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Old 05-07-16, 08:52 PM   #10
jeff5may
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I have been trying to integrate an efficient and effective defrost algorithm into my arduino uno controller all winter. None of the schemes I came up with did the job to my satisfaction. Either the unit went into defrost mode every so often (whether it needed it or not)faithfully, or the thing would not defrost until the outdoor coil was a block of ice. The factory add-on defrost modules work better.

As fate would have it, someone found a family of universal a/c control systems on the internet. I just had to have one. Thanks, Xringer.

Quick detour to this thread:

http://ecorenovator.org/forum/geothe...it-system.html

Before wiring shot:

During rigging gut shot:


Made by Qunda, the model I picked up is part of a family of 3 dozen models of controllers. It is on the expensive end of the line, yet it shipped to my door for under $50. The model I bought can be used with packaged or split units, and has separate relays to drive indoor and outdoor fans. It also has a relay for auxiliary heating.

I would have had the thing wired super easily in one afternoon, but the reversing valve output of the board is active in heating mode instead of cooling mode. Instead of re-plumbing my reversing valve, I modded the board, intercepting and inverting the control signal to the reversing valve relay with two resistors and one transistor.

Last edited by jeff5may; 05-08-16 at 12:04 AM..
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