@batpred That makes sense! Thanks for the information.

I have just had a heat geek survey, with no radiator changes and keeping my existing unvented cylinder. They quote a guaranteed efficiency of 370%. Is this the same as SCOP?

As somebody has already noted, heat geek do not provide a flow temperature until commissioning.

Prior to heat geek coming round I had done my own heat loss calculations, the old-fashioned way, using a spreadsheet. It took ages. My house was built in the 1920s, but has been extensively remodelled and extended. The study which is a 14 x 12’ room has a 1970’s 2140 X 600 double panel radiator with no fins which Google tells me has a delta T 50 output  of 2.1 Kw.

The heat geek heat loss for this room  was 1.17Kw. Using my heat loss spreadsheet, the radiator in that room would need a flow temperature of 55.5 to provide 1.17 kW of heat

My heat loss for this room  was 1.25Kw. Using my heat loss spreadsheet the radiator in that room would need a flow temperature of 56 to provide 1.17 kW of heat. I used a design temperature for the room of 21°.

Another room has similar results.

Is a flow temperature of 55° compatible with an efficiency of 370%?

I also understand that the quoted efficiency of 370% also includes heating the hot water.

Posted by: @david-2

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They quote a guaranteed efficiency of 370%. Is this the same as SCOP?

Quite probably, does the guarantee come with any definitions of terms

Posted by: @david-2

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Is a flow temperature of 55° compatible with an efficiency of 370%?

 

Quite possibly yes, albeit perhaps surprisingly.  Here is a plot from Openenergymonitor of SCOP vs design flow temperature for 169 systems.  These are actual measurements SOFAIK. 

That said I would not be surprised if they are betting on actual FT being lower than 55/the survey results would indicate, perhaps because of assumptions about air change rate which have a tendency to be pessimistic relative to real life.  Heat Geek have a lot of data from (generally it appears) well designed systems which they appear to be using to good effect in coming up with relatively low disruption ways to achieve good performance..

@jamespa 

‘The Industry Leading Heat Geek Performance Guarantee assures your installation (incl. heating and hot water!) will meet the efficiency stated in your system proposal at minimum. The installation will be remotely monitored and if it comes short of this efficiency, or unable to get your home up to temperature on the coldest days of the year, we will upgrade your system as necessary completely free of charge.’

I should add that there is a lot about the Heat Geek offer which is somewhat opaque. For example, the contract is between the customer and Heat Geek. Heat Geek gets all the money; they appoint the installer and they supply all the equipment. However, when I asked about, for example, a delay to my system commissioning report Ì was told to contact the installer which at the time seemed very odd to me. I have since found out that their installer sets the labour cost. I had assumed, wrongly, that these were Heat Geek installations with the installer acting as Heat Geek’s nominated installer.

Starting again, I might look at Heat Geek HQ in a different light. That said, I cannot fault my installer. His two guys did an excellent job. Whether the minimum SCOP guarantee is anymore important than a design temperature of 45degrees at -3C only time will tell. Since mid-April when the system was installed my system efficiency has been 3.77: this is with a 8 year old unvented cylinder.

Posted by: @l8again

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@jamespa 

‘The Industry Leading Heat Geek Performance Guarantee assures your installation (incl. heating and hot water!) will meet the efficiency stated in your system proposal at minimum. The installation will be remotely monitored and if it comes short of this efficiency, or unable to get your home up to temperature on the coldest days of the year, we will upgrade your system as necessary completely free of charge.’

 

I can imagine 'get outs' but doubt they will use them.  Heat Geek do appear to be 'industry leading' in offering this guarantee, and everything we hear suggests that it's based on a combination of in-field experience accumulated over many installs plus sound training. 

By avoiding over engineering, which others do to create margin against uncertainty, they reduce their install cost.  Very likely only some of the saving is passed onto the customer.

This probably allows them to 'play the numbers game', if a small percentage of installs 'fail' the guarantee then the cost of fixing is probably a days labour and a few radiators, or a swapped heat pump which they can reuse elsewhere.  If you are doing enough installs and get the vast majority right, this will be viable financially.

If this guess (and it is a guess) about what heat geek do is correct, they are to be applauded.  Just like the Octopus 'triage' and productize approach, which is somewhat complementary, it's what the industry needs if it is to 'grow up'.

