Many thanks to everyone who contributes here especially Trystan Lea.
My take from this thread and others is as follows.
It still seems to be the case far too many heat pumps are being forced on customers with oversized capacity, I have not yet got my own but I am very concerned over this as not only does it rely on potentially less knowledgable customers spotting this soon enough, but also being able to successfully get it replaced and not being stuck permanently with an incorrectly sized system. This seems to be both down to bad suppliers/fitters and bad guidance by the MCS.
My second view is that this suggests to me an urgent need for ALL heat pumps to have monitoring systems fitted as standard and for this to be made a legal compulsory requirement for all new installations. This could be for local only reporting but should also allow the option for customers to connect to online reporting system(s) of their choice. A local reporting system could be via either the included control panel or a device similar to an energy smart meter’s IHD (In Home Display) or a mobile app. It should provide monitoring/sensors equivalent to those used in the EoH trial and/or OpenEnergyMonitor. I sadly feel that many (not all) suppliers/fitters rely on customers being in the dark regarding the actual performance of the systems.
and surveyors… primarily I’d suggest. But they might be one and the same.
From the comments I’ve read here generally, an accurate record of the ‘conventional’ heating load is also an extremely useful number to have, yet I suspect the proportion of heat pump proposals where this is/has been available is vanishingly small.
The EV charging standards legislation enforced this (as well as demand supply reduction and smart capabilities) so would be a reasonable baseline to follow. Requires the data to be available to the user for 12 months.
I guess hardening the EVSE legislation (increasing costs and reducing competition) probably wasn’t as big a risk to EV adoption which looks like it will continue to grow without any continued interventions.
Another perspective (on human nature as much as anything):
Suppose (in very round numbers) that your un-optimised heat pump consumes 1kW x 16h/day x 200 days/yr = 3200kWh/y, and that you could reduce this by 20% through diligent optimisation (and maybe spending up to £1000 on monitoring gear). So you could save 640kWh/y or about £130/y (at £0.2/kWh). A fair financial payback, but at the cost of considerable effort on your part (not to mention your partner’s tolerance…).
Now suppose (again round numbers) that your (petrol-powered) car is driven 10000miles/y at 10miles/litre = 1000litres/y, and that you could reduce this by just 10% by driving better (gentler acceleration, minimum braking etc.). Then you could save 100litre/y or about £140/y (at £1.4/litre).
Same payback, at zero investment, and just a little patience and anticipation required. From what I’ve seen, not many car drivers think about driving more economically. So it’s not surprising that not many heat pump owners worry about that last 0.1 on CoP.
(Sorry for the rant, must be reading too much @Marko_Cosic).
One difference perhaps being that one is an investment (pain once, then set and forget for 20 years) whereas the other is an operating expense (effort required every day for 20 years) when it comes to “spending your sanity” or “spending your partner’s patience.”
Agreed that the final 10-20% extra from.ypur electricity (COP 3.75 to 4.2-4.6ish) is perhaps for enthusiasts.
The first 50% extra from.ypur electricity to get from COP 2.5 to COP 3.75 should come from the initial installation and is well worth the investment.
We see in the trial data that some of the installers are doing this already whereas others are not.
Add in equipment longevity (from not wearing itself into oblivion with starts and stops; from water quality not being an air riddled soup; from pumps not filling with iron and valves not getting warm away etc) and avoiding the basics COP2.5 crow mistakes become as much an investment no brainer as not driving the car into every pillar in every car park/not grinding the tyres again every kerb/changing the oils and filters in a car etc?
The underlying data feeds used for each dashboard are now easily accessible. The number of feeds is listed in the table, click through to open the emoncms feeds page for the system. Some systems have feeds that I’ve not made use of yet such as brine in/out temperatures for ground source systems.
I’ve made an initial start on flagging systems with metering errors as identified here. I’ve only done this for a hand full of systems so far, if anyone would like to help with identifying metering errors that would be much appreciated!
Any help with identifying metering errors would be much appreciated. I will build a mechanism to make it easier to submit comments on systems both for metering errors and identifying the much more prevalent configuration issues but in the mean time any additions to the following example list would be much appreciated!
"EOH0323","Metering error, Boiler heat included in heat pump output"
"EOH1046","Metering error, Boiler heat included in heat pump output"
"EOH2012","Metering error, Boiler heat included in heat pump output"
"EOH0018","Metering error, Boiler heat included in heat pump output"
"EOH1022","Metering error, Boiler heat included in heat pump output"
"EOH2963","Metering error, Boiler heat included in heat pump output"
"EOH1725","Metering error, No heat during hot water only period"
"EOH3095","Metering error, SPF much too high for measured system temperatures"
"EOH1285","Only ~25% of ideal carnot, this is most likely a heat meter error, either an under read of flow rate (dirt in Sontex heat meter) or incorrect DT measurement."
