Anyone know much about setting up ASHP?

[Aspman]

So we finally get in our new house and we have the expectation that it's a new build all new standards insulated up the wahoo etc, gonna be cheap to live...

Roll on a couple of months and get the almighty kick in the nads that is our electric bill.

 

I had expected the bill to be sizable since we're electric everything and it's a pretty big house. But knockng on the door of £600 a month for leccy seems somewhat painful to me.

I suspect the ASHP is the main source of power usage but tbh the damn thing doesn't even heat the house very well.

The underfloor heating is on pretty much 24/7 controlled by 5 zone thermostats and the upstairs has huge radiators to deal with the lower water temp.

 

It is appearing to me that ASHP only work if your house is sealed up like a tupperware container. Which doesn't work when building control make you knock holes in practically every door to ensure airflow.

 

the ous eis also in a pretty windy area which means cold air finds its way in every little nook and cranny it can. I'm looking to deal up most of the window vents since they can't cope with wind and leak cold air.

Also the builder failed to seal under most of the window sills so we're leaking air there in many rooms. I'm just bought some expanding foam to try to deal with some of the more recessed bits prior to pushing for a tidy up with mastic.

 

But if anyone can advise on an economical setup I'd be appreciative.

[PetrolDave]

Sounds like ASHP is only suitable for a fully sealed eco-house?

[DEL80Y]

I have watched a lot of videos on Youtube cause I was thinking this is the future but after watching the horror stories about them I went with GSH again.

https://www.youtube.com/watch?v=GhAKMAcmJFg&t=359s

https://www.youtube.com/watch?v=pFl8jcLOiP8

As you say the spec of the radiators are massive to transfer the low heat 

Not suited to where I live at all

https://www.greenmatch.co.uk/blog/2016/02/pros-and-cons-of-air-source-heat-pumps

Edited 10 January, 2022 by DEL80Y

[Morph]

I live in an 11 year old house with an ASHP. It’s great when things are working well but it has been a pain in the arse. 
My electricity bills treble or quadruple during the winter but then they are near nothing in the summer (thermal solar as well).

Ideally you need to make sure it’s set up correctly as this can cause cost issues - for instance mine was set to heat the hot water too hot which meant it ran continuously to try and get to a temperature it couldn’t reach. 
If flows are not good to each zone this can cause similar problems and hence give you higher bills. 

[Morph]

Just to add that at real cold times supplementary heating is required with ASHP’s as they struggle to get to and maintain appropriate temperatures  -  this is one of the big untold truths with ASHP I believe. 

[Aspman]

3 hours ago, Morph said:

Just to add that at real cold times supplementary heating is required with ASHP’s as they struggle to get to and maintain appropriate temperatures  -  this is one of the big untold truths with ASHP I believe. 

 

Ours will alledgedly work down to -14C but even at 0C it's going to be working pretty hard to pull heat from that air.

I've turned off the heating in the utility since it just couldn't bring it up to temp. I can't see that it got any colder after that but the pump isn't running quite as much.

We've a WBS as well and that's been used lots to bring the house up to temp but it's a double edge sword that one since if the underfloor isn't heating the base plate is cooling.

[cheezemonkhai]

I've been looking into these a lot at our boiler is getting to that age, so water, ground and even air to an extent have been considered.

Plus we have a pair of air  heat pumps, so I've got a reasonable idea on how to run them efficiently and some of the foibles.

 

Firstly, all the guff about 4 : 1 efficiency just isnt true in winter, especially up your way.

It's certainly better in autumn/spring, but Dec-Feb, we see ours drop to about 1.1-1.5:1, eg a bit better than electric heating but not too much.

