise the cycling of the boiler is normal, the radiators/convectors can not dissipate as much heat as the boiler absorbs from the heat sources.

@ScottG did ask about the circulation pump, and the answer was a bit vague. For troubleshooting purposes run the Alde on electric, then you can hear/feel the circulation pump without the additional noise from the propane burner and exhaust fan.

otr_320 · December 5

DIYerTAB320 said:

My Alde system switches off and then back on even though the cabin temperature has not reached the set point. Is there a thermal cut-off somewhere in the system, and if so, then implies that my system is malfunctioning in some way?

I'm considering adding a 12v computer fan into the radiator compartment in the center rear in hopes of heating the cabin faster. But I want to understand why it's cycling on and off first.

Our '23 320's Alde 3020 will turn off active heating of the glycol when one of two things happen, 1) the wall thermostat reaches its target temperature, and/or 2) the glycol reaches 175-178f. Active heating of the glycol resumes again when the glycol cools down to approx. 165f.

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Thermal cut-off switch in Alde system?

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