Question about Sanyo STW0923H2 Thru-Wall/Window Air Conditioner

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Electric Heater Coils Always On

I have a Sanyo through the wall heat pump unit. When I plug it in the heater coils start heating even with the dial in the off position. No matter where I turn the dial; heat,fan, or cool the heater coils stay on. The compressor seems to be working fine and the reverse switch seems to be working but with the electric heating coils on all the time of course all I get is heat. This is also very dangerous because as I said the coils stay on even with the fan off causing the unit to overheat and start smoking. Any help is sincerely appreciated.

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Re: Electric Heater Coils Always On

We use the STW0925H! in 60 rooms on this property and have encountered similar problems that were caused by weldedd contacts on one of two relays that controls the electric strip heat. They can be replaced if needed.

PTHP's and PTACs employ thermal fuses as well as a bimetal limit stat on the heating element to limit risk if fan motor were to fail and the heating element were to remain energized. It would be wise to check that both are fuctioning properly while you are servicing the unit.

Posted on Mar 07, 2008

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Re: Electric Heater Coils Always On

I suggest that the thermostat or the switch is at fault, contacts may be stuck. hope this helps

Posted on Mar 04, 2007

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What's the difference between EM HEAT and AUX HEAT?

Sorry, neither of these answers are completely correct.
You have a heat pump (or the wrong thermostat). Let's assume you have a heat pump.

In air conditioning mode, it works like every air conditioner you have ever had, but...

In heat mode, it reverses its operation. Have you ever felt the air coming out of the outdoor unit of your A/C unit? It's hot, isn't it. And the air coming out of the indoor unit (out of the registers) is cold. Now for a heat pump to produce heat it simply runs the air conditioner in reverse and the heat comes out in the house and the cold is released outside. Neat, huh!

Here's the problem with heat pumps...when it is really cold outside the heat pump can't produce enough heat to heat your home. So it has an additional heat source called "Auxiliary Heat". This heat comes on automatically when the house doesn't get warm enough. The source of this heat is based on the region of the country you are in. North/Northeast generally have oil heat, other regions have gas, and still others have to use electricity to heat. In Texas, we usually use electricity as the supplementary heat on heat pumps. VERY EXPENSIVE!

Now the "Emergency Heat"...this is exactly as stated in Solution #2. This is manually turned on by YOU at the thermostat when your heat pump fails. This turns on the auxilliary heaters and turns off the heat pump (remember, the reverse air conditioner). Again, this can be quite expensive to run if your heat source uses electricity! Gas and oil may be cheaper. The emergency heat is only designed (normally) to keep the house livable (not comfortable) until the Heating Tech can get out to you and fix your heat pump.

Something else you should know. It is normal for a heat pump's outdoor coil to frost up during heating mode. It will detect this and go into DEFROST mode and melt the frost off the coil. While it is doing this, it will turn on the auxilliary heater to keep the air blowing in the house at a reasonable "warm" temperature, but it will not be as hot as normal. In fact, heat pumps produce a lower temperature heat than traditional heaters. So the air may feel cooler during heating than you are use to anyway. This is normal and is not a sign of a problem.

So what do you do: Set your thermostat to the temperature you want and set the controls for HEAT/COOL and FAN-AUTO/ON and leave the EMERG HEAT off unless your heat pump breaks.

As always, keep your filters clean and your outdoor unit's coils clean and free of debris.

Hope this explains your question for you!

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