Ask Dave: Why does heat blow out of RV’s ceiling vents but not floor?

Dear Dave,
Previously, the RV’s electric heat option would blow out the roof vents and floor. The last couple times I’ve turned it on, it’s only been coming out the roof vents. I’m stumped on what’s going on. —Richard, 2022 Keystone 377FL

Dear Richard,
When you state the “electric heat option,” I assume you are referring to the setting on the thermostat that is labeled “Elec Heat”?

This is very confusing for owners as it looks like your furnace will run on either propane or 120-volt power, so if you are plugged in, you don’t waste propane.

Heat pump

This setting is actually for the heat pump that is incorporated into the roof air conditioners and is only ducted through the roof vents. I run into this almost every year when the Surf Ballroom (Clear Lake, Iowa) has the Winter Dance Party in February. Winnebago and local owners donate the use of RVs for the musicians as the Surf has no dressing or staging rooms. They park the units out back in a semicircle. Every year I get a call that a furnace is not working or the 120 volt went out.

Typically, they plug in 3-4 ceramic space heaters as these old bands from warmer climates can’t take the cold temperatures. The amp draw is too high for the electrical system in the early 1950s building. Fortunately they upgraded the system, but we still have them plugging into 30-amp or even 20-amp outlets and running everything. Most RV manufacturers use the cheapest GFCI-protected outlet. After it trips several times, it usually is no good. We replace these every year with a quality GFCI outlet from our local wholesale supplier.

Electric heat

Back to the electric heat. I also get a call every year that the heater is not working, just blowing cold air. When I check, the thermostat is on the Elec Heat setting and cold air is blowing. The heat pump feature, from what I was told, actually runs the roof air conditioner compressor in reverse. Therefore, it is drawing interior air into the return air and extracting heat. More specifically, it draws BTU’s from the outside air through the coolant coils in the back of the condenser coils and runs it through the evaporator to warm the air.

The RV heat pump is only effective if the temperature outside is above 50 degrees and designed to just “top off” cool temperatures. Although it is technically “electric heat,” it is not going to replace the LP heater and heat the coach. I get to the Surf and all the LP tanks have been run dry, so someone decided “Heh, let’s just use the electric heaters.”

With the Coleman system pictured earlier, you typically can run just the heat pump option or the onboard heater. You would have heat coming out of either the ceiling vents with the heat pump, or the floor vents with the furnace.

Thermostat

However, I believe your system has been designed with the Dometic model. The thermostat is an automatic version that can be set to a specific temperature and uses both to provide an even temperature.

My guess is the thermostat has been reset and only the RV heat pump feature is on. Turn on the thermostat and see if there is a setting for just the furnace and verify it turns on. If not, there is something wrong with the onboard furnace. If it does, check to see if there is a setting to use both.

 You might also enjoy this from Dave 

Why is there no airflow from one of my RV’s furnace vents?

Dear Dave,
How can I get to the vent piping to find out why one of the three heat vents isn’t
putting out heat? The other two are putting out plenty. I’ve taken the cover off, but
can’t see anything. —Cynthia, 2012 Thor Four Winds

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here. 

HAVE A QUESTION FOR DAVE?

Send your inquiries to him using the form below.

##RVDT2496