Dual A/C Units in Fifth Wheel

[CoreyJSUBB]

Good Morning All,
I recently upgraded from a TT to a Fifth Wheel 2015 Montana Mountaineer. Coming from an Outback TT with one AC unit to having dual units the fifth wheel I am alittle confused. First Trip out, we ran AC and the up stairs smaller unit cycled the compressor on and off every 7 sec. I called the dealer and took the unit back to them for evaluation. They told me the second unit had been installed but not connected to the duct work in the RV and repaired. Second trip out its a little better but still cycles alot. The larger unit in the Bunk house hardly even even comes on.

I think the main thermostat in the livingspace controls both units but I have no idea where the temp. input comes from ofr the second upstairs unit. There is no device upstairs to monitor the temp.

Anyone ever been involved with this type issue? Any feedback would be
Greatly appreciated.

Thanks

[gearhead]

There should be a thermostat knob on the bedroom unit plastic cover, where the outlet vents are.... assuming it is a Dometic.

[CoreyJSUBB]

There is no knob but it may be becasue the central controller has Zone 1 and Zone 2 in it. I thoght there should have been a detector for ambient temp in the upstairs room but the documentation for the central controller say no input needed for Zone 2. Not sure how this setup is suppose to work.

Thanks for your reply any info helps.

[bsmith0404]

Your unit should be the same as mine. Zone two is your bedroom unit. If your controller has a zone 2 setting like you are saying, there has to be a sensor in zone 2. Mine is just a small round white sensor on the bedroom wall about waist high. Are you sure there isn't a sensor somewhere in there? If there isn't, then there is a problem, the thermostat would be confused and not know what the temp in the room actually is.

[CoreyJSUBB]

Bsmith0404

Thanks for your reply, that is exactly what I was thinking also. Zone 2 is the upper bedroom. There is a detector in the bunk house but nothing in master bedroom. When I mentioned that to the dealer they said the control for the bedroom unit was built into the central controller which doesn't make since to me.

Not sure what to do now.

[JRTJH]

You didn't say what brand of system you have so it's difficult to provide information on the specifics of the thermostat. Dometic, Duo-therm, Coleman all have different ways of wiring the thermostat and different features so there's really no comparison. You could do an online search at the specific manufacturer's website and find the installation instructions for the thermostat. It will tell you exactly how to wire it, install it and how to troubleshoot it. If there is no mention of a "second zone monitor" built into the thermostat and if there's instructions on how and where to connect the wiring for both the front and rear monitors, that would pretty much indicate that the dealer isn't completely familiar with your unit (nice way of saying he's blowing smoke). If, however, the installation instructions give information on how to wire the rear monitor and state that the thermostat should be installed in a location where it will monitor the primary zone...... Well, you get the idea.

Do some research on the thermostat manufacturer's website, you'll probably find what you're looking for.

Good Luck

[CoreyJSUBB]

Sorry I forgot to include info. Dometic 15000 BTU in Bunk House and 13500 BTU secondary unit in master bedroom upstairs. Controlled by Dometic CCC2 Thermostat with Zoned control.

[bsmith0404]

That is the same type of set-up I have on my Alpine. Where is your thermostat located? If it is in the hallway between the two zones like most, I would still guess that there should be a sensor in the bedroom. If the thermostat is located in the bedroom, then it would most likely be the sensor.

I will say this, the two zones are a little tricky to get used to at first. You need to check the zone settings and the mode. I'm guessing your rear unit has a heat pump, but the front doesn't so the correct mode and settings can make a world of difference.

[bobbecky]

If your thermostat is close to the upstairs, then they have it controlling the front A/C directly, and then have the rear A/C use a remote temperature sensor downstairs in the rear of the trailer. Your thermostat is probably too far away from the rear unit to effectively control it. Ours is the opposite, but it doesn't really matter. When we are in very high temp areas, and want to use the A/C at night when sleeping, we turn the front A/C fan control to low, instead of auto. That way, it isn't going on and off all night, just stays on and the compressor cycles as needed, which is much less irritating. We have also just used the rear A/C at night, which is also ducted to the bedroom, and turn it on to low to continuously circulate the air. You just need to experiment to find what works for you.

[CoreyJSUBB]

Thanks for the Reply and Great Info

Bsmith0404 - The thermostat is located at the bottom of the stairs just inside the entry door to the living area. My thought was heat rises and it would be to far from the smaller unit to affectively control it. I will check the settings.

bobbecky - I like the fan on low trick I will try that and see how it works.

[bsmith0404]

That's what I figured. IMO, you should have a temp sensor in the bedroom similar to the one in this link.

http://www.ebay.com/itm/like/3611758...lpid=82&chn=ps