Line Voltage Thermostat for roof a/c

[Scott & Heather]

I know I could use relays and make some complicated system to run a normal 24v tstat, but to keep things simple, I really want to install a line voltage 110v thermostat for my roof shaker in the bedroom. Wife can't reach the  ceiling controls on a 9" raised roof so I tried to splice and extend the wiring and controls down to the wall, but then the oem tstat isn't where it needs to be and the unit freezes up. Someone walk me through this. If I install said line voltage tsat, it would turn the fan and compressor on (high setting only) when temp called for it. Then both back off when temp is reached. This could cause it to cycle on and off a lot which could be annoying but I'ved ducted it, so it's a lot quieter. So two questions:

1. Any reason this won't work? Wire both compressor and fan power to tstat and hope it doesn't blow my 20amp breaker when they kick on together...

2. If I wanted to slowly ramp up the fan motor each time it was energized, how would I do this?

[eagle19952]

A LEVITON remote might be a more suitable mod.... i think it might work altho a relay might still be in involved...

[Darkspeed]

Scott you can get time delay relays in different time values so you can delay the start of the second unit by xxxx seconds.

Look at HVAC Time Delay Relay

[Lin]

I once installed a line voltage t-stat in a motorhome I had many years back.  I did it because I did not like all the fan noise and wanted to to just shut it down if it wasn't actually cooling.  It worked as far as that went, but there was a different problem.  The unit was designed to sense when to turn on/off by sampling the return air.  So the cooling mode would turn off just fine, but there was a real lag in the unit turning on again.  The result was it would warm up more than we liked before the AC would turn on again.  I just abandoned it.  I think there could be some work around for this, but I did not bother.

[belfert]

A lot of rooftops use the same motor for both condenser and evaporator.  I'm not sure you want the motor to start slowly when the A/C starts up.

[chessie4905]

Use a baseboard heat  wall mount thermostat.

[Scott & Heather]

Lin, I would abandon the oem Tstat so that wouldn't be an issue. But good point on that...eagle, they are expensive and not quite what I want I think from my little web searching....time delay relays? Cool, might put that to use to prevent both from popping on simultaneously. Chessie, I'm thinking I'll try that first. Cheap and easy. I can't find them in box stores anywhere. Will have to order one I guess


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[luvrbus]

I thought you could buy the control box for a Coleman roof top to change from the unit mount t-stats to the wall mounted T-stats

[Lin]

I really had not thought about this in many years.  Probably even my system would have been okay if the t-stat could have had or been adjusted to narrower on/off differential.  A +/-1 differential will keep the temp within a 2 degree range but will cycle more.  A+/-2 differential will keep the temp in a 4 degree range, which may be acceptable depending on the person, and will cycle less.  At the time, I did not know or consider the cycling differential, but it was too wide for us.  I guess this would be something you might want to evaluate when buy the t-stat.

[Scott & Heather]

you can, but they aren't $14 (line voltage tstat) and it's more complicated in some ways.

[Rick 74 MC-8]

Scott

I just did this on an air conditioner that I got for free the circuit board was burned out. I just used 24 volt cube relays 30 amp. Use 3 relays 1 for high fan 1 for low fan and one for the compressor. If I set it to auto the fan turns off with the compressor or I can put it on fan and just the compressor cycles. Total cost under 15 bucks

Rick

[TomC]

Why does your wife need to reach the thermostat? The whole purpose of the thermostat is to properly set it to what is comfortable for you, then leave it alone to do its job. On my roof tops I found that the 9 o'clock position on the thermostat is right at the 70 degree mark. Just experiment. Turn down the thermostat all the way cold, then when it is at the temp you want slowly turn it up until the compressor turns off, and whala-it's set. Then you wife doesn't need to touch it.
If you want to turn the unit on and off, extending the fan control is easy. Good Luck, TomC

[Scott & Heather]

Lol. Tom, I wish you could be a fly on a wall in our bus. If it were that simple....she's 36 weeks preggo and swaps from hot to cold faster than an 8v92TA overheats on a 9% grade on a 117 degree day. The problem is that our roof shaker Tstat stinks. It doesn't regulate the temp properly. It could work perfect and then we get a 65 degree night and it will freeze up. If i raise the temp a little it just never really kicks on when it should. I've ducted the unit even though it isn't designed that way so that doesn't help. I need a better Tstat


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[TomC]

Make sure the T-stat bulb is right in the air way on the air intake. My front A/C wasn't cold enough, so I wrapped the bulb in electrical tape-now colder, but still controls temp. My Colemans have a pretty good t-stat.Good Luck, TomC

[chessie4905]

Tom must be single.Yeah, tell her to leave the tstat alone.lol
http://www.lowes.com/pd_252766-13468-TKIT-1BW___?productId=50207369&pl=1&Ntt=electric+heat+wall+thermostat