Bad ASHP Install on New Build - Legal Stand Point?

farmerjj

My wife and I bought a new property in January this year (2024) which was sold as a heat efficient modern new build that would be low on bills due to the air source heat pump installed.
We started seeing our electric usage look rather high and after a lot of investigation, and cost to have reports done of the heat pump, it was found that the install was done very badly. The wrong size unit (according to 3 Heat Pump installers) had been installed along with wrong fittings, pipe sizes, and terrible lagging on the pipes.

I was told that new build houses like ours should easily meet an efficiency rating of 300% (3.0 COP). Ours is currently running at 1, or 0%.
After contacting the people that designed the underfloor system, I was told they had designed the system to work with a gas boiler not an Air source heat pump. I also have the building reg sign off for the heating system which states a smaller different brand of unit was fitted.

I have spoken to the developer and they don’t want to help or cover the cost to make good even with 3 experts saying the same thing.

I feel we have been hugely miss sold the property and it’s currently costing us around 300% more in electric than the correct install would be.

I feel we have lots of evidence but can we take them to court? Do we have any ground to stand on to get this system corrected at their cost? We’ve had quotes of around £10,000 to rectify, as well as the bills that with a correctly fitted system we shouldn’t have had to pay for.

MikeJXE

Think carefully before you take a construction company to court

I did that to one of the big four

I was asking my solicitors why do they keep going when they know they will loose 

The reply was they are making you put up more arguments hoping you run out of money 

The company in question made an offer 3 days before the hearing 

Not the amount in question but I had to take it as I had run out of funds 

matelodave

As suggested above, you really need to consult a solicitor.

The collective wisdom on the forum may have opinions and agree with you etc but when it comes to the law, it can become very costly and there's no guarantee that you'll win or cover your legal costs even if you do win.

Netexporter

If the house has been built under an NHBC warranty you should be covered for poor design/installation.

ComicGeek

First of all there is some confusion in the statements above. It is very unlikely that the underfloor heating system design would fundamentally change between a gas boiler or heat pump system (the exception being whether you have a blending valve or not on the underfloor heating manifold) - the limitation is normally the surface temperature of the floor, which would normally limit the heating flow temperture to maximum 45-50 degrees. With a new build property with modern insulation etc, you would expect that to be at the bottom end, with maximum 45 degrees.  

If you have radiators in other parts of the house, then yes these could be sized for a higher water temperature which could cause issues - but that is separate to the underfloor heating. 

Do you have a MCS certificate for the heating system? You can check with MCS at https://mcscertified.com/consumers-communities/certificate-queries/ to see if one exists. This is supposed to protect consumers from badly designed and installed systems, but unfortunately isn't a mandatory requirement.

Are the other installers saying it's too small? What is your house total floor area, and what is the heat pump model installed?

What is the flow temperature of the heat pump set to? Does it vary according to outside temperature?

You need a qualified designer to look at the whole system and identify issues - installers don't always understand the sizing calcs. 

farmerjj

Thanks for the reply.

The installers were not MCS certified.

3 independent reports are saying the following (full report below):

- Heat pump way oversized for house

- Blending valve and other pumps fitted when not needed

- Pipework not lagged correctly

Currently our SCOP is running at 1.

Weather Comp is set up and was told this was fine by the other experts.

Samsung 12Kw Heat Pump

Total Floor Area of new build is: 1850Sq Ft (171m sq)
3 bedroom bungalow.

Thanks.

REPORT:

Heat loss and unit size

I have carried out a heat loss survey on the property and found the total heat loss to be somewhere between 3.5 and 5kW, meaning the installed unit is grossly oversized, by a factor of 2 or 3.

Primary pipe sizing

The pipework connecting the outdoor unit to the cylinder is undersized for the flow rates required, and should have been minimum 28mm copper, possibly 35mm copper (28mm pushfit have been used which is too restrictive, with a pressure drop of over 1kPa/m). As it happens, the pipework would be sufficient for a 5kW unit which should have been specified).

Outdoor Pipework

The outdoor primary pipework is very poorly installed and needs removing and refitting, the pipes should be fully insulated and sealed to prevent water ingress (wet insulation has virtually no insulating qualities), clips should be fitted outside the insulation, and pipes should be insulated and sleeved as they pass through the wall. If lever valves are installed outside, they should have long stem handles and be fully insulated and sealed.

