We recently (back in July) had a heat pump install, moving from a condensing gas boiler. They did all the usual MCS things before the install. One thing they proposed was to increase the size of all all my downstairs rads by approx 50% output and decrease the size of all my upstairs radiators by 50%. All of the 20+ rads were changed out. Previously the house had been relatively warm and uniform throughout. Following the install, the downstairs rooms remain warm and the upstairs rooms are freezing, running between 5-7C below design temperature.
At the time of the install I very heavily challenged what they were doing, as to me it’s common sense that in moving from deltaT50 to deltaT30, halving the radiator size effective reduces the heat output by 75%. But they insisted that this is what their heat loss survey indicated. We had added approximately 200mm of loft insulation, bring it up to the 300mm standard, but surely that alone won’t reduce the heat requirement by 75%.
They have now agreed to repeat the heat loss survey using a revised methodology. Am I best to allow them to continue this or should I, in parallel, contact MCS and get them to initiate an investigation via their professional certification body. The installer has been a little slow but did act when I collected my own data using remote sensing devices in several rooms. My instinct tells me to give the installer room to remediate before starting a formal complaint, or am I being naive please?
One thing they proposed was to increase the size of all all my downstairs rads by approx 50% output and decrease the size of all my upstairs radiators by 50%. All of the 20+ rads were changed out.
Reducing radiator size is just plain madness in most cases, whatever the survey may say. You can always turn them down. Why on earth would you waste money unnecessarily?
Based on what we hear from people here, MCS will do nothing and even if they do will certainly insist on allowing the installer time to remediate. If you have the interest to do so Id be tempted to suggest you do your own heat loss calculations. Certainly I would ask them to produce theirs (old and new) including the assumptions so you can check where they are going wrong because obviously they are! I recommend to keep all correspondence and careful notes in case you end up in the small claims court.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
thanks, yes it seemed mad to me. An exert from the heat loss report for one of the rooms is below.
I told them prior to and during the install, pushed back three times. It was a partial grant, the local authority flex scheme for those whom don’t qualify for standard ECO 4. Unfortunately the supplier had the sole supplier contract (I’m sure brown envelopes were involved), so we had no choice of contractor. As it’s partially via the local authority I may be able to use them as leverage, I also made sure I paid £100 of it on credit card too, just in case. I will try to do my own heat calcs, I think there are tools available online. They are coming next week to repeat.
thanks, yes it seemed mad to me. An exert from the heat loss report for one of the rooms is below.
I told them prior to and during the install, pushed back three times. It was a partial grant, the local authority flex scheme for those whom don’t qualify for standard ECO 4. Unfortunately the supplier had the sole supplier contract (I’m sure brown envelopes were involved), so we had no choice of contractor. As it’s partially via the local authority I may be able to use them as leverage, I also made sure I paid £100 of it on credit card too, just in case. I will try to do my own heat calcs, I think there are tools available online. They are coming next week to repeat.
thanks for advice
Total and complete madness! Better would have been to leave the upstairs rads, make the downstairs ones bigger if there is room, and drop FT, or just leave the upstairs rads and turn them down.
Nothing obviously wrong about the assumptions although 28W/sq m suggests pretty good insulation assumed. It might be worth interrogating the materials/U values assumed. Is there any chance you have cavity walls that aren't filled at the top (a common problem apparently).
Its just possible that some rebalancing will fix the problem, but not particularly likely. Just don't let them increase the FT to fix it because it will cost you. Rads are cheap and changing them easy, so I hope it wont be too difficult to persuade them just to swap it back. TBH I'm surprised they are bothering to do another survey, for the cost they could swap two or three rads and still have change and the fact your rooms are cold tells them more than a survey ever can, because its a real measurement not GIGO what-iffery!
The underlying problem we have is that hardly anyone in the heating industry understands heating, they just follow (if you are lucky) instructions. Decades of lazy design, when gas from the North sea was dirt cheap, is arguably to blame for that together with the fact that, as a nation, we have little or no respect for 'manual trades' and prefer instead celebrities and influencers.
