Criticisms please

[waxingsatirical]

Hi All,

 

I'm on the verge of accepting a quote for install of ASHP into my property, would any of you mind giving me your opinions on the setup?

 

I'll just try and give you the key information, as obviously there is a lot of detail, but please ask if I've left anything important out.

 

This is for a 4 bed property, 1500sq ft, traditional radiators, well insulated, mostly filled cavity, some unfilled cavity.

 

Building Max Heat Loss: 5.6kW

Daily Hot Water Demand: 45L

Hot Water Temperature: 50C

Legionella Purge Temp: 60C

Legionella Purge Freq: Weekly

 

Samsung Mono R290 - integrated pump and expansion vessel

Cylinder "sized to heat input requirements"

Solar PV 7 panels (this is all there is space for)

 

Thanks in advance

[Nickfromwales]

Are the radiators and pipework being upgraded as part of this install?

[sharpener]

45 l seems a very small HW demand for a 4 bed house, usual planning rule is 50 l x (# of bedrooms +1) per day.

 

If you are medically fit and using a reasonable amount of HW say >50% of the tank per day then legionella cycle prob unnecessary but you can disable it later anyway.

 

Heat load is <40W/ sq m, this is quite low, what is the age of the house? Have you got max loft insulation, if not this is a quick win.

 

The key question though is what is the design flow temp at what OAT? This will determine the CoP you can achieve. As @Nickfromwales implies you may need bigger rads depending on what you had before. (I beat my installers down to changing only 6 of the 10 rads when moving from oil to HP.)

 

Are you getting battery storage to go with the panels? Best to think about this while you are getting the electrics modified to take the HP and PV or you will end up with an unsightly maze of meter tails and Henley blocks.

 

 

Edited October 1 by sharpener

[JohnMo]

If you want it via a grant MCS DHW sizing apply. So 45L is meaningless.

 

The only important bit missing is design flow temperature. Ideal 35, just about acceptable 45, 50 and above, walk away.

 

1 zone or loads of zones, buffer etc, what are the details?

 

[waxingsatirical]

4 hours ago, Nickfromwales said:

Are the radiators and pipework being upgraded as part of this install?

The radiators are already oversized, there may be some that need to be swapped out for larger ones, but I have agreed to do this at a later date if needed

[waxingsatirical]

4 hours ago, sharpener said:

45 l seems a very small HW demand for a 4 bed house, usual planning rule is 50 l x (# of bedrooms +1) per day.

Thank you, I will query this with them

4 hours ago, sharpener said:

The key question though is what is the design flow temp at what OAT? This will determine the CoP you can achieve. As @Nickfromwales implies you may need bigger rads depending on what you had before. (I beat my installers down to changing only 6 of the 10 rads when moving from oil to HP.)

 

Looks like they have used 50C out 45C return.

 

4 hours ago, sharpener said:

Are you getting battery storage to go with the panels? Best to think about this while you are getting the electrics modified to take the HP and PV or you will end up with an unsightly maze of meter tails and Henley blocks.

I'm getting an electric car, which I'm sure will mop up any unused electricity. I am asking them to fit a charge point at the same time.

[waxingsatirical]

3 hours ago, JohnMo said:

The only important bit missing is design flow temperature. Ideal 35, just about acceptable 45, 50 and above, walk away.

 

1 zone or loads of zones, buffer etc, what are the details?

 

Yes the calcs use 50C out 45C return, single zone. The buffer tank is integrated into the heat pump apparently, can't see how you'd fit much of a tank in there or why having it outside is a good idea.

[JohnMo]

13 minutes ago, waxingsatirical said:

Yes the calcs use 50C out 45C return

The heating isn't going to be cheap to run at that flow temp. 

 

24 minutes ago, waxingsatirical said:

there may be some that need to be swapped out for larger ones, but I have agreed to do this at a later date if needed

So I would expect the installer scope is very limited, would expect the cost to be no more that the grant money really, if the existing heating system isn't being upgraded. 

[PhilT]

My house is very similar in size and spec to yours, with oversized rads and the same peak heat loss of between 5 and 6kW. My installers also spec'd a design flow temp of 50degC but that is the absolute maximum. My guess is that they build in an average downtime for night time set back or timed off. My flow temps only reached 50 at outside temp -12degC. In reality, if you run continuously like I do, with little or no set back, the vast majority of the time it stays between 30 and 40, and only gets above 40 on the very coldest Winter days.

