ASHP - Investigations and calculations
Re: ASHP - Investigations and calculations
OK, so I've had the new heat loss survey and received the quotation from Greenhome.
They use the Heatgeek methods, and most different from Octopus, they assume much lower air exchange rates for the rooms - to the point where their total heat loss comes in at 9.4kW, against my self calc at 12.5kW and Octopus at 14.5kW (although they would not consider the insulated solid walls as it was 'the wrong sort of insulation'.)
I rechecked my calcs with lower air exchange rates and it does cut a big chunk off the total.
He reckoned that a 10kW ASHP would just about do it, but gave me the option to be conservative, so I opted for a 12kW. I'm now not 100% sure this is the right way to go - I would normally tend on the cautious side, but as this is intended to be worst case scenario, at 21 degrees downstairs, which we never use, and we do have a log burner to top things up - I do wonder if it might be better to go with the 10kW?
Based on that, they have quoted for Vaillant Arotherm Plus 12kW, with Vaillant 200l water tank and all the associated controls, including only 2 radiator changes.
They have calculated flow temp for worst case days at 50 degrees, and expected SCOP of 3.6.
Price is, not surprisingly, up from the £5k of Octopus to £9.5k (on top of the BUS grant).
The only thing not included is electrical work - I asked them to look into fitting a mini consumer unit and running an EV charger supply at the same time as the heat pump, to save on getting someone out again later on, and they are still putting together a cost for that.
Would be interested to hear peoples thoughts
They use the Heatgeek methods, and most different from Octopus, they assume much lower air exchange rates for the rooms - to the point where their total heat loss comes in at 9.4kW, against my self calc at 12.5kW and Octopus at 14.5kW (although they would not consider the insulated solid walls as it was 'the wrong sort of insulation'.)
I rechecked my calcs with lower air exchange rates and it does cut a big chunk off the total.
He reckoned that a 10kW ASHP would just about do it, but gave me the option to be conservative, so I opted for a 12kW. I'm now not 100% sure this is the right way to go - I would normally tend on the cautious side, but as this is intended to be worst case scenario, at 21 degrees downstairs, which we never use, and we do have a log burner to top things up - I do wonder if it might be better to go with the 10kW?
Based on that, they have quoted for Vaillant Arotherm Plus 12kW, with Vaillant 200l water tank and all the associated controls, including only 2 radiator changes.
They have calculated flow temp for worst case days at 50 degrees, and expected SCOP of 3.6.
Price is, not surprisingly, up from the £5k of Octopus to £9.5k (on top of the BUS grant).
The only thing not included is electrical work - I asked them to look into fitting a mini consumer unit and running an EV charger supply at the same time as the heat pump, to save on getting someone out again later on, and they are still putting together a cost for that.
Would be interested to hear peoples thoughts
Solar PV since July '22:
5.6kWp east/west facing
3.6kW Sunsynk hybrid inverter
2x 5.12kWh Sunsynk batteries
1.6kWp Hoymiles East/West facing PV on the man cave
Ripple DW 2kW
Ripple WB 200W
5.6kWp east/west facing
3.6kW Sunsynk hybrid inverter
2x 5.12kWh Sunsynk batteries
1.6kWp Hoymiles East/West facing PV on the man cave
Ripple DW 2kW
Ripple WB 200W
Re: ASHP - Investigations and calculations
Another thing to consider is inverter vs on/off type hp. An inverter will run lower power to fit under solar generation. On/off may be drawing a lot of power in its cycles.
Inverter more expensive parts. On off generally simpler to fix from what I can see.
Have you tried running your heating system with the temp turned down. You can record the burner on/off time and then work out heat input into the house. I did that and it was pretty accurate. What you have to consider is that when it super cold it isn’t windy. Tends to be g high pressure say over the UK. Then the air changes are negligible. Our house can use similar power at -5 as at zero on a windy day.
Inverter more expensive parts. On off generally simpler to fix from what I can see.
Have you tried running your heating system with the temp turned down. You can record the burner on/off time and then work out heat input into the house. I did that and it was pretty accurate. What you have to consider is that when it super cold it isn’t windy. Tends to be g high pressure say over the UK. Then the air changes are negligible. Our house can use similar power at -5 as at zero on a windy day.
Last edited by Andy on Mon Feb 12, 2024 10:02 am, edited 1 time in total.
Re: ASHP - Investigations and calculations
I would er on the side of smaller where HPs are concerned. Even the most thorough heat-loss surveys tend to be conservative and the vast majority of the heating season is comfortably above the design conditions. Better to go with the smallest HP the installer will allow and rely on aux heating (eg WBS, a SH, or even ordinary resistive) to get the house up to 21℃ In the very coldest weather.richbee wrote: ↑Mon Feb 12, 2024 9:19 am OK, so I've had the new heat loss survey and received the quotation from Greenhome.
