Changing a/c controls from unit to wall mount

shineysideup · 02-15-2010, 07:17 PM

I am wondering if anyone has changed their a/c mounted controls (thermostat and fan speeds) to a wall mounted unit. I would like to do this for a couple reasons. The a/c fan in our t.t. is on all the time. It is quite loud, even on low speed. I would like the fan to turn off and on with the thermostat setting. I can hear the compressor kicking in and out so I am confident that there would be some off time. Is this viable?

Any info is appreciated,

shineysideup

LadyWindrider · 02-15-2010, 11:14 PM

Based on what I can find out, the controls mounted on the AC unit actually switch 120 Volts AC. The best home style digital thermostat is only rated to switch 24 volt AC. The second concern would be that the temp sensor for the air is located in the return air plenum. If you stop the fan and the compressor at the same time, I'm not sure you would get an accurate reading. The heat may build up, and/or it may cause the "A" coil to stay too cold and freeze up. I looked at doing this to mine, as I have an electric hoist bed that covers the controls when up, but found it was not worth the effort. I also would have to run wire mold across the ceiling and down the wall. Might could be done with the addition of two relays, one for fan, one for compressor, but you will still be stuck with the fan speed switch, and only have the fan speed available at the wall that the speed switch is set for. I found it too complicated for a simple mod, and decided it was probably better to have the air circulating from the fan always on a benefit. I'm also usually on shore power and not running a generator, which may make a difference. Good luck.

**Bama Rambler** · 02-17-2010, 09:10 AM

While you can convert from mechanical controls to electronic controls (i.e. wall t-stat) it requires the air distribution box and controls to be removed and new electronic control kit be installed, t-stat wiring be run, 12vdc power to be ran to the unit, etc. So you see, it's not a simple job. I'm not trying to discourage you from doing it I just want you to be prepared for all that's required. Your best bet might be to find the controls out of an old unit to save you some money.

shineysideup · 02-17-2010, 07:00 PM

Thanks for the reply's guys. From what I had read I thought it was quite an involved change. Personally I don't think the benefit would be worth the effort. Guess in my next trailer (or lifetime!) I will look for a wall mount controlled a/c unit.

Maybe I misunderstood the whole operation of a wall mounted thermostat a/c unit. The fan does cycle off and on when the compressor is not running, right? Guess this should really have been my first question!

thanks again,

**Bama Rambler** · 02-18-2010, 07:43 AM

Yes, in an analog (wall t-stat) unit there is a switch that either allows the fan to cycle on and off with the compressor or run all the time. At night we run our fan continously because the sudden sound of it starting up will startle you awake.

shineysideup · 02-18-2010, 11:53 PM

Quote:

Originally Posted by Bama Rambler

Yes, in an analog (wall t-stat) unit there is a switch that either allows the fan to cycle on and off with the compressor or run all the time. At night we run our fan continously because the sudden sound of it starting up will startle you awake.

I know exactly what you mean although it is the furnace that sounds like a leaf blower starting when it kicks on. I have since figured out that a little electric ceramic heater will keep the trailer warm 98% of the time. This also saves propane! Gotta figure out how to make that puppy a little quieter!

shineysideup · 03-25-2010, 12:25 PM

Quote:

Originally Posted by shineysideup

Thanks for the reply's guys. From what I had read I thought it was quite an involved change. Personally I don't think the benefit would be worth the effort. Guess in my next trailer (or lifetime!) I will look for a wall mount controlled a/c unit.

Maybe I misunderstood the whole operation of a wall mounted thermostat a/c unit. The fan does cycle off and on when the compressor is not running, right? Guess this should really have been my first question!

thanks again,

O.k., I've been thinking of this still... I don't want to get into changing the controls to a wall mount for obvious reasons (a lot of effort! ). Could I change out the fan speed switch to a variable rate switch? I would also like to put in the heat strip (that is an option on my unit) and get rid of the portable heater (storage, fire hazard etc.). It would be great if I could slow that fan down. Maybe I could try and install some kind of sound insulation also?