[waxingsatirical]

1 hour ago, JohnMo said:

 

So I would expect the installer scope is very limited, would expect the cost to be no more that the grant money really, if the existing heating system isn't being upgraded. 

Ha ha, no it's loads! But it's hard to even find someone to do the work, I've been chasing these guys for the last year to try and get an install date.

 

Besides, I thought the point of the grant was to bring the cost down to an amount comparable to that of getting a new gas boiler? Not to hand out free heating systems.

[waxingsatirical]

1 hour ago, PhilT said:

My house is very similar in size and spec to yours, with oversized rads and the same peak heat loss of between 5 and 6kW. My installers also spec'd a design flow temp of 50degC but that is the absolute maximum. My guess is that they build in an average downtime for night time set back or timed off. My flow temps only reached 50 at outside temp -12degC. In reality, if you run continuously like I do, with little or no set back, the vast majority of the time it stays between 30 and 40, and only gets above 40 on the very coldest Winter days.

Thanks for your input, I value actual experience over predictions from models.

 

I measured my home's heat loss last winter, in a cold snap, and it came out to 3.5kW, well below the calculated value. See the inflammatory chain started by me last spring. I figure I'll be able to run lower than 50.

[JohnMo]

Just now, waxingsatirical said:

Ha ha, no it's loads! But it's hard to even find someone to do the work, I've been chasing these guys for the last year to try and get an install date.

 

Besides, I thought the point of the grant was to bring the cost down to an amount comparable to that of getting a new gas boiler? Not to hand out free heating systems.

The grant is up to £7500. If your install costs £8000, you pay £500, if it cost £15,000, you pay £7500. Cylinder is around £1000, Heat pump £2500, and £500 to £1000 for stuff, if they are not changing the system much, you have a few days of work for the plumber and a day for the electrician. Anything more than that is just profiteering, ripping you and the tax payer off.

[ReedRichards]

7 minutes ago, waxingsatirical said:

But it's hard to even find someone to do the work

Have you tried Octopus?

[waxingsatirical]

57 minutes ago, ReedRichards said:

Have you tried Octopus?

Good shout. I just did the online Octopus quote, which takes literally 20 seconds. It came out a few grand cheaper, but once they've done the survey I'm sure would go up a bit.

[Andehh]

Definitely check it all the same! At least they won't be total cowboys,octopus are a good brand.

[JamesPa]

3 hours ago, waxingsatirical said:

 

8 hours ago, sharpener said:

Are you getting battery storage to go with the panels? Best to think about this while you are getting the electrics modified to take the HP and PV or you will end up with an unsightly maze of meter tails and Henley blocks.

I'm getting an electric car, which I'm sure will mop up any unused electricity. I am asking them to fit a charge point at the same time.

One problem with an electric car is that they generally take a fixed (high) load or at best have a high minimum load.  So they cant easily 'mop up' excess electricity when the amount available is less than the minimum, without also importing.  

 

Various options:

 

• Ignore 
• Batteries (best functionally but expensive)
• Solar diverter to heat DHW (which can mop up variable amounts of electricity to match available excess, but, depending on your panel capacity and DHW use, unlikely to be sufficient load on its own over the day in height of summer
• Solar diverter plus car, arranged so that the car charges when there is sufficient excess (decide for yourself what 'sufficient' is

 

Im currently experimenting with the last of these as I already had a diverter and just bought an electric car.  |An automation in HA switches on the car when the amount being exported exceeds half the load taken by the car, tested every 10 mins. 

 

The amounts to be saved, particularly if you are paid for export, aren't great, so 'ignore' is also definitely an option.  Certainly there are more cost effective (or enjoyable) ways to spend time!

 

 

[PNAmble]

10 hours ago, JamesPa said:

One problem with an electric car is that they generally take a fixed (high) load or at best have a high minimum load. 

I think most cars require 1.4kW to charge as a minimum.  Some chargers have a hybrid mode which takes from the grid to make it to that level. But obviously that is likely to use peak or shoulder tariffs.

 

We have diverter, battery, car.  The diverter can take a minimum of about 300w so is good in mopping up and in summer boosts the water to about 58 , which then means I don’t need to heat pump it.