They use the Heatgeek methods, and most different from Octopus, they assume much lower air exchange rates for the rooms - to the point where their total heat loss comes in at 9.4kW, against my self calc at 12.5kW and Octopus at 14.5kW (although they would not consider the insulated solid walls as it was 'the wrong sort of insulation'.)
I rechecked my calcs with lower air exchange rates and it does cut a big chunk off the total.
He reckoned that a 10kW ASHP would just about do it, but gave me the option to be conservative, so I opted for a 12kW. I'm now not 100% sure this is the right way to go - I would normally tend on the cautious side, but as this is intended to be worst case scenario, at 21 degrees downstairs, which we never use, and we do have a log burner to top things up - I do wonder if it might be better to go with the 10kW?
Based on that, they have quoted for Vaillant Arotherm Plus 12kW, with Vaillant 200l water tank and all the associated controls, including only 2 radiator changes.
They have calculated flow temp for worst case days at 50 degrees, and expected SCOP of 3.6.
Price is, not surprisingly, up from the £5k of Octopus to £9.5k (on top of the BUS grant).
The only thing not included is electrical work - I asked them to look into fitting a mini consumer unit and running an EV charger supply at the same time as the heat pump, to save on getting someone out again later on, and they are still putting together a cost for that.
Would be interested to hear peoples thoughts
By upsizing you lose more through excessive cycling in mild weather you gain in exceptionally cold conditions.
12x 340W JA Solar panels (4.08kWp)
3x 380W JA Solar panels (1.14kWp)
5x 2.4kWh Pylontech batteries (12kWh)
LuxPower inverter/charger
(Artist formally known as ******, well it should be obvious enough to those for whom such things are important.)
3x 380W JA Solar panels (1.14kWp)
5x 2.4kWh Pylontech batteries (12kWh)
LuxPower inverter/charger
(Artist formally known as ******, well it should be obvious enough to those for whom such things are important.)
Re: ASHP - Investigations and calculations
The smaller heat pumps tend to be more efficient. It won’t cycle as much which will be better for the life span I should think. If you have a log burner then they tend to be 4-5kw minimum which almost gives 50% more than the 10kW unit.
Re: ASHP - Investigations and calculations
For the size issue, apparently the 10kW and 12kW models are at least on the same chassis, not sure how much varies internally. I've asked the guy to see if he can confirm what level of modulation each one goes down to - He suspected they could be the same but wasn't sure.
I tend to assume that all the modern HPs are inverter controlled to help with modulation & efficiency, but I haven't asked TBH
The other thing I've just noticed is that both are pretty big units - 1.6m tall, and will fall foul of the permitted development limits of <0.6m3 (they are more like 0.8). I'm hoping that doesn't mean I have to pay for planning permission![FingersCrossed :xx:](./images/smilies/Fingers-Crossed.gif)
I tend to assume that all the modern HPs are inverter controlled to help with modulation & efficiency, but I haven't asked TBH
The other thing I've just noticed is that both are pretty big units - 1.6m tall, and will fall foul of the permitted development limits of <0.6m3 (they are more like 0.8). I'm hoping that doesn't mean I have to pay for planning permission
![FingersCrossed :xx:](./images/smilies/Fingers-Crossed.gif)
Solar PV since July '22:
5.6kWp east/west facing
3.6kW Sunsynk hybrid inverter
2x 5.12kWh Sunsynk batteries
1.6kWp Hoymiles East/West facing PV on the man cave
Ripple DW 2kW
Ripple WB 200W
5.6kWp east/west facing
3.6kW Sunsynk hybrid inverter
2x 5.12kWh Sunsynk batteries
1.6kWp Hoymiles East/West facing PV on the man cave
Ripple DW 2kW
Ripple WB 200W
Re: ASHP - Investigations and calculations
The 10kW unit shows "Heat output, minimum/maximum, A7/W35 5.40 to 12.50 kW"
whilst the 12kW shows "Heat output, minimum/maximum, A7/W35 5.40 to 14.00 kW"
whilst the 12kW shows "Heat output, minimum/maximum, A7/W35 5.40 to 14.00 kW"
3.87kWp PV
10.24kWp PV SolarEdge system
Tesla Powerwall 2
100 x 47mm Navitron tubes (still being installed!) Now likely to be removed for more PV.
