HVAC question

DRPNGOUT · 05-09-2011, 10:59 AM

Firstly - Hello everyone from Southern Ontario

. Brand new to the RV world. Been lurking since picking up the RV end of March trying to learn as much as I can. Took it out Saturday night for the first time to a conservation area near home and had a great time.

I have a question about the HVAC. The RV has two ACs, one in the bedroom and one in the living area. There are also two thermostats, also in the bedroom and living area. The thermostat in the living area also controls the LPG furnace. Since it was cold Saturday night I set the living area thermostat to "Furnace", set the fan to "Auto" and set the temperature. What I discovered was everytime the LPG furnace would start, I could hear a relay type clicking in the living area AC clicking about 15-20 times. Then when I hear the furnace flame extinguish, the AC will click only once. It does this each and every time the LPG furnace comes on. Does anyone know what that clicking noise is?

The RV is a 2011 Georgetown 327. The thermostat is the Dometic Single Zone LCD Thermostat 3313189 (image attached) and the AC is Dometic Brisk Air 457915.

Thanks
Kim & Rick

polkatronron · 05-09-2011, 11:11 AM

Does your AC have a heat strip...

grhodes50 · 05-09-2011, 11:16 AM

Or you sure it was coming from the AC and not the furnace. I know they aren't located next to each other and it should be easy to tell the difference, but I'm just wondering if you maybe hearing the furnace igniting.

DRPNGOUT · 05-09-2011, 12:31 PM

I believe it has a heat strip because one of the things it says on the inside label is "Heat element 1530 Watts".

I'm positive it is coming from the living area AC over head versus the furnace at floor level.

Rick

polkatronron · 05-09-2011, 04:28 PM

well, there has to be a control for the heat strip...I see your thermostat is electronic..take a look at the instructions for the thermostat...I bet there is a heat strip program on that thermostat and the heat strip is turned on...another way is to unplug your motorhome and run your furnace on battery...then see if the noise is still there.

Randyman · 05-10-2011, 01:42 PM

Hello everyone, I have a 2011 Cardinal 3425 RT and I have the exact same issue. Mine does not have the heat strip in the rear A\C and it does make the same clicking noise as described above. The furnace works great, just is annoying to hear the clicking every time it gets ready to start. Any ideas as to what is going on? It will make the same noise whether the camper is plugged in or just on battery. It is definitely coming from the rear A\C unit.

DRPNGOUT · 05-13-2011, 08:20 AM

I tried another test last night this time with the 5500 watt generator running and this time the AC clicked quietly only once on start and once on stop of the furnace. This seemed normal. So I retested again on battery only and again on 15 amp shore power and it worked properly both times. I can't guess what the problem was other than it was the first time I had run the furnace with the generator and the extra current finally made the relay connect?

Doing some research I am assuming now I don't have a heat strip or else they would have installed the Dometic thermostat model with the "Heat Strip" setting.

Randyman · 05-13-2011, 09:47 AM

We're heading out this weekend and I haven't tried running the A\C unit yet. I don't have a generator so I'll see if breaking in the A\C unit changes my situation. Still curious as to why it's doing what it is doing and that someone else has the exact same problem.

Randyman · 05-16-2011, 02:39 PM

Think I finally figured out the clicking relay in the rear A\C when the furnace comes on. In the thermostats instruction manual it shows that you need to "initialize" the thermostat before it's first use. I had tried that originally to no avail. While we were camped and I was getting annoyed listening to the relay clicking up to 25 times before the furnace would kick on I got the manual out again and redid the initialization as I did before. This time it must have took, no more clicking and the furnace worked great, just as it did before, minus the clicking. Hope this helps anyone else with the same issue.

DRPNGOUT · 05-17-2011, 08:15 AM

Is it the same Dometic Single Zone thermostat that I have? I included the picture in the first post. If so, what was the procedure to initialize.

I have noticed now that the clicking returns after a few uses which makes me think it is an electric issue. Each time I start the generator it is fine. But then after a few cycles running on 15 amp or battery it clicks again.

Randyman · 05-17-2011, 09:47 AM

Yes, mine is the same thermostat and I don't have a heat strip in the A\C that the clicking sound comes out of. Here goes: Make sure the Single Zone LCD thermostat is in the Off condition. Press the "+" button and, while holding it, also press and hold the On/Off Mode button for 3 seconds. LCD will show --. Press the On/Off Mode button again to turn system off. This completes the initialization. The furnace On/Off temperature differential should be set at this time.
"Furnace"- Furnace Mode
In the FURNACE mode the system will cycle the RV's furnace On and Off based on the room air temperature and the temperature set-point on the Single Zone LCD thermostat. The system can be configured to operate using an On/Off differential of either 1 degree F or 2 degree F. This feature is programmed during the system initialization. To set the temperature differential the system must be Off. Press the "-" button and, while holding it, also press and hold the On/Off Mode button for three seconds. Release the On/Off Mode button. Then release the "-" button. Press the "+" button to toggle between "d1 and d2", "d1" for 1 degree F differential and "d2" for 2 degrees F differential.

