Not Happy with Air Source Heating

[kevobain]

Hi there. I'm new to the forums and was looking for a little bit of advice.

In August 2011 I moved in to my new-build, ICF house. When I was deciding what I wanted my house to be like during the design phase I decided that I wanted it to be very well insulated, warm and energy efficient. Unfortunately, I only seem to have achieved one of those three goals and I feel a bit cheated to be honest.

My house has excellent insulation due to the ICF construction. It feels solid, quiet and at the right temperature is a very pleasant place to be indeed. That part of the build was incredibly successful.

The problems come with the heating system which was recommended to me. I have an air source heat pump (ASHP) which 'warms' the water for my underfloor heating downstairs and my radiators upstairs. It also 'warms' my hot water with an immersion taking it the rest of the way up. Last winter, I have to admit that we never really knew how to work the system as it was never fully explained to us and there were a few teething problems going on at the time. This winter, I'm just finding it to be really inefficient at heating my house. It also seems to be crazy expensive on electricity. I have an Economy 10 energy tariff which gives me 3 cheap periods per day. I make sure my heating only comes on during those periods. I'm worried it's not enough though. My thermostats for my underfloor heating are set to 21 degrees but are only achieving 18 at the moment. I don't want to put the heating on during the standard rate periods as my electricity would be even more expensive than it is now. I'm already paying a direct debit of £150/month which isn't even covering my bills. Looking at it over the last year and a half I think it's going to average out more like £200/month which is just insane for a new, well insulated house surely?

Anyway, I was looking for some advice. Am I being unrealistic in my expectations of the system? Should I be on a different electricity tariff? I would also quite like to know how easy it would be to take the system out and replace it with an oil based system? Would it just slot straight in to the water system I already have for the ASHP?

Also, it'd be nice to hear from anyone who has similar or different experiences with ASHPs.

Cheers,

Kev

 

[Dan Robinson]

The user here called Eaton is the one to ask. Hopefully he will see this post and respond.

He or I can send you a spreadsheet that can be used to work out the best ASHP loading for your house (my details are in my profile).

One thing to double check though, are you being penalised for being on an Island in respect of your Unit price for energy?

Can you post more details about your house?


There have been similar complaints here in civilisation where the doughnut developers have specified the wrong equipment.

Radio 4 even tried to be clever hand crucify an ASHP, despite the fact that it was patently obvious from R4;s own report that was was purchased was totally the wiring product.

shameful thing is I doubt most of the listeners would have understood the argument put forward. Hey ho. the joys of living in the UK I suppose.

 

[kevobain]

Thanks for the reply Dan. I'll keep a look out for Eaton on the boards then. Like I said, I'm just new here so I'm still having a good look around.

Can't say if I'm being penalised or not for living in Orkney. My energy prices from my last bill in November (probably had at least two price rises since then!!!!) were 10.02p off peak, 17.3p standard and a daily standing charge of 14.09p.

My house is a 186 square metre, 1.75 storey, ICF constructed house. The ICF blocks used had a 60mm inner and outer polystyrene skin and the cavity was filled with 150mm of reinforced concrete. On the outside of the house we fitted a further 60mm of polystyrene sheeting to further improve the insulation and rendered all with an acrylic render. The windows and doors are all energy rated, double glazed uPVC. There are 4 bedrooms and an internal garage. The ASHP fitted is a Grant Aerona model but I can't remember the output and I'm offshore right now so can't check. Going by their brochure though it's definitely the mid-sized model so must be either 8.5, 11 or 13KW. We also have a heat recovery system fitted. I hope that gives you a bit more idea about the house?

It'd be great if I could get the whole system working efficiently but it all seems so over-complicated and the user manual isn't really up to much.

Any help you can offer would be greatly appreciated. Wish I'd found this forum earlier!!

 

[dcawkwell]

The air source heat pump should be economical.
However be careful some of the air source heat pumps use
an immersion heater to boost the temperature up.
Check your manual for your air source heat pump very carefully.