 

Couple of things to check:

 

• What water temperature do you have set for the radiator circuit?
  You want it to be as low as possible (I've been told 35 if you can, but max 45). As you get hotter more electric is needed to apply extra heating.
• Keep the water temperature lowish (50) but make sure there is a boost to 60 in there to kill of the nasties.
  Most do this automatically, but make sure it's doing it during the day when it's warmer or before you're using it, not during the coldest part of the night.
• Leave the underfloor heating on 24/7 and keep the rooms at a temperature you want. If it's 18/19/20 then leave it there and perhaps lower the temperature by 1-2 degrees when you leave the floor overnight.
  (Underfloor is slow to react and needs to be on all the time really, but the heat does rise).
• Make sure the pipes from the F-Gas heat exchanger to the water tank are lagged both ways and also that any pipes in the house or loft are well insulated.
  (I'm guessing they're plastic, which will help for sure, but if they're copper you'll need to do something).
• Make sure the flow rates are set correctly around the rooms (Especially the underfloor)
• Make sure the f-gas is at the correct level, as some forget to add extra gas for the extra distance.

You'll certainly want to sort out those draughts, but rather than expanding foam, I'd make sure the correct cavity closers etc were used, then have it sealed with appropriate materials.

 

What floor coverings do you have on the UFC floor? Some underlays, carpets and surfaces have such a high tog rating, the UFC is basically non functional as they keep all the heat below.

 

Finally, as the hot water is going to be a big culpret for using up electric, you could consider a solar hot water into the tank, or if you have solar PV an immersion heater diverter to allow the solar PV to do a big chunk of the heating the water up to 60.

 

 

Edited 11 January, 2022 by cheezemonkhai

[Chorlton]

Perhaps your ASHP is just undersized for the task at hand.  If heat loss>heat supplied no form of heating will work properly.  The first step is to make sure heat loss calculations have been carried out as accurately as possible. 

 

There's a lot of info on here:

 

https://forum.buildhub.org.uk/topic/439-fabric-and-ventilation-heat-loss-calculator/

[cheezemonkhai]

Just curious @Aspmandid you sort this out?

[Aspman]

Morning all,

 

Apologies for long delays life is very fast right now.

Thanks Cheeze for the suggestions -

 

• What water temperature do you have set for the radiator circuit?
  You want it to be as low as possible (I've been told 35 if you can, but max 45). As you get hotter more electric is needed to apply extra heating.

Yep there with that. Curcuit is at about 32-34 normally going by the thermometer strip on the manifold. It does have an eco mode but tbh it didn't warm the house at all, we called in the builder then because we were so cold.

• Keep the water temperature lowish (50) but make sure there is a boost to 60 in there to kill of the nasties

Not sure what the settign is here but I'd say our hw is not excessively scalding nor is there a huge amount of it. Enough for a couple of showers that's all. HW charges for 2hr in the morning and 1hr in the afternoon and the heating curcuits close during those periods. I

• Most do this automatically, but make sure it's doing it during the day when it's warmer or before you're using it, not during the coldest part of the night.

Yeah that's a hard one, obvs right now it's charging hw at the worst time at the coldest point of the night. Might need to experiment to see if teh tank will stay warm enough if we charge hw during the day only.

• Leave the underfloor heating on 24/7 and keep the rooms at a temperature you want. If it's 18/19/20 then leave it there and perhaps lower the temperature by 1-2 degrees when you leave the floor overnight.
  (Underfloor is slow to react and needs to be on all the time really, but the heat does rise).

 

Yes we do exactly that. Most rooms set at 18/19 right now, only the family room is set at 21. That room get the most solar gain anyway. Rooms are all set to drop 2C through the night.

 

• Make sure the pipes from the F-Gas heat exchanger to the water tank are lagged both ways and also that any pipes in the house or loft are well insulated.

Yep, but is there enough insulation. It looks a little light to me. Two passes of glass wool at right angles to each other. Prob 300mm at most.

 

• (I'm guessing they're plastic, which will help for sure, but if they're copper you'll need to do something).

Copper and lagged both ways

 

• Make sure the flow rates are set correctly around the rooms (Especially the underfloor)

Not done right now, tried to alter but was a bit wary that they were going to snap. System will be due a service in summer so might see if they offer tuning as a service

 

• Make sure the f-gas is at the correct level, as some forget to add extra gas for the extra distance.

Servicing again.

 

Lots of leaks filled but I have resorted to taping up the trickle vents in teh windows. I don't understant planners, they insist on ypu putting in loads of insulation them insist on poking holes in your walls and windows everywhere.

