Furnace not sufficient

ElBlondie · 09-09-2020, 04:59 PM

We purchased a 2020 Seneca HJ. We were set to go on a trip starting today but last night we got about 12” of snow and the temperature dropped to 27 degrees. I built an insulated garage to store the RV but because of Covid-19 the garage doors are on back order. I do have 50 amp service in the garage so I closed the slide outs, put both the front and back furnaces on. I also put the water heater on and made sure the water lines were not under pressure.
I checked all night and even though I had the thermostats set at 70, the interior of the coach never got above 50. Is this normal? I would have thought the furnaces were large enough to handle colder weather. Does anyone have any thoughts?

Robbbyr · 09-09-2020, 05:15 PM

Furnaces?

You should have one propane furnace and one heat pump (incorporated into one of your air conditioners). If outside temperature below 40 to 42 degrees the heat pump will not work, there isn't enough heat in outside air to work.

The propane furnace should have done better with slides closed and the unit inside a structure. You should hear the furnace fan first come on, then in a few seconds the burner should ignite and heat should flow from the lower vents.

Grumpy · 09-09-2020, 06:08 PM

Did the slides cover any of the vents? If so the furnace high temp switch may have been shutting it down due to insufficient air flow.

ElBlondie · 09-09-2020, 06:28 PM

I didn’t check that! I will check to see. Thanks!

RogerR · 09-09-2020, 07:30 PM

You might consider one or two small electric heaters. I did some calculations and in small purchases it was actually cheaper to heat with electricity than LP.

RVermont · 09-09-2020, 07:55 PM

We have a ts with one furnance and two ac's with heat pumps. When selecting the front unit on electric the unit will automatically switch to the gas furnace if the temperature requested is greater then 10 degree of the actual temperature in the unit. The rear unit will run via the heat pump.

I am not sure which unit has the heat pumps in the new units and which is just an ac unit.

I can run my furnace in my rig and not need any electric heaters down to about 15 degrees and it will keep the unit in the high 60s. Below that I need to add some heaters to keep the cab area comfortable.

Where is the heat coming from. If it is the ceilings then it is from you ac units. If it is coming from the floor then it is your furnance. It is possible that the heater lines have come off the unit and you are blowing more hot air into the basement then it is supposed to.

Gunfighter · 09-09-2020, 09:15 PM

As you push the bottom pad on your thermostat in the living room/front you should see it go from ac to heat/electric then heat/gas. As others have stated you should hear the propane kick in and a fan running the lower vents.

RyRoRyan · 09-10-2020, 12:56 PM

One of the biggest issues with my Seneca and the engineering comes with the heater. I personally think the furnace is underrated. As stated earlier, the front thermostat is connected to both the heat pump and the furnace, If the outside temp is below 35 or so degrees the heat pumps just wont work...they will blow cold air. The thermostats are somewhat smart in the fact that if they dont see the temperature rising over time with the heat pumps, they will turn off and lockout the heatpumps so they are not blowing cold air. HOWEVER being two different independent thermostats there is a BIG problem with this. What I saw happen was this, the front thermostat would fire the heat pump realize its not heating and then turn on the furnace and lockout the heatpump for a set time. The furnace would heat the house. The rear thermostat would run, and if turned on the exact same time as the front one, would shut down the heat pump and just stay off (since it cant fire the furnace). Here is where the problem sits. After the first lockout timeout, the rear thermostat will turn the heat pump back on and it will be dumping out cold air while the furnace dumps out hot air. They will fight, but the temp wont really drop, but it wont gain much either. The rear thermostat does not see a drop in temp and therefor does not turn off the heat pump dumping cold air. This results in basically the two systems fighting and you just wasting a ton of propane and power.

The solution here is to leave the rear thermostat OFF if you know the temperature outside will be below 40 degrees. What I do is I have an oil based plug in radiant heater and I plug that in the master bedroom and that does a pretty good job of heating that area. Then I close the door and let the front thermostat do its thing, again only choosing gas if I know the temps are going to be below 40 so I dont have to worry about it even kicking on the heat pump to "try" to see if it will heat. Sometimes I put another radiant heater in the galley to help keep the front warm but I make sure that I have it set so it wont do the entire heating on its own and never run the furnace. I want the furnace to run as well so it can keep the basement water areas heated if I know it will be below freezing.

Quick note I learned yesterday. No matter what, if you are going to go below freezing, turn off and disconnect your ice maker line. The fridge itself has a heated line, but the small short little 8 inch or so line between the larger PEX water source and the fridge valve will never see heat and cant handle the cold like the larger pex line can. I had a small dripping leak from that hose that was going for about 12 hours yesterday before I noticed it and had to clean up water under the fridge and around the furnace unit. We got an odd storm through central NM. On Monday it was 92 degrees and yesterday the high was 36 with a low of 32. I didnt winterize as I still have some plans, that and the temps are supposed to be back in the upper 70's lower 80's this weekend.

pconroy · 09-10-2020, 04:36 PM

Quote:

Originally Posted by RyRoRyan

On Monday it was 92 degrees and yesterday the high was 36 with a low of 32.

Here too. Monday topped at almost 95* F, our low was the same.
Crazy.

JimD · 09-10-2020, 05:34 PM

You mentioned having the furnaces on all night. The big question is did they ever cycle off or did they constantly output heat?

If they cycled off, something is amiss as they should have continued to run until they hit 70 degrees as set by your thermostat. If they ran continuously without ever really warming up the rig, then I would say they are not sized for the area they need to heat.

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