"EOH3045","Only ~21% of ideal carnot, this is most likely a heat meter error, either an under read of flow rate (dirt in Sontex heat meter) or incorrect DT measurement. Immersion heater electric included twice in our heat pump dashboard but not in EoH SPF hence even lower apparent performance, to fix."
Sounds like they should produce a version for landlords that includes a data SIM. They’re pretty cheap.
When I had a petrol car, I started thinking about it when I bought a car that showed the instantaneous MPG in the display in front of me It was a good game on long drives.
But is it legel under the housing stardard regulations to only allow tenants with a mobile phone to control their heating? Or does Homely now have a local control unit?
How is it practical for a landlord to keep registering new tenant’s mobiles to control heating when letting agent staff have such a low level of practical ability?
It’s also legal to provide no control over the jeating whatsoever.
(e.g. weather compensated to achieve approx 20C with windows closed; and if people open windows they get cold; or indeed TRVs with locking pins to prevent them being turned up beyond 21C and/or electronic control with open window interlocks)
Tenants need to pay the electricity bills in this scenario. Else the landlord is welcome to a 2kW electric heater I’m each room and controlling temperature by opening the windows.
Or bills are included (for heating and ventilation; landlord managed) but electricity for lights and sockets is on a submetered supply and recharged along with rent by the landlord.
No, no. The Homely unit (or whatever is trying to make a connection - EVSE’s do it) makes a connection directly to its server via the Internet over 4g/5g or whatever. The tenant is not involved. If the tenant is supposed to interact with it then it presumably needs some sort of user interface?
I’ve added the installation cost information as an option to explore. The study does caveat that these prices may not reflect market rates (these were the costs to the EoH project). It looks like plenty of money was spent on the installs including radiator upgrades. It doesn’t look like a simple case of cheap installs resulting in low performance results. There’s plenty of systems that cost a similar amount to Damon’s SCOP 5 Viessman Vitocal (£17.5k) but deliver performance as low as SPF 2.3 though more typically around 3.
My system (EOH2283) is the most expensive OVO installation on the list! However I previously had gas powered warm air heating and a vented hot water cylinder with an immersion, so the price includes absolutely everything: radiators, all pipework, unvented cylinder etc. as well as the heat pump indoor and outdoor “fridge split” units.
(The old system was not removed by the EoH project).
It is very dissapointing to see such poor performance from the Vaillant Arotherms. I haven’t read all the reports fully, but was there any questioning of the performance achieved vs the specification of the heat pump?
It seems an obvious step that should have been carried out.
There is a comparison of calculated SCOP using the MCS methodology vs monitored results. This section just notes that a performance gap is seen in the data. A fairly vague statement is given as to why they see this difference : “This indicates that there may be issues in the design process resulting in this difference between the calculated ‘as designed’ SCOP and in-situ SPF”.
The optimisation report lists most of the reasons why a heat pump will perform badly, but does not link this to the monitored data. E.g it does say that poor configuration of weather compensation is a reason for poor heat pump performance but it does not say how many systems in the study have poorly configured weather compensation curves…
1. Weighted average metrics and error detection metrics
Weighted average flow temperature by heat delivered
Weighted average outside temperature by heat delivered
Weighted average flow minus outside temperature by heat delivered
Weighted average difference between flow and return temperature by heat delivered
Weighted average % of ideal carnot COP (weighted by heat delivered)
Error detection
% of heat delivered at above 70% of ideal carnot COP (this is outside of the performance range that we would expect and typically indicate metering errors such as including boiler heat in heat pump heat output or DT error on temperature sensors…
% of heat delivered below a COP of 1: Heat meter error, not accounting for immersion heater or booster heater heat in heat output (I need to do a bit more work on the immersion heater and booster heater treatment in the data).
% of electric consumption with zero heat output recorded by the heat meter (excluding standby) the air detection algorithm we already use.
There are a lot of heat pumps on the list that have very low weighted average % of ideal carnot cop values, e.g <35%. We’d generally expect heat pumps to fall between 40% and 60% of ideal carnot, with the majority between 45-50%.
A low % carnot value is obtained when the heat output as measured by the heat meter is lower than we would expect for the given system temperatures. An extreme example is system EOH3045, It’s apparently only delivering 1940W of heat whilst consuming 1602W of electric. It is running hot at 50C but we would still expect a lot more heat output under these conditions.
I’ve improved the % carnot calculation, I think it’s more accurate now and it cuts the number of systems below 35% carnot from 50% to about 20% and zooming into the data for a hand full of systems the average result does seem to be more representative.
).
It was a good game on long drives.