 

Last month was down to only £350 for leccy woo

[cheezemonkhai]

Fingers crossed you get it sorted it sounds like you've tried manythings.

Daft question, but have they sized it big enough as it sounds like it could well be undersized, particularly if it's always on electric heat.

 

As for trickle vents... I mentioned them on a window thread.

Planning requires an appropriate way to provide ventilation to deal humidity/CO2 levels in the house.

 

Does your house have a mechanical heat recovery system already? If so I am not sure the vents are needed (but you would need to check).

If not then if I was a betting man I'd say heat loss is probably more than the system was sized for (Assuming it was correctly sized).

[Aspman]

It's a pretty beefy 16kW unit. I've asked that question of a few people and the answer has always been that it is big enough to heat the house.

 

We don't have heat recovery but I think the house is in a very windy spot which hasn't been accounted for and our losses might be more than expected.

 

With the energy price so high and vat being remved on eco measure we're going to look again at renewable generation with battery storage

[cheezemonkhai]

16 minutes ago, Aspman said:

It's a pretty beefy 16kW unit. I've asked that question of a few people and the answer has always been that it is big enough to heat the house.

 

We don't have heat recovery but I think the house is in a very windy spot which hasn't been accounted for and our losses might be more than expected.

 

With the energy price so high and vat being remved on eco measure we're going to look again at renewable generation with battery storage

 

If you have air bricks under a suspended floor, one thing you can do to help reduce wind losses is to fit those facing the wind directions with these sort of things:

 

http://flooddoor.co.uk/self-sealing-airbricks.php

 

If you don't have mechanical heat recovery, then yeah those night vents are going to allow a lot of draughts in, but they are required to provide suitable ventialtion for moisture and CO2 etc.

 

Is is a new house or an older one?

If new, get onto the house builder as something might not be right.

If older, then I'd look at moving to mechanical ventilation (MHRC)  and leaving the vents closed/not having them when windows next replaced.

 

Other things I can think of are:

 

• Making sure that there was suitable insulation laid below the underfloor heating
• Getting them to check system flow rates
• Moving that hot water heat to end of the previous day (Whilst it is still warm) and having it do the higher heat then too when needed.
  A decent insulated tank should keep that to a 5-10 degree overnight drop (Ours drops less, albeit on gas) and then you need less heat in the morning.
• check under door frames etc, to make sure there is mastic in place to reduce draughts to the property.
• If it's dab wall, make sure they bothered to put the solid bars of plaster at the top to reduce wind movement.

 

EDIT: Sorry re-read first post and remembered it's new.

I'd think you'll be wanting to get them in whilst it's less than 2 years old and seeing if your dab walls are very cold/draughty too.

Edited 8 April, 2022 by cheezemonkhai

[Aspman]

We found they'd forgotton to mastic round the window sills. Gaps you could fit your hand in. It was effectively chilling the house around the windows. They're fixed now bar a couple of points that have still been missed.

Still a few things to try though cheers

[mac11irl]

how big is the house? 16kw sounds big, but as you said - a miscalculation (or just ignoring and using the average) on the wind effect losses could make it under sized. it may enough to heat the house, but not enough to also supply how water...

[cheezemonkhai]

On 08/04/2022 at 16:39, Aspman said:

We found they'd forgotton to mastic round the window sills. Gaps you could fit your hand in. It was effectively chilling the house around the windows. They're fixed now bar a couple of points that have still been missed.

Still a few things to try though cheers

 

New build inspector or just luck that you found it?

 

Had similar on one door, however it’s sadly not uncommon.  With dab houses, such gaps tend to freeze the whole house if the dab isn’t applied with a sealing bead (again not uncommon).

 

Is the house at least able to heat now?

 

 

Edited 9 April, 2022 by cheezemonkhai

[fabdavrav]

Planning regs now try to make the house air tight so that the only air leakage is the required amount via air vents..its then easier to calculate your total heat loss.