 

Re car charging  reckon (system only running since beginning of July in our self build) solar will only works for about 4 months.

 

the true saving ROI re the battery is that I should time shift  almost all my electricity (I’ve just gone to Tomato and get six hours of 5p), which in winter when there is limited solar means my ASHP running a good COP on very low electricity costs. 

[sharpener]

22 hours ago, JamesPa said:

Solar diverter plus car, arranged so that the car charges when there is sufficient excess (decide for yourself what 'sufficient' is

 

Yes. lacking the sophistication of @JamesPa when I want to charge the car I turn the diverter off manually until late in the afternoon when the PV generation has fallen below the 1.4 kW min the car needs. A bit of a gamble that there will still be enough sun for the hot water.

 

12 hours ago, PNAmble said:

I’ve just gone to Tomato and get six hours of 5p

 

Can you post a link? Tried to investigate this but they have an automatic lookup so I cannot see their smart meter tariffs as it's not going to be installed until tomorrow.

[PNAmble]

10 minutes ago, sharpener said:

Can you post a link? Tried to investigate this but they have an automatic lookup so I cannot see their smart meter tariffs as it's not going to be installed until tomorrow.

the quote on the website is dependent upon what you have, my quote with heat pump EV, Battery,Solar is shown below.   There is no link until you ask for a quote.  The other big thing was also the 40p standing charge as opposed to OIG which was going up to 72p.  

Edited October 2 by PNAmble

[sharpener]

Thanks. The shoulder price at 13.37p is not much more than the Cosy cheap price of 12.11p. But the cheap period is all in one lump so I would not be able to round-trip the batteries 3x per day. Time for some serious modelling.

 

Once I have the smart meter I will certainly ask Tomato for a quote. How have you found their customer service?

[PNAmble]

7 hours ago, sharpener said:

How have you found their customer service?

The cheap slot enables me to  fill my battery and put a good charge in my car (low mileage).  If predbat needs to top up during the day it uses a bit during the shoulder period.  
 

However my heating hasn’t come on yet so that test is still to be had. 
 

Only joined a few days ago, they have problems billing apparently and their mywhatts site is ropey. But I’m sure it will get fixed.  Im in a complaint with octopus and their customer service has fallen off a cliff.  To me, I record my info, I down load my DCC data, so I don’t really care what the service is like as long as I get power as cheap as possible. 

Edited October 3 by PNAmble

[PhilT]

On 01/10/2024 at 20:15, waxingsatirical said:

Good shout. I just did the online Octopus quote, which takes literally 20 seconds. It came out a few grand cheaper, but once they've done the survey I'm sure would go up a bit.

I would be very interested to hear if you go for this as I have a couple of friends and relatives who are looking into the same option

[waxingsatirical]

For anyone following this, thought I'd give some updates. House has now been running on ASHP for about a month. There is no problem heating the house, haven't changed any rads but still mainly runs between 30 and 40 degrees.

 

For second half Nov/ first half of December it's used on average 15.5kWH per day, which includes hot water, COP (according to the device itself) is about 3.25, but again this is including hot water. The heat loss matches pretty well to my measured heat loss from last winter, but the heat loss calculation was over by a significant amount.

 

As for the installer, still have some issues to resolve with them, might give a detailed update once everything settled. Still haven't paid. Won't be recommending the local company. Octopus would have probably been a better choice.

[PhilT]

21 hours ago, waxingsatirical said:

For anyone following this, thought I'd give some updates. House has now been running on ASHP for about a month. There is no problem heating the house, haven't changed any rads but still mainly runs between 30 and 40 degrees.

 

For second half Nov/ first half of December it's used on average 15.5kWH per day, which includes hot water, COP (according to the device itself) is about 3.25, but again this is including hot water. The heat loss matches pretty well to my measured heat loss from last winter, but the heat loss calculation was over by a significant amount.

 

As for the installer, still have some issues to resolve with them, might give a detailed update once everything settled. Still haven't paid. Won't be recommending the local company. Octopus would have probably been a better choice.

15.5kWh average total input per day for that period is very good, for your house spec. Mine was around 20 for the same period but my COP was 4.2 but I only heat my DHW once a day to 40degC (using "Eco" setting) and never run a legionella cycle. 50degC and a Legionella cycle would probably explain much of your poor COP