In the attached pic can someone explain the purpose of the 2 trim pots on the back of the Duo-Therm 5-button Comfort Control?
My front AC on heat pump setting seems to short cycle compared to the rear AC. Same goes for when it is set to aquahot furnace. I'm wondering if the trim pots control the high/low temperature range.
Hi Mark,
Those aren't trim pots on the 5 button thermostat, they are base mountings for the two display bulbs.
Jim
2002 U320
Thanks Jim. Guess everyone now knows I'm not an electrical engineer. Actually not even real observant come to think of it! :-[
So, is there some way to adjust the temperature cycle range on the thermostat?
Mark,
By 'cycle range' do you mean how long it remains on a displayed temperature...no adjustment other than the up and down buttons. Accuracy of the temperature selected is approximately 2 degrees. The thermostat will cycle the heating or cooling on and off according to the air temperature near it.
However, if the thermistor is faulty (the electronic temperature sensing device in the thermostat or at the remote locations), then it may not cycle at the temperature that you desire. Seldom is this a problem though it can be corrected.
Did I answer your question?
Jim
2002 U320
Jim - I think I understand what you are saying.
But I still don't understand why, when the front AC/heat pump or the front aquahot is activated (putting out heat), the length of time is so much shorter (about a third of the amount of time) than when the rear AC/heat pump or rear aquahot is activated. Does this mean that the temperature goes up about 3 times faster in the front of the coach than in the rear?
Mark,
Whatever time is needed to achieve set zone temperature will vary. Unlike a house with one thermostat (sensor), the coach zones are individual areas each with sensors. In addition, the kitchen-living room zone has two floor registers plus the dash register; the bathroom and bedroom areas have only one register per zone each because they are smaller spaces. Presuming you have set all zones for the same temperature then some zones may achieve their set temperature at different times.
If you desire some zones to be warmer or cooler than others then the fans will cycle on and off accordingly. This is all normal.
Jim
2002 U320
Mark, jim covered it for you but i will add one small influence. As i said, i agree it normal behavior but have found this.. If i have the vent vanes from the ceiling adjusted toward the thermostat, it may react a little differently, sensing temp change which is not quite representative of the room and cycle a little differently than if i adjust the vanes away from the thermostat.
Applies to floor furnace too but i have less ability to direct that except from the dash vents.
This is minor impact though. (I have not tried a fan to simply circulate the air in the room, distribute the ac/heat and gather you really only concerned about the different cycling, not a comfort thing.)
Mark, the big dash fan that comes on when you are using your AquaHot makes noise and heats up the area where the tstat is quicker than the rest of the main part of the coach. You can add a switch into the line that goes to the relay thatbturns on this fan whne the tsat calls for heat and the AquaHot comes on. It is not hard to do, getting to the relay is a bit tight. We rarely have the front fan on. The other AH heat exchangers run longer and the temperature is more uniform. I have speed controls for all of the AH heat exchanger fans as well but after the switch to the front fan worked so well I haven't put them in. Running those fans slower means they will run longer too and may improve the heat distribution even more. Running the fans slower probably won't use any less power so the net is that overall you might use more because they run longer.
See
Aqua Hot Dash Blower Fan Override (http://www.foreforums.com/index.php?topic=23713.msg185057#msg185057)
Yes thought about that awhile back and adjusted away from the thermostatbut really no difference - thanks Michael.
Roger - I read your post on the dash fan switch addition and it sounded very useful. But that is for heating with aquahot. The short cycle problem happens using the heat pump also. That is why I started to question the thermostat setup since the problem is happening with 2 different heat sources. Of course now the temps are back up in the mid 70s so it is a non-issue for the moment.
OK Mark, if you are using the heat pump then you must be connected to a landline. The 120v side of the AH keeps us comfy down to about 40°. Heat pumps seem pretty noisy to us.
I've never used AH on 120v only. What happens if it can't keep up? Does it just start blowing cooler? Does something bad happen? Curious minds want to know...
Give it a try. If we drive for 3-4 hrs AH is hot enough to heat all night w/o diesel or 120v in the low 50s. Turn the 120v on when you hook up. Moderate water use and heating should be goos into the low 40's. We were in the Tetons for two weeks, in the 40s most nights, showered heated to 68-70 in the evenings, 64 overnight never ran the diesel. Turned the 120v on when we were there, off when we were not. Cold to hot in about two hours on 120v, about 20-30 min on diesel.
Seven months on the road this year. Used the diesel side of AH maybe a half dozen times, usually at Camp Walmart or if want lots of very hot water. Of course I run it for one or two heat cycles once a month all year round. Same with the gen.
It is a great system, work with it, figure out its comfort range for you in your coach.
The electric element turn on is 185 degrees. The diesel burner is 175.
So the electric will be on seperate from the diesel.
If the electric cannot keep the boiler above 175 the diesel comes on in addition to the electric if both switches are on and 110 volt present from shoreline or gen.
Mark,
1. We run ours most of the time on 120v.
2.Ours will just blow cold air.
3. refer to #2
4. Not to the A/H unless you are way below zero then the domestic water loop could freeze. By then your feet will inform you to turn on the diesel or head south.
Pamela
Thanks folks. When it cools down again I'll give it a try now that I know I can't reasonably break something!
Hey Mark, see you next week.
The rear air conditioner (cooling) seemed to short cycle in our coach. I closed the vent above the thermostat in the bedroom. The short cycling seemed less frequent after the change. The ducted air system for the roof units allows some choice in the distribution of cooled air. Away from the thermostat seems to work better for us.