Furnace has a "defrost" cycle - how do I turn that damned thing off?

SamSpade

Well-Known Member
Some of you may be familiar with this - your heat pump may have a "defrost" cycle where for short periods of time - it actually runs in REVERSE and is intended to "defrost" the outer unit because it assumes the unit is frosted over or needs to be de-iced. So - it choose to pump COLD air into your house - during the winter, when you're trying to heat the home - and put heat OUT to "defrost" the blades.

This has been - necessary - maybe 1% of the time. It's doing it right NOW - when it's about 40 degrees outside and virtually zero chance of ice on the blades - because somewhere inside, it thinks it needs it.

WHAT do I do to turn the feature off? If it can't be - is there a way to outsmart it?
 

Ken King

A little rusty but not crusty
PREMO Member
That ain't blade defrost, it is coil defrost as the coil ices up while it is making your heat. Best way to defeat it is get rid of the heat pump and get a furnace.
 

limblips

Well-Known Member
PREMO Member
http://www.greenbuildingadvisor.com...-make-your-dumb-heat-pump-defrost-intelligent

Read this and then determine is it is worth the cost. Personally, I don't think so.

A couple of points to consider: 1. Most heap pumps will turn off the inside blower (air handler) when it goes in to defrost mode. If yours doesn't check owners manual or google your model and see if it is supposed to. 2. Even though the outside air temp is above freezing, frost can occur due to dew point issues. That is the reason manufacturers have the defrost set point above 32F.
 

black dog

Free America
Oil or gas heat will cure it, use the heatpump down to 40° and have it kick the oil or gas on when it's colder than that.
 

SamSpade

Well-Known Member
Oil or gas heat will cure it, use the heatpump down to 40° and have it kick the oil or gas on when it's colder than that.

Is there a temperature setting for this cycle? I can't seem to figure out where it is, let alone change the features.

What exasperates me most is, it kicks on at temperatures considerably higher than freezing, and I am thinking it's just doing it because it thinks it's been running too long.
 

black dog

Free America
Is there a temperature setting for this cycle? I can't seem to figure out where it is, let alone change the features.

What exasperates me most is, it kicks on at temperatures considerably higher than freezing, and I am thinking it's just doing it because it thinks it's been running too long.

I'm not a hvac guy, but I would guess that there is either a trim pot or dip switches on the board in the furnace to change the settings. My be with newer furnaces through the thermostat.. I'm not sure.
 

Ken King

A little rusty but not crusty
PREMO Member
Have you changed your filters lately? Low airflow can lead to indoor coil freezing. Water dripping on the outdoor unit can cause the outdoor coil to freeze.
 

PeoplesElbow

Well-Known Member
Your air conditioner can freeze up even if it is 90 degrees outside, it is the temperature of the coils, not the outside air temp that matters.
 
Your air conditioner can freeze up even if it is 90 degrees outside, it is the temperature of the coils, not the outside air temp that matters.

Most have a setting on the condensing unit 30/60/90 min Time / Temp defrost . The temp. coming out of the outdoor unit is 20-30 degrees colder {extracting the cold from home} it will defrost in this time frame 30/60/90 .I has to if not will be a block of ice and create mega problems's ..Can disconect defrost , wouldn't do it. In turn your back up heating element / or what ever you have for a "back up" heat oil/gas should keep house tempered while defrosting if blowing cold air , your indoor system is not doing what it's suppose to...have it checked..
 
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