@jonathan Sad news regarding the Vaillant heat pump- hope you get a proper resolution soon. Sounds as though you have exercised due diligence and done all that might be expected of you too! Very good news about the battery though; I have 27 kWh of Powerwall and have not regretted it (Octopus Energy Cosy tariff here). Regards, Toodles
Toodles, he heats his home with cold draughts and cooks his food with magnets.
Obviously this should be resolved for you by your supplier.
However if it isn't for some reason it isn't, I wouldn't be too despondent. Looking at the reports you posted (and assuming I understand them correctly) you have UFH everywhere except in the kitchen where you have a radiator. The system is set to run at 50C to suit one radiator, and presumably blended down for the UFH. This is a bit mad, you are throwing away the efficiency available from UFH for the sake of one room and its costing you the difference between a SCOP at the heat pump of 3.65 and one of 4.3, roughly 20% on your electricity bill. You are losing further efficiency through the complex controls etc that @johnmo refers to.
If instead you ran it a 35 to suit the UFH then your heat pump will do 8.8kW at -3, not that far short of the 10.3kW the Vaillant report says you need. Furthermore it will run a lot more efficiently In the south of England there are only a very few days in the year (and some years there are none) when it goes down to -3 for more than a few hours at night, so the vast majority of the time you will have sufficient output from your heat pump.
So for the vast majority of the year it will work, and for the very few days when it doesn't a bit of supplementary heating will do the trick. As a matter of fact that should be the case (but less so) even running at 50, where the heat pump will do 7.9kW at -3, if its operated properly. However your current set up is not conducive to most efficient operation.
As a fallback to it being sorted out by your supplier (and anyway to reduce your electric bills) I would put some thought into
how you could replace/supplement the rad in the kitchen (fan radiator?, or additional radiator?) so you can drop the FT from the HP to 35.
which of the simplifications suggested by @johnmo could be done to give your heat pump a fighting chance of working.
Currently you are very likely hobbling your heat pump in addition to it being a little undersized. You are paying much more than you should be and changing the heat pump alone wont fix this. Of course your supplier should have sorted this out, but they didn't.
I hope your supplier sorts this all out for you, but if they don't or its taking too long (which, sadly, is possible given what we hear on this forum) then please do keep posting and you will certainly receive good advice.
Obviously this should be resolved for you by your supplier.
However if it isn't for some reason it isn't, I wouldn't be too despondent. Looking at the reports you posted (and assuming I understand them correctly) you have UFH everywhere except in the kitchen where you have a radiator. The system is set to run at 50C to suit one radiator, and presumably blended down for the UFH. This is a bit mad, you are throwing away the efficiency available from UFH for the sake of one room and its costing you the difference between a SCOP at the heat pump of 3.65 and one of 4.3, roughly 20% on your electricity bill. You are losing further efficiency through the complex controls etc that @johnmo refers to.
If instead you ran it a 35 to suit the UFH then your heat pump will do 8.8kW at -3, not that far short of the 10.3kW the Vaillant report says you need. Furthermore it will run a lot more efficiently In the south of England there are only a very few days in the year (and some years there are none) when it goes down to -3 for more than a few hours at night, so the vast majority of the time you will have sufficient output from your heat pump.
So for the vast majority of the year it will work, and for the very few days when it doesn't a bit of supplementary heating will do the trick. As a matter of fact that should be the case (but less so) even running at 50, where the heat pump will do 7.9kW at -3, if its operated properly. However your current set up is not conducive to most efficient operation.
As a fallback to it being sorted out by your supplier (and anyway to reduce your electric bills) I would put some thought into
how you could replace/supplement the rad in the kitchen (fan radiator?, or additional radiator?) so you can drop the FT from the HP to 35.
which of the simplifications suggested by @johnmo could be done to give your heat pump a fighting chance of working.
Currently you are very likely hobbling your heat pump in addition to it being a little undersized. You are paying much more than you should be and changing the heat pump alone wont fix this. Of course your supplier should have sorted this out, but they didn't.
I hope your supplier sorts this all out for you, but if they don't or its taking too long (which, sadly, is possible given what we hear on this forum) then please do keep posting and you will certainly receive good advice.
Thank you spending the time to address by problem.
There are no radiators in my house, all is UFH. I do have towel rails in each of the 4 bathrooms.
Hi Jonathan
The Vaillant report you posted and as I read it says you have a radiator in the kitchen, and also says you are running at a flow temp of 50, which is where I got this information from.
If its running at 50 to suit the towel rails, and being blended down for the UFH, then you are sacrificing a lot of efficiency (and capacity) for them.
What flow temperature is it actually running at at the design temp of -2?
Obviously this should be resolved for you by your supplier.
However if it isn't for some reason it isn't, I wouldn't be too despondent.
Thats not saying its ideal, just saying that, if for some reason your supplier/the industry abandons you, the problem is not completely insoluble.
The Vaillant '7kW' heat pump is actually capable of 8.8kW at -3 if run at 35C flow temp, which is where I would expect it to be run for UFH. Even at 50C its capable of 7.9kW. Neither of these is so far short of the 10.3kW that the Vaillant report says your house needs. What that means is that for the vast majority of the time your '7kW' unit is capable of supplying sufficient energy to heat your house if properly set up, as there are only a very few days in the year when its -3 for any significant number of hours. So in the event that you are abandoned, it can be made to work for most days of the year. A bit of supplementary heating will sort out the remaining few days, eg the Vaillant 'backup heater'. Not perfect but far from a disaster and indeed a design choice which some will make for other reasons ( a close neighbour of mine has in fact just been advised to do exactly this by Heat Geek, to circumvent a planning refusal)
This post was modified 5 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.
The relevant ones are, I think, the below. There is some room for interpretation but limited. Is your grant in doubt? You might want to be a bit circumspect and/or be prepared to think out of the box. For example the definition of a heat pump does not appear to exclude a system including a supplementary heater so long as the overall scop is at least 2.8.
Requirements for heat pumps
9.—(1) A heat pump meets the requirements in this paragraph where—
(a)no part of the heat pump which generates heat, other than the ground loop in the case of a subsequent heat pump installation in relation to a shared ground loop system, was used before the plant was first commissioned,
(b)it has a capacity of no more than 45 kilowatt thermal, or, in the case of a shared ground loop system, the system has a capacity of no more than 45 kilowatt thermal,
(c)it meets the requirements set out in the standards for heat pumps approved by the Secretary of State under regulation 4(1)(b) which are applicable when the plant is first commissioned,
(d)it has a seasonal coefficient of performance of at least 2.8, determined in accordance with the standard approved by the Secretary of State under regulation 4(1)(c) which is applicable when the plant is first commissioned,
(e)it uses a compressor which is driven by electricity, and
(f)if it is an air source heat pump, it is not designed to use heat in air which has been expelled from an appliance or building
2) A heat pump meets the suitability criteria in relation to the eligible property, or a property to which regulation 14(1)(b) applies, for which it is installed where—
(a)it provides heating—
(i)solely to that property, or to both that property and any related property, and
(ii)for the purpose of both space heating and hot water heating, using liquid as a medium for delivering that heat,
(b)it is capable of meeting the full space heating and hot water heating demands of that property, and
(b)it is capable of meeting the full space heating and hot water heating demands of that property, and
(c)it replaces the heat generating components of the original heating system installed in that property (where applicable), other than any—
(i)supplementary electric heater, including any immersion heater,
(ii)circulation pump, or
(iii)solar thermal collector
I stress that this should be sorted out by your installer, I'm just trying to cover the possibility that it isn't.
This post was modified 5 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.
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