Pipework in loft

Pipework in loft in very poorly insulated, sometimes not insulated at all. As the loft is outside the thermal envelope, the same insulating practices should be used as outdoors, with fully mitred joints, and clips over the insulation

Poor control strategy, unnecessary components and bad hydronic design, resulting on a very poor COP

The current heat pump system is not optimized for efficiency due to a poor control strategy and unnecessary components. Ideally, a heat pump should operate using a weather compensation curve, which adjusts the heat output to match the property's heat loss at varying outdoor temperatures. This approach ensures optimal efficiency, as each 1ºC increase in flow temperature can lead to approximately a 3% decrease in efficiency. Unfortunately, the existing system functions similarly to a gas boiler, with multiple on/off controls and elevated flow temperatures. Additionally, the presence of a redundant mixing valve on the underfloor heating manifold, which is unnecessary for systems not running at high temperatures, further complicates the system. These factors contribute to a suboptimal coefficient of performance (COP) and highlight the need for a revised control strategy and system design.

The COP since install according to the HIU is 1.17, barely more than what would be achieved with plug in radiators and an immersion heater (which would be a COP of 1 and a fraction of the cost to install). The minimum efficiency a system should work at according to MCS is 2.8, although really you should be aiming for 4+ on a new build with such a low heat loss.

Reed_Richards

The spacing of the pipes in your UFH can make a difference.  For a heat pump you want them as closely spaced as possible so you can get the heat output you need with a low water temperature.  If they were further apart you would need to run them hotter, not much of an issue for a gas boiler but with a heat pump that could give your efficiency a significant hit.    

FreeBear

ComicGeek said:

First of all there is some confusion in the statements above. It is very unlikely that the underfloor heating system design would fundamentally change between a gas boiler or heat pump system (the exception being whether you have a blending valve or not on the underfloor heating manifold) - the limitation is normally the surface temperature of the floor, which would normally limit the heating flow temperature to maximum 45-50 degrees. With a new build property with modern insulation etc, you would expect that to be at the bottom end, with maximum 45 degrees.  

If you have radiators in other parts of the house, then yes these could be sized for a higher water temperature which could cause issues - but that is separate to the underfloor heating.

Building Rgulations, Part L, Section 5.10 states that a wet system should be designed with a maximum flow temperature of 55°C. And from what little I know of wet UFH, the design temperature should be between 35°C and 45°C.

Netexporter

Also the floor finish will have a bearing on UFH. Stone, ceramic, timber and vinyl would probably be OK with the piping at 150mm centres but carpet would almost certainly require 100mm centres and the carpet must be low TOG rating. No mention of that in the engineer's report, which may i9ndicate there was nothing amiss, but worth checking if you have any doubts.

ComicGeek

FreeBear said:

ComicGeek said:

First of all there is some confusion in the statements above. It is very unlikely that the underfloor heating system design would fundamentally change between a gas boiler or heat pump system (the exception being whether you have a blending valve or not on the underfloor heating manifold) - the limitation is normally the surface temperature of the floor, which would normally limit the heating flow temperature to maximum 45-50 degrees. With a new build property with modern insulation etc, you would expect that to be at the bottom end, with maximum 45 degrees.  

If you have radiators in other parts of the house, then yes these could be sized for a higher water temperature which could cause issues - but that is separate to the underfloor heating.

Building Rgulations, Part L, Section 5.10 states that a wet system should be designed with a maximum flow temperature of 55°C. And from what little I know of wet UFH, the design temperature should be between 35°C and 45°C.

That's assuming that it was built under Part L 2021 - it's very possible that it was still built out under Part L 2013 and without those design restrictions. Most UFH designers will still design to 45 degree flow temps unless asked otherwise - they may be able to reduce flow temps by reducing loop spacing, but that is an extra capital cost that developers aren't willing to pay, just the screwed up system that we currently have.

ComicGeek

farmerjj said:

Thanks for the reply.

The installers were not MCS certified.

3 independent reports are saying the following (full report below):

- Heat pump way oversized for house

- Blending valve and other pumps fitted when not needed

- Pipework not lagged correctly

Currently our SCOP is running at 1.

Weather Comp is set up and was told this was fine by the other experts.

Samsung 12Kw Heat Pump

Total Floor Area of new build is: 1850Sq Ft (171m sq)
3 bedroom bungalow.

Thanks.

