Air Source Heat Pumps

paceinternet

Post 626:
Salt based solutions are primarily for the plastic piped ground loop and ss heat exchangers of a GSHP which would be tolerant to salt.

A domestic heating circuit would not like salt, particularly radiators and pumps.

Maybe if you have a separate buffer tank circuit separating the heat pump and heating circuits you might use it.

Generally though, a normal rust inhibiting type of additive is all that is used in the water circuit of an ASHP.

richardc1983

I think its the water circuit that circulates the outdoor unit he is reffering to? Not sure if this is then passed to another heat circuit inside as it does the hot water also so perhaps there is a tank that uses separate water circuit to the heat pump.

Andy_WSM

Yes, the water in the heat pump water exchanger goes around a coil in a hot water tank and also around the radiators (in the same way a normal boiler circuit would), so salt is definitely out. Reading on the other forum that Richard linked to though, car Anti-Freeze is fine to use

richardc1983

Yep and relatively cheap!!!

Andy_WSM

Well, it's survived the first night of -3C temps, which I am sure would have given me problems in the loft again. Caught it on a defrost cycle just now, clouds of steam going up into the air - all that would have been going back into my loft wouldn't it?!?! The drain is blocked with ice already, but at least outside it doesn't matter!

House & hot water all at correct temperature and pump running at about 70% duty cycle I reckon. (i.e. on for 30 mins, off for 10 mins)

paceinternet

When it is on a defrost cycle, how much effect is there on your radiator temperature?
And if you are still routing the heating through the hot water tank coil first, does the water tank temperature go down?

Andy_WSM

paceinternet wrote: »

When it is on a defrost cycle, how much effect is there on your radiator temperature?
And if you are still routing the heating through the hot water tank coil first, does the water tank temperature go down?

It's not really noticeable to me at all as the radiators themselves regulate on & off to maintain the room temperature. The defrost cycle isn't long enough to drag the water tank temperature down far enough to notice either. I think the defrost cycle only lasts about 30 seconds or so!

greendwarf

Andy_WSM wrote: »

Due to a change in available helping hands, the heat pump move is happening today!

I have just disconnected all the pipework & cables and am awaiting my "lift" out of the loft onto the back wall. I should have it back up & running before it gets dark this afternoon!

I assume you're aware that this technically still needs planning permission?

Andy_WSM

greendwarf wrote: »

I assume you're aware that this technically still needs planning permission?

Yes, technically it does. But I have ZERO respect for stupid laws, of which this is one.

I have no immediate neighbours anyway, so out of sight, out of mind.

greendwarf

Lucky:beer: