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Old 10-19-2020, 05:09 AM   #1
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Issue Running furnace on electric

I have a 2021 Montana Legacy 3855BR.

When we use the heat pump - electric - we set furnace temp to 68. It wonít kick on until it drops 6 degrees under the setting. At about 62 in here - or unless I give up and force it on by kicking the temp way up to like 77, then when itís on, turn temp back down and it stays on and heats up.

When itís on gas setting, as soon as it drops 1-2 degrees under it kicks right on. Obviously I prefer electric - so I donít have to burn through my propane.

Why does my temp have to drop so many degrees under the setting before the heat kicks in? Is that normal?

We take the rig in on Saturday for some other minor items. Wondering if this is an item we should add to the list or if this if normal.
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Old 10-19-2020, 06:16 AM   #2
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For all the problems we have had with the Dometic thermostats, this is not one of them. I would think this is not normal. Are you certain about the temperature variance? IOW, did you measure with another thermometer? I purchased a 4 sensor thermometer and put one in the basement, garage (we have a pull out tray under the living room at the rear) and one outside, and the main inside. For whatever reason, my thermostat is on a short wall above the coffee bar under a cabinet. There is always a 5-7 degree variance in the temp there as opposed to the main kitchen area. I tested with an infrared thermometer. I couldn't figure out why I was freezing in the mornings until I realized the coffee maker is heating up the thermostat about 6 inches away. Duh!
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Old 10-19-2020, 08:40 AM   #3
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Thanks for the reply.

I did not use another thermometer to actually check the temperature. But don't think I need to. Even if it's off a few degrees in temp, it doesn't matter if I have it set to warmer or lower.

For example, it could be 69 degrees in here, and if I have the thermostat set to 71 - I would expect it to kick on. When on gas, if does kick on once there is a 2 degree variance. But for the electric, it won't kick on until there is a 6 degree variance. So to get that furnace to kick on again when it's 69, i have to turn it up to 75. If it's set to 75, but is only 72, I have to bump it up to 78. As soon as I bump it up so there is a 6 degree variance, it will kick on, and then, I can bump it back down to the temp I want, and it will heat until it hits that temp on the display.

So basically, I'm messing with it all day long to get it to kick on, but not get too boiling hot in here.

A 6 degree variance just seems like it's a little too much. At least its consistent. I'm just wondering if it's a setting , and can be changed so it kicks on with a 2-3 degree variance.
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Old 10-19-2020, 11:13 AM   #4
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The furnace and "furnace" setting on the thermostat has nothing whatsoever to do with the HP. You must use the "HP" setting on the thermosta to run the electric HP built in to the roof unit.
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Old 10-19-2020, 12:40 PM   #5
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I think what you are experiencing is pretty normal. We keep a separate indoor-outdoor thermometer beside the thermostat to compare the actual temperature with the setting at the thermostat. And like you, there is a much wider variance with the heat pump than with the furnace. In fact, in order to achieve the same temperature, (say 71 degrees), the furnace has to be set to about 73, whereas the heat pump has to be set to about 78. Then the temperature inside stays about the same.

Now, when the outside temperature nears 40-45 degrees, the heat pump begins to fail. It just can't keep up, and by the time the outside temperatures reach 40 or below, the heat pump quits blowing warm. Heat pumps have a very limited range. Above 45 they work pretty good. Below 45 and they start blowing cooloer and cooler air, until it just blows nothing but cold air.

My heat pump works best when the outside temperatures range from about 50 to 70. Above 70 and it will roast you out. Below 50, and that "variance" gets bigger and bigger until it just won't throw heat at all.

And an FYI, we keep the indoor-outdoor thermometer right at the thermostat because our camper has such an inside temperature variation, its insane.

The thermometer may read 71 degrees, but the upper living room (front living room model with no wall between the lower level, may be 80 degrees and the lower level at the themometer will be 71, and the bedroom (at the end of trailer) may be 65, and the bathroom 85. (This is with the propane furnace running).

On the heat pump (in the front of the trailer), the upper living room area is warmest, the kitchen (middle area on the main floor) is next, the bedroom (even with the door closed) is third, and the bathroom is the coldest.

On air conditioning, with both air conditioners running, the bathroom is the coldest room if the door is closed, and the kitchen is second coolest. The bedroom can turn into an ice box and the front living room a sauna if only the back (bedroom) air conditioner is running in 90 degree weather outside.

Finding a happy medium in all locations in the camper just takes time to figure out.

Hope this helps some.
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Old 11-20-2020, 09:55 PM   #6
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Could be control board in air conditioner. My 2019 Montana wouldn’t control air temp everything else worked OK. When it would shut down it wouldn’t start again until I set thermostat to air again. Press set and up buttons at same time and hold till you see two dashes release and wait for it to clear. That will sink thermostat with control board.
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Old 11-21-2020, 06:14 PM   #7
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It may depend on where you are measuring the temperature. In a 5th wheel the heat pump blows heat from the ceiling so cold air settles in the lower rear part of the camper, in our case the livingroom. The thermostat is on the wall halfway up the hallway stair so the heat from the ceiling shuts it off while the livingroom stays cold. The furnace, however, blows heat from the floor and so the livingroom is far more comfortable. The only way we can comfortably use the heat pump is to either add the fireplace or a small electric heater to the mix to take cold air off the floor and heat it seperately.
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Old 11-23-2020, 04:37 PM   #8
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We use a couple of Lasko towers rather than the heat pump. The Laskos are portable, much quieter, have two heat settings, thermostat settings and do a better job when cold out and the HP won't work at all.
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Old 11-23-2020, 05:21 PM   #9
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I donít think it working correctly and would add it to you list of items to have the dealer to look at. On my 2021 Montana 3120RL You either select ELECTRIC or GAS. Sounds like others may say HP or FURNACE. But if I select ELECTRIC as soon as the temp on the thermostat drops one degree below the setting the Heat Pump comes on. But if the heat pump isnít able to hold or raise the temperature and the temperature reading on the thermostat decreases to 6 degrees below the setting the gas furnace will kick on. Or if when first setting the thermostat to ELECTRIC and the temperature reading on the thermostat is 6 degrees or more below the setting, both the heat pump and the furnace will come on to warm the room up quicker. This is known as two stage heating. Sounds like your thermostat is mis wired or mis programmed and the heat pump is cycling at the second stage setting instead at the first stage setting and then from what stated the furnace isnít coming on at all when the thermostat is set to ELECTRIC.
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Old 11-26-2020, 07:39 AM   #10
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? can you run the heat pump in front and air conditioner in the bedroom at the same time? Seems like that should be ok but not sure. It gets so hot in the bedroom, hot air rises
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