EPC rated air pump as "poor"

Jemma01

cannugec5 said:

We have an ASHP installed 2023 and an EPC immediately afterwards. 

We have a star rating (Scotland) and we were given 4 out of a possible 5 for our heating, with 3 for hot water. 

I find it odd that a comment was that we “should” install TRVs and have zoned thermostatic control. We have both, but clearly the assessor did not notice! 

Sorry might be a very daft question. Do you understand why you got 3 for water? Does it not heat the water efficiently enough? Or does it not keep the water hot? Or maybe it doesn't heat the water well? 🤕

Netexporter

You generally get a lower COP heating DHW because the heat pump has to operate at a higher temperature. Ideally, you want a flow temperature, in the heating system, as near as 30 degrees as you can manage. DHW has to be heated to perhaps 50 degrees, depending on how large your cylinder is, so the heat pump has to have a flow temperature even higher than that, which lowers the COP. However, that is for a relatively short time (ideally at night when the leccy is cheaper) so doesn't affect the SCOP too badly. Periodically DHW has to heated even higher, as a legionella precaution, which lowers COP further, although some systems us an immersion heater to assist in that.

cannugec5

Jemma01 said:

cannugec5 said:

We have an ASHP installed 2023 and an EPC immediately afterwards. 

We have a star rating (Scotland) and we were given 4 out of a possible 5 for our heating, with 3 for hot water. 

I find it odd that a comment was that we “should” install TRVs and have zoned thermostatic control. We have both, but clearly the assessor did not notice! 

Sorry might be a very daft question. Do you understand why you got 3 for water? Does it not heat the water efficiently enough? Or does it not keep the water hot? Or maybe it doesn't heat the water well? 🤕

I think Netexporter has answered the question. 

But to reassure we have plenty of hot water whenever we need it, and it remains hot. 

Jemma01

Thanks @Netexporter and @cannugec5 , much appreciated. I feel slightly less nervous about about the venture. I'll get someone to check the installation for peace of mind if my offer is accepted.

matelodave

The energy performance of a heatpump is quoted as a COP for specific input/output temperatures so varies widely and can get as low as 2 on a freezing cold day when you might have the highest flow temperatures but could easily achieve 4-5 in the summer when its just heating the hot water so most systems are rated with an SCOP (Seasonal Coefficient of Performance) which attempts to average it it out over the whole year.

We've had ours for some fourteen years and after learning how to use it properly rather than like a gas boiler, a bit of tweaking of the controls to suit our lifestyle (and to satisfy my wife etc) ours works and works well. It does take a bit of understanding how to get the best out of it and many of the scare stories are the result of poor specification, poor installation and poor user knowledge.

Dont get hung up on all the myths about DHW, legionella, defrosting etc, again most of these are because people dont understand what is going on or how to configure the system properly. We have plenty of hot water but only keep it at around 45 degrees which is hot enough to shower with without adding gallons of cold water (its a bit count intuitive but why heat hot water to 60-70 degrees and then mix in lots of cold water to bring it down to a usable temperature) It take about an hour a day to heat the tank.

The our legionella function that winds people up means that the water temp gets boosted from 45 to 60 degrees for about an hour once a week (Saturdays for us)  and as the heatpump can get it to 55 it means that the immersion is on for about half an hour. As the water is a hotter than normal the hot water doesn't need to heat on Sundays so TBH the cost is negligible.

Same for the defrost, it takes about five minutes when it does it but again usually when it freezing cold outside. Our systems has worked down to -14C and we've not needed to use the boost heater.

Regarding cost, yes leccy is more expensive than gas and unreasonably so, but it wasn't always like that and if you can get leccy for around three times the price of gas then there's not a lot of difference in the cost of running it and you have the advantage of not paying the standing charge for gas.

As said above, the EPC was designed for efficient gas systems with all the added  hangon's like TRV,s zone controls and anything else that the building regs demanded at the time. Heatpumps dont work like that but EPCs and the assessors (if you can find one who has a vague idea of what he should be doing) still haven't managed to adapt to the new reality (I'm not even sure that the building regs have  either.

I think most people have a jaundiced view about EPC's and the assessors (most of whom have got their qualification over the internet or via a correspondence course) but the government still puts great store on an outdated and flawed EPC system which isn't fit for its purpose anymore (if it ever was) and they seem incapable of sorting it out - just my opinion you understand

Jemma01

matelodave said:

The energy performance of a heatpump is quoted as a COP for specific input/output temperatures so varies widely and can get as low as 2 on a freezing cold day when you might have the highest flow temperatures but could easily achieve 4-5 in the summer when its just heating the hot water so most systems are rated with an SCOP (Seasonal Coefficient of Performance) which attempts to average it it out over the whole year.

