oranjeboom

ASHP with small buffer for UFH?

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So my installer asked whether I wanted to go with a small 100litre buffer for my UFH. As I think the house will have areas that will be colder (older bungalow areas) I fitted room stats in each room, so now reverting to a one zone approach would not enable us to control room temps individually.

 

Is there anything I should be aware of with having a buffer tank? The buffer vessel will have some heat loss, but will be within the heated envelope rather than attic, so not a big issue. 

 

Although I keep coming back to Mitsubishi, the installer is looking to get a CTC Eco Air unit (Swedish) so parts may be a bit more pricey with fewer experts around to service the latter I guess.

 

Any particular buffer tank I should be considering? I came across this unit (only 2yr warranty though) but was thinking that the 3kW element may be useful for limited heat if there's ever any issues with the ASHP. https://www.advanceappliances.co.uk/product/141-buffer-stores/

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3 minutes ago, ProDave said:

Is it this heat pump?  https://www.ctc-heating.com/products/air-to-water-heat-pumps/ctc-ecoair-400

 

No mention there of inverter drive.  That does not mean it does not have inverter drive but that is a question I would want a definite answer to before I bought one of those.

 

I should have mentioned model! It was the 510M which has an inverter: https://ctc-uk.com/wp-content/uploads/2017/08/CTC-Data-Sheet-EcoAir-510-520.pdf

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I have a buffer tank with mine (recommended on here by the heating welsh wizard!) and in winter the ASHP permenantly keeps it topped up to 40’ and when the roomstat calls for heat fir the UFH there is less time lag waiting fir the ASHP to get up to temp. It also stops any short cycling. The buffer also has an immersion as a back up in case of ASHP failure.

 

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3 hours ago, oranjeboom said:

So my installer asked whether I wanted to go with a small 100litre buffer for my UFH

 

Isn't' 100L fairly large for a buffer tank? My guy recommended 25L. 

 

2 hours ago, joe90 said:

The buffer also has an immersion as a back up in case of ASHP failure

Sounds a good idea, might do this even if it's not wired in initially.

 

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25 litre is tiny - not much more than a low loss header.

 

You can get 60-80 litre ones for about £150

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8 hours ago, joth said:

 

Isn't' 100L fairly large for a buffer tank? My guy recommended 25L. 

Depends on floor area I think.

 

IIRC I have around 170sqm for UFH.

 

11 hours ago, joe90 said:

I have a buffer tank with mine (recommended on here by the heating welsh wizard!) and in winter the ASHP permenantly keeps it topped up to 40’ and when the roomstat calls for heat fir the UFH there is less time lag waiting fir the ASHP to get up to temp. It also stops any short cycling. The buffer also has an immersion as a back up in case of ASHP failure.

 

 

Do you know what model you went for Joe?

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Our HP (Misubishi) doesn’t need a buffer tank but we went with one anyway as we wanted to be able to a) heat with an immersion if the HP had issues and b) divert some solar to it if the DHW tank was already warm

 

as Joe said ours works the same, stays at 40c then can supply water instantly when zones open. I think our HP would do that anyway without a larger buffer tho so it may slightly increase running costs due to the buffer tank losses. 

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1 hour ago, oranjeboom said:

Do you know what model you went for Joe?

 

Yes, Telford Tempest, PM @Nickfromwales for contact details and a possible discount fir buildhub members.

 

1 hour ago, Benjseb said:

so it may slightly increase running costs due to the buffer tank losses. 

 

Any losses from the tank only heats the house so for most of the year it’s not really a loss.

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