GSHP frost stat requirement?

[Digmixfill]

I'm nowhere near needing to purchase my GSHP yet, but I am at the point where I need to decide where it will live. Ideally it will be in its own weather proof hut on the outside of the building.

Whilst mulling things over earlier I remembered something that was mentioned a while ago by a chap a Kensa. The chap said that the Evo could be housed externally but it would require a frost stat that would turn on the heat pump to prevent freezing if the outside temperature dropped below 5C.

 

Having looked inside an older Kensa GSHP I couldn't see anything that would require frost prevention. The control PCB was conformally coated and all of the liquids contained antifreeze.

Does anyone here have their heat pump housed  externally and do you have a frost stat for < 5C?

 

 

[ProDave]

The ground loop circuit will be full of brine so won't freeze, and the water circuit if filled with ordinary inhibitor / antifreeze won't be at risk either.

 

I have an ASHP and by it's very nature that is outside. The water circuit if filled with 25% standard central heating glycol based inhibitor / antifreeze that will give protection down to -10

 

My ASHP has an inbuilt function that if it detects the water circuit to be getting close to 0, it turns on the circulating pump (not the heat pump) for a few minutes to mix the water around a bit and get some less cold water from that part of the circuit in the house into the heat pump.

[Digmixfill]

The circulation pump agitating the water for a short time sounds sensible enough.

 

The Kensa information i received was

 

"The heat pump is extremely robust, what isnt, is the water within the machine on the heating side, if the heating is off because its the middle of the night and the temp drops below 5°C the frost stat will override the programmer an switch on the heating system to stop it freezing"

 

If that information came from a reseller or installer i'd just assume they were talking bobbins but the information was from Kensa themselves.

I did ask in a reply why that should be the case if all liquids had antifreeze but never got any further response.

 

[PeterW]

I think most of the equipment providers anticipate the worst and therefore assume you haven’t put antifreeze or other additives in the system. 

 

However there is that strange quirk of physics that shows that hot water freezes faster than cold ... So is circulating hot water a good thing to stop freezing ..?? Despite this I have to say I have actually included this in an ASHP control system to circulate when the pump has not run for 2 hours and the the outside temperature is below 1c, purely as a precautionary measure !

[Digmixfill]

The things that bother me about the Kensa information are a) 5C as a trigger point to activate the system seems awfully high, it would run the system on many days here. b) activating the the entire system seems wasteful if there is no call for heat.

 

@PeterW your choice of 1C activation temperature is much more sensible.