We've had ours for some fourteen years and after learning how to use it properly rather than like a gas boiler, a bit of tweaking of the controls to suit our lifestyle (and to satisfy my wife etc) ours works and works well. It does take a bit of understanding how to get the best out of it and many of the scare stories are the result of poor specification, poor installation and poor user knowledge.

Dont get hung up on all the myths about DHW, legionella, defrosting etc, again most of these are because people dont understand what is going on or how to configure the system properly. We have plenty of hot water but only keep it at around 45 degrees which is hot enough to shower with without adding gallons of cold water (its a bit count intuitive but why heat hot water to 60-70 degrees and then mix in lots of cold water to bring it down to a usable temperature) It take about an hour a day to heat the tank.

The our legionella function that winds people up means that the water temp gets boosted from 45 to 60 degrees for about an hour once a week (Saturdays for us)  and as the heatpump can get it to 55 it means that the immersion is on for about half an hour. As the water is a hotter than normal the hot water doesn't need to heat on Sundays so TBH the cost is negligible.

Same for the defrost, it takes about five minutes when it does it but again usually when it freezing cold outside. Our systems has worked down to -14C and we've not needed to use the boost heater.

Regarding cost, yes leccy is more expensive than gas and unreasonably so, but it wasn't always like that and if you can get leccy for around three times the price of gas then there's not a lot of difference in the cost of running it and you have the advantage of not paying the standing charge for gas.

As said above, the EPC was designed for efficient gas systems with all the added  hangon's like TRV,s zone controls and anything else that the building regs demanded at the time. Heatpumps dont work like that but EPCs and the assessors (if you can find one who has a vague idea of what he should be doing) still haven't managed to adapt to the new reality (I'm not even sure that the building regs have  either.

I think most people have a jaundiced view about EPC's and the assessors (most of whom have got their qualification over the internet or via a correspondence course) but the government still puts great store on an outdated and flawed EPC system which isn't fit for its purpose anymore (if it ever was) and they seem incapable of sorting it out - just my opinion you understand

Very appreciative of your thorough response. From watching youtube reviews from homeowners, it seems that once you've got the hang of it, it's no longer an issue. It is just the mindset of shuffling from gas to this. Having lived in an electric-only home for 6 years now that doesn't have radiators even, it sounds like it is just a matter of getting used to the control part of it, and getting the right settings for it to be efficient for the cost (likely I'll get someone else to assess this for me and show me how to fine-tune it for my usage).

Again, thanks a lot, very helpful.

Strummer22

Reed_Richards said:

Netexporter said:

I find it odd that a comment was that we “should” install TRVs and have zoned thermostatic control. We have both, but clearly the assessor did not notice! 

The current wisdom is that you shouldn't have zones or any other obstructions. Best SCOPs are achieved by having  correctly sized emitters but relying on weather compensation to regulate the flow temperature.

That's the current wisdom for the most economical operation of a heat pump; it's not necessarily what gives you the most comfort.  I don't believe any installer will have enough time to properly balance a set of radiators to match each room to the temperature you want it to be so TRVs are a quick fix.  They are mandated because before people had them, rooms tended to get overheated, wasting money and energy.  Anyway, TRVs shut off gradually so if you are trying to achieve a constant temperature 24/7 then it doesn't make much odds whether you have these or just carefully throttled valves.

My heat pump is a retrofit and we've kept the same radiators (for now). No way the radiators could all be perfectly balanced. Fitting TRVs has really improved usability and made no noticeable difference to the COP. It will have reduced overall electricity consumption though as we can turn off the flow to any rooms that are temporarily not in use. 

@matelodave I don't think it's just your opinion that EPCs aren't fit for purpose. It's pretty evident that the whole EPC system needs an overhaul. As an example, my EPC states that my property's estimated energy needs are about 30,000 kWh per year, so using 7,500 kWh of electricity if the heat pump achieves a SCOP of 4. It also states that my property will produce 9.8 tonnes of CO2 per year. That's equivalent to 1.3 kg of CO2 per kWh used. Even burning coal to generate electricity produces less than 1 kg CO2/kWh (according to https://www.energydashboard.co.uk). Taking the grid average from last year of 162 gCO2/kWh, heating my home would result in only 1.2 tonnes of CO2 emissions. How come my EPC is full of such gubbins?   

Baxter100

Ultimately the EPC is based on cost, and heat pumps are generally pretty expensive to run.

Strummer22

Baxter100 said:

Ultimately the EPC is based on cost, and heat pumps are generally pretty expensive to run.

Heat pumps cost about the same to run as a gas boiler... 

Baxter100

In a small selection of circumstances, yes.