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wsexton1 · 06-30-14, 08:47 AM

Hi AC hacker,

I have finally managed to read through the wealth of knowledge available on this thread, and I've got to mention how impressed I am.

So to the build...As per your advice I analysed the heating load on the building (new build, 2 years old) and discovered a max heating load of 5kW for the room to be heated. Luckily the underfloor heating circuit was installed recently in a 75mm thick insulated screed floor with 150mm spacing. Which I believe allows for a relatively low flow temp (40-50C).

Onto the borehole (actually 80m deep), which after speaking to a local expert informed me of an extractable heat of around 59W per m giving around 16000 Btu/hr.

Progressing to the heat pump. I have decided to start off on a smaller scale to get some practise and teething errors out the way first time around and see what sort of COP is possible before purchasing a bigger compressor. Potentially putting the second heat pump in series with the first to have the capability of having the system on 'half power' (which I hear may be more efficient anyway). Having purchased an old 14000 Btu/hr mini split unit and having discharged it, I'm now in the process of getting hold of some heat exchangers. This is my question for you at current. Why is it essential for the heat exchangers to be sweat fittings? Only because there are much cheaper threaded versions available here in England.

Additionally, I've estimated the water flow through the ground loop to need to be around 1.8m3/hr (7.9Gpm), for turbulent flow. Requiring around a 160W circulating pump. Is this similar to your loops pumps? Only I happen to have a central heating circulating pump banging around, and I'm more tempted to reuse that than go ahead and buy a great new pump!

Thanks again as always.

William

06-30-14, 08:47 AM	#1696
wsexton1 Lurking Renovator Join Date: Jun 2014 Location: England Posts: 2 Thanks: 0 Thanked 0 Times in 0 Posts	Hi AC hacker, I have finally managed to read through the wealth of knowledge available on this thread, and I've got to mention how impressed I am. So to the build...As per your advice I analysed the heating load on the building (new build, 2 years old) and discovered a max heating load of 5kW for the room to be heated. Luckily the underfloor heating circuit was installed recently in a 75mm thick insulated screed floor with 150mm spacing. Which I believe allows for a relatively low flow temp (40-50C). Onto the borehole (actually 80m deep), which after speaking to a local expert informed me of an extractable heat of around 59W per m giving around 16000 Btu/hr. Progressing to the heat pump. I have decided to start off on a smaller scale to get some practise and teething errors out the way first time around and see what sort of COP is possible before purchasing a bigger compressor. Potentially putting the second heat pump in series with the first to have the capability of having the system on 'half power' (which I hear may be more efficient anyway). Having purchased an old 14000 Btu/hr mini split unit and having discharged it, I'm now in the process of getting hold of some heat exchangers. This is my question for you at current. Why is it essential for the heat exchangers to be sweat fittings? Only because there are much cheaper threaded versions available here in England. Additionally, I've estimated the water flow through the ground loop to need to be around 1.8m3/hr (7.9Gpm), for turbulent flow. Requiring around a 160W circulating pump. Is this similar to your loops pumps? Only I happen to have a central heating circulating pump banging around, and I'm more tempted to reuse that than go ahead and buy a great new pump! Thanks again as always. William