Spoogster Posted January 25, 2021 Share Posted January 25, 2021 Hi all We are planning a Air Source Heat Pump for our yr.2000 4 bed detached house in SE UK. The rough installer plan is for a c.8.5kW ASHP (Ecodan) with a UVC and low temp radiators. We are waiting to see the exact spec and brands/models for all the parts, as at early stage at the moment. Would replace a 28kW Worcester Bosch A rated boiler (5 yrs old) and Megaflo mains pressure 170l tank. Very rough heat loss calc produced, more detailed one to come. House is c.130sqm internal floor area. We have over the past week used 400kWh heating our home, average 18.5-19 deg C at stat but 22 deg C in living room from 0600-2100 hrs (15 hours per day roughly). Over the past day (15 hours) at zero C outside we used 100kWh gas. The boiler has been working quite hard all day yesterday. On other slightly less cold days we have been using c.85kWh gas per day. We have ordered new triple glazing (U=0.9) and doors which will be installed 1 March, replacing 1999 double glazing (assumed U=3.1, and very poor quality developer installed windows). Q: at this peak winter energy usage does 8.5kW ASHP sound up to the job? Or is it more an issue of the size of the radiators and model/spec? I think the existing windows and doors are so poor and leaky that a lot of heat is being lost from those rather than general leakage in the house fabric. We don't have any insulation (that I am aware of) in the block and beam floor but then mostly wood and carpet and floors don't feel especially cold. Walls are 300mm thick and cavity insulated. Loft now has 300mm insulation but two bath fans are weak spots that I should really address. Thanks in advance! Link to comment Share on other sites More sharing options...
Temp Posted January 25, 2021 Share Posted January 25, 2021 Why switch from mains gas to an ASHP? Running costs likely to be at least double at the moment.. https://nottenergy.com/resources/energy-cost-comparison/ Scroll down to the table and see "Pence per kWh (after boiler efficiency)" Link to comment Share on other sites More sharing options...
SteamyTea Posted January 25, 2021 Share Posted January 25, 2021 If you use 100 kWh in 15 hours, that is about 7 kW power delivery. Now some of that will be for DHW. Do you may want to go to the next size up to be on the safe side and benefit from a better CoP. Link to comment Share on other sites More sharing options...
Gone West Posted January 25, 2021 Share Posted January 25, 2021 (edited) 45 minutes ago, Spoogster said: The rough installer plan is for a c.8.5kW ASHP (Ecodan) with a UVC and low temp radiators. We are waiting to see the exact spec and brands/models for all the parts, as at early stage at the moment. Would replace a 28kW Worcester Bosch A rated boiler (5 yrs old) and Megaflo mains pressure 170l tank. That is not something I would contemplate. I would improve the doors, windows and insulation but is there anything wrong with the five year old boiler and tank. I think having an ASHP fitted could well involve a lot more in running costs and there may be issues finding ASHP repair companies. Welcome to the forum by the way. Edited January 25, 2021 by PeterStarck Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 10 minutes ago, PeterStarck said: That is not something I would contemplate. I would improve the doors, windows and insulation but is there anything wrong with the five year old boiler and tank. I think having an ASHP fitted could well involve a lot more in running costs and there may be issues finding ASHP repair companies. Welcome to the forum by the way. The tank needs replacing anyway, so that would be £1500 plus fitting. Keeping one eye on the future I strongly suspect over the next 10 years gas is likely to become more expensive (due to carbon disincentives) and electricity better value. When is right to make the switch if not now, that I assume is the question...??? Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 24 minutes ago, SteamyTea said: If you use 100 kWh in 15 hours, that is about 7 kW power delivery. Now some of that will be for DHW. Do you may want to go to the next size up to be on the safe side and benefit from a better CoP. I suspect we would run the ASHP all day in future and just vary temps at night and middle of day. To some degree our switch from heating only for an hour in the morning and 4 hours evening means we dont have much energy stored in our house fabric, but I am noticing the more we have the heating on (Uni kids back at moment) the less cold it gets at night after 9pm. Link to comment Share on other sites More sharing options...
ProDave Posted January 25, 2021 Share Posted January 25, 2021 What is wrong with a 5 year old tank that it needs replacing? As much as I like ASHP's I would not be swapping in this case. I would fix (assuming it is faulty) the boiler or replace it. You will not get cheaper heating than mains gas and an ASHP WILL cost more to run. Link to comment Share on other sites More sharing options...
TonyT Posted January 25, 2021 Share Posted January 25, 2021 I would replace the tank and ensure the coil it has is sized for a heat pump so in future the tank can stay when the boiler packs in. until then insulate insulate insulate Link to comment Share on other sites More sharing options...
