ASHP installation cost

brewerdave

As a matter of interest ,how much more does it cost to "put the house right" after the completion ie carpets ,decoration etc ?

Reed_Richards

Old radiators tend to drip dirty water as they are removed from the house.  We have predominantly floating wood floors so any drips were easily wiped up.  I was assured that the fitters would have used dust sheets had we had carpets.  Each radiator went where the old radiator had been so generally no need for redecoration.  In a few cases the wall area occupied by the new radiator was smaller than the one it replaced so we had to touch-up decoration that had previously been hidden behind the ends of the old radiator.  So had I just been replacing old radiators the cost to "put the house right" could have been zero or just a bit of DIY labour.
  
In my case we moved the pipes from under the floor (those ones are still there) to via the loft and there was some decoration cost associated with that, for example we cut round bits of spare floor board to fill the holes where the old pipes had come through.         

matelodave

brewerdave said:

As a matter of interest ,how much more does it cost to "put the house right" after the completion ie carpets ,decoration etc ?

how long is a piece of string. It all depends on how much disruption there may or may not be be. In many cases, a lot of the existing pipework can be used. However the location of the old boiler compared to where the heatpump is being installed as well the hot water tank may have a major or minor impact on plumbing.

As R_R says even the new rads may not take up much more space so it's all determined by how much work needs to be done and what you can get away with depending on SWMBO's attitude to leaving the place tidy or not (my mate got away with a half finished bathroom for the best part of 20 years, I would be hard pushed to manage 20 hours before mine started twitching)

Ours cost quite a bit as we were replacing old storage heaters with underfloor heating and completely replumbing the place. We also knocked a wall down, Installed a couple of doorways and completely gutted  and refurbed the bathroom, kitchen and utility room. Replaced all the ceilings, coving, redecorated and installed new carpet throughout (but not all of it was a consequence of fitting an ASHP 

LolekUK

brewerdave said:

As a matter of interest ,how much more does it cost to "put the house right" after the completion ie carpets ,decoration etc ?

As everyone else says, all depends on what is being done. 

I am removing old storage heaters myself - filling the holes and decorating rooms. Installer said, they will pick up the carpet (1st floor, to run plumbing underfloor) and will try to put it back down but advised that a carpet person might be required. Luckily I've got a neighbour (carpet fitter) who will happily pop over for couple of hours once the heating is done. Ground floor I'm having pipes dropped down by the wall into rads locations and again I'll be decorating where required. So in my case, the cost will be zero (as have left over paints from previous owners) or just a case of beer for the carpet fitter neighbour.

Btw. I'm opting in for for the 11.2 kW heat pump. Not worth the risk and sounds as it will be needed. I guess it won't be using more electricity as it will take less time to heat the system? Hopefully loan is approved in couple of days and get book install for late August

matelodave

Keep us posted - the more info we get the more informed we'll all be

Reed_Richards

The first thing that should happen after you have put down a deposit is that your installer (or somebody acting on their behalf) should come and survey every room in your house, put the heat loss details into a software package and, probably a few days later, present you with a heat loss calculation that lists every area in your house and what radiator size is required.  Your installer will almost certainly have done something approximate already but you and your RHI need the pukka calculation.  You may be allowed to choose between a fat radiator that occupies less wall space or a thinner one of larger area.  

Add up the total heat requirement for the house, add about 10% (?) and that will tell you what size heat pump you need.  If this is more than 11.2 kW for heavens sake get a bigger heat pump.  If it is significantly less than 11.2 kW I strongly recommend you consider over-sizing the radiators (i.e. getting ones of larger output than the calculated requirement).  This will add very little to the cost but allow you to warm-up the house more quickly from cold (or raise the room temperature more quickly).

Have you got your EPC sorted?  You need one that is less than 2 years old to claim the RHI and it must not recommend adding loft or cavity wall insulation.  My installer arranged for somebody to come and perform the EPC but they don't all do that.           

Cardew

It has always been my understanding that you should not oversize an ASHP.

Loads of websites on this subject - Google 'oversizing an ASHP'

matelodave

Cardew said:

It has always been my understanding that you should not oversize an ASHP.

Loads of websites on this subject - Google 'oversizing an ASHP'

Agreed, but there have been many, many installations where the unit has been undersized and the customer has had to resort to using the backup/boost heater.

In the end the unit should be sized appropriately and that's the job of the MCS installer. As I suggested, do a sanity check by making some of your own calculations so you can determine if it's in the right ball-park. It's a bit too late if the unit doesn't perform as you either hoped or expected,

My heat loss calcs suggested that I needed 10.5kw and the installer I used suggested that the 11kw unit would be appropriate with perhaps around 50 hours a year of back-up heating from the 6kw heater - this was in accordance with the Daikin simulator.

