Central aircon with old ducting

danrv

Hi
Just wondering if anybody has fitted an ASHP to work with 1970’s steel ducting?
I’d like to replace my E10 electric warm air storage heater (10kw) and the ducting and vents are already in place.
A suggestion was to fit a ducted inverter like this:
https://www.daikin.co.nz/our-product-range/ducted-heat-pumps/inverter-ducted#:~:text=A%20Daikin%20ducted%20heat%20pump%20consists%20of%20an,positioned%20in%20a%20discreet%20location%20outside%20your%20home

The storage heater sits on a plenum and there’s about 3m of galvanised steel ducting that feeds six rooms. It’s not insulated but could be lagged.
Being an electric only property, I’m really limited to aircon or storage heaters.
A multi split A/C system might be a bit more efficient with selective room heating/cooling and no heat loss. With ducting in place though and discreet room vents, I’d like to look into adapting the current system.
Any help appreciated.
Unidare R10/73 storage heater:

Reed_Richards

Most people talking about an ASHP mean one that heats water rather than air.  But as the heated water temperature has to be much higher than the heated air temperature then air-to-air should be much more efficient and therefore economical that air-to-water.  If you have pre-existing ducts then I think it is a great idea.  I don't think insulation is necessary if the ducting is within the fabric of the building that needs to be heated although condensation might be a problem if operated in cooling mode.

A few people post here who use or plan to use an air-to-air heat pump for heating but I have not come across anyone here with pre-existing ducts - but you never know.  I myself have air-to-water.   

danrv

Thanks for the reply.
Just need an aircon company or installer with a bit of flexibility and experience in retrofits.
May be more popular in the US as they use ducted aircon a lot.

Cardew

danrv said:

Thanks for the reply.
Just need an aircon company or installer with a bit of flexibility and experience in retrofits.
May be more popular in the US as they use ducted aircon a lot.

Yes I had a ducted air to air heat pump/aircon in a property I owned in the USA.

The COP tends to higher than air to water, and they will be particularly efficient in the shoulder months(ie.April/May & Sep/Oct) however you don't get any RHI subsidy.

Bear in mind the larger units can be noisy

danrv

Thanks for the replies.
Didn’t realize how wide the indoor fan coil units are. A 10kw or 12kw capacity one would need to be installed on it’s end in the storage heater cupboard.
This website has quite a few options.
https://www.orionairsales.co.uk/mitsubishi-heavy-industries-air-conditioning-fdum100vh-ducted-ceiling-concealed-10kw34000btu-r32-a-15027-p.asp

danrv

Reed_Richards said:

If you have pre-existing ducts then I think it is a great idea.  

Thanks. With a high possibility though of it never materialising.
Waiting to hear back from Daikin but not holding out much hope.  I get plenty of ads for aircon installation and free site survey but they’re ductless systems.

Someone I know has had a 10kw ducted install done on a large garage conversion/studio. All from scratch with no retrofitting so optimized to all work together.
An outdoor unit with an indoor heat exchanger that is floor mounted and would fit in my storage heater cupboard.
There are numerous vent outlets in the ceilings but also return vents to counteract pressure.
Ducting material is American manufactured paper/foil type. 

What I need is a very low pressure feed of warm air through 3m of steel ducting to six single room vents. The fan in the Unidare warm air heater is only 5W I think.
I even considered somehow routing fan fed warm air from a modern storage heater but the largest size available is nowhere near the 10kw of the warm air heater.

danrv

Have had another Aircon company take a look. 
Again have said that the steel ducting won’t be suitable for any retrofit. The route though could be used.
Looking at a two zone ducted Aircon system with upper and lower distribution units feeding ceiling mounted vents.

Reed_Richards

I can't help thinking that UK houses will eventually be built with ducted warm air heating supplied by a heat pump as the most economic way of heating a building in our relatively mild climate.

coffeehound

Reed_Richards said:

I can't help thinking that UK houses will eventually be built with ducted warm air heating supplied by a heat pump as the most economic way of heating a building in our relatively mild climate.

It would work for flats as well since the evaporator can be wall-hung.   Something of a fly in the ointment with the current incentive situation, particularly in Scotland where there are more flats per capita.

Reed_Richards

Clearly there is a blind spot with regard to offering incentives for air-to-air heat pumps.  Or perhaps the powers that be are afraid that the potential to use these for cooling would mitigate against reducing energy usage.  

Swipe

Reed_Richards said:

Clearly there is a blind spot with regard to offering incentives for air-to-air heat pumps.  Or perhaps the powers that be are afraid that the potential to use these for cooling would mitigate against reducing energy usage.  

I've had two heat pumps for the last decade and can count the number of times on one hand when I've ever felt the need to use them in cooling mode. My bungalow rarely gets warmer than 23C in summer and in winter I'd kill for 23C so occasionally I'll just switch them on in fan only mode instead.