HVAC Crankcase Heater

[BearsFan315]

recently had to replace the cap on my HVAC Heatpump unit as it was not kicking in the compressor only running Heat Strip. also installed a hard start kit while in there.

tech told me i should get a crankcase heater and install it, said he could do it but would be expensive and i could order one and knock it out myself. save $$

it is a 2.0 Ton unit, and i bought a Tutco Finger Style Heater 240V 2 Wire, came in today.

Question is HOW should i wire it up ?? i know they draw very little power.

1- Hard Wire it to always be on ?? to the contractor HOT side 240v

2- Hardwire it on the contactor 1 Side hot and 1 side on Compressor side of contactor. so it is on when compressor is not, and off when compreesor is.

3- Other

 

[samss]

Wire it to be constantly hot. Otherwise the oil will get cold during the compressor's off cycle, and that's not good. If you have a scroll compressor, some mfgs say the heater is not needed.

 

[Dagny]

Do you run your AC in the cold weather? If not you don't need it.

 

[engineer2]

Hard Wire it to always be on is the normal way to do it. The only precaution is to turn off the breaker before any service work is performed.

 

[mrobins297aaa]

Back in the seventies when most of the units had them, I believe that they were wired hot all the time.
I remember we told customers to remove the fuses or turn off the circuit breaker in the fall and to turn it back on in the spring at least 24 hrs. before first use.

 

[bobbyjean]

bf315- you should alway's have a crankcase heater, it should be wired per your #2..on while comp is off. Scroll comp. do seem tougher than recips but still need heater's as compressors don't like liquid

 

[BearsFan315]

OK, it is a Heat Pump so I use it all year round. AC in Summer heat in Winter. Has Aux Heat Strip (Elect)
It is an older Recip Compressor.


option 2- Hardwire it on the contactor 1 Side hot and 1 side on Compressor side of contactor. so it is on when compressor is not, and off when compreesor is.

When compressor is NOT running it would be on keeping it warm, then it would cut off when Compressor kicks on.

Have a kill switch/ box at the unit Compressor Outside, so when it is serviced it it pulled so NO power to unit, also have one on the Air Handler in attic same reason !!

 

[OccupantRJ]

Simply wire it to a double pole double throw 240 rated "light" switch in a handy box and turn it on when cooler weather gets here. To advance things, wire it to a line voltage thermostat and set it for the temperature you want it on. It then becomes automatic.

 

[Done That]

Usually wired always on at contactor and then you get a unit with a built in snap disc thermostat that switches it off above a predetermined temp.

 

[BearsFan315]

actually found my manual and wired it up per that since it was noted on the diagram. pretty much option 2.

tested and seems to work. pretty easy to hook up and get working. i am **** so took my time did it right, ******* wires, and made it look professional, well neat at least

 

[LS6 Tommy]

Option 2 is not correct. You are only feeding the heater 120VAC. A CCH gets wired to L1 & L2 on the contactor. It is on all the time.

Tommy

 

[BearsFan315]

with the set up i have it has 240v running to it
metered it on and off cycle, and with the crankcase heater on.

think it feeds 240 via the coil

 

[bobbyjean]

your compressor thanks you ..... that heater will help to boil off any liquid in the compressor so at startup oil is available for lube....

 

[LS6 Tommy]

with the set up i have it has 240v running to it
metered it on and off cycle, and with the crankcase heater on.

think it feeds 240 via the coil

I don't quite understand what you're describing. The coil is 24VAC. CCHs always go on L1 & L2 and are energized all the time unless they are controlled by a thermostat that shuts them off above 65° outside air temp, like on some heat pumps.

Tommy

 

[peter2772000]

To be clear, the only reason for the crankcase heater is to boil off any liquefied refrigerant in the crankcase. It has nothing to do with keeping the oil warm, though it surely can't hurt.

When we start up commercial rooftop or split units, the manufacturer insists we apply power for 24 hrs prior to start up. And I remember older Carrier semi-hermetics would have a relay wired so that the heater was only energized on power-off, which makes sense.

 

[RAM2940]

BF315 The way you describe #2 the CCH will run only when the compressor is called to run.

 

[BearsFan315]

yeah that is what i thought.

here is a youtube i found that looks like what i did

 

[Dagny]

If the heater is hooked up right there will never be any liquid in the oil thats why it's there.

 

[LS6 Tommy]

yeah that is what i thought.

here is a youtube i found that looks like what i did

Although it does accomplish having the CCH only run when the contactor is open, it runs your CCH on 120VAC instead of 240VAC, as most are designed.

Tommy

 

[BearsFan315]

I Did not believe the wiring diagram Volt meter says 240VAC when idle compressor NOT running, then when compressor kicks in 0VAC.

i will go back and check it with a meter again to validate this...

will take a picture if i can of what it is

 

[willf650]

Although it does accomplish having the CCH only run when the contactor is open, it runs your CCH on 120VAC instead of 240VAC, as most are designed.

Tommy

It will be 240v minus the voltage drop created by the compressor winding which will be minimal. It's wired to a phase on the line side of the contactor and the circuit is completed to b phase by feeding through the compressor winding. When the contactor closes both sides of the heater will be fed from the same phase there by breaking the circuit.

The contactor is cheap and only breaks one pole of the circuit. The other side of the contactor is always closed. It's basically a brass bar instead of a contact that opens.

 

[RAM2940]

After watching the video, they are using the path of least resistance. When the compressor is not running power goes through CCH ( contactor open ) then through compressor windings, When contactor closes bypasses CCH (CCH has more R than closed contactor. Also not mentioned, if you have a 2 pole contactor you can use a set of auxillary contacts that mount on the side of the contactor, its on when contactor is off.

 

[LS6 Tommy]

It will be 240v minus the voltage drop created by the compressor winding which will be minimal. It's wired to a phase on the line side of the contactor and the circuit is completed to b phase by feeding through the compressor winding. When the contactor closes both sides of the heater will be fed from the same phase there by breaking the circuit.

The contactor is cheap and only breaks one pole of the circuit. The other side of the contactor is always closed. It's basically a brass bar instead of a contact that opens.

Ahh, he didn't mention it was a single pole contactor. That works just fine.

Tommy