Exhaust Air Heat Pumps

[SimonG]

Here's a few questions for those in the know on these units. I've only had a brief look at these after reading a couple of other posts on here.

Just to reinforce what I think I know, the unit extracts warm air from house via ductwork and uses that heat to generate hot water.
What volumes of air do these units extract? and i take it make up air is from outside through vents?
So in winter you are sucking out warm air and replacing with cold, therefore needing extra heating within these rooms?
Do the units run continuously? i.e overnight.
If the units run through the day could you have ductwork into roof space, say on temperature controlled damper. Very warm in loft space when suns out, lost many a pint or two in sweat working in attics etc.
Whats the recovery rate like? What back up / top systems can you have, immersion, boiler?
What size ductwork is required?

Questions, Questions, Questions!

Whilst I'm on who has the best unit, and which would you fit?

Simon.

 

[Nat]

Yes the units pull in air from the 'wet' areas of your home ie kitchen and bathroom. You can use 125mm rectangular flat duct or equivalent round one. The unit needs to be set up to extract specific amounts of air from kitchen and bathroom using an air flow meter at commissioning stage. Can't remember exact rates but was something like 12 and 20 l/s. 100mm cores need drilling out in bedrooms and living room to fit vents to allow air to flow in, also, doors must be undercut do air can flow underneath when doors are shut.

Exhaust ductwork needs to be lagged as it is very cold and can cause condensation. Intake ductwork could be lagged if you wanted but probably alright to just lay loft insulation in top of it.

They have an immersion which boosts the heating and cold water when it is really cold. Heard they are expensive to run but should save you money on an equivalent gas setup over the course of the year (or this is what manufacturer told me).

Fairly straightforward to fit in new build but more tricky in existing house due to routing of ductwork. Quite large and heavy to move. 200kg!

Have only had experience fitting nibe.

 

[Nat]

Forgot to mention they run continuously. Fan buzzed away 24/7 365 but not too loud. Turning them on and off just makes them consume more energy. Another added bonus is that you don't need any ventilation as they do the job for you.

 

[mickie]

how can they extract any heat from outside through the winter when its -20 ? when you need it most ?

sorry to just jump in

 

[ecowarm]

These are great Home Heating Systems UK, Ireland - Earth Save Products Ltd

 

[SimonG]

how can they extract any heat from outside through the winter when its -20 ? when you need it most ?

sorry to just jump in

The more the merrier. They extract from inside the house, but thats one thing I was trying to get my head around. They are drawing warm air from within the building kitchen/bathroom yet make up air will have to come in from outside and lets say it is winter and its -5. With the cold air being drawn in your heating system will have to work harder to compensate?

 

[SimonG]

These are great Home Heating Systems UK, Ireland - Earth Save Products Ltd

Cheers Eco, I think it was one of your previous posts and the one today from unguided that got me thinking about these units.

 

[unguided1]

I have fitted loads of different types over the last few years, I do not rate the Nibe 360 fighter as the build quality is not very good and also there are some problems with them that if Nibe pay me I will be more than happy to explain to them where they went wrong with this unit.
When looking at this type of unit I would only look at an MCS accredited unit because you know that they are built and function to recognised standard, unfortunately the muppets in government have not yet worked out the benfits of these units so there are no plans to put them on the RHI