Dear All,
I need help in the debate of GSHP V ASHP. I realise this topic has been covered ad infinitum, but I am still cannot decide what to do and in fairness now very confused!
.
The background into looking at this type of heating is twofold, firstly the environment and secondly as I have an oil fired heating system, the cost, (as I live in the UK).
The plan from the below company is to install a slinky type coil in a 900m2 area of our garden, (Our house os @300m2), the ground conditions are we border the fens arae of the UK and it is clay based soil about 1ft down but very close to the water table.
I am not a DIY enthusiast so I have asked a Company to quote me, below is their quote and charts for both GSHP and ASHP,
1. What do you experts think?
2. Those of you that have either source which would you choose (if given the option again?)
3. Is there a cheaper way of doing what I am trying to achieve?
4. Should I bother?
Here is the quote:
Your coldest day average of -3C heating requirement has been calculated to be 17.5kW.
The cost to install a 3 phase 19kW Ciat/Sofath ground source heat pump system would roughly be £15,700 + vat at 5% less grant of £1200 plus the cost of installing 3 phase electricity @ £2000. This would work with your existing hot water tank providing hot water to 45C when the heating is operated. Outside of this off peak electricity will need to be used. Note that the hot water temperature will need to be heated to 60C once a week to prevent legionella bacteria risk. This can be done with timer on the immersion circuit. Total = @£15,300 + 3 phase installation
To install a 19kW single phase twin compressor heat pump would cost an additional £2000. No grant would be available on this model so that would be an additional cost of this option would be £3200. Total @£18,500
I can also supply an 18.8kW single phase Sanyo inverter air source heat pump using an Airpac heat exchanger. Inverter heat pumps provide the highest efficiency. On the coldest day averaging -3C the output would drop to about 13kW. Your oil system could be used as a backup if required. It may be possible to automate this changeover. This heat pump system would provide most of your heating requirement as temperatures rarely fall to this level over a long period. The shortfall is just 3.5kW. A 3 kW electric backup could also be used. This option would cost about £7,500
I have estimated your heating costs for air source and ground source heating systems. These estimates are based on current electricity prices using Southern Electric Economy 10 tariff. The unit costs are 12.96p peak and 7.27p off peak. Oil price 55p /litre
Assuming that your radiators meet the specification set out in the quotation the quotation the savings is estimated to be 50% for ground source and 40% for air source. This assumes that 65% of the electricity is used at peak rates and 35% is used at off peak rates.
These estimates are based on a flow temperature of 45C which corresponds to radiators that are 2 times oversized and are based on manufacturer’s data.
Ground source COP 3.5
Air source seasonal COP 2.9
I need help in the debate of GSHP V ASHP. I realise this topic has been covered ad infinitum, but I am still cannot decide what to do and in fairness now very confused!
.
The background into looking at this type of heating is twofold, firstly the environment and secondly as I have an oil fired heating system, the cost, (as I live in the UK).
The plan from the below company is to install a slinky type coil in a 900m2 area of our garden, (Our house os @300m2), the ground conditions are we border the fens arae of the UK and it is clay based soil about 1ft down but very close to the water table.
I am not a DIY enthusiast so I have asked a Company to quote me, below is their quote and charts for both GSHP and ASHP,
1. What do you experts think?
2. Those of you that have either source which would you choose (if given the option again?)
3. Is there a cheaper way of doing what I am trying to achieve?
4. Should I bother?
Here is the quote:
Your coldest day average of -3C heating requirement has been calculated to be 17.5kW.
The cost to install a 3 phase 19kW Ciat/Sofath ground source heat pump system would roughly be £15,700 + vat at 5% less grant of £1200 plus the cost of installing 3 phase electricity @ £2000. This would work with your existing hot water tank providing hot water to 45C when the heating is operated. Outside of this off peak electricity will need to be used. Note that the hot water temperature will need to be heated to 60C once a week to prevent legionella bacteria risk. This can be done with timer on the immersion circuit. Total = @£15,300 + 3 phase installation
To install a 19kW single phase twin compressor heat pump would cost an additional £2000. No grant would be available on this model so that would be an additional cost of this option would be £3200. Total @£18,500
I can also supply an 18.8kW single phase Sanyo inverter air source heat pump using an Airpac heat exchanger. Inverter heat pumps provide the highest efficiency. On the coldest day averaging -3C the output would drop to about 13kW. Your oil system could be used as a backup if required. It may be possible to automate this changeover. This heat pump system would provide most of your heating requirement as temperatures rarely fall to this level over a long period. The shortfall is just 3.5kW. A 3 kW electric backup could also be used. This option would cost about £7,500
I have estimated your heating costs for air source and ground source heating systems. These estimates are based on current electricity prices using Southern Electric Economy 10 tariff. The unit costs are 12.96p peak and 7.27p off peak. Oil price 55p /litre
Assuming that your radiators meet the specification set out in the quotation the quotation the savings is estimated to be 50% for ground source and 40% for air source. This assumes that 65% of the electricity is used at peak rates and 35% is used at off peak rates.
These estimates are based on a flow temperature of 45C which corresponds to radiators that are 2 times oversized and are based on manufacturer’s data.
Ground source COP 3.5
Air source seasonal COP 2.9