Frost protection valve, detect air or water temp?

[DannyNotAPlumber]

Hi,

Short version:
Do frost protection valves trigger when the water in the pipe gets to threshold, or when the air temp drops?

Long version:
I'd rather use frost protection + anti-freeze cycle on my mitsubishi ecodan heat pump. The warranty is apparently fine with that combination, and it avoids efficiency-reducing (and wildly expensive) glycol. Will position the frost valves (altecnic) at the coldest place, on the connection between the exterior wall and the compressor unit, so they should be the first to experience low temps.

My worry is that if the valves dump the water when the air temp gets to at 3C, that will happen quite a few times each winter (south west uk). I don't mind topping up the system its more that I wont have heating when the air temp is low and thats exactly when I want heating.

If they trigger when the water temp is below 3C thats fine, as that shouldn't happen unless there is a powercut during very cold weather (and I wouldn't have heating then anyway). They wouldn't trigger just because the air temp is low because between the normal heating cycles and the frost protection running the pump when the water is below 6C (I called mitsubishi and warranty demands the trigger temp is no lower than 6C), the water wouldn't get below 3, so no problems.

Does anyone have one or know for sure how they work? Because frankly, if they go by air temp I think I'll go down the glycol route, cos I don't want the heating system disabled right when it gets cold!

Thanks!!!!

 

[ShaunCorbs]

Water temp valves and just for your information if you loose power the warranty will be void (and it freezes)

But the unit itself has built in frost protection via the outdoor sensor eg pump runs

 

[DannyNotAPlumber]

Water temp valves and just for your information if you loose power the warranty will be void (and it freezes)

But the unit itself has built in frost protection via the outdoor sensor eg pump runs

Really, that seems to go against an awful lot of what I've read, what altecnic say in their literature and youtube vids - I don't think they are just for information, they seem to be to stop water icing up and cracking components in the pump (not to mention pipework), and regarding the warranty: what mitsubishi say (I spoke to them). Just to summarize my understanding: the valves dump the water when the air (or the water - my original question) get below 3C, by dropping the water out of the system they avoid ice damage. Mitsubishi have reasured me that frost protection mode (at 6C minimum) + frost protection valves keeps the warranty intact.

 

[ShaunCorbs]

Really, that seems to go against an awful lot of what I've read, what altecnic say in their literature and youtube vids - I don't think they are just for information, they seem to be to stop water icing up and cracking components in the pump (not to mention pipework), and regarding the warranty: what mitsubishi say (I spoke to them). Just to summarize my understanding: the valves dump the water when the air (or the water - my original question) get below 3C, by dropping the water out of the system they avoid ice damage. Mitsubishi have reasured me that frost protection mode (at 6C minimum) + frost protection valves keeps the warranty intact.

But they don’t drain the system so can still freeze just take the pressure off etc hence why mit will say if you loose power and a frost happens and any damage won’t be cover by warranty as not a manufacturing issue ask them if frost damage occurs would they cover the cost of the damage

I would choose anti freeze valves over gycol any day as with ashp you need a cop of min 4 to be worth it and get the system designed for max 45dc rad flow temp ideally 40c