The two quotes I got from purveyors of Ecodan both quoted 8.5kw units which I reckoned were at least 2kw undersized and probaly would have need significant use of the back-up heater. Our system has coped even when the temperature outside has dropped to -14 (I've disabled the back-up heater)

IMHO it's better to have a kw or so in hand which you could turn down a bit than to have a unit that's a kw or so undersized requiring use of the back-up heater on peak rates or having to break out a fan heater (again on peak rate) if it can't cope.

Reed_Richards

Cardew said:

It has always been my understanding that you should not oversize an ASHP.

Loads of websites on this subject - Google 'oversizing an ASHP'

Okay I Googled it but I could not find a lot of sense.  There is a lot of myth and cod science surrounding heat pumps.  Some of the earlier ones were not installed properly or sized properly or did not work properly.  They are often used in conjunction with underfloor heating then people mistake the behaviour of underfloor heating for the behaviour of the heat pump.  @Cardew ,  you seem to be a bit of an armchair critic of ASHPs; can you work out why you should not over-size them?
  
Here are my thought as someone who actually owns a heat pump and (because I have solar panels) who can see a graphical display of the amount of electrical power the house has used throughout the day. 

• If your heat pump is sized for a cold day in winter (which it should be) then most of the time it will not need its full capacity so for 11 months out of 12 it is oversized.  My heat pump is nominally right-sized but it's normal behaviour is to cycle.  My smart thermostat had to be told it was a gas boiler to limit the cycles to one every 20 minutes.
• Most heat pumps can do weather compensation but very few can do load compensation (Vaillant may be an exception).  Without both the heat pump does not really know how hard it needs to run so it will overrun and cycle
• One thing a heat pump cannot do is modulate down to a low percentage of its full output.  I've read that 30% is the minimum but who knows if that is correct.  So if you over-size the heat pump then the minimum output is increased.  Does that really matter?  It would if the heat pump could actually manage to run continuously at near-minimum power but mine has never managed to do that

      
Perhaps I should add that my heat pump does not have a back-up heater like the one that @matelodave has  (except possibly there is a small heater to aid defrosting).  There is an immersion heater mounted in the buffer tank but it is has no electrical connection.
     

Cardew

Reed_Richards said:

Cardew said:

It has always been my understanding that you should not oversize an ASHP.

Loads of websites on this subject - Google 'oversizing an ASHP'

Okay I Googled it but I could not find a lot of sense.  There is a lot of myth and cod science surrounding heat pumps.  Some of the earlier ones were not installed properly or sized properly or did not work properly.  They are often used in conjunction with underfloor heating then people mistake the behaviour of underfloor heating for the behaviour of the heat pump.  @Cardew ,  you seem to be a bit of an armchair critic of ASHPs; can you work out why you should not over-size them?
  
Here are my thought as someone who actually owns a heat pump -------

On an internet forum I would have thought most posts are made from an ‘armchair’.

On most subjects I glean the majority of information from ‘research’ on the internet.   You might not be able to find a lot of sense from Googling about over-sizing heat pumps; however it might be clearer to other interested parties??

Indeed I have not found a technical article that advocates a heat pump should be over-sized as you suggest i.e. ‘I think there is a case to be made for over-sizing the radiators and the heat pump.’

If you feel that owning a heat pump is a prerequisite for commenting on the subject in this forum, I have only owned one property with a heat pump – which I didn’t have installed (I have one installed in my tumble dryer ).

So, even with my technical background as a chartered electrical engineer, I wouldn’t dream of contradicting what appears to be prevailing wisdom about over-sizing heat pumps in all the technical reports I have read; including the MCS Guide. https://mcscertified.com/wp-content/uploads/2020/07/Heat-Pump-Guide.pdf

I would agree with you that there is a lot of ‘myth and cod science’ about heat pumps. However from my perspective as a self-confessed ‘armchair critic’, much of that is down to the manufacturers and installers who produce brochures that come very close to breaching Advertising Standard Authority(ASA)  regulations in their performance claims.

You can find realistic appraisals of heat pump performance in the EST trials or this lengthy Government publication

– https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf  which also has a section on HP sizing.  However it is not fair to expect non- technical potential customers to have to interpret such reports.  

In addition whilst MCS may lay down installation procedures, as far as I am aware they have no routine mechanism to enforce those procedures in the manner that Councils enforce building regulations.

Lastly there are many heat pump owners who seek to justify their decisions with questionable data. I am NOT (repeat NOT) pointing fingers and anyone who has contributed to this thread.