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Author Topic: mini-split use in bus  (Read 3720 times)
pvcces
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« Reply #15 on: July 07, 2008, 08:01:12 PM »

I just found an updated manual for the mini-splits that we bought. It answers some questions that were not dealt with in the original version. There is a note in the operation section that says:

Important: Heating opertion will cease at aproximately 15 degrees F outdoor temperature due to a sensor located in the outdoor unit. This product does not contain supplemental electric heat, there fore other means of heat need to be used when this system ceases operation at low outdoor ambients.

In the troubleshooting section, there is another reference to the problem under "Heat pump system ceases operation in heating mode". Under cause, it says "Check to see if outdoor temperature is below 15 degrees F. If so, operation will not resume until the outdoor temperature rises above 17 degrees F.

From the above, I think that it is pretty clear that when the temperature hits 15 degrees, the unit will shut down. We were already planning for backup heat. The main reason for not using it was just to keep the fuel cost down.

If anyone should want a copy of the PDF file, I am saving it and could post or email it. It's a much better manual.

Thanks for all your help.

Tom Caffrey
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Tom Caffrey PD4106-2576
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Ketchikan, Alaska
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« Reply #16 on: July 08, 2008, 12:00:01 AM »

Well I was waiting for someone to get on here and let you in on the secret of heat pumps in the heating mode.  It is actually pretty simple.  You need to keep the head pressure up.  And that is done by reducing air flow over the condenser which is the indoor coil.  When you raise the head pressure, what happens to the suction pressure?  If you answered it goes up too, you must be in this business and therefore are enlightened.  Many a heat pump has been able to operate at much lower temperatures when this simple trick is understood.  And yes you have to jump out the low ambient stat, but better to put a manual one on it and do some testing a low temps to see just how low you can go.  Bill T. 
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pvcces
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« Reply #17 on: July 08, 2008, 11:02:26 PM »

Thanks, Bill. I can see that I will have a little fun when it gets cold out next winter!

Tom Caffrey
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Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska
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