Air Source Heat Pump

rangor gubbins

rangor gubbins

rangor gubbins

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Joined
5 Aug 2006
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1,080
Location
Kent, UK
About to start a house refurb including putting in underfloor heating throughout.
Our heating is currently provided by an old Worcester Bosch boiler running off an LPG tank sat in the drive. Its pretty expensive to run, the tank looks horrible, and is in a stupid location. So we are planning to get rid of the LPG tank and boiler and install an Air Source Heat Pump to supply our heating and hot water.
Anyone have any experience / advice with an ASHP?

We're also thinking about install photovoltaics on the roof to help offset the extra electricity usage, but as we are out all day at work I'm sure how much benefit the PVs will give because maximum heat demand will be when the sun is either not yet up or has gone to bed.
 
I don't know the numbers but you will get a kick back (feed in tarrif etc) even if you don't use what you generate. You also have options like the Tesla Powerwall which is a big battery you can use to store generated energy for use at night etc. Even Ikea have one. I guess they'll all start to come down in price eventually.

If you have any specific technical questions regarding ASHPs I can ask a colleague nicely if you get stuck, he used to run a renewables branch of our company which dealt with them (now no longer trading) but he's primarily a product designer who has amongst other things designed several renewable products. We have an ASHP in our office, it's pretty noisy due to all the fans even though it's in its own "renewable" room with all the PV kit too!
 
Air source heat pumps okay but aren't brilliant. Basically you use electricity to heat water to 35-40C and get approx 3 times the heat out as the electricity you put in. Any hotter and the efficiency rapidly falls, the low temperatures mean you can't use radiators (unless they are seriously massive). To be economic you really need an economy 7 electricity tariff. The heat pump is no use for hot water for taps / shower. Here the solar PV can help by dumping all its output into your hot water tank / thermal store during the day (instead of exporting for a pittance).
 
Thanks for the info.
I was hoping people would say they are using them to heat their home and hot water and it all works great and is cost effective.
I've looked into battery storage, but seems quite expensive at the moment. Powerwall and the cheaper Powervault.
We don't have enough accessible ground space for a ground source heat pump so would have to drill bore holes which hugely increases installation cost.
 
clv101 said:
Air source heat pumps okay but aren't brilliant. Basically you use electricity to heat water to 35-40C and get approx 3 times the heat out as the electricity you put in. Any hotter and the efficiency rapidly falls, the low temperatures mean you can't use radiators (unless they are seriously massive). To be economic you really need an economy 7 electricity tariff. The heat pump is no use for hot water for taps / shower. Here the solar PV can help by dumping all its output into your hot water tank / thermal store during the day (instead of exporting for a pittance).
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Conventionally sure. But do you have to build a conventional system.
There's no need for scolding hot water. For taps or showers and underfloor heating is ideal for low temp.
As long as you have enough water pressure from the tank why do you need anything hotter than ~40c,no idea if any systems are designed like this.

It may be worth the drive to go here
http://www.nsbrc.co.uk
It's very good with lots of companies to talk to on their showdays and get help etc and generaly find what's on the market.
 
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clv101 said:
Air source heat pumps okay but aren't brilliant. Basically you use electricity to heat water to 35-40C and get approx 3 times the heat out as the electricity you put in. Any hotter and the efficiency rapidly falls, the low temperatures mean you can't use radiators (unless they are seriously massive). To be economic you really need an economy 7 electricity tariff. The heat pump is no use for hot water for taps / shower. Here the solar PV can help by dumping all its output into your hot water tank / thermal store during the day (instead of exporting for a pittance).
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Not sure we're you got your info from but it's wrong. Ours heats the rads fine, granted it's not you regular boiler hot but it heats the house up fine, yes you need larger radiators than a normal system but massive is a complete over exaggeration. it's also fine for heating hot water which is perfectly fine for baths and showers as in you need cold otherwise you would burn yourself.
If you don't have gas like us it's by far the most cost effective way of heating your home/hot water.
Not to mention the incentive scheme... Money back I believe.
As pho said with the solar PV you get paid for the power you generate and for the power you push out to the grid, they call that deemed export and it's basically 50% of what you generate and the best thing is you get paid that even if you use all the electricity you generate
 
Glaucus said:
Conventionally sure. But do you have to build a conventional system.
There's no need for scolding hot water. For taps or showers and underfloor heating is ideal for low temp.
As long as you have enough water pressure from the tank why do you need anything hotter than ~40c,no idea if any systems are designed like this.

It may be worth the drive to go here
http://www.nsbrc.co.uk
It's very good with lots of companies to talk to on their showdays and get help etc and generaly find what's on the market.
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Ever heard of legionnaires disease ?

from what i understand and ive only ever helped fit one system, the heating system needs to be new with 22mm pipework throughout the house and turning down to 15mm for 3 rads and so on, all the radiators need to be massively over sized..

The cylinder gets heated to a certain temp which ive forgot and to top the heat up comes from an immersion heater to kill off the disease at 60c minimum, the solution which i have also forgot off the top of my head is like an anti freeze and works at lower temps.. I was just there a few years ago helping the guy out on the plumbing side.
 