Posted by: @l8again

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I should add that there is a lot about the Heat Geek offer which is somewhat opaque. For example, the contract is between the customer and Heat Geek. Heat Geek gets all the money; they appoint the installer and they supply all the equipment.

i agree that, in most cases, heat geek appoints the installer. 
But we used heat geek after choosing the installer. It is just a matter of getting a referral link for the installer at the initial stage. 
We also noticed that heat geek was not easy to reach (except using email) and they generally referred us to the installer for any queries. 
The quality and loyalty of many installers to heat geek is what we found to make the difference. They also have very strict processes and i think focus on a small number of designs, so seem to have a small hq team. 

@batpred Which is what I did and I am very happy with the quality of the work that has been done. I have happily recommended my installer to others. 

My point is that Heat Geek offer is a bit light on contractual detail. They would prefer that the customers deal directly with the installer when Heat Geek HQ is the contracted party. 

Posted by: @l8again

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My point is that Heat Geek offer is a bit light on contractual detail. They would prefer that the customers deal directly with the installer when Heat Geek HQ is the contracted party. 

Yes, and this is another point I agree. We did find a few contractual glitches along the way. On the main we accepted this small theoretical risk and are ultimately very happy. 

We had a flexible installer that (for example) accepted we would manage some of the rad upgrades and they would only do one. HG would always be happy with customers that upgrade and where their guaranteed SCOP was for SCOP prior to the upgrade..  

From what I read here, my case of being happy with the Heat Geek installer is very common. 

And, in my search, I found a couple of (former?) local Heat Geek installers that grew their own companies and where their sales staff/process was creating bloated proposals... 

@david-2 There are some very useful Valliant heat pump graphs in the Czech version of the Valliant manuals. There is a lot posted about Valliant efficiencies on the OpenEnergyMonitor forum.

When I last looked a SCOP of 3.91 on a 7kW Valliant gave a flow temperature of 45C at the design minimum outside air temperature. My HG warranty gives a minimum SCOP of 4.

https://community.openenergymonitor.org/t/vaillant-arotherm-owners-thread/21891

Posted by: @batpred

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And, in my search, I found a couple of (former?) local Heat Geek installers that grew their own companies and where their sales staff/process was creating bloated proposals... 

Posted by: @l8again

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My point is that Heat Geek is a bit light on contractual detail. They would prefer that the customers deal directly with the installer when Heat Geek HQ is the contracted party. 

I suspect it's a deliberate decision by Heat Geek to cut the backside covering mass of words, which most will neither read nor understand, and just tell the customer the minimum they need to know.  Most customers really don't want a text book on replacing their boiler, they just want a warm house.

If they subsequently do a good job, which it appears they generally do, then the approach has merit.  

As the industry matures I'm guessing we will see more of this.

Posted by: @jamespa

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Posted by: @l8again

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My point is that Heat Geek is a bit light on contractual detail. They would prefer that the customers deal directly with the installer when Heat Geek HQ is the contracted party. 

I suspect it's a deliberate decision by Heat Geek to cut the backside covering mass of words, which most will neither read nor understand, and just tell the customer the minimum they need to know.  Most customers really don't want a text book on replacing their boiler, they just want a warm house.

If they subsequently do a good job, which it appears they generally do, then the approach has merit.  

The Heat geek contract had various get-out clauses with generic wording unlike most building contracts (which is what I mostly see an ASHP install as). 

They also want to make sure their processes stay highly automated. I think in this they have it right, as an ASHP install involves more specialities than gas (no matter how unjustified).  

I emailed heat geek and asked them what the design flow temperature was, the reply was that it would be either 46 or 47°, depending on which of their proposals I accepted.

One proposal was no changes, the other proposal was to change the hot water cylinder and the hall radiator.

As I said in my original post there is a 1960s or 70s radiator in my study.  We were not metric back then, the radiator measures 7 by two foot. Google says the delta T50 Output of a 7 by 2 foot radiator with no fins would be between 1580 and1700 W.

7 by 2 foot is 2140 by 600 millimetres, Google says the delta T50 output of this radiator would be 2100 W any comments on this discrepancy?

I calculate that at a flow temperature of 47° the output of a delta T 50 1700W radiator would be 637 W , a 2100W  radiator would be 787W. Either of these is lower than the 1170 W heat loss that heat geek found on their survey. Does my calculation seem reasonable.

I thought to get the government grand the installer how to show that all the rooms would be heated to an adequate temperature.