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Grant Aerona: Is there a setting to keep the 2-port valve open during pump blockade

 
Air Source Heat Pumps (ASHPs)
Last Post by Unsure 46 minutes ago
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 Unsure
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Topic starter 24/11/2025 2:58 pm  

My setup is as follows: Aerona R32 6kw and Smart Controller with oversize rads (single zone) in a small two bed house with excellent insulation.

I use a WC curve of 0.7 and shift of 0 (despite Grant saying rads should have a curve between 1.2-1.6). Although I don’t achieve a reliable balance (the WC always requires tweaking), it will do for now.

The problem I have and am looking to resolve is the constant running of the in-built circulating pump. To date, I have pump blockade on, so that when the compressor stops, the pump stops 30 seconds afterwards. More importantly, during setback the pump is not running all night. This has worked fine for much of the year, but now winter temperatures are falling below 4 degrees the circulating pump goes into frost protection mode.

Pump blockade not only allows the circulation pump to pause, but it also shuts of the 2-port flow valve. So in defrost mode, the pump is pushing against the Bypass valve (ABV) causing the flow to drop to around 5-6 lpm.  If the outside temp sits at 4 degree or below all night, then the pump is under stress pushing water through the ABV during that time.

The Grant manual appears to hint that the pump and/or valve is affected when pump blockade is on. Does anyone know of a way to keep the 2-port valve open during pump blockade to allow the water to flow during frost protection mode?



   
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