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Old 12-15-2003, 10:44 AM   #1
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Comfort Control Center

Apparently Airstream is not providing much documentation for the Comfort Control Center thermostat that comes on most Classic and Limited Trailers. There is a card that hangs from the thermostat that contains some basic information but is woefully inadequate regarding the real workings of the unit. I called Dometic and they sent me a copy of their documention for this thermostat. Here is a couple of things that aren't on the card that is supplied with your new unit.

First thing to know, if you have the heat pump equipped A/C unit, you only have two fan speeds (Hi & Lo). The non heat pump units have three. The extra speed is medium.

Secondly the heat pump has a defrost cycle that functions once temperatures drop below 40 degrees. What happens is after the heat pump has been running continously for 25 minutes, the fan will shut off but the compressor will continue to run. At that point the refrigerant flow is reversed which apparently will remove any frost that has accumulated on the outer evaporator coils. This process will continue for 3-5 minutes after which the refrigerant flow is again reversed and the fan will start blowing again. I thought I had a problem the first time I experienced this......but that's the way it works.

Next issue, if you use the fan speed on automatic when you are running the air conditioner how does the system know what speed to use? Apparently if you thermostat set point is 8 degrees or more that the inside temperature of the trailer, the fan will come on at high speed. Less than that it comes in on low.

Am I right to assume that if you set the fan speed to low or high that this will force the unit into a continous fan state or will it still cycle? The manual isn't clear on this fact.

Jack
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Old 12-15-2003, 11:24 AM   #2
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Re: Comfort Control Center

Quote:
Originally posted by jcanavera
Next issue, if you use the fan speed on automatic when you are running the air conditioner how does the system know what speed to use? Apparently if you thermostat set point is 8 degrees or more that the inside temperature of the trailer, the fan will come on at high speed. Less than that it comes in on low.

Am I right to assume that if you set the fan speed to low or high that this will force the unit into a continous fan state or will it still cycle? The manual isn't clear on this fact. Jack
This sounds like the climate control in my car and the new window air conditioner I put in an upstairs bedroom (our central air doesn't do the upstairs room that well).

On both, by using the climate control the fan defaults to what is required. For instance, when you first set up somewhere and the interior temperature of the trailer is say, 90 degrees and you set the thermostat to 68, the fan should come on high speed and as it nears it's target temperature (68) automatically start dropping down to a slower speed by itself. Whereas, you turn the air on and also press the high speed (for the fan), you just over-rode the automatic fan speed and it will continue to stay on high fan, regardless the change in temperature. It should work this way for the heater too.

I hope that makes sense, and is applicable to your Climat Control. This is the way it works in my car and window air conditioner.
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Old 12-15-2003, 11:54 AM   #3
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I wonder ...

if failing to defrost is the problem I am having with my heat pump.

After running for a long time at low temperatures, there is a thumping sound like the fan may be hitting something. Once, it became quite loud and ultimately blew the breaker.

I thought that it was the compressor going out when the breaker popped, but I ran the heat pump successfully at Blanco this last weekend. It ran fine, but started the thumping after a few hours. I switched it to furnace when it started the noise, so I don't know whether the breaker would have blown ultimately or not.
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Old 12-15-2003, 01:32 PM   #4
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When you set the fan on auto, it comes on when the compressor is on and turns off when the compressor goes off. I find this wakes me up, so I leave the fan set on Low.

Reverse cycling is common with heat pumps. It's taking heat OUT of the house (or Airstream in this case) to defrost the exterior coil. When it does it on home units, the backup resistance strips come on to provide that heat and prevent cold air from coming out of the registers. There's a reversing valve that is activated when this happens, and you could be hearing that as the thump. The compressor often sounds different while reversed... sort of a lower-pitched sound.

If the compressor cuts off due to low voltage when the valve is activating, and then tries to restart when head pressure is high, it will certainly trip a breaker.
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Old 12-15-2003, 01:50 PM   #5
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Quote:
Originally posted by RoadKingMoe
When you set the fan on auto, it comes on when the compressor is on and turns off when the compressor goes off. I find this wakes me up, so I leave the fan set on Low.
The problem with a continual fan operation is the reintroduction of humidity back into the trailer due to the moisture in the coils evaporating due to the constant air flow. I think nightime will be ok and auto will work great.

I think the hole in the logic in the auto fan setting is during the heat of the day, where the low fan speed is too low to provide the cooling level you need, and to get to high speed you need to be 8 degrees over set point. Your only choice is to override with the fan on high, but the fan won't shut down at set point thusly reintroducing the moisture into the trailer. Personally I would have liked that temperature differential on auto to be a little lower. Possibly as low as 3 degrees above set point. Would be nice if there was a tweak we could make.

Jack
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Old 12-15-2003, 02:04 PM   #6
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Quote:
Originally posted by RoadKingMoe
There's a reversing valve that is activated when this happens, and you could be hearing that as the thump. The compressor often sounds different while reversed... sort of a lower-pitched sound.
The thumping is a continuous series as if the fan blade were hitting the shroud. Loud enough that some friends heard it and commented on it when we were standing a good distance from the trailer. It also seemed to make a difference if I thumped on the inner shroud when it was happening.

The time the breaker blew, the noise was much louder and awoke me from a deep sleep. I thought a train was running by outside. About the time I got my eyes open, the breaker popped overhead. I don't think the voltage was low since the RV park was new, well wired, and fairly empty. Everyone else near me (all Airstreams) were using furnace and not resistance heat.
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Old 12-15-2003, 02:51 PM   #7
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John:

It is possible the Squirrel cage is loose. Fro myour descriptions of the noise you are experiencing.
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Old 12-15-2003, 03:00 PM   #8
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That would make sense

Quote:
Originally posted by JPAIRSTREAM
John:

It is possible the Squirrel cage is loose. From your descriptions of the noise you are experiencing.
I did notice that each time it turns off, there are about 3 or 4 repetitions of a scraping sound that could very well be the squirrel cage slipping on the shaft. I only hear that if I am standing under it when it turns off.
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Old 12-15-2003, 03:19 PM   #9
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This is only held on by an allen screw. This can be accessed from the top taking the shroud off.
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