Samsung ASHP Gen 6. Antifreeze cycle

[Ultima357]

Calling all owners of Samsung Gen6 ASHP (maybe others too). I have found on my system that when the exterior temperature drops to 2deg or below, if the pump is not working for heat/DHW, it enters a frost prevention programme where it runs the main circulation pump and operates the DHW valve. This means it is sucking heat out of your hot water tank to prevent the external unit getting the shivers. Quite why is the good question when mine and I suspect everyone's is filled with antifreeze protector. We've posed the query via our contractor to Samsung as the contractor is as puzzled as I am as to why it should do it. I discovered this by accident as I set the internal overnight temps back a degree or so at 22:00. One frosty night walking past the kit cupboard at 24:00ish I heard the circulation pump running and discovered this. On a fully cold night it takes around 8 to 10 degrees # out of the hot water tank (400l). I've now bypassed the DHW valve with a switch so it pulls it out of the buffer instead whilst we wait for Samsung to reply. Note the pump runs several times a night for around 5 mins a time. 

 

#We're passive insulated and EPC A, so room temps barely fall a degree overnight. 

 

It seems mad to me to have this put in the programme with no way to adjust it. If it could be set to only do when say the outside temperature falls towards the freeze point of your mix then fine, but otherwise this is just wasting heat. 

[ProDave]

I can't help directly buy my LG ASHP does a similar thing.  Annoyingly it is not a documented function and I can find no way to turn it off.

 

The LG one operates slightly different that it opens the heating valve and so sucks it's heat out of the heating loop, but as the UFH is no energised at the time it only has a relatively short length of pipe run to keep recirculating.  Nonetheless it does still suck some heat out of the house.

[dpmiller]

you can probably find a setting to change that cycle time?

[joth]

11 minutes ago, ProDave said:

I can't help directly buy my LG ASHP does a similar thing.  Annoyingly it is not a documented function and I can find no way to turn it off.

 

The LG one operates slightly different that it opens the heating valve and so sucks it's heat out of the heating loop, but as the UFH is no energised at the time it only has a relatively short length of pipe run to keep recirculating.  Nonetheless it does still suck some heat out of the house.

 

39 minutes ago, Ultima357 said:

Quite why is the good question when mine and I suspect everyone's is filled with antifreeze protector. We've posed the query via our contractor to Samsung as the contractor is as puzzled as I am as to why it should do it.

Maybe it's less about pipes freezing and more about the rest of the unit turning into a block of ice?

 

So thinking out loud

- It needs to stop itself freezing over completely otherwise it will not start again when the eventual call to heat arrives [or at least, take a long time to do so as it thaws out before being able to turn motors etc]

- stopping itself defrosting is always going to waste some energy (heating up a the great outdoors is the entropy end game). The question is how to do so the most efficiently

- if it can, pulling heat from the UFH circuit makes sense, as this is likely the biggest buffer of warmth it can draw from, and the lowest cost to replenish (low temp UFH => achieves the highest COP while charging it back up)

 

¯\_(ツ)_/¯