Most heat pumps will heat water up to about 50 degree before using
an immersion booster.

Ensure your heat from the heat pump is below this or the immersion will come on.

You only need to heat the hot water up to about 50 degree in the hot water tank. Just boosting it to over 60 degree once a week to kill any bacteria.

In very cold weather like now the heat pump produces less power and therefore may not be producing enough to heat the property. For example a 12 kW heat pump when it is freezing outside may only be product 6-7 kW. If your heat pump is less then you are getting even less.

Only heat the hot water tank once or twice a day that is plenty.

The heat pump system should be system. The heat pump is really only a heat source so works as any boiler does.
The heat recovery must be something separate for recovering heat from waste hot water?

 

[dcawkwell]

Check section 11 of your manual.

Ensure that the setting for the immersion heat means it won't come on.
So set it very low I think. But haven't read it in detail.

 

[Peter1919]

Setting the underfloor heating to 21 degrees seems high to me, generally underfloor heating doesn't need to be as hot as radiators as its a more efficient way of heating. Also with a well insulted house it should not take as much energy to get the floor back up to 18 degrees again.

 

[Dan Robinson]

21° is 21° regardless of house you get there

 

[Peter1919]

True and point taken, I suppose I mean that 18 degrees with underfloor heating will generally result in a warmer room over all compared to heating with radiators as the heat is throughout the whole room not just near the radiators

I would also say that although I am not an expert IMHO ASHPs are not great as a heating source for hot water. They work more efficiently when heating water to around the 40 degree mark which is pretty much ideal for underfloor heating but not hot enough for hot water use and certainly not hot enough for indirect heating of hot water.

 

[Norcon]

Wouldn't take the gift of an air source heat pump. Especially one made by Grant.
They specialise in oil boilers and only got into renewables a few years ago.
The Aerona is a fixed speed unit that Grant say can be installed without a buffer.
JonG wrote

This would never be countenanced by the Nordic pioneers of HP technology, because it has to deliver all of its heat whenever its on. Therefore during autumn and spring when the heat load drops, the heat output (sized at minus 3 perhaps) cannot be absorbed by the house and the unit starts to cycle, which is expensive and causes premature compressor wear.

Have to agree with that.

That said have a look at Live heat pump.
http://www.liveheatpump.be/t/en/p/meting/c/nl/d/11022012/s/day/h/6/woning/SCHI
http://www.liveheatpump.be/t/en/p/degezinnen/c/nl/d/11022012/s/day/h/6

Brother has a 300sq/m home in Ireland heated via GSHP and his yearly total leccy bill is between 1200 - 1500 euro.
He's very happy with that.
Five in his family plus usually at least a couple of foreign european girls who stay for the year. Three at the moment I believe.

You should pop this question on Navitron also in the Heat pump section and you can hear what JonG has to say maybe.
Some soundings being made on the Fujitsu Waterstage ASHP also.
Another guy over there claims a Danfoss AQ ashp unit cut his heating bill in half.
I'm no fan of any of them.

 

[ALEC1]

turning thngs on and off is hugely wasteful, assuming the house is occupied 18hours a day (most are!)

you need to temperature profile, that is 21c in the evenings, 20 in the morning, and may be 18c or so at night...

A new house with decent insulation wont loose tha much heat..also look at the kwH not the bill...

 

[Boilerman2]

Oh the joys of the "hidden" costs of running ASHP units that the makers would rather you did not know about untill it is too late!

 

[kevobain]

Anyone got a lid for my can of worms? Thank you all for your advice. Some really interesting points there.

I spoke to my builder today who has the same system fitted. He's not happy with his either during this cold spell. It begs the question, what is the point of a heating system that doesn't work very well when it's cold outside?!?!?