MK2 PV router DHW diverter
Morso 5kW WBS
Vaillant AroTherm 10kW ASHP
Nissan Leaf
10.24kWp PV SolarEdge system
Tesla Powerwall 2
100 x 47mm Navitron tubes (still being installed!) Now likely to be removed for more PV.
MK2 PV router DHW diverter
Morso 5kW WBS
Vaillant AroTherm 10kW ASHP
Nissan Leaf
Re: ASHP - Investigations and calculations
The heat loss calculation I did using Heat Engineer software gave a 9.33kW heat loss so I've opted for the 10kW Arotherm Plus.richbee wrote: ↑Mon Feb 12, 2024 9:19 am Based on that, they have quoted for Vaillant Arotherm Plus 12kW, with Vaillant 200l water tank and all the associated controls, including only 2 radiator changes.
They have calculated flow temp for worst case days at 50 degrees, and expected SCOP of 3.6.
Price is, not surprisingly, up from the £5k of Octopus to £9.5k (on top of the BUS grant).
The only thing not included is electrical work - I asked them to look into fitting a mini consumer unit and running an EV charger supply at the same time as the heat pump, to save on getting someone out again later on, and they are still putting together a cost for that.
Would be interested to hear peoples thoughts
The quote I accepted came in at £13449 less £9000 grant, this includes 4 new K3 radiators and a large output towel rail but I am installing the primary pipework and the radiators along with HP base (pipes and fittings supplied by company).
3.87kWp PV
10.24kWp PV SolarEdge system
Tesla Powerwall 2
100 x 47mm Navitron tubes (still being installed!) Now likely to be removed for more PV.
MK2 PV router DHW diverter
Morso 5kW WBS
Vaillant AroTherm 10kW ASHP
Nissan Leaf
10.24kWp PV SolarEdge system
Tesla Powerwall 2
100 x 47mm Navitron tubes (still being installed!) Now likely to be removed for more PV.
MK2 PV router DHW diverter
Morso 5kW WBS
Vaillant AroTherm 10kW ASHP
Nissan Leaf
Re: ASHP - Investigations and calculations
That sounds promising - if the minimum output is the same for both units - doesn't it?
Solar PV since July '22:
5.6kWp east/west facing
3.6kW Sunsynk hybrid inverter
2x 5.12kWh Sunsynk batteries
1.6kWp Hoymiles East/West facing PV on the man cave
Ripple DW 2kW
Ripple WB 200W
5.6kWp east/west facing
3.6kW Sunsynk hybrid inverter
2x 5.12kWh Sunsynk batteries
1.6kWp Hoymiles East/West facing PV on the man cave
Ripple DW 2kW
Ripple WB 200W
Re: ASHP - Investigations and calculations
It gives a 57% reduction and a 61% reduction from max resp.
I'm hoping to use mine purely on weather compensation to control the indoor temperature.
![FingersCrossed :xx:](./images/smilies/Fingers-Crossed.gif)
3.87kWp PV
10.24kWp PV SolarEdge system
Tesla Powerwall 2
100 x 47mm Navitron tubes (still being installed!) Now likely to be removed for more PV.
MK2 PV router DHW diverter
Morso 5kW WBS
Vaillant AroTherm 10kW ASHP
Nissan Leaf
10.24kWp PV SolarEdge system
Tesla Powerwall 2
100 x 47mm Navitron tubes (still being installed!) Now likely to be removed for more PV.
MK2 PV router DHW diverter
Morso 5kW WBS
Vaillant AroTherm 10kW ASHP
Nissan Leaf
Re: ASHP - Investigations and calculations
There is a detailed Vaillant output chart available AFAIK only on their Czech web site(!) and also this FB group which confirms that the 10kW has identical performance to the 12 except the top two columns of compressor speed or so are missing from the chart. So not a lot to be saved by specifying the 10, I don't even know why they make the two different models, maybe there is some Euro regulation it just squeezes into.
Yes the twin fan Aerotherm plus models require specific planning permission as they are too big for deemed PP.
16 x 230W Upsolar panels S Devon, 4kW Steca, 3.9 MWh FITs/yr
8 x 405W Longi panels, 250/60 MPPT, 3.3 MWh/yr
Victron MultiPlus II-GX 48/5000/70-50
10.65 kWh Pylontec Force-L2
zappi 7kW EVCS
Villavent whole-house MVHR
5000l rainwater system
Vaillant 12kW HP
8 x 405W Longi panels, 250/60 MPPT, 3.3 MWh/yr
Victron MultiPlus II-GX 48/5000/70-50
10.65 kWh Pylontec Force-L2
zappi 7kW EVCS
Villavent whole-house MVHR
5000l rainwater system
Vaillant 12kW HP