Any ideas on where I could find a variable rate switch to accomplish this or am I talking crazy stuff here?

cheers,

shineysideup

LadyWindrider · 03-25-2010, 12:44 PM

The heat strip is easy, but not near as efficient as a ceramic heater. My Roof AC has a 3 speed fan switch already on it, what are you thinking now exactly? This is not a house AC, and too little air movement across the coils, and it will freeze up. If it freezes, it may take over a day to thaw, and that's one day you want have air, right in the middle of July. Then every time you check to see if it's working, you only add to the problem, and now it's a day and a half. This is not anything like a house AC, and was never meant to operate like one. Any modifications on air flow are not advised. That is my two cents. By the way, I was told during walk through on my camper, to always run the AC fan on high for risk of freeze up. I told them, I would run it on low and test it, and if it froze up, they could fix it. The manufacturer put low speed on it, and it better work there. I haven't had any problems in July, on low, but I wouldn't want the fan any slower.

NWJeeper · 03-25-2010, 01:17 PM

Quote:

Originally Posted by shineysideup

O.k., I've been thinking of this still... I don't want to get into changing the controls to a wall mount for obvious reasons (a lot of effort! ). Could I change out the fan speed switch to a variable rate switch? I would also like to put in the heat strip (that is an option on my unit) and get rid of the portable heater (storage, fire hazard etc.). It would be great if I could slow that fan down. Maybe I could try and install some kind of sound insulation also?

Any ideas on where I could find a variable rate switch to accomplish this or am I talking crazy stuff here?

cheers,

shineysideup

I installed one of the heat strip kits on our old rig, they come with everything you need. Most A/C units selector switches already have a "heat" setting they are just not used unless you install the kit. However in my experience with ours the fan unit on the A/C is horribly loud and the unit runs continuously. The thermostat unit only turns off the coils not the fan. I wound up never using it because of this. I much prefer the portable space heater like Windrider mentioned. Most all of them these days have tip over protection that will shut them off if they fall over accidentally. Been using space heaters of some sort for over 10 years with no problems.

NWJeeper · 03-25-2010, 01:19 PM

Quote:

Originally Posted by windrider

The heat strip is easy, but not near as efficient as a ceramic heater. My Roof AC has a 3 speed fan switch already on it, what are you thinking now exactly? This is not a house AC, and too little air movement across the coils, and it will freeze up. If it freezes, it may take over a day to thaw, and that's one day you want have air, right in the middle of July. Then every time you check to see if it's working, you only add to the problem, and now it's a day and a half. This is not anything like a house AC, and was never meant to operate like one. Any modifications on air flow are not advised. That is my two cents. By the way, I was told during walk through on my camper, to always run the AC fan on high for risk of freeze up. I told them, I would run it on low and test it, and if it froze up, they could fix it. The manufacturer put low speed on it, and it better work there. I haven't had any problems in July, on low, but I wouldn't want the fan any slower.

Windrider, With the heat strip units the A/C does not run the compressor so there would be no freeze up of anything. However the fan does run continuously like I posted above so the noise is the major problem I had with the heat strip kits.

LadyWindrider · 03-25-2010, 04:22 PM

Sorry for the confusion. I know the heat portion will not run the AC compressor. I was just wondering why he wanted to change the AC fan to variable rate, when it already has 3 speeds if it is like most.

dirtengineer · 03-25-2010, 06:42 PM

Quote:

Originally Posted by windrider

The heat strip is easy, but not near as efficient as a ceramic heater. My Roof AC has a 3 speed fan switch already on it, what are you thinking now exactly? This is not a house AC, and too little air movement across the coils, and it will freeze up. If it freezes, it may take over a day to thaw, and that's one day you want have air, right in the middle of July. Then every time you check to see if it's working, you only add to the problem, and now it's a day and a half. This is not anything like a house AC, and was never meant to operate like one. Any modifications on air flow are not advised. That is my two cents. By the way, I was told during walk through on my camper, to always run the AC fan on high for risk of freeze up. I told them, I would run it on low and test it, and if it froze up, they could fix it. The manufacturer put low speed on it, and it better work there. I haven't had any problems in July, on low, but I wouldn't want the fan any slower.