At the end of the day, the cost of the ASHP isn't the main issue although it does factor in. No method of heating is cheap these days it seems. I just don't like it when I'm away working and my other half tells me on the phone that the house is cold. I'm a bit old fashioned in that I believe if I turn on or turn up the heating in a room, it should become warm. I grudge paying for something which doesn't seem to work very well. I know the price of oil is scandalous and it's only going to go up but I also know that it's a system which gives decent heat on demand. I maybe should have done more homework before I installed the system but like many others, I just believed the hype without question. I imagine if I start running the heat pump all day then I could solve the problem of the cold house but that would mean using electricity during the expensive, standard times. One option is to change my tariff to have a fixed rate regardless of the time of day but I'm a bit reluctant to do that.

Another avenue I've not went down is my hot water. My ASHP does indeed heat my water and it comes on 3 times per day at the same time as the heating. Maybe I could cut that down a bit and increase the heating times to balance out the cost.

At the moment though, I'm definitely still thinking of converting to oil. Does anyone know how invasive that job will be from my air-water system? Will I need new pipes and new radiators or will the boiler basically replace the ASHP and run the same system? Knowing exactly what I'm using for heating by checking a level in an oil tank in my garden is very appealing to me at the moment. Also, I reckon that since the house is so well insulated, the extra heat of oil will heat the house quicker and therefore need to be on a lot less. That's my theory anyway. I'm just a bit disillusioned with my ASHP and need some options.

Thanks again for all the input. Keep em coming!!!

 

[Kev F]

Helllooooooooo

Ok in Scotland for an mcs install you would be designing a system so the unit runs to at least -5, me personally I'd design it to about -7, if customer had any data on actual average land temps of that area we could adjust the curve accordingly, lets start here

What's the unit?
You should have it programmed to run at 20c in day and no lower than 18c at night, its best to run 20c from morning to night with no off times during the day, the units I use come with a back up heater but we ALWAYS disable it as we don't like to use them as running costs can rocket.

Other factors t check is what was the underfloor loop set at ie 120mm centres or 200mm? If 120 great were onto a good start, if 200mm its ok. You want a flow temp from the unit set to about 45-47c max on Ufh. I'd personally if loops were 120 set it so my curve was from 37c in milder weather and 45c for days like now. This lets the weather comp kit control flow temps and I've found that pretty stable in most places. On your floor area your looking at 16kw unit.
If you can provide as much info as needed we can look deeper. I don't come on here much but I'm sure the lads will keep me informed

 

[Kev F]

On the note about high cost in winter you have to ignore that, you have to take a 12month period and then compare with other months, had a customer who was running a 5 bed house at nearly same cost as oil last winter, issue was it was colder than previous year and cost of elec had gone up he has his 12 month bill in, his oil would cost around £1600 a year, his whole house elec bill inc all his touch screen tvs and lights was £1300, he now understands its a 12 month look at prices and not a 3 month check. I've heard nothing but issues about the grant, so much so that people have taken out and put another in throwing units back at grant. Ashp can be very efficient even more so than natural gas, but they must be set up and sized correctly or they can cost twice as much as oil I've seen some horrendous installs and its getting a bad name because of theses installs.

 

[snb]

have experienced high electric consumption before with people turning the system on and off.

you will need to run the air sorce for a minimum of 18 hours a day but preferable to leave it on 24hrs per day.

reason is purely the following.

when the heat pump first turns on it uses the immersion (direct electric element only 3 or 6kw) to get the flow above 15 degrees.

this is the period when it uses huge amounts of electric.

because you have underfloor it is possible when the system cools down slightly that you could be in a situation where the flow temp doesn't get above 15 for a couple of hours or more.


your electric tariff is also very high. change to single rate but you should get a good deal because of your high usage. don't expect to use less than 12000 kwh per year for heating but could be as high as 20000 kw/h

at present best to have heating on 24/7 and to time the hot water for the cheap periods. also change the underfloor temp to a lower temp from 11pm to 7am ( will reduce demand on air source unit when it is not as efficient due to colder outside temps.)