 

Personally I prefer my house to breathe, so basically treat the house as two units like stacking dolls. Inner one is the insulated air tight envelope...then the outer skin is the weather tight & between the two is the air breather space which gets rid of moisture as hopefully this is where the dew point will occur. There have always been regs on the number of air changes per hour in each room depending on room type & usage etc.. The only way to have air changes & no heat loss is for full air heat recovery ventilation in every room. This unfortunately requires back up power in case of a power cut...or just leave the windows open!!!

 

 

Main problem with air source fitted to existing rads is that the rads are not increased in size to cope with the lower delta (max temp of water in rads) that air source provides:-

 

In older (over 16yrs old) heating systems (could still be condensing boiler) the rads usually were sized for delta 60C (85C flow/75C return/20C room)....

ASHP usually run at delta 30C (55C flow/45C return/20C room). In all calculations the outside air temp is assumed to be 0C. If the outside air is lower or the room temp is higher, say you have -5C outside & +22C inside you'll need MORE delta!!..

 

So if you had a Stelrad double panel/double fin (K2) rad that was 1,000mm long x 600mm high & thus produced 2,418 watts at delta 60C....

You'll now need to have a 2,200mm long x 700mm high (K2) rad to produce 2,278 watts at delta 30C for ASHP

 

If you had say a single panel single fin (K1) that was 600mm long x 600mm high & thus produced 797 watts at delta 60C....

You would now need to have at least a 1,200mm long x 700mm high (K1) rad to produce 706 watts at delta 30C for ASHP

 

 

Regarding the lack of adequate hot water with ASHP:-

 

In my house (100+yrs old thick stone walls)  the total heat loss is 13.7kW  using the maximum air changes & max regulation temps for each room.

 

However the building heat loss is NOT the maximum demand on my heating system..!!...Its the Hot water tank!!

 

As I have an indirect unvented mains pressure system I have a Heatrae Sadia Megaflo 170lt tank which has a coil of pipe (which the hot rad water flows through to heat the water up)...that is rated at 24kW...!!

 

So my boiler needs to be able to put out with 24kW, which is why I have a 24kW gas boiler. Unfortunately it only ramps down as low as 8kW, (usually all boilers go down to 1/3rd of max) & 1yr after I did my install WB produced an 18kW version of my boiler & I recon I could have gotten way with it as that ramps down to 6kW & would have only affected the heat up times of the tank very slightly!

 

If your heating system is efficient & fast you don't need to add the heat loss & DHW requirements (13.7kW & 24kW in my case) together.....just size for the maximum single demand...

[Aspman]

We're brand new and basically built for the ASHP to work. So underfloor heating across the whole house on ground floor and large rads upstairs.
It is a big house, 5 bed on paper but we dropped one in a redesign. We have a lot of glass but the doubgle galsing does appear to be good (now after much tweaking) other than the trickle vents which can't cope with the wind.

 

The house is warm enought to be livable at least but at significant cost. If gas is 4x leccy then in our worst month we'd be about £150 for the energy on the house which for the size of it I wouldn't be complaining about but we're 26p a kWh right now and will jump to 40p at least next year.

Bill for last month was £310.

I think I'm going to block up some of the air bricks on the windward side until I can get something in like Cheeze has suggested. It's bound to be howling through the foundations.

I wouldn't want a bigger ASHP even if it would make a different, can you imaging how much power the damn thing would eat

[Aspman]

Blocking airbrick does seem to be a no no and those self closing options are for flood water but you prompted me to search and you do get airbrick cowls to reduce wind blast on them

[fabdavrav]

45 minutes ago, Aspman said:

I wouldn't want a bigger ASHP even if it would make a different, can you imaging how much power the damn thing would eat

 

& this is where the whole system falls down & where the green washing marketing has mislead people....

 

Doesn't matter if your heating is powered by gas, electric, wood, coal, or fairy dust......if your house has 13.7kW of heat loss thats that you need 13.7kW...if your hot water tank has a 24kW coil in it..it requires 24kW of heat...simples...

 

Anything less will mean "not adequate"..& is the reason why so many people are having problems with various heat pumps etc..

[Aspman]

4 hours ago, fabdavrav said:

 

& this is where the whole system falls down & where the green washing marketing has mislead people....

