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Dometic AC/furnace question.


Mcb
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I turned on the furnace this morning and the AC came on instead. The furnace has been working fine up to this point ( as has the AC) so I was surprise. The thermostat scrolls through all the options in “mode”, shows the little heat icon properly, but when selected, the AC comes on. Checked the fuses, checked the gas, checked the owners manual where there isn’t much useful advice for this particular issue.. 

Anyone run into this before? Thanks!

 

Mark & Deb..2020 Elite II..Dearie..Hull #685..2016 Tundra

 

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https://www.dometic.com/en-us/us/support/faq/electric-heater-option
 

Why don’t you just trip the AC circuit breaker until you get it figured out? That will kill the AC completely , including its built in heat strip.

If the furnace still does not come on, there is some basic troubleshooting you must do like check for combustion chamber air blockage, or failure of the board, sail switch or igniter. They are spelled out in your furnace manual. There are a few things you can do but anything major requires removal of the furnace. 

If the furnace works fine, keep the AC breaker tripped or look to the thermostat itself. Get the systems separated as much as possible, then troubleshoot the one that has the failure.

My Ollie does not have this AC system so I am not 100% reliable here.... 😐   This is why you should always have a little electric box heater for backup. Compared to residential units, these RV ones are a lot more prone to failures. Good luck.

John Davies

Spokane WA

 

Edited by John E Davies

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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Are you sure your on the correct setting - are you trying to engage just the furnace - not the heat strip in the AC unit?  I know i did that early on - when learning how to operate the system. Good luck.

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Cindy,  Russell and  "Harley dog" . Home is our little farm near Winchester TN

2018 Oliver Legacy Elite II - 2018 GMC 2500 Duramax 

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Mcb, 

If the fan is set to high or low (anything but auto) the a/c fan will blow with the furnace.

I’m going on memory but, change the mode to auto (not heat or cool) then change the fan using the up or down arrows to auto (not high or low)

D

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David and Vicky | Burns, TN | 2020 LEII #686 | 2017 Ford F-250 4x4 6.2L
 

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57 minutes ago, BlueHighways said:

If the fan is set to high or low (anything but auto) the a/c fan will blow with the furnace.

I’m sure that’s it. It’s an easy setting to change inadvertently.

And it’s also very unintuitive. 

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LOL this sounds as if more than a few folks have a learning curve problem with the heat strip. Like leaving the outside shower knobs both fully turned on (when you are not using it) will bypass hot to cold and turn your INSIDE hot water to lukewarm water.... if you haven’t had that happen, you sooner or later will, but you will learn your lesson and not repeat it.😊. These are complicated systems and take some learning and adjusting to. As I said, my AC (the small Atwood Air Command) does not have the heat strip, so I have avoided this one.

John Davies

Spokane WA

Edited by John E Davies

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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1 hour ago, BlueHighways said:

Mcb, 

If the fan is set to high or low (anything but auto) the a/c fan will blow with the furnace.

I’m going on memory but, change the mode to auto (not heat or cool) then change the fan using the up or down arrows to auto (not high or low)

D

Bingo!! Thanks a lot!👍👍👍

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Mark & Deb..2020 Elite II..Dearie..Hull #685..2016 Tundra

 

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If the setting were linked to the heat strip, then I’d understand, but it isn’t. I’m trying to imagine why anyone would want the AC fan running while the furnace is on. Someone who likes to pretend that they’re camped next to an airport?

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So does the heat strip come on by itself in Auto, then after a few minutes the furnace kicks on in addition, or does the AC fan then shut down? It seems like both going at once would be really loud and windy.
 

EDIT - Overland beat me to this comment by a few seconds. “airport” ☺️

John Davies

Spokane WA

Edited by John E Davies

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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I don’t think I have a heat strip, and wasn’t expecting the roar of the AC when I thought I was turning on the furnace.. if the furnace was indeed on I sure couldn’t hear it, nor Deb asking me why the heck I’d turned on the cold air..

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Mark & Deb..2020 Elite II..Dearie..Hull #685..2016 Tundra

 

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Mcb, I know you are visiting Florida and being a native I can tell you from experience, we sometimes run the heat in the morning and the A/C in the afternoon, so it seems like you’ve figured out the solution.😅😅  

My thermostat has the words "heat strip" after "furnace" in the bottom left corner that I see when running through the mode selector.

