UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

ar44898

Hi all,

I have been following this thread with great interest.

Me and my boyfriend have just bought a 3 bed semi detached house and are completely renovating it. We currently have storage heaters, but would like to put in a better heating system. We have loft insultation and will be externally insulating - no cavities and render needs redoing. The house is about 70m2 floor area. We would want hot water and space heating and will be using 7 high efficiency Ecovector radiators, similar efficency to under floor heating. We have two hot water sinks and 1 shower.

What power ASHP would we need? What else would we need - I have been looking at pressurised water cylinders (150ltrs).

Any help would be great and recommended makes/models. We have a fairly tight budget but would like to get it right and do not want to install an oil boiler if poss (not on mains gas).

Thanks,

Amy

thechippy

You'll get differing opinions on this, but if I was starting from scratch, as you....

I'd use an ashp for the space heating, but not the wet system with either the high efficiency or oversized rads, but normal dx air handling units.
They have the benefit of virtually instant heat input into the rooms and often incorporate electronic plasma air filters. Very cost effective to run!
For hot water, I'd just use an on demand high efficiency gas boiler. These can be had for around £350. They have simple plumbing, cold in, hot out and a gas supply. They don't even require an electric supply, as the water flow operates a tiny generator which will supply the ignitor. They are simple and reliable.

ar44898

we're not on mains gas so can't go with gas!

paceinternet

A wet system could be the right solution for you.
Ecovector radiators are similar to some other fan assisted brands, but also recognise that if you can fit the right size conventional radiator in, then for some rooms, it may be a better/quieter answer.
Using a heat pump at say 50 deg C water outlet temperature can be used to heat hot water in an indirect tank.
For a low budget solution, you can use a basic 140 litre indirect cylinder, although you have to run the system for longer due to the slower temperature transfer. You need to add a timed immersion heater to boost the temperature from 50 to 60 for an hour a day (or week) to prevent legionella type bacteria developing.
There are some other posts in the forum about users doing exactly this.
You can get a good, lower cost, wet ASHP solution if you understand the limitatons correctly, and provide ways of managing those situations.

rothers8080

Not been on the forum as much as I'd have liked this year (disaster cropped up early in 2009), but thought I'd give an update on our ASHP heating this this freezing few weeks.

As some of you will remember I live on the edge of the Pennines in County Durham, we have had snow on the ground now for almost 3 weeks, it's around 10 inches right now.

It's currently -7 outside.

It's 23 degrees inside.

We have 2 inverter ASHPs, a EcoAir and a Daikin + 2 more to fit.

They are working very very well in this cold weather, the Daikin is the more 'professional' unit, I especially like its night time mode - this is great in the bedroom, nice and silent but keeps us warm all night.

Running costs are tiny - less than gas. Both have a COP of 4.

We are going to insulate the house this week (it's an old place, full of holes!) and I hope that will lower the costs even more.

I do all the fitting myself, you just need a flair tool, vac pump, hose kit and diamond drill for the wall. Takes about 3 hours to do a good job.

All 4 units + fitting have cost us less than £1000. I bought 2 second hand for next to nothing - one had only 6 months use. I recommend places like builders reclamation yards for them - they tend to be in most office buildings - and office buildings get demolished all the time.

Last bit of advice would be to stick to inverter units - don't go with the older type, they don't work well in the home and are noisy and don't do a good job of keeping the temperature - although if you must B&Q do a 'though the wall' unit for £150 which is damned good value.

richardc1983

HI Craigix.

Are yours air to air systems, so in affect air con units? These are best at getting the heat into rooms and getting the temp up.

These are what I have and very happy with them. Its -2 here now and were coping well.

Do you leave the system operating 24/7 in this weather with nightset back temps?

Any chance of some pics? WOuld be good idea to post this post in here also as this is an ongoing topic...

http://forums.moneysavingexpert.com/showthread.html?t=702257&page=18

rothers8080

Yep air to air, love the instant heat.

I started the original (I think) thread on here about them in 2007 when I installed the first one, so I've had over a year with them now.

We leave the daikin one on in the bedroom at 16 degrees when we are not in there mainly because the timer system on it is complex, the ecoair one in the living room has an easier timer system so we turn that one off whenever we are out to come back on approx 15 mins before we come in.

I forgot we have a though-the-wall unit from B&Q in the back bedroom, they are cheap but loud and pretty awful at keeping an exact temp - plus they are forever defrosting. £150 is a good price and they are A rated but... hmmm only for a spare room and they only work if your wall is THIN! We tried one though the front of the house (3 bricks thick) and it didn't work at all. Oh and they take longer to fit than a normal unit.

I don't have on in the bathroom because I'm waiting to hear if it is a good idea to install one in there (and if it meets building regs).

We don't have gas here but as usual everyone else around here is suspicious of this technology and are sticking to their oil/storage heaters/electric heaters.

Such a shame for them, I could never go back to anything else, I'd have these over gas heating.

Ah, one thing I have been worried about in this -7 cold is the water pipe on the outdoor units freezing up and the unit overflowing. I've been keeping an eye on that.

I'll take some photos.

richardc1983

It wouldnt be wise to have one in your bathroom I dont think they do units small enough.


You would have to get a ducted one, eg one that could do the landling and the bathroom you wouldnt be able to have them in a bathroom as they are not protected I dont think. YOu might be able to get special units though.

The water pipe yes some people have mentioned same problems, guess nowt can be done though.

Im very impressed temps dropped to -5 here now, its freezing cold god knows what its gonna be tonight!!!!

Were still maintaining 22C in here though so im very happy with this!!!

What room temps do you maintain in your lounge? WHat temps is it outdoors now?

How about uploading some pics, some pics of our systems in the other ongoing thread.

bobmedley

Off on a bit of a tangent, but I noticed that in the heat pump threads people often mention the outdoor units, their noise, possible planning issues, lack of space etc.

You can get units where everything is indoors e.g

http://store.comfortableclimate.co.uk/product_details.php?category_id=23&item_id=33

This is purely a public service announcement - I don't know anything else about them & am not linked in anyway with selling them

richardc1983

Hi bodmedley.

The problem with the units that you have listed is that they are not that powerful and the compressor etc is in the same unit so you will hear the compressor noise.

They are also not energy efficient and have a fixed speed non inverter compressor.

They will also not perform below freezing for heating, most are rated down to about 10C heating, any less and they either do not work or wont run.