Selecting 30, 60, 90 defrost timer.
Is the recommended setting in the install manual or what?
I'm not understanding why there should be options since
the temp sensor doesn't have an option (and there is no
I'm not having any particular issues at work. I'm merely
reading up on heat pumps and I thought maybe an explanation
of the need for these various timer options would provide
insight into an icing problem were I to encounter one.
Thank you. (Expect another heat pump question in the
next few days. I'm still reading.)
Units located in shady areas will require more frequent defrost intervals. By setting the board timer from 90 to 60 it means that after defrost stat closes it won't have to run for an extended amount of time before a defrost.
I suppose it would depend on where you live. Units in Fl may only need 90 while units in the north need 30 min intervals.
I'm a 90 minute guy & I'm in humid SC. It doesn't get that cold normally but we have a lot of damp 30 & 40 degree weather here.
On a rare occasion I'll set one at 60 but its usually because the customer complains about frost some times & doesn't wait for it to defrost off. If you set them at 30 you'll probably have more complaints about cold air blowing before the strips kick in during defrost.
I think heat pumps should not have any sequencers on their heat strips so they can come on immediately to offset that initial blast of cold air during defrost.
The best things in life are free but not everyone is willing to pay the price.
+1. I don't see why they just don't use contactors. Sure they may be noiser, but it shouldn't be a problem for most installations. Contactors could use time delays so they don't all kick on at the same time.
Originally Posted by garyed
On my Own unit , I can set it 60 minutes during mild winters , but if it snows alot , or freezing rain , I will set to 30 min , otherwise it will frost up pretty good if I dont
So if you set it for 30 minutes in mild winters, couldn't we assume that the
thing wouldn't go into defrost often, and were it to go into defrost, it would
be brief? What would the downside be of setting it to 30 minutes in mild
if you have it set at 30 , it will defrost every 30 min ( as long as its cold enough )
Originally Posted by georgelass
How long it stays in defrost is determined by the sensor on the coil. When it senses the coil is clear it will turn off defrost.
It will only defrost if the defrost thermostat is closed.
Originally Posted by Snapperhead
90 minute setting should be used whenever possible to avoid unnecessary defrost cycles. You should only increase defrost frequency if you are experiencing problems with ice build up on the coil. After a while you should get a sense of what the optimal setting is for your area or for special circumstances like equipment located in cold damp environments.
"The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
"Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
To best answer this question, I think its better to understand the defrost cycle on heat pumps. In a timed-temperature defrost, both timed (defrost timer motor) and temperature (temperature sensor) conditions must be met in order to initiate defrost. All the temp sensor does is close when the outdoor coil has reached a temperature below freezing. In environments with erratic temperature swings, the coil temp could vary in and out of the sensors threshold. Defrost cycle on heat pumps is inefficient because it initiates cooling and tempers the supply air by energizing the auxiliary heat. This is why another condition must be met in order to ensure the defrost cycle is needed. The timer motor does a brief trial defrost every 30, 60, or 90 minutes. In colder areas of the country, your unit might require more frequent defrost cycles, thus the timed portion of defrost is adjustable to occur more often and visa versa in warmer parts of the country. Hope this helps
It depends on how humid your climate is. In dry climates, you will not need defrost very often. In humid climates, the moisture in the air condenses on the outdoor coil during heating mode. If the outdoor coil temperature is below 32 degrees, it turns to frost. In those humid climates, there is more moisture in the air, so defrost will be needed more often.
Remember, Air Conditioning begins with AIR.
I have always chosen 60, in central Indiana. And that's 60 RUN minutes.
I have always said that if you can get a heat pump to defrost, you won't get called back, even if its not running exactly perfect.
As iron sharpens iron so one man sharpens another Proverbs 27:17 NIV84
Here in central texas I use 90.