REPORT:

Heat loss and unit size

I have carried out a heat loss survey on the property and found the total heat loss to be somewhere between 3.5 and 5kW, meaning the installed unit is grossly oversized, by a factor of 2 or 3.

Primary pipe sizing

The pipework connecting the outdoor unit to the cylinder is undersized for the flow rates required, and should have been minimum 28mm copper, possibly 35mm copper (28mm pushfit have been used which is too restrictive, with a pressure drop of over 1kPa/m). As it happens, the pipework would be sufficient for a 5kW unit which should have been specified).

Outdoor Pipework

The outdoor primary pipework is very poorly installed and needs removing and refitting, the pipes should be fully insulated and sealed to prevent water ingress (wet insulation has virtually no insulating qualities), clips should be fitted outside the insulation, and pipes should be insulated and sleeved as they pass through the wall. If lever valves are installed outside, they should have long stem handles and be fully insulated and sealed.

Pipework in loft

Pipework in loft in very poorly insulated, sometimes not insulated at all. As the loft is outside the thermal envelope, the same insulating practices should be used as outdoors, with fully mitred joints, and clips over the insulation

Poor control strategy, unnecessary components and bad hydronic design, resulting on a very poor COP

The current heat pump system is not optimized for efficiency due to a poor control strategy and unnecessary components. Ideally, a heat pump should operate using a weather compensation curve, which adjusts the heat output to match the property's heat loss at varying outdoor temperatures. This approach ensures optimal efficiency, as each 1ºC increase in flow temperature can lead to approximately a 3% decrease in efficiency. Unfortunately, the existing system functions similarly to a gas boiler, with multiple on/off controls and elevated flow temperatures. Additionally, the presence of a redundant mixing valve on the underfloor heating manifold, which is unnecessary for systems not running at high temperatures, further complicates the system. These factors contribute to a suboptimal coefficient of performance (COP) and highlight the need for a revised control strategy and system design.

The COP since install according to the HIU is 1.17, barely more than what would be achieved with plug in radiators and an immersion heater (which would be a COP of 1 and a fraction of the cost to install). The minimum efficiency a system should work at according to MCS is 2.8, although really you should be aiming for 4+ on a new build with such a low heat loss.

That is a large bungalow at 171m2 - very low chance that the calculated heat loss will only be 3.5-5 kW unless it has incredible (ie not just building regs compliant) levels of airtightness and insulation. Typical heat losses would still be around 50 W/m2 for a bungalow, so minimum of 9 kW for the property. The Samsung outputs drop off as the external temp drops, so the 12kW unit is probably the next unit size with around 10 kW output at -3 outside. The heat loss calculations are a worst case scenario with no internal heat gains (ie people, lights, cooking etc) and no beneficial solar gain, and happening when it's really cold outside (ie -3 degrees) - that's probably only about 0.4% of the year, with the other 99.6% of hours needing a lower heat demand than that.

If they had installed a 5kW unit you would have been complaining about high bills and poor performance during the first cold spell - I do heat loss calculations for new builds almost every day at work, that is just rubbish! 

The issue of a mixing valve on the UFH manifold is also a non issue - I have this argument with heat pump installers multiple times a week. The mixing valve is there to guarantee that the floor is not damaged by high temperature water - the installer cannot guarantee that the heat pump will always generate water below the floor safe temp, even user error can cause problems. The additional pump set and hydronic break between the UFH and primary circuit do not affect system efficiency, and IMO I see it as a positive safety/control device. 

The fundamental question is: what is the flow temperature set for the system? The report states 'elevated flow temperatures' but do you know what this actually is? If you're keeping the UFH running constantly then drop the flow temperature until it only just achieves your required internal temperature - then when it gets too cold you can just increase it for a few hours. 

I'm not convinced about pipework size being a major issue, these units generally have a 1 inch pipework connection - that will depend on what the design water temps are for the system, whether they have sized for 5, 7 or 10 degree difference between flow and return. Less of an issue where there are separate UFH manifold pumps as well.

Insulation would be an issue, and yes improving the insulation to the external and loft pipework will help efficiencies. But COP of 1 is so low that there must be a larger issue - the last time I saw a COP that low the unit had been installed inside a shed, and there was a layer of ice inside as it couldn't get any air through the unit!

Do you have a backup heater installed? I've seen some installed to supplement heat pumps, and these are just direct electric heaters - would be worth checking that something hasn't been installed (and left on) to boost the water temp.