When I did this originally I thought it would be better to have d1 as the setting. I still had the clicking. When I got fed up last weekend listening to the clicking I did the initialization again and this time I set if for d2. Don't know if that did the trick or just redoing the initialization again, but it worked with no more clicks. Hope this helps fix yours as I know what you are going through.

DRPNGOUT · 05-17-2011, 10:30 AM

Uh oh. omg. I wonder...

One of the first things I did was change the differential setting to 1 degree. I thought it would be more comfortable with less of a temperature swing. Thanks for the info and I will definitely try the reset and change back the setting this Friday night.

cfsoistman · 05-17-2011, 11:47 AM

A one degree differential should never be used for any HVAC system. It's too close of a tolerance. It really shouldn't be offered by the manufacturer. With only one degree the system will be on and off too frequently, while burning propane and electricity. I've been in the HVAC field since 1976 and never have heard of a one degree differential until now. 2 degrees is the norm, while 3 to 4 is more commonly used for auto-changeover from Heat to AC. You don't want the system working against itself to maintain a temperature by switching back and forth. Hopefully it solves your clicking issue but still seems strange. Have you called Dometic Technical Service for any help?

Randyman · 05-17-2011, 12:13 PM

I spoke with my dealer, (who is 250 miles away) and he spoke with the techs at Dometic. They wanted him to check voltage at the relay thinking it would be low and causing the click. I wasn't ready to make a 500 mile round to have the voltage checked for fear that they would still be at a loss and I would have to return again. I was willing to wait till it quit altogether or I had some other warranty issues to make the trip. I turned to this forum for ideas and may have solved it myself. ( I hope) So far so good.

brianb · 05-17-2011, 12:21 PM

I can safely say that is the world's most confusing thermostat. You would think the lack of buttons would make it easier but it just makes it harder to operate. Just turning the a/c fan to auto when the furnace is on is like programming a VCR. Would a "on/auto" switch killed them?

blightle · 07-14-2011, 03:38 PM

Has anyone ordered this new digital thermostat to replace the analog version. My 2011 came with the old Analog thermostat but I would like to update it to the new digital version. Dometic sells just the thermostat for around $35 (part # 3313192.019) but they are telling me that I need a kit that includes a relay board as the digital thermostat will not work correctly with an analog relay board. Kit is $96 (part #: 3313189.015). In a house you never have to replace a relay board if adding a digital thermostat so this just sounded odd to me. Thought others may know or have done the replacement.

Thanks

Brian

polkatronron · 07-14-2011, 06:51 PM

Well, don't do it. I have had both ...the digital one does not work nearly as good as the manual one. I have had lots of trouble with the digital ones and the analog ones work much better.

Mistral · 10-19-2011, 04:11 PM

Hi !
Anyone has a solution for this problem as hi have the same thing appenning to me with the same thermostat but my a/c is Dometic model 57915.751 and I really want the 1 degree differential for my comfort.

Thank you and sorry for my bad english.

cfsoistman · 10-20-2011, 06:22 AM

Quote:

Originally Posted by Mistral

Hi !
Anyone has a solution for this problem as hi have the same thing appenning to me with the same thermostat but my a/c is Dometic model 57915.751 and I really want the 1 degree differential for my comfort.

Thank you and sorry for my bad english.

to the Forums. If you check in previous posts there is a kit needed in order for the digital T-stat to operate with an older model AC unit. Most likely this new board provides low voltage to the stat for the digital display as well as maintaining the memory of the t-stat. I don't believe it has battery back-up like most residential digital t-stats. I'd keep the analog t-stat and buy a decent digital thermometer that will read the temperature of the room and adjust your t-stat based on the reading of the thermometer. It would definitely cost less and help you avoid adding problems with the newer digital t-stat.

Mistral · 10-20-2011, 03:58 PM

I already have the Single Zone Thermostat AND the control box in the A/C, it was in the RV when I got it this spring in april. The RV is new and still on warranty and it curently in service at the dealer but I only wanted to know what was the fix if a fix there is ?

Thank you.

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