I thought that all electric heaters are nearly 100% efficient, if you disregard the fan power usage. Why is a heat strip less efficient?

PumaPro · 03-25-2010, 09:55 PM

It's the same air conditioner unit, but completely different controls up inside the ADB. It's not impossible, but it will be a bear to do. Especially running that t-stat wire through the laminated construction.
What the wall T-stat does in a "standard ducted" A&E system is: send 12 volts from the t-stat to the control package in the a/c. It converts the 12 VDC to 7.5 VDC, which is then sent back to the T-stat to control the furnace. This is also why you can't switch between a Coleman A/C & Dometic (A&E) A/C. Just some more food for thought. With some doing, wall controls could be made to work, but it would be complex.

LadyWindrider · 03-25-2010, 10:56 PM

My day for mistakes. The heat strip is probably efficient, it's just not very big in the BTU output, only 5600 BTU as far as I can find, which is close to a 1500 watt ceramic heater. Couple that with the fact it is in the ceiling, and heat is going up, it would have to work pretty hard to get the heat halfway down. I know that a ceramic heater on the floor lets the heat rise also, but it goes by you, warming you on the way up. Also the fan speed on a ceramic heater is more tuned for heat. Any HVAC person will tell you, move ac fast, and heat slow. That's why your home unit has a two speed fan, one for heat, and one for AC.

dirtengineer · 03-25-2010, 11:45 PM

Ahhh, efficient, but not necessarily as effective at making the inside feel warm. I can buy that. Thanks for the clarification Windrider.

NWJeeper · 03-26-2010, 12:10 AM

Quote:

Originally Posted by windrider

My day for mistakes. The heat strip is probably efficient, it's just not very big in the BTU output, only 5600 BTU as far as I can find, which is close to a 1500 watt ceramic heater. Couple that with the fact it is in the ceiling, and heat is going up, it would have to work pretty hard to get the heat halfway down. I know that a ceramic heater on the floor lets the heat rise also, but it goes by you, warming you on the way up. Also the fan speed on a ceramic heater is more tuned for heat. Any HVAC person will tell you, move ac fast, and heat slow. That's why your home unit has a two speed fan, one for heat, and one for AC.

Entirely correct and from my experience with these heaters in the A/C they are good for emergency only if your propane should run out but they will run constantly and they are NOISY! I much prefer the portable space heaters for the reasons Windrider points out.

cfsoistman · 03-26-2010, 06:42 AM

Quote:

Originally Posted by windrider

My day for mistakes. The heat strip is probably efficient, it's just not very big in the BTU output, only 5600 BTU as far as I can find, which is close to a 1500 watt ceramic heater. Couple that with the fact it is in the ceiling, and heat is going up, it would have to work pretty hard to get the heat halfway down. I know that a ceramic heater on the floor lets the heat rise also, but it goes by you, warming you on the way up. Also the fan speed on a ceramic heater is more tuned for heat. Any HVAC person will tell you, move ac fast, and heat slow. That's why your home unit has a two speed fan, one for heat, and one for AC.

I'm a HVAC guy for more than 34 years, damn I am getting old, and you're 100% correct. The biggest problem with the strip heat in the AC unit is the return is in the ceiling as well so it's pulling the warm air back through the unit. The positive part is higher return air temperature the higher the supply air temperature. Negative is you're never pulling the cold air off the floor. We have two strip heaters and we use them when the temperatures are not too severe 40 degrees at night plus. I run the fan on the low setting from each wall t-stat and the units will cycle off, but you still have the noise factor. Personnaly I like the oil filled radiator type electric heaters because there's no noise the heat drifts throughout the area. I have a choice of 3 settings 6,000 or 9,000 or 15,000 Watts. Plus it still radiates heat once the t-stat is satisfied without using any electric until the t-stat calls again. Downfall is you have to let them cool down before you pack them away.

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