My parents have solar panels and battery. I think the battery was about £3500 and consists of 2 rack mount batteries and an inverter tucked in a downstairs cupboard next to the meter. They have economy 7 and a smart meter. The battery charges off the panels during the day, and partially fills from the cheaper electricity during the night. There are some new tarrifs about now where you get free electric when the grid gas too much, you might be able to just use a battery with one of these tarrifs to get store up cheap/free electricity without getting panels.
 
When i moved to my last home the "affordable houses" all had air source heat pumps.
They make a horrible low pitch humming noise, especially in cold weather.
In the end the council did some noise measurements and boxed them in. This did not cure the issue and at night it was very annoying.
Council came back and re-took measurements. 5 months later they were all ripped out and replaced with high efficiency boilers.
I spoke to the owners on numerous occasions and running costs in winter were very poor.
 
Great info, thanks people!
As part of the house refurb we will be greatly improving the insulation in the roof, floor, windows and walls, so I'm hoping the running costs of the air source heat pump will not be too bad.

zooankski said:
When i moved to my last home the "affordable houses" all had air source heat pumps.
They make a horrible low pitch humming noise, especially in cold weather....
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Do you remember what make and model those heat pumps were?
 
We have a Mitsubishi eco dan ASHP setup to replace an aging oil system.

We changed our rads to double thickness ones and the house is nice and toasty, the only issue we were told about is you cant heat the house and heat water at the same time which I though would be a massive issue, but to be honest hasn’t really be an issue for us.

The system has been set to heat the water to 50c as it’s hot enough for baths and showers etc, although every 3 days it has a program kicks in to heat the tank to 60 for legionaries.

It does make a hum which I don’t really notice anymore, and it’s a lot cheaper than the oil system we had and don’t have to look at an oil tank in the garden.
 
I have a Worcester heat pump unit on a wall. Just the one unit for hot air. To be honest it heats most of the house on its own. It's cheaper than storage heaters. Slight hum from it when it's on, but it is mounted on an external wall of the house.

The only time it has struggled was during the -5 degree temps we've been having. It was still working, but much less efficient than normal.
 
Shoeyuk said:
We have a Mitsubishi eco dan ASHP setup to replace an aging oil system.

We changed our rads to double thickness ones and the house is nice and toasty, the only issue we were told about is you cant heat the house and heat water at the same time which I though would be a massive issue, but to be honest hasn’t really be an issue for us.

The system has been set to heat the water to 50c as it’s hot enough for baths and showers etc, although every 3 days it has a program kicks in to heat the tank to 60 for legionaries.

It does make a hum which I don’t really notice anymore, and it’s a lot cheaper than the oil system we had and don’t have to look at an oil tank in the garden.
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Same as mine lot cheaper than storage heaters
 
I install them and also have one myself. I've got a Mitsubishi Ecodan. If you're off gas, then it's pretty much perfect. Currently getting 10k back from the RHI scheme which has covered all my costs.

Poster above who has the legionella cycle set to every 3 days, that should be set to once a week. To 60c. That will improve your efficiency.

Happy to help with any questions.
 
Kimi said:
I install them and also have one myself. I've got a Mitsubishi Ecodan. If you're off gas, then it's pretty much perfect. Currently getting 10k back from the RHI scheme which has covered all my costs.

Poster above who has the legionella cycle set to every 3 days, that should be set to once a week. To 60c. That will improve your efficiency.

Happy to help with any questions.
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Awesome, thanks Kimi. the company we've contacted have recommended we install a Nibe - F2040 12kW + SMO20 + VST 05, with Nibe UKV40 buffer vessel and a Joule - Cyclone 250 litre Cylinder, and no hydrobox (whatever that is). We only have single phase electricity supply available and i understand this limits us slightly in what we can install.
How does Nibe compare with the Ecodan?
Do you think he 250 l cylinder is big enough for a 4 bedroom house? My partner is fond of long hot showers and she's a bit concerned that the ASHP will struggle to keep up.
Is there a cheap way of maximising the benefits of having an ASHP + photovoltaics? e.g. setting the heat pump to come on in the middle of the day?
 
Just some quick thoughts.
Single phase supply isnt a problem for 99% of domestic installs. We dont get many requests for Nibe so cant comment on their equipment really. If i was fitting one in my house again, after servicing and repairing most of the models out there i wouldn't change what i fitted. Ive got a Ecodan with the Mitsubishi pre plumbed cylinder. You dont need a buffer tank with those because of the low loss header, thats a big space saver for most houses. Mitsubishi are a good 5 years ahead of the rest of them imo

A 250L tank should be fine, but i would consider going for a 300L if you like the long showers or a couple of baths back to back. The price difference isnt much so for future proofing and even peace of mind a 300L tank would be worth considering.

With your solar panels you can do quite a few things, one house we done we had it so the solar panels would do the hot water, then the heat pump would kick in if wasnt getting current and the water temp was down. Id have to check the numbers but i think he heated the hot water for free all summer. Although the panels cost quite a bit:)

The most important thing and it really is vital. You need to make sure your heat loss survey is right. This will effect your radiator sizes or underfloor heating pipe spacing. The amount of houses we've been to and the heat pump has been either to big or to small is ridiculas. Also when they do your radiator sizes, see what flow temp they are going to set it at. The lower the better, i would assume you will be fitting new rads so it shouldnt be anything over 45.

Funny enough we are starting an installation next week for someone swapping out their LPG tank.
 
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