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Anyone managed to get an indoor air-to-water heat pump in their loft?


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Does anyone install indoor Air Source Heat Pumps (to heat central heating water & hot water tank) indoors?

Most of the units I can find are external and I've nowhere to put one - mostly because I've no back garden and they tend not to be pretty and as I'm in a quiet rural kind of terrace, any perceptible noise at a couple of meters wouldn't be tolerated. Putting one in the loft with the hot water tank etc, would solve the visual issues and would surely allow for sound proofing. Obviously I'd need to duct the incoming and outgoing air with large diameter pipes. We can't get gas and I don't want another oil boiler, I think bore hole ground source is likely to be too expensive.

Googling for "Indoor air-to-water heat pumps" and "Internal Air Source Heat Pump" I can only find a discontinued commercial unit requiring 3 phase and a German system that seems not to be sold anywhere.

Does no-one sell proper built in heat pumps?
Is the issue that people tend to either have gas or enough space to hide an external unit?
Another forum expressed the concern that if the ducts were smaller than the external unit's fans then you'd need a higher air speed which might be noisier but I've seen things suggesting a centrifugal fan can be quieter than an axial (proppeter type) fan, and don't mind big ducts.
There was also concern about the loft getting hot - but ours is an aircraft hangar sized loft and could easily be vented.

Edited by HampshireHedgehog
added info about why ashp
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Welcome.

 

The volume of air that needs to flow through a heat pump in order to be able to extract enough heat for heating a house and providing hot water is large, so trying to duct air for even a fairly small unit, like ours, would mean using ducts around 600mm to 800mm in diameter, which probably isn't practical.    Trying to use smaller ducts with a higher flow rate is going to significantly increase the flow noise, and would probably result in so much noise at the external terminals as to cause a noise nuisance (the flow rates are going to be similar to those from a commercial kitchen extractor).

 

There are hot water only heat pumps that use smaller ducts, typically around 150mm to 160mm in diameter, but they are only really powerful enough to heat a modest sized hot water cylinder over a period of a few hours.

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Thanks - I guess a duct bigger than a dustbin might raise some eyebrows and fail to get aesthetic approval from the other freeholders - I could hide it on one side of the roof but to separate them you'd probably want one vent each side.

Sounds like oil is my option then until a GSHP gets less expensive.

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29 minutes ago, HampshireHedgehog said:

Thanks - I guess a duct bigger than a dustbin might raise some eyebrows and fail to get aesthetic approval from the other freeholders - I could hide it on one side of the roof but to separate them you'd probably want one vent each side.

Sounds like oil is my option then until a GSHP gets less expensive.

 

 

Depends very much on how much heating you need, as that determines the air flow rate needed.  A low power unit, like the one linked to above, will work OK for hot water, and only needs ducts that are around 150mm to 160mm in diameter, but even that flows a LOT of air in order to just heat a hot water over a period of a few hours.  Heating a very low energy house with an exhaust air heat pump works OK, but it needs careful design in order to ensure that it can work well with the required heat recovery ventilation system. 

 

There are units made by companies like Genvex that integrate heat recovery ventilation with a hot water cylinder and warm air heating that can work well, but only for a house that has a pretty low heating requirement.  We have a Genvex heat recovery ventilation system that can heat the house with its integral air to air heat pump, but its maximum heat output is about 1.5 kW.  That would be fine for our passive house, but it would be maybe a tenth of the heat that our old 3 bedroom bungalow would have needed.

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We're in a electric only village and looked at ground & air source and due to our age we've decided against both.
But, as for hot water, It would really depends on how you use your hot water. We have an electric shower so the only hot water we need it for hand washing & washing up. We're going to try a cheap 5l water heater. £80 and will cost about 10-20p a day to run.

As for heating? again it depends on you really - some people need the whole house hot, we don't heat the bedrooms never have. But, yes that's still in the air but for now we are not installing radiators. We are going to have a 2k German electric rad in the dining/kitchen and a multi-fuel stove in the living room I think - may include the option to run rads off that, not worked the cost out yet.

 

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We have a Genvex Combi 185LS compact unit which provides MVHR, warm air heating and DHW using an EASHP. IIRC it weighs 210kg before plumbed in and over 400kg when full. It requires a base suitable to support 500kg/m2, not really suitable for a loft installation. Nilan are another company offering similar products.

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In the course of investigating my own requirement for cooling -

- I did come across the Unico Boiler that can do something similar on a small scale, if the heat pump version is chosen.

 

It's a through-the-wall 2.5 kW unit (requiring a pair of 160 or 200mm holes), not very pretty, that can either chill or heat the air, as well as heating a 50L hot water tank (which takes priority over the air treating). I get the impression that it's more targeted at the southern European market and haven't followed it up any further yet, though I may. However at 2,700€ it's not cheap, but maybe there are better deals around. The manual is available to download from here.

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Sadly this will never be a very low energy house, so the linked options are interesting examples of what can be done but wouldn't work for me.
Since the oil boiler died, we're currently "heating" it by moving 2 x 2KW fan heaters and a 1.5KW electric radiator about and it takes a few hours in the morning for them to raise the temperature to tolerable.
There's plenty of insulation work that can be done: secondary glazing, loft insulation (currently just plaster and lath ceilings with a fully boarded loft above) but there's a limit to what's practical in a Victorian house.
(~10mx10m footprint - ground floor 4m ceilings - upstairs 3.5 m high, South aspect has single glazed sash windows, North is sheltered and double glazed, neighbours houses attached to east and west. At least the walls are thick and we've thick curtains)

Edited by HampshireHedgehog
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I know this isn't what you asked, but gas/oil boilers will eventually be banned and ASHPs will become the normal way to heat a house and people will have to get used to the look and sound of them.

 

Is the issue that you don't think the neighbours will like the noise or that you don't like the look of the ASHP. When you say you have no back garden, you would only need the width of a walkway behind your house which I assume you have as you say that there are houses on each side, but I could be wrong.

 

12 hours ago, HampshireHedgehog said:

any perceptible noise at a couple of meters wouldn't be tolerated

 

ASHPs are permitted development and neighbours cannot stop you putting one in if you meet the criteria. The quietest pumps are only 45dB at one metre which really shouldn't disturb anyone.

 

https://www.planningportal.co.uk/info/200130/common_projects/27/heat_pumps/2

 

However, you mentioned needing aesthetic approval from the other freeholders. Is there some kind of joint freehold where you need approval to do things? You can get slatted wooden covers which hide an ASHP, I do not know how they affect the efficiency.

 

Also I would get that loft insulated as soon as possible. You are going to be losing a crazy amount of heat from there. An ASHP would not be a good idea until the insulation is sorted out. You would probably need new larger radiators also. It might be worth trying to figure out how many kW of heat you were using with your old oil boiler as it sounds like 5.5kW struggles to heat only part of the house at the moment.

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