Vaillant 7kw % efficiency rating for BREL Part L

[Post and beam]

I think i have seen on here somewhere or possibly been directed to a site that lists the % efficiency ratings as they relate to the Building Regs Part L and the SAP assessment process.

 

My as designed sap report gives a % of 219% at Para 4 space heating.

 

So, does this percentage directly relate to the COP/SCOP?

 

My intended ASHP will be a Vaillant aroTHERM 7kw

[PNAmble]

Ours said 231.1% with a flow temp of 55.  Based on our 5kw Ecodan.   Which is probably true.  What does your report say the flow temp is ?
 

We are intending to run our radiators at 35 so when we do as built I’ll make sure this is corrected.   Our design also stated 35 but I couldn’t be bothered to argue as it was still an A95. 

[Post and beam]

16 hours ago, PNAmble said:

What does your report say the flow temp is ?

It didn't say anything. It does not mention what make or model of heat pump either. It was created by my TF company and before i go back and ask them where the 219% figure comes from i was hoping to have a little more knowledge.

I want to run the UFH flow at 35 degrees maximum.

 

I have  emailed Vaillant tech support to see if they can point me at some credible facts and figures.  If, in fact, the 219% refers to COP/SCOP then i know Vaillants own site is up over 4.

[PNAmble]

1 hour ago, Post and beam said:

didn't say anything

mine has this .. we hadn’t decided on a hot water cylinder when we got it done.

 

 

Edited February 3 by PNAmble

[sharpener]

Here you go:

 

[Post and beam]

?

[Dan F]

46 minutes ago, sharpener said:

Here you go:

 

 

Thats COP not SCOP though.  The values used for SAP are up on MCS website. Values for 35-55C design flow temp.   4.36 was used for my SAP AFAIK.

 

[Dan F]

My MCS certificate (for 7kW aroTherm Plus) says:

I'm unsure if/how this is used in SAP though.. anyone know?  Or if SAP uses it's own numbers

 

SAP Worksheets looks like it says "381.57 efficiency", no idea where this comes from though..

Edited February 3 by Dan F

[Post and beam]

6 hours ago, Dan F said:

I'm unsure if/how this is used in SAP though.. anyone know?  Or if SAP uses it's own numbers

Exactly that question. Difficult to decipher how 4.36 and 219% relate to each other.

[Dan F]

4 minutes ago, Post and beam said:

Exactly that question. Difficult to decipher how 4.36 and 219% relate to each other.

 

Or, in my case 4.36 and 381.57.   Where do you see the 219%, I'm seeing 381.57 here:

 

[JohnMo]

On 02/02/2024 at 18:35, Post and beam said:

I think i have seen on here somewhere or possibly been directed to a site that lists the % efficiency ratings as they relate to the Building Regs Part L and the SAP assessment process.

 

My as designed sap report gives a % of 219% at Para 4 space heating.

 

So, does this percentage directly relate to the COP/SCOP?

 

My intended ASHP will be a Vaillant aroTHERM 7kw

 

Everything you need if you can be bothered reading

 

 

STP11-HP-01_Heat_Pumps.pdf

[Post and beam]

15 hours ago, Dan F said:

Where do you see the 219%

Here Dude

 

[Post and beam]

And if i look in the full SAP report that i have just re discovered i get this....

 

[MikeSharp01]

15 hours ago, JohnMo said:

Everything you need if you can be bothered reading

That is a very interesting read - would be good to see the research the default tables are based on and how the 'where this data is made available' is asked of the manufacturers.

[Post and beam]

 

15 hours ago, JohnMo said:

Everything you need if you can be bothered reading

I note that the report dates from 2011. I wonder if its still accurate enough to be relevant

[JohnMo]

On 02/02/2024 at 18:35, Post and beam said:

as designed sap report gives a % of 219% at Para 4 space heating.

Mine gave the following for a named gas boiler in my as built - Efficiency: 89.7%,

 

Even though I was running at 35 degs max flow temp, against a declared heating efficiency from the manufacturer of 109.7% for the same running condition. Checked against certified heat meter and actual gas consumption, I was getting very close to that figure.

 

There just numbers to enable a comparison of one building to another on similar basis, at the end of the day. Move on to the next battle.

[Post and beam]

15 hours ago, JohnMo said:

Everything you need if you can be bothered reading

 Having now read the thing i also note that the author decides to discount low side values that are too far from the average becuase they must be unreliable. I wonder on what basis he made that call.

[Dan F]

1 hour ago, Post and beam said:

 Having now read the thing i also note that the author decides to discount low side values that are too far from the average becuase they must be unreliable. I wonder on what basis he made that call.

 

I thought defaults from table a were only used if there was no SCOP on MCS certificate (or no MCS), but maybe it's not that simple. 

[JohnMo]

12 minutes ago, Dan F said:

I thought defaults from table a were only used if there was no SCOP on MCS certificate (or no MCS), but maybe it's not that simple. 

 

Just got to read the number of issues people have in a ASHP section of this forum, with rubbish CoP.  Bit like car manufacturer MPG claims, real world isn't the same a laboratory conditions.

 

You can get great CoP figures, until the owner or installer, starts adding lots of zones, controlling temperature via thermostats, buffers (of poor design) to compensate, immersion heaters, etc.

 

An arbitrary figure of efficiency saying your heat pump has about 2.6 better than a gas boiler (during the heating season) is probably good enough to cover the good and bad install.

Edited February 4 by JohnMo

[sharpener]

2 hours ago, Post and beam said:

 

I note that the report dates from 2011. I wonder if its still accurate enough to be relevant

Pre-dates widespread use of R290 refrigerant so I would have thought badly out of date now. A bit like Council Tax bands.

[Beelbeebub]

1 hour ago, JohnMo said:

 

Just got to read the number of issues people have in a ASHP section of this forum, with rubbish CoP.  Bit like car manufacturer MPG claims, real world isn't the same a laboratory conditions.

 

You can get great CoP figures, until the owner or installer, starts adding lots of zones, controlling temperature via thermostats, buffers (of poor design) to compensate, immersion heaters, etc.

 

An arbitrary figure of efficiency saying your heat pump has about 2.6 better than a gas boiler (during the heating season) is probably good enough to cover the good and bad install.

I think the instantaneous Cop figures are pretty solid (not that many manufacturers provide these). 

 

The issue comes that the outside temp and inside temp demanded are continuously varying so rather than getting one point on the graph, you wander around it sometimes getting good cop and sometimes not.  The Scop tries to capture this, but is (like the car mpg) only ever an approximation based on idealised standard conditions. 

 

Part of the problem in the UK is that our elec/gas unit price ratio is around 3.5 to 1. In order to achive price parity your installation needs to be fairly well done. Typical industry practice (sloppy heat calculation, buffers, zones etc) does not reliably hit this performance - hence tales of disappointment. 

 

If the ratio were (say) 2.75 to 1 then many more installs would better that and we would have far fewer "my heatpump costs more to run" stories for the daily mail and telegraph to print. 

 

If we had a ratio closer to 2 to 1 then people woukd be falling over themselves for Heatpumps as even a fairly sloppy install coukd save you money and a good one woukd save significant sums.