Dometic AC fan speed...

[footdoc]

I have a 2 zone T stat...fan speeds...low, high, auto....It's set up on auto to run on low unless the set point is at least 7 degrees from ambient temp...so I need to run it on high fan...that's ok until the set point is reached...then the fan only runs, undoing all the dehumidifying accomplished....Is there a fix to changing the fan to run on high all the way to the set point without coasting on low/??

[footdoc]

I have a 2 zone T stat...fan speeds...low, high, auto....It's set up on auto to run on low unless the set point is at least 7 degrees from ambient temp...so I need to run it on high fan...that's ok until the set point is reached...then the fan only runs, undoing all the dehumidifying accomplished....Is there a fix to changing the fan to run on high all the way to the set point without coasting on low/??

[M&EM]

My similar system does what you require when run on auto. It will do the high speed,then slow when close to satisfying cooling, then off at the end of the compressor run cycle

[RV Wizard]

Larry, a fix would be easy. Simply remove the slow speed fan conductor from the relay and add a jumper from relay to high speed connection. No matter if the control board calls for low or hi it can only run on high speed. Once the T'stat is satisfied it will shut down. Good luck and keep us posted.

[footdoc]

thanks...and that will work the same on the heat pump side???

[footdoc]

Mike...I played with it today and the results were NOT good...I dont have a schematic except some wierd stuff on the CB cover...nothing showing fan wiring...I traced the wires from the fan to the board...I figgered it would be red and black...I disconnected one and cranked the gen and had low speed only...then put it back and disconnected the other...high speed only...good! The fan ran on high speed with the black wire connected...so I spliced the red (former low speed) into the black.
Tested again...the fan and compressor would run on high, but when the t stat was satisfied, the fan only cut off and compressor kept running..then I put it on fan only and after a short while smelled something hot and the fan shut down...went on the roof and found the fan motor blazing hot...sooooooo....put everything back and it seems to works again now that the fan cooled down...I obviously guessed wrong at how to do this..Do you know from this what I did wrong? I have a Dometic 15K heat pump....2006 vintage...

[M&EM]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by footdoc:
the set point is reached...then the fan only runs, undoing all the dehumidifying accomplished....Is there a fix to changing the fan to run on high all the way to the set point without coasting on low/?? </div></BLOCKQUOTE>

Checked out my 2 zone system and noticed compressor running even when the low speed kicks in. When system satisfies the thermostat, the compressor AND the low speed blower motor stop running. I think my system is running as it should.

Marty

[footdoc]

If you leave the fan on auto...yes...but on mine if it's set on low or high....the fan will continue to dance without its compressor partner!

[Gary RVRoamer]

footdoc,
Can't you make the fan speed wiring changes at the thermostat rather then at the a/c en?. You want to change the speeds the t-stat is calling for on Auto, not what the a/c itself does when the signal arrives.

Is your t-stat the Atwood Comfort Control System or one of the other models? Some work differently than others.

[footdoc]

its a Duotherm by Dometic..and they say 'that's the way it is.....' but someone who knows more than me will be able to modify its operation, I'm sure....BUT that's not me...I'm quitting before I burn up something with no schematic

[Ray,IN]

Go to this download site, select your model# heat pump, and download the installation manual. It also contains complete instructions for the 2 zone thermostat.
We have the same setup,heat pumps and 2 zone thermostat with 3 fan settings; constant low fan, constant high fan,and auto fan which works as you describe.

[RV Wizard]

Larry, you cannot run both speeds of the motor at the same time. You have to disconnect the low speed of the motor. Pull the red wire off the control board and tape it off. Make a jumper wire so you can now jump from that board location to the high speed (black) wire. Now when the controller wants to switch fan speeds it still feeds and only feeds the hi speed side of the motor. If this is not clear then do not attempt. I am sorry but you have already shortened the life of the motor by trying to make it run 2 speeds at once. Keep us posted.

[footdoc]

Ooops I got it now....how badly do you think I hurt the motor?...no smoke but really hot before it shut down after about a minute..thanks for the info....I do understand now...

[footdoc]

thanks for the info Ray...