Hi Sam,

As Morgan says, your problem is not with your ASHP, but where it is located.

Before spending £6000 on having gas piped to your property, why don't you at least let me have a closer look and see if there are ways to resolve your problem at much less cost.

@derek-m

That's extremely kind, Derek, but before deciding to switch to gas, we have had a couple of people look at the pump. Whilst it may not meet the 1m from a boundary rule, none of them felt that the fence was causing the problem as they are designed to pull energy from much lower temps.

I do now have our heat loss calculation from Omnie.

It says 5.38 kw, which seems remarkable in a 2650sqft house. I've been told by other people that a figure like that could only be achieved in a house with triple glazed windows and cutting edge insulation. This is a standard brick built property.

Does anyone out there have the ability to read a loss calculation and understand it's accuracy? At the moment the builder can claim the figures are all correct and therefore the pump more than big enough.

I apologise for my negativity, but this has had an enormous impact on my wellbeing, causing anxiety and necessitating months of research to achieve nothing, so I'm sure my decision to give up and warn others is understandable. 

@sam I fully appreciate your concerns about keeping warm and not getting on with your ASHP. But to then conclude your experience should apply to everyone else is incorrect. There are thousands of happy ASHP customers I’m sure. 
Have you got an independent ASHP heating engineer to run the numbers? Or the ASHP manufacturer?

Hi Sam,

Whilst ASHP's will still work down to -15C or even -20C, below +5C their efficiency starts to reduce, and gets worse the lower the temperature falls. What I feel certain is happening with your installation, from the air temperature test that you carried out, is that the cold air being exhausted from your ASHP, is being pulled back into the intake, before it has chance to be dissipated out into the atmosphere. Your machine is therefore always getting a supply of colder air rather than the warmer air it requires for optimum efficiency. If you remember the results from the test you carried out, with an outside air temperature of 20C, your ASHP was getting an air supply at 10C. So if the ambient air temperature is 10C, then the air supply to your ASHP would probably be 0C, if the ambient air temperature falls to 0C, then the air supply to your ASHP would probably be in the region of -10C. Do you follow my logic, at ambient temperatures below +15C, your ASHP is probably already losing its efficiency.

The test I would like to perform is to try to arrange for your ASHP to receive a supply of air at ambient temperature and then see how this affects its efficiency. I would be happy to come to your home and carry out the test if you do not feel able to do it yourself.

I have spent much of my career solving and rectifying problems on highly complex systems, problems that people though unsolvable. To correctly solve a problem it is first of all necessary to identify its root cause.

In the meantime, if you would like to pass whatever documentation you have been provided by the designer/installer, I will check to see if their calculations are indeed correct. My e-mail address is:- derek_marsh_aicss@yahoo.com

I look forward to hearing from you.

Regards,

Derek.

Posted by: @sam

It says 5.38 kw, which seems remarkable in a 2650sqft house.  

Ours is 6.5kW for a nominal 166 m2 house, which is 39W/m2.  Yours is about 22.  Is that feasible?  I don't know.   But do be careful what you're comparing; in the MCS calculations, the internal dimensions of the rooms are used to work out heat loss. Using that, our house is 127 sq m, giving 50W/m2.  Our house is 166 on the EPC and 165 on the estate egents blurb when we bought it.  That's 30% more. 

So, in the ongoing battle against my builder regarding the issues with my LG heat pump not heating my house in cold weather, I've finally been sent the heat loss calculations done by Omnie - the system designers.

It was dated April 2021, and we moved in in September 2020 

As we bought the property before it was finished, we were lucky enough to be able to change the layout, remove bathrooms etc.

The calculation document shows rooms that may have existed in the original brochure, but were never built in the house. Ensuite 4, which we removed from the plan and a master bedroom, which we changed the size and position of. This proves that Omnie were never even at the property to do a calculation as these rooms were never constructed, as interior walls were never built for them.

Whilst I appreciate the overall house size hasn't changed, can anyone with any experience say whether a calculation estimation on rooms from a brochure can be remotely accurate for sizing a heat pump appropriately? Is this acceptable practise within the industry?

Please help, as I suspect I may have found the problem and an explanation of how a 2650 sq ft house can have a 5.38 heat loss! I suspect they have calculated it to prove they were right and to show that their 9kw pump is big enough - despite the evidence from actually living with it.

Desperately seeking opinions from those with experience of the industry,

Sam.

