When all else fails, read the instructions? The basic setup is the same for most heat pump systems except for details like TXV vs piston/orifice. But the control electronics (typically on a defrost control board) can do anything, like totally shut down below some temp. Might be worth downloading and browsing the owners' manual (or might not; some are much worse than others).
-----Original Message----- From: Mercedes On Behalf Of Kaleb Striplin via Mercedes Sent: Monday, February 15, 2021 11:52 PM To: Kaleb Striplin via Mercedes <[email protected]> Cc: Kaleb Striplin <[email protected]> Subject: Re: [MBZ] Heat pump question Sounds like the unit just kicked back on. Guess we shall see how the night goes. Sent from my iPhone > On Feb 15, 2021, at 10:44 PM, Kaleb Striplin via Mercedes > <[email protected]> wrote: > > I will be damned if it isn’t shut off again. Can say for sure about last > time but this time code is for low pressure switch open, not the same low > pressure lockout as before. Don’t see any loose or damaged wires to any > pressure switches. Jumping the pins didn’t reset it either. Guess it will be > expensive aux heat tonight. > > Sent from my iPhone > >> On Feb 15, 2021, at 10:23 PM, Kaleb Striplin <[email protected]> wrote: >> >> Just noticed outside unit was shut off again. Coils had no frost on them at >> all but it was in low pressure lockout. Reset it and forced a defrost away >> way. It’s down to -4 at the moment. I wonder if it’s just too damn cold for >> it and pressure is dropping, or if it really is low on charge. If so, can >> these things even be charged in the winter? Or do they have to be done >> during the warmer months? Btw supposed to get down to -14 tonight. >> >> Sent from my iPhone >> >>>> On Feb 15, 2021, at 5:23 PM, Kaleb Striplin <[email protected]> wrote: >>> >>> Checked it a little while ago and the coils are clear. >>> >>>>> On 2/15/2021 3:22 PM, Kaleb Striplin wrote: >>>> It’s been running all day without issue. I can’t say I have noticed if >>>> it’s ran a defrost cycle or not. I think here shortly I will go out and >>>> look at the coils and see if they are clear or have started frosting up >>>> again. >>>> >>>> Sent from my iPhone >>>> >>>>>> On Feb 15, 2021, at 2:17 PM, Scott Ritchey via Mercedes >>>>>> <[email protected]> wrote: >>>>> >>>>> Probably, given the outside temps and state of charge, the gas pressure >>>>> going into the compressor gets too low if ice prevents the coils from >>>>> absorbing enough heat to raise the pressure (from that very cold air). >>>>> >>>>> -----Original Message----- >>>>> From: Mercedes On Behalf Of Kaleb Striplin via Mercedes >>>>> Sent: Monday, February 15, 2021 10:31 AM >>>>> To: [email protected] >>>>> Cc: Kaleb Striplin <[email protected]> >>>>> Subject: Re: [MBZ] Heat pump question >>>>> >>>>> Well I went out and checked it. When I looked at in there was no frost >>>>> on the coils that I could see in the center part. I pulled the cover and >>>>> sure enough it was blinking a low pressure lockout. With the side cover >>>>> off I could see some frost on the outside of the coils, not a whole lot >>>>> though. I shorted the test pins to reset it and it kicked back on. I >>>>> shorted them again to force a defrost. Defrost ran for about 5-10 >>>>> minutes and once frost was clear it kicked back into heat mode. >>>>> >>>>> Since replacing the defrost board with attached sensor last year, I have >>>>> not had a problem sense. Why the heck did it happen again? I know it >>>>> has a temp sensor for the coils. Do these work by going into a defrost >>>>> cycle on a timed basis if the temp sensor is below a certain temp? Or do >>>>> they sense the coils are freezing up and enter defrost when needed (not >>>>> on a timed scheduled). >>>>> >>>>> From what I recall, some old systems did not have a temp sensor and just >>>>> went into defrost every so often. I think some systems sense when it >>>>> needs to be done. Others I think are still timed but only do it when >>>>> temp is below a certain point. This is a 2008 Rheem running on 410 so I >>>>> am not sure. If mine runs on a timer only when temp gets low maybe it is >>>>> so cold that it simply did not reach its run time to defrost soon enough >>>>> before it started frosting up, or perhaps it is sucking in blowing snow >>>>> which caused it to frost up faster? >>>>> >>>>>> On 2/15/2021 9:03 AM, Kaleb Striplin via Mercedes wrote: >>>>>> It is now -3 outside, not sure how low it got last night. Anyway, >>>>>> heat pump has been running pretty much non stop for the last few >>>>>> days with the aux heat kicking on occasionally. Yesterday >>>>>> afternoon aux heat was on quite a bit as it never got over 4 >>>>>> yesterday. This morning when I woke up outside unit was running >>>>>> as normal. A little while later I happen to look out and it is >>>>>> shut down. Normally when it goes into defrost it will shut down for a >>>>>> moment then fire back up pretty quick. >>>>>> It did not appear to be in a defrost cycle. I had issues before >>>>>> where the temp sensor on the coils was evidentially bad because >>>>>> when it got below freezing it would seemingly randomly never >>>>>> enter defrost cycle and would frost over, which would then put it >>>>>> in a low pressure lockout. I would have to jump the pins on the >>>>>> board to reset it and force a defrost then it would be fine again >>>>>> for a while. Last year I replaced the defrost board which has the temp >>>>>> sensor hard wired on it. >>>>>> Never had a problem since. >>>>>> >>>>>> Anyway I was about to throw on a coat and go outside and pull the >>>>>> cover and see if the board was flashing an error code and it >>>>>> started back up. It is now about an hour later and I notice the >>>>>> outside unit is not running again. I am not sure how long it has >>>>>> not been running but I know its probably be at least 10-15 >>>>>> minutes. Is there some sort of reason at these low temps that >>>>>> the outside unit would shut itself down for a period of time then >>>>>> fire back up? Does the system determine that it is so cold >>>>>> outside that the outside unit is not producing any heat anyway >>>>>> and shuts itself down for a while? I will wait a little bit >>>>>> longer and see what happens then go out in the blowing snow to >>>>>> pull the cover and check the board to see if its blinking any codes. >>>>>> >>>>>> >>>>>> _______________________________________ >>>>>> http://www.okiebenz.com >>>>>> >>>>>> To search list archives http://www.okiebenz.com/archive/ >>>>>> >>>>>> To Unsubscribe or change delivery options go to: >>>>>> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com >>>>>> >>>>> _______________________________________ >>>>> http://www.okiebenz.com >>>>> >>>>> To search list archives http://www.okiebenz.com/archive/ >>>>> >>>>> To Unsubscribe or change delivery options go to: >>>>> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com >>>>> >>>>> >>>>> >>>>> _______________________________________ >>>>> http://www.okiebenz.com >>>>> >>>>> To search list archives http://www.okiebenz.com/archive/ >>>>> >>>>> To Unsubscribe or change delivery options go to: >>>>> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com >>>>> >>> >>> _______________________________________ >>> http://www.okiebenz.com >>> >>> To search list archives http://www.okiebenz.com/archive/ >>> >>> To Unsubscribe or change delivery options go to: >>> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com >>> _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