Conor Posted January 25, 2021 Share Posted January 25, 2021 I second the comments above, save the £8k or so on a heat pump installation and put it towards more insulation/ fabric improvements in the house. Gas isn't going away anytime in the next 30 years, prices can't go up too much as will push millions of people in to fuel poverty. Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 39 minutes ago, Temp said: Why switch from mains gas to an ASHP? Running costs likely to be at least double at the moment.. https://nottenergy.com/resources/energy-cost-comparison/ Scroll down to the table and see "Pence per kWh (after boiler efficiency)" We are on Octpus Agile tariff which over the year is giving as 5p/kWh for the cheapest 4 hr period and 10.5p for all periods except 4pm-7pm. I suppose we could ramp the ASHP right down 4-7 so that we dont get hit from the 35p/kWh charges? Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 Something fairly key I missed on saying is that we are near joining the OVO Heat Trial where we will be getting all this kit fitted FOC. Makes a difference to the man maths. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 25, 2021 Share Posted January 25, 2021 @Spoogster Do you live in s hard water area and not use any water softening. An extra person in a house will deliver about 200W, or around 5 kWh/day (ish). Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 3 minutes ago, SteamyTea said: @Spoogster Do you live in s hard water area and not use any water softening. An extra person in a house will deliver about 200W, or around 5 kWh/day (ish). Very hard water area - wreaks havoc with everything wet in the home Link to comment Share on other sites More sharing options...
SteamyTea Posted January 25, 2021 Share Posted January 25, 2021 So might be time to decalcify. Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 1 minute ago, SteamyTea said: So might be time to decalcify. Good idea Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 12 minutes ago, Spoogster said: We are on Octpus Agile tariff which over the year is giving as 5p/kWh for the cheapest 4 hr period and 10.5p for all periods except 4pm-7pm. I suppose we could ramp the ASHP right down 4-7 so that we dont get hit from the 35p/kWh charges? Reason for ASHP is that we have been selected to join the OVO Govt heat trial so all the kit and install are free Link to comment Share on other sites More sharing options...
Gone West Posted January 25, 2021 Share Posted January 25, 2021 12 minutes ago, Spoogster said: Something fairly key I missed on saying is that we are near joining the OVO Heat Trial where we will be getting all this kit fitted FOC. Makes a difference to the man maths. 'Fairly key' is a bit of an understatement as far as installation is concerned. Link to comment Share on other sites More sharing options...
ProDave Posted January 25, 2021 Share Posted January 25, 2021 3 minutes ago, Spoogster said: Reason for ASHP is that we have been selected to join the OVO Govt heat trial so all the kit and install are free If you are going to do that, them make sure you get a written comitment that the system supplied will maintain a specified internal temperature in the house under all weather conditions with a comitment to upgrade it if it does not. You would not be the first to get a "free" system installed and then find it wanting for performance. so you have raved about your Octopus tarif but are switching to Ovo instead? Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 1 minute ago, PeterStarck said: 'Fairly key' is a bit of an understatement as far as installation is concerned. I agree! I just wanted an untainted view on my question, but I appreciate getting all the kit for nothing changes the dynamics.! Question revised then: would you go ahead if Govt was paying for it, even if the running costs are higher? Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 (edited) 14 minutes ago, ProDave said: If you are going to do that, them make sure you get a written comitment that the system supplied will maintain a specified internal temperature in the house under all weather conditions with a comitment to upgrade it if it does not. You would not be the first to get a "free" system installed and then find it wanting for performance. so you have raved about your Octopus tarif but are switching to Ovo instead? Thanks for the advice re min energy requirement. There is no requirement to switch to OVO with this Govt install Edited January 25, 2021 by Spoogster Link to comment Share on other sites More sharing options...
ProDave Posted January 25, 2021 Share Posted January 25, 2021 So, Pro's: System installed for free, and assuming it works, it saves you having to fix the cylinder so saving £1500 Con's: The running cost WILL be higher by perhaps 1/4? So on that rough basis, how much is a 1/4 of a years heating bill? and how many years of paying that higher cost would it take to cover the £1500 repair bill if you were to stick with gas? Also, would you still be using gas e.g for an oven or hob? If so if those were the only thing using gas, the standing charge for the gas might be a significant fraction of the bill and you might want to swap those to electric and scrap the gas supply? Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 6 minutes ago, ProDave said: So, Pro's: System installed for free, and assuming it works, it saves you having to fix the cylinder so saving £1500 Con's: The running cost WILL be higher by perhaps 1/4? So on that rough basis, how much is a 1/4 of a years heating bill? and how many years of paying that higher cost would it take to cover the £1500 repair bill if you were to stick with gas? Or put it another way, cost benefit of future proofing your DHW and heat installation? An intangible benefit? Link to comment Share on other sites More sharing options...
Gone West Posted January 25, 2021 Share Posted January 25, 2021 12 minutes ago, ProDave said: System installed for free, and assuming it works Why do I keep thinking of Zoot's thread. 1 Link to comment Share on other sites More sharing options...
Spoogster Posted January 25, 2021 Author Share Posted January 25, 2021 1 minute ago, PeterStarck said: Why do I keep thinking of Zoot's thread. Please enlighten me? 1 Link to comment Share on other sites More sharing options...
ProDave Posted January 25, 2021 Share Posted January 25, 2021 now you have done it @PeterStarck 2 Link to comment Share on other sites More sharing options...
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