AC compressor heater - can I disconnect this?

[Peabody]

I have central air, and the condenser unit outside is fairly old. While replacing the contactor last year, I noticed there is a compressor heater that's on all the time - it's connected to the mains side of the contactor. I doubt the heater uses all that much power, but I would like to save however much that is.

My understanding is that modern compressors don't use heaters, and I just wondered if it's generally considered acceptable to disconnect it on the old models. Actually, I'm not clear exactly what the heater accomplishes, but if there's no danger of shortening the remaining life of the compressor, I'd like to disconnect the heater.

What do you think?

[Steve B.]

Not a good idea to disconnect it. The system was designed for use with a heater. If you disconnect it you risk blowing out your compressor which would be a death sentence for an old system.

Steve B.

[Edwin Pawlowski]

I think the engineers that desinged the unit probably know more about it than you and I do. I'd leave it.

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[John Grabowski]

As I understand it the heater is there to warm the compressor so that the oil will be drawn to the moving parts. Therefore when the compressor starts it is already coated with some lubrication so that it is not starting dry. Removing the heat would stop the oil from coating the parts and it would not get lubricated until the compressor is operating. Based on that I guess it would shorten the life of your compressor if you disconnected the heater. Try it and let us know.

[Art Todesco]

[Telstra]

The refrigerant in the system migrates to and condenses in the coldest part, which at night time is the compressor. The Refrigerant is miscible and dilutes the oil which reduces its viscosity. In addition on start the refrigerant will boil out of the oil causing it to foam and enter the cylinders which as it's non-compresible will damage the valves. The oil will then be carried to the evaporator which will reduce it's capacity ETC The crankcase heater is only about 50W and is well worth the COST.

[Ralph Mowery]

Finally an answer that I agree with. The heater on some systems are cut off when the compressor is started to save the small ammount of enegery. It is most needed when the compressor is off and the crankcase is cold. .

[Stormin Mormon]

Heater helps displace the refrigerant "freon" to other parts of the system. Leaving the oil behind. It's splitting hairs, I know. But....

Anyhow, the result is the same. Lack of heater can result in early compressor failure.

To the original poster: There should be a big disconnect box, on the wall near the outdoor unit. It's OK to disconnect the power there, during the season you don't use the AC. Just remember to connect the power in the spring a day or two before you actually use the AC, to let the heater resume its job.

[ransley]

I would only turn it off in winter or let it warm for a few hours before the summers use.

[Peabody]

Thanks for the replies. I think it's unanimous.

I've been pulling the big fuse on the whole system during the winter, but reconnecting everything a day or two before switching to AC for the summer. I'll just keep doing it that way.

But based on what everyone says, it seems I was told wrong about modern compressors not having heaters. Is that right? It made sense because I thought they would figure out a way to save every last KW of power, and doing with out a heater would be one obvious possibility. But from the explanations, it seems a heater is really needed.

[M Q]

Some new ones have crankcase heaters and some don't. I think the bigger ones are more likely to. I had a 4 ton Carrier that had a 40 W always on (no thermostat) heater, and I have a 2 ton and a 3 ton Trane, neither of which have heaters. I hear that the 4 ton version of the Tranes that I have have heaters.

40 watts 24 hours/day adds up. I would shut off the breaker when I would not be using it.