Help understanding operation of my AC unit with de-humidistat
 

Hope this is the right forum. Did not see All about airconditioners and things forum :)

I am testing my de-humidistat before I drift north for the summer. Thinking there may be some experts out here that can describe what I am seeing before my AC person comes over for the yearly inspection.

My de-humidistat is wired in series with the thermostat. When I am here in TV, I leave the de-humidistat in the ON position, so AC is controlled by the thermostat alone. In this mode all works as expected. Now I test the de-humidistat.

I set the thermostat to 70 degrees (colder than room temperature). I then turned the humidistat to 30%. The Trane XR80 air handler in garage and the compressor outside came on. This is good.

I leave the thermostat at 70 degrees and I next turned the de-humidistat to 80%. Now the air handler in the garage is ON but the compressor outside is OFF.

I now leave thermostat at 70 degrees and turn de-humidistat to OFF. The air handler in the garage is still running, but the compressor never comes on.

Without the de-humidistat, I do not think I ever hear the circulator ON when the compressor is OFF. Does what I am seeing make sense?

Thanks
Alan

Most compressors will have a delay in starting and in turning off as a means to "milk" the most of the energy from the cooling/heating operation's last cycle... so it may be that you ran your cycle tests a little too close together. If that happened, try again but wait maybe 10 minutes before conducting the next cycle test in the series.

It sounds to me that the humidistat was wired in the compressor circuit. Leaving the fan to operate from the thermostat. If that's the case the fan will run all the time when the thermostat setting is below room temp. I'm sure your A/C guy will make sure it is set up properly.

Bob

When de-humidistat is at 80% (or OFF) and thermostat is set below room tempurature the air handler never shuts off (40 minutes this AM) and compressor never comes on.

Thank you, that is interesting. Make sense to this layman. As I understand it unless the air handler can take humidity out of the air, this is NOT the way it should be wired and is likely why I saw no savings last year using a de-humidistat as my air handler never shut off.

Does what I just typed make technical sense?

Yes it makes sense. The air passing over a cold coil is what removes the moisture.

Let us know what your AC guy says.

Bob

This all makes my head hurt!

When we leave we put he humidistat on %60 and the thermostat at 79 degrees.Worked great last year!

That is what I was hoping for but....
 

When I do this my air handler in the garage NEVER shuts off.

When I go up North, I leave the de-humidifier on 60% and don't really concern myself with where the thermostat is set to. When the de-humidifier is set at 60%, the thermostat is not being used so it can really be set for any temperature. Have done this for the last two years and have had no problems with mold whatsoever.

de-humidstat hookup?
 

Does anyone know how to hook-up one of these de-humidstats???? Like to put one in but not to sure how to do it. Do they come with instructions how to hook it up to your thermostat?? Thanks for any input!!!

This is true with a caveat. If they are wired in series the thermostat has to be set to a number low enough to ask for AC when the de-humidistat does. If they are wired in series, the temperature in the room must exceed the thermostat AND the humidity must exceed the de-humidistat setting. If the thermostat is set for 92 degrees it will not call for AC regardless of humidity until room temp is greater than 92 if I understand system correctly.

PS. Thanks for all the suggestions and references in PMs. I do have an AC guy coming over in a week or so.

First I know nothing about how to wire the de-humidistat. We had one installed by a handyman in TV when we were not there. We thought it was working as it should, but then our AC stopped working. When Munns checked out the A/C they discovered the de-humidistat was wired wrong. They corrected the problem and since then the de-humiidstat and A/C have been working properly. We have a very low electric bill in the summer when our house is unoccupied due to using the de-humidistat. So long story short is could be wired wrong.

We had ours
 

put in by Munns.Maybe that's why we haven't had any problems!! jmho!

Resolution
 

Alan
Have you found anything out yet about why the air handler continues to run when trying to use the dehumidistat?

Today was the day for the annual inspection/cleaning of the AC at 8 AM. Same company that installed the dehumidistat. The person who did the cleaning did not know why my problem was happening, but he called the owner. Have not heard back yet, but will bring closure to the thread when I do.

The installer is a person highly recommended on TOTV, so am very interested how this plays out and will report back. I expected looking into the problem to be handled during this 8 AM appointment, but will blame that on folks that setup the appointment and give some leeway for now.

Hw much does a dehumidistat cost including installation??

I paid $175 for a cleaning and dehumidistat last year, so I would guess the de-humidistat was $120 - $125 installed.

Well, I have been told this is the way it works....
 

I am just the messenger, I do not have the knowledge (YET) to know which is right or wrong, or if other parameters exist for the decision, but I have no reason to not trust this installer (Chuck Farrell).

I spoke to Chuck this AM and was told this is how he wires them per Trane. He says the Trane air handler is extremely efficient and should run when the temperature in the room exceeds the thermostat regardless of the humidity level.

I know Munn's does not install a dehumidistats this way. I know this as my Dad's air handler will not come on until the temperature is high AND the humidity is high.


I guess I have a little research to do..... :shrug:

Ours is wired as Munn's recommends (temp AND humidity must exceed levels set for AC to turn on) ... does anyone know why you would want the air handler to run by itself without AC?

John

No idea - My guess is that there is some benefit to circulating the air in the house even if it isn't being cooled/dehumidified. I don't think the circulating fan requires very much energy to do its thing.

Did Chuck recommend temperature and humidistat settings? It seems to me if the thermostat is set low the air handler would be running all the time, or if set to high the compressor won't come on when the humidistat calls for dehumidification.
We install a humidistat to cut our electric bills and have less wear and tear on our equiptment while we are away. While keeping mold from forming in our homes. I'm not sure this is the best way to accomplish this.

Bob

Today he said:

Tempurature: 85
Humidity: 60%

These numbers were different last year, I wrote down 82 degrees and 60% after the installation. I am crafting an email to Trane support as another resource. Like I said, I have no idea the right answer, but want to know why different installers use different techniques to solve the same problem.

I think you are probably correct ... we run a couple of ceiling fans on low ... I think I am getting the same effect ... YMMV