Air Source Heat Pumps

Stuwat

Hi

I am looking for some advice/opinions and help.

We are currently getting a new build home built for us. Initially we were told we would have oil heating. But the building control have came back to our building contractor and advised them we should go with a ASHP.
I have read a lot of information on ASHP's on this forum and others, some good and some not so good.
Our house will be well insulated - above the minimum requirements. We will also have underfloor heating which I believe will help if we install ASHP.
Our building contractor has told us the system fitted will be of the highest spec and we should have no issues.
What is the best ASHP system to be fitted?
Today it is minus 4 this morning. We live in the North East of Scotland. Does this affect the running of the system?
Do they take long to heat the home?
Apologies if I'm rambling or not coming across very well. I am totally confused with what we should do.
I work away for half of the year and I don't want to leave my wife and 2 young children to deal with heating and hot water problems.

Advice, pros/cons and a bit of help to allow me to gain some clarity would be very much appreciated.

Thanks

matelodave

We've got a Daikin ASHP which certainly works for us - it was around zero this morning and it coped when the weather has been down to -14. However that said, it is fitted with a back-up heater which can kick in when the outside temperature drops below what's called it's "equilibrium point". That's the point at which the unit hasn't got enough power to cope with the heating load.

The cut-over point can be adjusted (ours is -5 and in fact I've got it turned off) although it's a balance between having an overspec'd pump (which costs more) and using the back-up heater. A properly configured system should be spec'd for the optimum.

ASHP's are better suited to running most of the time at low temperatures (ours is around 30-35 which increases to 40+ when it's below zero) and so cannot easily be compared with a normal boiler which tend to kick on & off with much higher flow temperatures.

We let our house get very cold a few years ago - we went away for a fortnight in the bad winter of 2010 and it took nigh on two days to get the house temperature back up.

We have the room temperatures set to around 17 degrees 24 hours a day with an uplift to 20 in the rooms that we use when we use them (ie lounge, study - all day), bathroom & bedrooms for a couple of hours in the mornings and evenings and the kitchen at about 18. (we are at home all day)

Our hot water temperature is kept at 45 degrees with a sterilisation boost on Saturdays (for legionella).

It works for us because the system was properly designed and I understand how it all works and have therefore been able to tweak it to my satisfaction. We had a very knowledgeable installer who had several different systems configured in his premises which allowed me to compare systems.

We have a polypipe overlay underfloor system in a 1986 built 140m2 detached bungalow out in the very exposed fenlands of Cambridgeshire

Our place is moderately well insulated, none under the suspended wooden floor, cavity wall insulation of indeterminate quality, 16 year old double glazing an around 400mm in the loft.

If you want more info and some details of my costs and power consumption please PM me.

Swipe

In north east Scotland with the cold temps up there I'd be more inclined to go with oil. At least you'd get instant heat as and when required. Last thing you want is an iced up pump when you need it most.

matelodave

Swipe wrote: »

In north east Scotland with the cold temps up there I'd be more inclined to go with oil. At least you'd get instant heat as and when required. Last thing you want is an iced up pump when you need it most.

Ours defrosts it'self when it ices up but make sure that the unit is installed over somewhere the water can drain to - I made that mistake when we had the drive laid and the drain water can freeze over when it's icy making the area around the outside unit very slippery.

Owain_Moneysaver

Stuwat wrote: »

We are currently getting a new build home built for us. Initially we were told we would have oil heating. But the building control have came back to our building contractor and advised them we should go with a ASHP.

Provided you comply with Building Standards for thermal efficiency it's none of building control's business what heating you have.

Sounds like typical council interfering greenybollox to me.

If you're in a rural area you may be more likely to have electricity cuts in bad weather. Oil central heating can be powered from a car battery and inverter as the controls and pumps only take a few hundred watts. With ASHP you're reliant on mains electricity.

matelodave

Our dilemma was oil, LPG or ASHP as in the end the incremental cost of the ASHP was about £2.5k more than a full blown oil or LPG installation as we'd decided to go with the overlay heating system anyway.

We do benefit from the RHi (Renewable Heat Incentive) to the tune of £5k over seven years although that wasn't taken into account during our deliberations as the government were still procrastinating at the time and it was by no means certain that they were going to go ahaed with it..

We didn't want the hassle of getting fuel deliveries, nor did we want a big tank in the garden. I also fancied the idea of being a bit greener - but not to the extent of paying silly money.

It's been running now for five years and we've had one "major" powercut and it was off for about 10 hours due to an overhead line failure. You can only mitigate a power cut with batteries and inverters or even a generator of you've already got the kit ready for when it happens and the system wired so you can swap supplies over

Most people around us have either LPG or oil and we have squadrons of tankers up & down the road during the year with quite a few extra when the weather is a bit colder than anticipated.

We get away with between 6000 and 7000kwh a year in leccy (thats around £750 on our present tariff) and that covers all our heating, lighting, hot water, cooking washing etc. Whereas others are forking out significantly more than that on their oil or LPG.

I'm not saying that it's the ultimate but its worth considering if you are starting with a clean sheet from the ground up.

Stuwat

Thanks matelodave for your information.

I like the idea of being a bit greener and hopefully the costs would be lower as well!

I don't think I would qualify for government incentives as it is a new build.

We currently have storage heating and I'm sure anything would be an improvement!

I will see what our developer comes with on Monday i.e. Makes and set up etc.

Thanks again.

matelodave

I'd be inclined to have word with an independent heating engineer/company to see what they would suggest.

I actually sent a specification of my requirements to six companies, three didn't bother, one wanted several hundred up front and two replied with a reasonable quotation. I visited both (they were about 20 miles away) and I chose the one who felt as though he wa more knowledgeable.

I did do some homework first, so I had a rough idea of my heating requirements (heat losses etc) and the choice of the overlay system was mine rather than tearing up the whole floor. I had worked out that it should cope with the low flow temperatures (30-35 is a bit lower than the recommended 40-45 for the polypipe system) and since the system was installed I tweaked the flow temperatures down from the initial 40 degree setting.

The ultimate would have been to tear up the floor and insulate underneath it but the disruption in time, effort and especially the budget wouldn't allow it.

I don't know how much it would have saved in energy cost's but as we only use about £350-£400 a year to heat the place, spending £2k to save perhaps £50 or even £100 a year just didn't seem cost effective'

lovesgshp

Have a look at the IVT AirX. It may come under the Worcester Bosch brand. It is very close in performance terms to a GSHP unit and came out best in trials in northern countries in Denmark against every other manufacturer.
In Italy, we are installing a lot of these units and feedback is very positive.

[Deleted User]

Swipe wrote: »

In north east Scotland with the cold temps up there I'd be more inclined to go with oil. At least you'd get instant heat as and when required. Last thing you want is an iced up pump when you need it most.

Rural Scotland here


Never had an issue with icing.


Not sure why I'd want instant heat when the house is always warm with the ASHP at a lower cost than the alternatives...


Cheers

[Deleted User]

Owain_Moneysaver wrote: »

Provided you comply with Building Standards for thermal efficiency it's none of building control's business what heating you have.

Sounds like typical council interfering greenybollox to me.

If you're in a rural area you may be more likely to have electricity cuts in bad weather. Oil central heating can be powered from a car battery and inverter as the controls and pumps only take a few hundred watts. With ASHP you're reliant on mains electricity.

Just had the one long electricity outage too.


Couple of log burners here and some candles/torches so not really much of an issue.


Assuming all ok with wiring and a suitable connection point a decent Honda generator [and keeping it maintained] is very expensive on top of an already expensive oil/lpg system.


Cheers