@sam A few questions:

Was it undertaken by an MCS accredited installer?  For the missing room(s) there would have been a radiator within said room (or UFH).  Is that radiator in the larger room?  From the assessment, what is the heat loss calculation per room and the heat demand per room?  So if two rooms in the assessment are now one room, does the heat demand and loss of the two rooms equate to the one room that was built?

What is the overall heat demand?  What temperature is the assessment made at?  Should down to say -5C (or whatever your local minimum temp is).  And if so what is the overall heat demand and throughout the year?  The installed 9kW ASHP from LG should be able to produce more heat (have the capacity) than the loss calculation at -5C (without using the backup heater) if the system has been correctly sized.

For example, my required heating capacity at -3.4C (average minimum temp where I live) is 11.11kW which is 100% covered by the HP.  At -6C it is 12.53kW when the back up heater maybe required for the last 3%

@sam

Hi Sam,

I feel for you I really do but personally I’m unable to help. Hands up I’m a dunce and fear a game of darts due to embarrassment at an inability to calculate.  However there is at least one person on here that has offered to review your figures and even visit your home to assess for you.  Derek perhaps.  Can I suggest that you engage with him personally?  It might save a lot of angst in the long run.   Good luck.

Hi Everyone,

To give you all an update, Sam was kind enough to send me a copy of the calculations provided by Omnie, which actually have led to a further set of questions which I feel they need to answer.

On one sheet they claim the 'average heat demand' is 22W/m2, giving an 'estimated building demand' of 5.3kW.

On a further more detailed sheet they claim the 'total heat load/gross floor area' is 37W/m2, and that the 'total heat load' is 8.593kW.

I have therefore suggested that Sam should ask them to clarify and explain the difference between the two sets of figures.

None of the figures provided by Omnie show any allowance for heating hot water and also I can see no evidence that they have de-rated the output from the ASHP for ambient air temperatures below +5C.

I have therefore suggested that Sam should ask Omnie, to justify, how they calculate that a 9kW ASHP would be adequate for her property.

That is before the siting of the ASHP (which would appear to be in a cold well) is even considered.

Sam has confirmed that both the smaller neighbouring properties have the similar 9kW ASHP, but that they are located in a more open area. Both neighbours have apparently not suffered from the same problems as Sam.

I do believe that there is a report in existence from LG, which indicates that they consider Sam's ASHP to be undersized for her property, as well as being poorly sited.

I have provided Sam with a list of question to ask Omnie, but am not aware that she has received any reply as yet.

Thanks to the new information that Sam has provided above, it would appear that Omnie's calculations do not even relate to the actual layout of Sam's home. I think that their answers, should they decide to make any, will make interesting reading.

Sam is in a difficult position, in that Omnie, who allegedly carried out the design and commission, where contracted to the builder, who appears to have decided upon the location of the ASHP and arranged for its installation. Obviously they both claim that there is no problem, and even if there was, they are not responsible.

Should they continue to not accept any responsibility, I have suggested various courses of action that Sam may wish to take, but not being a legal expert, I think Sam would appreciate any input from those who may be able to help.

@derek-m

Nice1 Derek.  Good luck Sam.

@derek-m, I'll leave the calculations and investigation to you, sounds like you may be onto something.  I would add that my MCS calculation did separate calculations, for each room, for the fabric heat loss and ventilation heat loss then added them together to get the total used in the sizing.  The total average for my house was 50W/m2.  

@sam, (apologies if you know all this) it would be normal for the contractual relationship in the house buying process to be between you and the builder.  If they employed Omnie as a sub-contractor they still are totally responsible for the work Omnie did, the same as if they'd done it themselves.  While it's helpful to the builder for you to chase Omnie, ultimately if Omnie have messed up it's for the builder to sort out.  If any compensation/action is due then the builder would pay you/do the work and then, if they want to, chase Omnie.  The information you're collecting is needed and if Omnie is willing to share it with you then that's fine, but unless Omnie was employed directly by you then you have no comeback with them. 

@sam, do you have legal cover on your house insurance?  Check your policy, its one of these annoying add ons they offer or some throuw it in free. If you do you should give them a call for some advice.  

Good Luck!

That's an excellent piece of advice @kev-m. I've just renewed our home insurance and we have legal cover for up to £100,000, I just wonder whether the policy would allow you a homeowner to take action or whether it's for 'defence' purposes only.