Air Source Heat Pumps

eugeneg

The ASHP is venting cold air through a hole in the wall and drawing ambient air in through the inside of the garage. The is no recirculating of air.

paceinternet

eugeneg wrote: »

I have a NIBE Fighter 2005 air source heat pump that the manual at
http://www.nibeonline.com/pdf/511517-5.pdf
says reqires up to 1750 cubic metres of air an hour. I have this in a single car garage and have drilled holes in the door to feed the required air. But have I drilled enough holes ?

How can I work out the area in square metres that is required to feed 1750 cubic metres an hour without the motor straining ?

1750 cubic meters an hour is 30 / min.
Your single garage must be about 28 - 30 cubic meters.
If so, you can see you need a full air change every minute.
The least you would need is the cross sectional area of the fan on the Nibe, and then it would be passing air at the same velocity as the Nibe fan.
I have often seen discussions about locating ASHP's, but it doesn't seem much temperature benefit can be gained by putting it in a building or loft because the air isn't around long enough to gain heat. Although, some gain may be better than no gain.
Some benefit may be worthwhile from a sheltered or indoor location to reduce noise or reduce freezing in snowy weather conditions.
But for most installations it is best outside.

arty68

I suppose the question is what is the reasoning behind putting it in the garage ?

eugeneg

There is no other suitable place. Even if there was, it is plumbed in now with pipes under 1 metre concrete, so it has to stay in the garage. I just need to know how much of an appeture to give to to allow minimum effort on the fan motor while not making a hole so large that security or weatherproofness are compromised.

richardc1983

Can you upload a photo we can then see if the airflow is correct.

You need to ensure fresh air is fed into the back of the unit and not just recirculated.

Even if you have hols in the door this is probably still going to recirculate a lot of the air from the garage.

Ideally they should be mounted in the outside air, 1750 cubic metres is a lot of air!

arty68

As pace has said , if you had a hole the same size as the fan you would have air coming in to the garage at the same velocity as coming out of the fan which is a bit of a draft. At a guess I would say you need the equilvent of 2 of these holes to be safe. Have you fitted a drain to take the condensation away ?

eugeneg

Yes, there is a drain. The input side of the ASHP in the garage is 80cm x 70cm and the output side is 53cm x 53cm. For ventillation I have a gap under the garage door of 3cm x 210cm and also I have drilled 101 holes of 3.5cm diameter.

richardc1983

A picture would help...

samtheman1k

Check the manual of your HP, it should tell you the minimum spacing required. Just ensure that all your tools don't get sucked out of your garage!!! If it's anything like an Ecodan, the air flow is huge!!!

stevehead

Hello thread-readers,
I now have a tally of all the KWh used by the 2 ASHP units I use to heat my house.
From 1st Dec 2008 to 31st Nov 2009 the combined total was 1407KWh.
Or about £140 per annum.

This has really skewed my ratios as my Gas bill is £240 per annum. This is for DHW & Cooking.
Of a total 12 month spend on heating of £380:
37% was on Space Heating
63% was on Hot Water and a bit of cooking



Parasitic Pilot Lights
My gas usage is pretty constant, and I feed iMeasure weekly with my meter readings giving me good access to the data.
I extinguished the pilot light in my GSH Boiler in June, and my gas usage plunged by 21% Yep, about a quid a week thats £50 a year.