compressor heater... always on with compressor ?

[knighty]

hi guys

I have a small'ish 3 phase compressor at work running a small room, it's setup to be a freezer, but its normally run as a fridge (just changing the temp on the thermostat)

just realised the other day that the compressor heater coil is powered up whenever the compressor is running... is this right ?

seam's like a hell of a waste cooling the motor windings with the gas return, then heating the oil (I'm guessing its the oil?) with an electric heating coil.... who not use the hot gas output ?

I'm guessing it shouldent be powered up all the time ? compressors run hot enough on there own !

[Perseus]

typically a crankcase heater is operating during the off cycle

[winfred.dela]

I use crankcase heater in large system to prevent migration of refrigerant to the compressor.
Since we have in our country a high ambient temperature, i don't even bother to install one in small systems.

For your purpose, i think you should only have it ON when the compressor is OFF. thus, saving some dime for your valued customer.

[Peter_1]

If the compressor is shutting off in pump down, then you even don't need one at all.

[refteach]

Normally they are off while running. Having it on when the compressor is running can increase the potential for breaking down the oil, if you have a higher than normal superheat. The heater serves to not only reduce the amount of refrigerant that may migrate back, but it also serves to warm the oil so everything gets oil at startup.

[US Iceman]

If the evaporator(s) are pumped down prior to the compressor shutting off, the crankcase heater is only needed if the crankcase temperature falls below the saturation temperature of the suction pressure.

In cold ambient conditions (around the compressor) the heat loss out of the crankcase can allow the oil to become diluted with refrigerant. This is what the heater is trying to prevent by keeping the oil warm.

[NoNickName]

To prevent the heater burning, interlock the heater with the compressor contactor normally closed contact, so that only on stop the heater is on, and viceversa.

[bernard]

Hi I would suspect the contactor has been changed at some time an rewired incorrectly.Check to see if the heater is wired through the normally closed contacts so when the contactor is energised the supply is taken off the heater.


Regards Bernard

[knighty]

it's wired right into the came contactor as the compressor... the wires for the compressor and heater are littrally joined

looks like another one for me to re-wire !

pity I didn't look at this sooner, would have saved me a fortune !

the compressor always pumps down when it turns off.... I wired this in myself in the main control box... the heater and compressor contactor is ontop of the room so I didn't see it

[jimbo 10]

agree with bernard make sue the heater supply is on an normally open contact on contactor or aux heater should be of when comp running

[jimbo 10]

sorry normally closed