This post was modified 2 months ago 3 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
We are running completely open loop and the upper floor rads are already reaching the same temp as the lower floor rads. So rebalancing can’t help, the room under it easily reaches design temp, I can’t change flow temp as that’s controlled by a homely optimiser. The heat pump is large, a 16kW double fan Samsung, I think it is oversized as it only runs 40%. We have about 4m2 of double glazed units in that room, 3 of the walls are effectively outside facing (the landing is unheated). Also above it, only 50% of the ceiling is 300m loft insulation, the remaining is taken up by a DIY room in roof with very minimal insulation. I’m certain the calcs are wrong, I will try it myself today.
it’s a bloody mess. Cheap to run though, I get great COPs and costs me 60% less than my gas did, although house is both hot and cold concurrently!
its weird. It’s -1.5C outside, I’ve been monitoring the temp of the radiator (not the room) and it’s only running at about 24 C. The current outlet temp on the heat pump is 38C, I would have expected more of the heat output to be reaching the radiator. Earlier today the heat pump was running at 26C output, but no big difference in radiator temp between 26c or 38c output.
its weird. It’s -1.5C outside, I’ve been monitoring the temp of the radiator (not the room) and it’s only running at about 24 C. The current outlet temp on the heat pump is 38C, I would have expected more of the heat output to be reaching the radiator. Earlier today the heat pump was running at 26C output, but no big difference in radiator temp between 26c or 38c output.
The corresponding room temp is
Well that puts a different light on it altogether! Radiators not getting warm would be due to one or more of
(a) valve blocked - note that TRV pins can get stuck if they are shut off for an extended period of time - check by removing the heads and seeing if the pin moves at all - the expected movement is only about 2mm. If it doesn't the judicious application of a hammer to the side of the valve directly opposite the rad inlet usually unsticks it!
(b) rad needs bleeding
(c) insufficient system pressure
(d) needs balancing
This post was modified 2 months ago 3 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
New rads, new TRVs, new lockshields, power flushed, new pump 37l/min flow, i bled all rads, 3 air removal valves on system, plumber balanced and not touched since. To the touch, upstairs and downstairs rads felt similar temps, but I’ll start to monitor both and see if they are the same. Thanks.
New rads, new TRVs, new lockshields, power flushed, new pump 37l/min flow, i bled all rads, 3 air removal valves on system, plumber balanced and not touched since. To the touch, upstairs and downstairs rads felt similar temps, but I’ll start to monitor both and see if they are the same. Thanks
Air comes out of solution over time. I had to bleed one radiator every second day for a month after the installation was done and only the other day one year after installation had to bleed again, notwithstanding that there are auto bleed valves. The radiator in question was stone cold to the bottom, basically full with air.
Definitely don't rule this out in any CH system whatever the heat source. Suggest you check system pressure, open the bleed valve on any cold rads to check that they dont need bleeding (never assume, it makes an ass of u and me!), bleed any that do and then recheck system pressure. Standard procedure for keeping CH systems operating!
This post was modified 2 months ago 2 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
Yes, last week I did it and there was a little air. I’ve been comparing radiator temp and the upstairs and downstairs are within 0.3C of each other. A 33C heat pump outlet temp was resulting in radiators at central location of 25.8.
So they are getting similar flow and receiving similar heat. I just think they are too small. It doesn’t help that the homely node keeps turning the heat pump off. It runs for about 50 mins, reaches the set point temp and turns off for about 40 minutes until the temp drops below the set point. On/off/on/off, 24 hrs a day. I used to live in Switzerland about 15 years ago and we had a brilliant heat pump, it would start in the autumn and run continuously until the spring, none of this on/off crap.
I used to live in Switzerland about 15 years ago and we had a brilliant heat pump, it would start in the autumn and run continuously until the spring, none of this on/off crap.
Switzerland is a lot drier than the UK which means defrost is less likely to occur. They also may have some heating engineers, whereas we have a lot of people that call themselves heating engineers, haven't got a scooby but can spout BS for England
I just think they are too small. It doesn’t help that the homely node keeps turning the heat pump off. It runs for about 50 mins, reaches the set point temp and turns off for about 40 minutes until the temp drops below the set point. On/off/on/off, 24 hrs a day.
Agreed. Why not considering disconnecting it and running on pure WC?
This post was modified 2 months ago 2 times by JamesPa
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
