ASHP - suitable with microbore ?

[burningoil]

Hello, We are looking at poss. upgrading our heating system in the next year or so. We have microbore pipework. We have been given a couple of quotes for a 16KW air source heat pump. I was a bit unsure that this would work ok with microbore, both companies quoting said it would be ok - they would install another pump to keep the water flowing. Does anyone have any experince of ashp's? It is a lot of money if we go ahead - maybe we should stick with oil and go for a condensing / unvented cylinder (we have a combi currently). Thanks

 

[wiffola]

Hello, We are looking at poss. upgrading our heating system in the next year or so. We have microbore pipework. We have been given a couple of quotes for a 16KW air source heat pump. I was a bit unsure that this would work ok with microbore, both companies quoting said it would be ok - they would install another pump to keep the water flowing. Does anyone have any experince of ashp's? It is a lot of money if we go ahead - maybe we should stick with oil and go for a condensing / unvented cylinder (we have a combi currently). Thanks

Hi Burningoil,

Did you get anywhere with finding out more with microbore and an ASHP?

Ddi you get an ASHP?

We are looking to get one (Dan Foss AQ) and are in the same boat with the pipework - Microbore 8mm and 10mm everywhere with 7 rads.

 

[Agile]

I dont see why microbore should give any ( additional ) problems if used with an ASHP heating source.


More important is ensuring the performance is going to be adequate when its very cold outside. Most fall below 0 C and its the output when its - 10 C which is the most critical.

However, whilst properly fitted 10mm pipe is usually OK, 8mm is so easily blocked!

Tony

 

[wiffola]

I dont see why microbore should give any ( additional ) problems if used with an ASHP heating source.


More important is ensuring the performance is going to be adequate when its very cold outside. Most fall below 0 C and its the output when its - 10 C which is the most critical.

However, whilst properly fitted 10mm pipe is usually OK, 8mm is so easily blocked!

Tony

Thanks Tony. A few people have mentioned that 8-10mm just cant get the flow rate required.

The installer said suck it and see....see how the ASHP performs, if it's not getting the house warm we might need to replace it for 15mm.

What do you think?

 

[Agile]

Two problems arise.

Firstly many microbore was installed as a budget system and many so long ago that lower target temperatures were planned.

Secondly, most microbore was designed for conventional boilers with a flow/return differential of 11 C and a flow temp of 82 C. That should be adequate differential for ASHP.

BUT.... most ASHPs cannot achieve more than about 50-60C and thats not going to give out much heat from a rad sized for an 82 C flow temp. It gets worse because as outside temps fall the maximum flow temp falls too which is just when you need the most heat !

Thats why ASHPs are far better suited to under floor heating where a flow temp of 30 C is usually adequate.

Tony Glazier

 

[dcawkwell]

Not difficult.
I could install a 12kw air source for under £2k all in.

Beware an air source heat pump performance drops as temperatures
drop. A 12kw unit will only be producing 6-7kw near freezing.

So you would probably need another booster source of heat in
very cold periods.

 

[DeltaT2]

The COP of all ASHPs plumit along with the temperatures. Regarding the microbore pipes, the flow rates can be an issue if the system is manky and the radiator sizes are never very big on microbore systems, cause the heat carrying capacity of 8 or 10mm is limited.

If you circulate directly from a ASHP to rads via 8-10mm F&Rs, then yes this can be a problem. However, if you use a 'buffer' tank then there's no issue.

I bet there's plenty regretting spending £12K on a ASHP system & looking down the throat of another <14C Winter............