That and the fact electricity costs 4x as much as gas for the same energy.

 

 It didn’t really matter how efficient the system is is going to cost you more to do the same. And I’m sure my ashp with its claimed 300% efficiency over gas doesn’t hit this figure when it’s -2C.

 

PLUS a domestic supply tops out at 100A. Many are 60A. Ashp is 20A, oven 20A, shower 20A, hob 20A and if we had an electric car charging we could fairly easily Max out our power supply. I’m not sure anyone is talking about fitting all domestic properties with a three phase but its going to be needed for some

[fabdavrav]

1 hour ago, Aspman said:

That and the fact electricity costs 4x as much as gas for the same energy.

 

 It didn’t really matter how efficient the system is is going to cost you more to do the same. And I’m sure my ashp with its claimed 300% efficiency over gas doesn’t hit this figure when it’s -2C.

 

PLUS a domestic supply tops out at 100A. Many are 60A. Ashp is 20A, oven 20A, shower 20A, hob 20A and if we had an electric car charging we could fairly easily Max out our power supply. I’m not sure anyone is talking about fitting all domestic properties with a three phase but its going to be needed for some

 

 

I did a big post on electricity requirements & cable capacities a few months back..(I used to work for the Hydro board).. the fact the whole infrastructure will need to be doubled in capacity to every house to cope with all the new loads such as electric heating, & car chargers...basically you cannot take the 100A..well you & maybe two other houses can & then the other 7 houses on that cable have nothing!!

 

Thats before you factor in the main national grid isn't big enough.....like Scotland can only export 6gigawatts of power to down south as thats all the grid can cope with. There is a planned 8GW seabed cable from Peterhead to down south...& apparently at least 18GW is actually required to meet the transmission demand for green energy generated in the north to the main cities down south....so thats another 4GW line that ned to be built!

 

(figures are approx. as trying to remember from a National Grid document I saw)

 

 

Re 300% efficiency..I've noticed that many claims are wrong....you need to deduct the electrical consumption of the plant itself...& many do not...you cannot get "free" energy...

[Aspman]

11 hours ago, fabdavrav said:

Re 300% efficiency..I've noticed that many claims are wrong....you need to deduct the electrical consumption of the plant itself...& many do not...you cannot get "free" energy...

Yep statistics and lies, unless the ASHP is running off new physics or zero-point energy, which going by the bills it ain't.

[cheezemonkhai]

18 hours ago, Aspman said:

Blocking airbrick does seem to be a no no and those self closing options are for flood water but you prompted me to search and you do get airbrick cowls to reduce wind blast on them

 

The flood ones, have the balls that get pushed up in strong gusts, but yes venting cowels will work for wind and are easier to fit too.

 

For the ASHP, we have a couple of air to air, which claim a rate of nearly 5, but that is in the best conditions when dumping heat from inside to outside.

Heating it's more like 3.8 and once the external temperatures drop below somewhere in thre 5-10 degrees range it drops.

I'd say 2:1 is realistic, which is great, but not for the bills when gas is still 25% of the price of electric.

 

Of course gas isn't 100% efficient, but even at a relatively low 80%, for every 100kWh of "heat output" that's about £12 of gas at 9p/kWh vs £20 of electric @40p/kWh. It's closer with electric at 28p/kWh, at £14 but still not cheaper.

 

It's a real pain, as unless you have a solar system to dump excess into the heating, then even "efficient" heat pumps are quite expensive.

 

It's no help to @Aspman, but GSHP/WSHP are obviously better for COP in cold conditions. It does also look like the next generation domestic ASHP that are starting to come out are both quieter and have better efficiency under cold (0 degree) conditions.

[PetrolDave]

3 hours ago, cheezemonkhai said:

It's a real pain, as unless you have a solar system to dump excess into the heating, then even "efficient" heat pumps are quite expensive.

I think the cost of running heat pumps (as well as the cost of swapping from gas fired boilers with the associated upsizing of radiators) is deliberately being ignored and/or understated.

 

This could be a big 'banana skin' for the 'green heating' movement IMHO.