Mossey

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Mike and Krunch   Lutz, FL   LEII #193 “the dog house”

 

 

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I ran into this issue as well, but in a different scenario.  We all know the furnace moves the heated air within and through the ducts in the basement areas.  I was trying to figure out how to run the furnace fan only to move warm cabin air around (and into the basement).  Every time I set the fan to low or high, the A/C would come on.  I poured over the furnace info and found it can't run in fan only mode.  What a bummer.  I know this is a travel trailer, but the heat and A/C systems and in particular the way they are configured to work - are all pretty lame.  Carrying and running an electric backup heater in the cabin is great for the cabin, but without air moving into the basement areas you could have a toasty cabin with frozen basement pipes.  I'm already wondering if there's another furnace that fits that has fan only capabilities.

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8 hours ago, NCeagle said:

I'm already wondering if there's another furnace that fits that has fan only capabilities.

I don’t think it would be too hard to figure out a Fan Only circuit to bypass all the normal controls. You would have to switch it on manually, maybe from a switch mounted near the inlet grill. OTH it is pretty loud and it would be better if you could throttle it down some, at the same time. These systems are indeed lame, they are built for a super low price point. I want a silent, fan free Alde hydronic heating system.... then you could just install an additional little “radiator” wherever you had a cold spot. I checked and they only sell their systems and parts to manufacturers and upfitters 😠

https://www.truckcampermagazine.com/camper-reviews/alde-hydronic-heating-system-test-and-review/

It would be a stellar system in an Ollie because with many low mounted “convectors and high vents, the double hull design would allow a bubble of warm air around the interior walls. I would gladly pay an extra $2000 for such a system.... a 20 pound bottle will last for two weeks (running just “furnace” and hot water) and it sips electricity.

John Davies

Spokane WA

 

 

 

Edited by John E Davies
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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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On 12/7/2020 at 4:37 AM, NCeagle said:

I ran into this issue as well, but in a different scenario.  We all know the furnace moves the heated air within and through the ducts in the basement areas.  I was trying to figure out how to run the furnace fan only to move warm cabin air around (and into the basement).  Every time I set the fan to low or high, the A/C would come on.  I poured over the furnace info and found it can't run in fan only mode.  What a bummer.  I know this is a travel trailer, but the heat and A/C systems and in particular the way they are configured to work - are all pretty lame.  Carrying and running an electric backup heater in the cabin is great for the cabin, but without air moving into the basement areas you could have a toasty cabin with frozen basement pipes.  I'm already wondering if there's another furnace that fits that has fan only capabilities.

The Max fan has a “ceiling fan” setting.. where the fan runs with the lid shut.. I’m not sure about how much air it really moves around but it may push warm air down to some degree. We’ve got a battery operated fan that does move air around pretty well, it think the brand is O2. 
If I was trying to heat the areas under the beds or seats, I’d try to get an outlet  under them. Maybe connect to the outlet by the dinette for the port side, and the exterior outlet for starboard. Then you could isolate those areas and manage the heat independently from the cabin, using lightbulbs, heating pads or whatever with a fan if needed to circulate the air into tough to get places. 
 

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Mark & Deb..2020 Elite II..Dearie..Hull #685..2016 Tundra

 

AZARCAFLMSNMOKPATNTXsm.jpg

 

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18 minutes ago, Mcb said:

The Max fan has a “ceiling fan” setting.. where the fan runs with the lid shut.. I’m not sure about how much air it really moves around but it may push warm air down to some degree. We’ve got a battery operated fan that does move air around pretty well, it think the brand is O2. 
If I was trying to heat the areas under the beds or seats, I’d try to get an outlet  under them. Maybe connect to the outlet by the dinette for the port side, and the exterior outlet for starboard. Then you could isolate those areas and manage the heat independently from the cabin, using lightbulbs, heating pads or whatever with a fan if needed to circulate the air into tough to get places. 
 

Yes - trying to find a way to get "electrically heated", warm cabin air circulated into the basement now that I have ducts on the street side as well.  I'm looking for a way to balance propane and electrical heat depending on the situation.  I'm not planning on winterizing so an all electric solution is desirable while docked at home too (with 30 Amp service).  All options are on the table right now and I'm trying to be as non-intrusive as possible.

On a separate but related note, have you or has anyone else had any success connecting to the thermostat with Bluetooth?  It's supposed to be Bluetooth (according to owners manual) but I can't seem to get my Bluetooth signal to come on at all.

 

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On 12/6/2020 at 10:28 AM, Overland said:

If the setting were linked to the heat strip, then I’d understand, but it isn’t. I’m trying to imagine why anyone would want the AC fan running while the furnace is on. Someone who likes to pretend that they’re camped next to an airport?

I've got an open ticket with Dometic technical support on this - specifically asking if it can be set up to run the fan on the furnace in heat mode and the fan on the A/C in cool mode when not in auto.  Dometic have asked for a picture of my thermostat, so I'll update this thread if I learn anything.

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