A/C return runs non stopq

HCWTHooligan · 05-12-2020, 08:39 PM

I have a 2002 Solaris T-320SR. I purchased late last year and went out for the first time this past weekend. It was in the 30’s so we used the furnace for heat. My question is, when running the furnace should the A/c return run non stop? I understand it runs to circulate the air but once the inside reaches the set temp as the furnace kicks off shouldn’t the fan also kick off after a short time? It continued to circulate chilly air causing the furnace to run more often. I ended up turning the thermostat off to preserve propane. After it dropped a few degrees I would turn it back on. First 24 hours we went thru almost a full 30 pound tank. After I used the control method we cut propane usage in almost half. Is this normal or do I need service?
Thank you for any help

**JohnB** · 05-13-2020, 09:31 PM

There is a mode on the AC unit wall thermostat that allows the fan to run by itself. Is the fan switch set to "on" or "auto"?

Does your thermostat cover look like this? See the "Fan" selector switch.

If it does, when the fan is on "auto" the fan will cycling on and off with the AC compressor when you are in cooling mode.

If the fan is set to "on" it will run all the time the "system" is on circulating air, but not cycling the AC compressor. Shutting the system off, would then stop the fan which sounds like what you did to stop the fan. If your fan switch is set to on, switch it to auto and see if that solves the problem. You really do not need the fan of the AC unit running when you use the furnace. The furnace has it own blower and ducting system.

That said, when in furnace mode, the AC unit compressor is not supposed to run. There is an interlock in the AC control board so that you cannot heat and cool at the same time. But the fan running may not be part of that interlock.

If setting the fan switch to Auto does not solve the problem and turn the fan off, come back to us with that info as something else is wrong.

If that fan is running all the time, even if the compressor never started, warm room air is drawn up into the cold attic will cool the air that is then pumped back into the camper. You will loose heat by that action which it seems you have already found out.

If by chance you did hear the AC unit compressor kick on and off through this event, there is for sure a problem with the AC unit control system.

Hope this helps

John

HCWTHooligan · 06-14-2020, 06:33 PM

Sorry for the late response. Took some time to get the picture. The fan runs all the time with either the furnace or A/C being used. The A/C condenser does not run the full time. Once the travel trailer gets to temp the condenser kicks off but the fan still runs. Same when running furnace. Thermostat is digital. I have attached photos of the thermostat.
The problem is with just the fan running it’s circulating warmer air during b a/c use And colder air when using the furnace.
Thanks in advance for any info. It’s the only issue I can’t seem to trouble shoot on my own.

j52wf · 06-14-2020, 08:11 PM

Do you have the fan speed (top left button) set to AU (Auto)? That is the setting needed for fan operation only during heating or cooling cycles, according to the manual for that t-stat.

j52wf · 06-14-2020, 08:18 PM

https://www.google.com/url?sa=t&sour...Zy7u-N2Nil0Gof

This might be the link to access your user manual. Don't know if it will work. If not, google the model number to get the manual.

j52wf · 06-14-2020, 08:28 PM

From the manual:

Fan Speed
Press the On/Off Mode button until the fan green LED is lit. The
LCD will show “Lo” (Low), “Hi” (High) or “Au” (Auto). Press the “+” or
“―” button to select the desired fan speed. See “Special Features”
on page 11 for more information on Auto Fan.

**JohnB** · 06-16-2020, 01:55 PM

Ah, this is different.

If you did not change the Tstat, then the prior owner did and it is not the original that Sunline shipped with your camper.

It's not a bad thing, but this also now begs the question did they upgrade the entire roof AC unit and the control box in the ceiling? I did not think that new Dometic digital T stat worked with the older analog control boards.

Assuming they upgraded the AC control box, that new style Tstat has many different settings then the older analog tstats'

From the link Jim posted on the bottom of page 8, it says this under Furnace mode. There appears to be and Au feature to put the system into auto, and the fan should shut off.

Quote:

“Furnace” - Furnace Mode
In this mode there are 3 fan speed selections:
Lo - (LOW): The fan operates continuously at low speed.
Hi - (HIGH): The fan operates continuously at high speed.
Au - (AUTO): The fan will be Off.
Note: If additional indoor air circulation provided by the air conditioner is not desired during Furnace Mode of operation, select Au
(AUTO) in the Fan Mode to shut the air conditioner fan off. If Lo
(LOW) or Hi (HIGH) is selected the air conditioner fan will continue
to operate on the selected speed.

And, if you want the fan to shut off with the compressor in AC mode, there is a setting for that too. Page 11 under special features

Hope this helps and let us know how you make out

John

John

j52wf · 06-16-2020, 04:29 PM

Quote:

Originally Posted by JohnB

Ah, this is different.

If you did not change the Tstat, then the prior owner did and it is not the original that Sunline shipped with your camper.

It's not a bad thing, but this also now begs the question did they upgrade the entire roof AC unit and the control box in the ceiling? I did not think that new Dometic digital T stat worked with the older analog control boards.

Assuming they upgraded the AC control box, that new style Tstat has many different settings then the older analog tstats'

From the link Jim posted on the bottom of page 8, it says this under Furnace mode. There appears to be and Au feature to put the system into auto, and the fan should shut off.

And, if you want the fan to shut off with the compressor in AC mode, there is a setting for that too. Page 11 under special features

Hope this helps and let us know how you make out

John

John

John,
I took a look at the manual for this t-stat. The "auto" setting for both ac and heat is in the fan control button. It would seem that this t-stat is designed for HVAC systems using the same fan for both heat and ac, where Sunline has different fans for heat and ac. I did not think about the compatability of the digital t-stat and an analog control board. That's above my pay grade. Lol