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Our toshiba ras13 skv a heat pump keeps going to pre def mode and not heating the house

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This happens when the outside temp is low, asthe outdoor unit blows cold when in heating (reverse) then the unit goes to pre def to avoid it freezing. You should hear a whoosh this is the heat being blasted to the outdoor unit to defrost it, then the heat has to build up again before the indoor unit fan runs up again and blows heat. Mine does the same every 20 mins or so (its -2 outside) brrrr

Posted on Jan 05, 2010


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1 Answer

What does the pre def mean?

It designates a state of pre-defrost. This is in reference to the cycle through which a heat pump goes through as outside temperature drops below inside temperature in order to prevent the unit freezing.

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I do not have a manual for my thermostat

You have a heat pump unit most of the time the unit will operate in normal mode heat setting on your thermostat but when the temp of house can't keep up the emergency heat will kick in. With that being said you can switch the t-stat to emergency mode and that will take the heat pump out of action and bring in the back up heat. You might have electrical heat strips or maybe a fuel such as natural gas or propane. hope that answers your question Ken

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Your oven sensor has gone bad and telling the control board/thermostat to keep heating. Find the model number on the range and go to a parts distributor like or and order you sensor. This is an easy repair.

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I have a Rheem Heat Pump unit. This winter, the outside unit fan at times trips off, but the inside unit keeps running continuously. I woke up one morning & it was 62 in the house. The inside unit ran...

Dear Friend!

Due to very low ambient temp, the fan will not run. Once the pressure build up, it's automatically run for some time and again cut off. But if you keep Heat mode and still tem not raised in your room means the reversable valve not working and hence the compressor and out side fan also will not work. Keep "Heat" mode and temp setting +29 to get better heat. Hope is it helpful?

Dec 10, 2010 | Heating & Cooling

1 Answer

My heat pump always go to pre def mode, im a first time user for heatpump. is that normal for heat pump and someone told me that its better to leave the unit on for days that to turn it on and off, for...

Heat Pumps, remove heat from the outdoors and transfer it, to the inside of the home, depending on the outdoor temp, this is a slow process, so the system is usually setup to use a back-up heat system. Sometimes it is a gas furnace, but usually it is electric heaters, anytime the system goes into defrost mode - which is basicly air conditioning. The control boards will shut off the fan on the unit outside, since it is trying to melt the frost of off the coil, we do not want anymore wind chill factors than we have to, now since we are basicly in the A/C mode, the air coming into the ductwork is cold, a backup heat source is turned on, to temper or warm the air a little bit, for comfort factors and so we do not lower the house temp. During this time it is not unusual to see stream, and water dripping of off the unit outside. All of this is normal and is all done by the system, without any input from the homeowner. The amount of steam and water dripping from the outdoor unit is related to the humidity levels outdoors.
Now,,, Most systems are set up to turn on the back up heat-"the electric elements usually", when there is a 2 degree drop in room temp, so either the heat pump can not keep the home warm by itself and needs help, or if you turn the heat up over 2 degrees, it says, either the heat pump can not keep up by itself or that the owner turned up the heat,,, the result is the same, the system will give you everything that it has, heat pump and backup heat.
So it is best to set the temp on the thermostat where you want it and then just leave it,, the only reason to turn it down is for your comfort, can't sleep in a warm house, ect,, but you do this for your comfort only and not for saving money. All heat pumps have a COP rating, basicly telling you, how much cheaper the heat pump costs to run via straight electric heat. Example: With a COP of 3, for every $ 1.00 of electricity that you spend the heat pump will give you $ 3.00 worth of heat.

One other thing to consider when heating or cooling a building, is the heat loss or heat gain of the structure. Heat is attracted to cold and the greater the temp difference is, the faster the heat transfer.
What does this mean to you? If it is 40 degrees outdoors and you set the heat to 70 degrees in the home, the higher that you turn up the heat, the faster the heat transfer is to the outdoors, meaning that you lose heat faster. An expample is; like in a hospital, they give you an I.V. drip, they put the needle in your arm and hang the bag on a stand, and let it drip into your arm, the higher the bag is, the faster it drips.
Now I'm rambling; this is a very involved subject:
Basic rules: Find a setting that you can live with and leave it.

If this has been helpful, please rate me and contact me back if I can help you with anymore questions.

Paul Gibson

May 04, 2010 | Heating & Cooling

1 Answer

Setting Amana Heat Pump Thermostat.

The 2H/1C is one stage cooling two heating. Is it s touch screen or not. I mean no buttons. If not go to mode setting. Push mode till you get to heat not emerency heat abd then set temp. Keep in touch. Rus

Nov 19, 2009 | Amana PTH123B25AJ Heat Pump Air...

5 Answers

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!

Oct 16, 2009 | Ruud Central System Air Conditioner

1 Answer

My heater will not work

the remote is the "brains to the heat pump/air con, low battery power or spent batteries will effect the cycle between indoor unit and outdoor unit, replace the batteries and turn off curcuit breaker at main switch board for a couple of minutes and turn back on. Try restarting unit.

Jun 05, 2009 | Heating & Cooling

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