Non-Standard Heat Pump Packaging

doodling

Hi,

 I have a 3 story house in a conservation area.  Total heating demand around 20kW at ~-3C although that is falling as I insulate.

I was looking at various options and one of them was to install a multi-split air to air system for the top floor bedrooms which would give heating and cooling and then replace the existing conventional boiler with an air to water heat pump to heat the lower two floors.

In an ideal word, the compressor for the multi-split system would go in the loft with ducting to the outside (I have at least 5 chimneys accessible from the loft that could be used for that purpose with the benefit of no external visual impact).

Does anyone make (or repackage off the shelf) systems designed to allow the normally external part to be used in a ducted fashion like that?

I'm aware of the individual room systems with through wall ducts to the outside and obviously there are a host of (no doubt expensive) custom industrial solutions - is there anything in between?

Netexporter

There are MVHR systems that incorporate heating/cooling, that might fit the bill.

tacpot12

I think the general arrangement you describe could work quite well. I understand the need to provide cooling to the uppermost bedrooms. 

I don't know of anyone who sells or even approves a ducting arrangement for the compressor, although the techique is not uncommon on stand-alone heat pumps that are designed to heat domestic hot water.

If I had the job to do, I would build a custom plenum behind the compressor, and feed this with fresh air from as many chimmneys as are needed to support the air flow required. I would build a custom plenum in front of the compressor and duct this to the eaves. The ducting will need to be insulated, and sealed so that moist air cannot reach the surface of the ducting to prevent problems with condensation. 

You'll also have to condsider the maintainability of the 'outdoor' unit if it is in the loft. You'll also want to take special precautions to avoid noise and vibrations. (The units get noisier as the fan bearings wear).

You might have to take a chance on whether you will get a warranty if the outdoor unit is ducted. Your installer might be happy to make warranty claims on your behalf without mentioning the ducting, but if the manufacturer sends one of their engineers out, the game may be up unless the configuration is clearly stated as being supported in the user manual or advice from the Manufactturer's technical support (you need this advice in writing before placing an order with your installer). 

wrf12345

Can't you just heavily insulate the floor of the loft and then vent all the chimneys into the space so that effectively it is an outdoor area? The other alternative is wall mounted all-in-one air/heat pumps that cost £800-1000 each and require two largish holes in the wall but no refrigerant work so can be DIY, usually on eBay.

Reed_Richards

wrf12345 said:

Can't you just heavily insulate the floor of the loft and then vent all the chimneys into the space so that effectively it is an outdoor area? The other alternative is wall mounted all-in-one air/heat pumps that cost £800-1000 each and require two largish holes in the wall but no refrigerant work so can be DIY, usually on eBay.

If you put a heat pump in a partially enclosed space then the danger is that it cools the surrounding air to less than the outside air temperature; in effect you create a sort of fridge.  if that happens then the heat pump would lose efficiency.  So you would need to ensure you had sufficient air flow that it didn't happen.