We have a 3 year old heat pump. When the heat kicks on, it hums really loud. No rattling just hums The weather has turned really cold this week, & it sounds like its running hard, Normally we just hear it kick on & then its quiet.
The noise is coming from under the house (possibly the air handler) The unit outside sounds normal?
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Re: Heat pump is humming loud>
When the heat is not on. Go to the T-stat and turn the fan to the on position. With the blower now running is it making the noise? If so you probably either have something in there such as the filter that was mentioned, a piece of paper etc. or one or more of the blades on the blower wheel is vibrating. Don't let the condition persist w/o having it checked out or you may turn a simple fix into a costly one.
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Your question does not include what type of system you are asking about, but the assumption is that it is a heat pump. The loud humming is the compressor running by itself while the fan is off.
This is the typical way a reasonably new heat pump operates:
There is a coil temperature sensor that initiates a defrost period to eliminate the frost/ice build up on the outdoor coil. In the defrost mode, the outdoor fan shuts off and the reversing valve in the heat pump reverses the direction of refrigerant flow to warm the outdoor coil. The same coil temperature sensor senses the temperature of the external surface of the coil and tells the defrost control when the frost is gone initiating another 'reverse cycle' to put it back into heating mode. In the heating mode, the outdoor fan runs again.
If you have the heat pump installed where snow drifts accumulate, you will have a problem extracting heat from the outdoor air, and coil frosting and freezing will be exaggerated. If you have excessive ice build up due to a defosting issue, the ice can actually stop the fan from rotating, but you would hear loud bangind and rattling for hours first as the fan blades come in contact with the ice.
If you do not have drifts, but continually have an excessive amount of ice build up, either the sensor is possibly faulty or the defrost control board is faulty. The sensor's clip could easily have been knocked loose from the coil by ice and is no longer sensing coil temperature and if so the result would be the lack of defrost initiation.
This could be an inoperative condenser fan.System will kick off on high pressure without proper air flow.The hum indicates voltage is present. Providing the fan motor is not locked up and will spin,Check your run capacitor which helps boost the motor voltage initially and will get it turning.If the cap is good,you may be faced with motor replacement....good luck
yes the start capasitor starts the fan motor and the contactor pulls together when the t-stat tells it to start and it has a spring in it that gets week , some brands of units have a delay in the outside units board to stop it from starting at the exact same time as the airhandler
When it hums, is it running? Or does it not run when it hums? I'm assuming it runs when you say you have to turn the therm off to get the noise off.. If it's humming and not running, you have big problemo friend..
a very subtle hum or buzz is normal and is the transformer that creates 24 volt control voltage continually. some are noisier than others . sometimes a tap or bending of the transformer will tweak the metal enough to make it quieter. they can also get loud if incoming voltage is not correct. incoming 120 volts on a furnace is not usually a problem but the transformers are usually wired to the available incoming 230 voltage or 208 voltage if it is a heat pump or electric heat. If it is powered by 230 or 208 volts as most heat pumps are ,then you need to verify which you have and connect the appropriate leads from the trans former to power . it tells you on the side of the transformer which to connect to 230 and which to connect to 208. tape or cap off any unused leads.since you have not mentioned any performance problems i assume the fan does come on when called for and that it is not the loud hum you hear. switching the fan switch at stat to on should bring the fan on right away. if it doesn't then you may hear a loud hum and then youll need to check the fan motor and capacitor. but it sounds like a noisey transformer from here.