Air conditioner mod help needed

[popeyemth]

Have a ceiling mounted air conditioner with no ductwork and controls mounted on the unit.
Have done the mod to change furnace thermostat to digital and would like to add a relay to the AC power line to the air conditioner controlled by that digital thermostat . With the air conditioner mounted thermostat set to max, a relay ,in the power line to the air conditioner ,controlled by the digital thermostat , will swich the air conditioner on and off to maintain the desired temperature .
What I need is help from the brain trust here in finding a relay with a 12 volt DC coil and contacts rated for 20 amps or better AC.
We have limited acess to the net here at home and any help with the research would be greatly appreciated. This mod has been done before but the write up referenced a "relay not found" when I tried to search for one .
Thanks,Mike

[marcsbigfoot20b]

popeyemth wrote:
Roy , it's the standard Dometic unit that came with our new Coachman



Do you know the Ham set up at Smokemont on Memorial Day?
Wanted to meet them but missed them after the thunderstorm 😞

I have the exact unit....Duo Therm brisk air by Dometic. What you want is the kit they already make for it at about $99-109
Duo-Therm Single Zone LCD Thermostat and Control Kit - Polar White

[popeyemth]

Roy , it's the standard Dometic unit that came with our new Coachman



Do you know the Ham set up at Smokemont on Memorial Day?
Wanted to meet them but missed them after the thunderstorm 😞

[popeyemth]

Found this on eBay :
http://www.ebay.com/itm/221377998676
Does this look like what I need?
Thanks,Mike

[RoyB]

I'm curious which Air Conditioner you installed in the ceiling. Most of those have a thermostat on the front panel and also use a built-in ceiling duct from one end of the trailer to the other. They have little round ceiling ducts situated along the way feeding the various different areas and rooms.

My 5th wheel ceiling mounted air conditioner AC POWER and Thermostat controls look like this


I have several of these round rotatable AC VENTS mounted along two built-in ceiling ducts running the whole length of the trailer.


The built-in thermostat has the large relay contacts to engage the air compressor.

I do not have an remoted controls mounted on the trailer walls anywhere - Just mounted on the ceiling A/C unit itself... Only my RV Furnace has a wall mounted thermostat control setup..

My air conditioner is a RV PRODUCTS MACH3 PLUS Model 8333D 13,500BTU model

Roy Ken

[YamaDooed]

I would look into using a Potter Brumfield SSR for this project. Depending on the duty cycle it runs you may have to mount it on a heatsink.

[Golden_HVAC]

Hi,

When I installed a new 5.7 GPM water pump, it's maximum draw exceeds my 7.5 amp relay. SO in 2003 I installed a 15 amp rated relay with a 24 VAC coil in the relay. It has worked fine for 10 years, don't think it could be a problem with the A/C unit.

Most 30 amp contactors are open type, where stray fingers around the contactor could get shocked if you touch the exposed shiny metal parts.

Many "Cube" relays are totally enclosed, and designed to fit into a socket, where changing the relay means unplug and plug in a new one. However most are only rated at max 10 or 12 amps. You could select a 10 amp 2 pole relay, then connect the compressor common wire to both poles, so that each will see only 1/2 the total amperage. 3 pole will also work well, with 1/3 of the amps per pole.

The indoor fan is only going to draw about 3 amps, so really easy to use a 1 pole cube relay. You can normally buy them in 12 VDC.

You will also need to decide if the fan will run on high speed or low speed, or install a switch to go between the two. You must never allow both speeds to be energized at the same time. You will also get a "Stray" voltage from the other speed. Such if you apply 120 volts to high speed, and the fan is running, then you might have 90 volts on the low speed wire. When you have 120 volts applied to the low speed, then you might have between 130 and 145 volts at the black high speed wire. Should you put 120 volts to both windings at once, your fan will not last long, and will require replacement soon.

Most thermostats only have one fan speed selection. Some RV thermostats have a high fan and low fan selection, so you can run high speed on warm days or while driving, and low speed at night so it is quiet.

Good luck,

Fred.

[ChooChooMan74]

Grainger is a good source.

List of all relays with 12vdc coils.