Calw Posted July 8, 2022 Share Posted July 8, 2022 I have the chance to purchase a full 300l system brand new unused for 800 Struggle to find information on them I was looking at ashp boilers but as it's only for my dhw this system might work out far cheaper Link to comment Share on other sites More sharing options...
JohnMo Posted July 8, 2022 Share Posted July 8, 2022 Info from users of SAHP's is a bit thin, not easy to get anyone to talk. They are either rubbish or the best thing ever. None of the data sheets, comply with the norms of a heat pump, so very little info there either. Link to comment Share on other sites More sharing options...
Calw Posted July 8, 2022 Author Share Posted July 8, 2022 4 hours ago, JohnMo said: Info from users of SAHP's is a bit thin, not easy to get anyone to talk. They are either rubbish or the best thing ever. None of the data sheets, comply with the norms of a heat pump, so very little info there either. I am not expecting it to generate all my hot water for free or cut my bills by 70% but if it was around 50% of my current DHW costs it would defo be worth it Link to comment Share on other sites More sharing options...
JohnMo Posted July 8, 2022 Share Posted July 8, 2022 Just looked at the datasheet, the average electric consumption is stated as 550W, the data sheet says it has a 7 hour charging time to heat cylinder. 0.55 x 7 = 3.85kWh per day 300L of water to heat from 30 to 55, requires 8.73kWh - so a CoP of 2.7. Direct immersion heating would cost 2.7 times more. This assumes the water temp drops that low before charging, if it only goes to 40 it only needs 5.24kWh, so CoP drops to 1.4. Electric cost at £0.3/kWh, is £1.15 per day. Gas at 0.0733 is (assuming 80% efficiency) is £0.77 per day. Link to comment Share on other sites More sharing options...
Calw Posted July 8, 2022 Author Share Posted July 8, 2022 4 minutes ago, JohnMo said: Just looked at the datasheet, the average electric consumption is stated as 550W, the data sheet says it has a 7 hour charging time to heat cylinder. 0.55 x 7 = 3.85kWh per day 300L of water to heat from 30 to 55, requires 8.73kWh - so a CoP of 2.7. Direct immersion heating would cost 2.7 times more. This assumes the water temp drops that low before charging, if it only goes to 40 it only needs 5.24kWh, so CoP drops to 1.4. Electric cost at £0.3/kWh, is £1.15 per day. Gas at 0.0733 is (assuming 80% efficiency) is £0.77 per day. Our DHW cylinder at is an old immersion In summer it uses around 8kw to heat the water to 55c 8 x 0.27ppkw is £2.16 per day In winter it varies to around 13kw 13 x 0.27ppkw is £3.51 per day But with electricity looking like increasing by 54% thouse figure will be more like 8 x 0.41ppkw is £3.20 per day 13 x 0.41ppkw is £5.33per day So assuming a CoP of 2.7 It should be around Summer would be 1.21 per day Winter would be 1.97 per day CoP at 1.4 Summer would be 2.34 per day Winter would be 3.80 per day Based on just cop Looks to be a significant saving based on the figures on paper and current electric costs Link to comment Share on other sites More sharing options...
JohnMo Posted July 8, 2022 Share Posted July 8, 2022 It's likely the worst CoP will be in winter and better CoP in the spring to autumn period. Link to comment Share on other sites More sharing options...
SteamyTea Posted July 9, 2022 Share Posted July 9, 2022 I have just had a quick look at my DHW usage since May 22nd, when I changed over to using just the top element in my 200 lt cylinder. 2.3 kWh/day. Prior to that it was 2.75 kWh/day. I am not sure if, for a saving of ~0.5 kWh/day, which is 10p, only having 'just enough' DHW is worth it. Link to comment Share on other sites More sharing options...
Calw Posted July 10, 2022 Author Share Posted July 10, 2022 On 08/07/2022 at 18:11, JohnMo said: Just looked at the datasheet, the average electric consumption is stated as 550W, the data sheet says it has a 7 hour charging time to heat cylinder. 0.55 x 7 = 3.85kWh per day 300L of water to heat from 30 to 55, requires 8.73kWh - so a CoP of 2.7. Direct immersion heating would cost 2.7 times more. This assumes the water temp drops that low before charging, if it only goes to 40 it only needs 5.24kWh, so CoP drops to 1.4. Electric cost at £0.3/kWh, is £1.15 per day. Gas at 0.0733 is (assuming 80% efficiency) is £0.77 per day. On 09/07/2022 at 07:56, SteamyTea said: I have just had a quick look at my DHW usage since May 22nd, when I changed over to using just the top element in my 200 lt cylinder. 2.3 kWh/day. Prior to that it was 2.75 kWh/day. I am not sure if, for a saving of ~0.5 kWh/day, which is 10p, only having 'just enough' DHW is worth it. Only 2.75kw a day seems low for 200litres... 200litres a day from 15c to 55c should take 9.3kw 200litres a day from 25c to 55c should take 6.99kw Link to comment Share on other sites More sharing options...
SteamyTea Posted July 10, 2022 Share Posted July 10, 2022 4 minutes ago, Calw said: 200litres a day from 15c to 55c should take 9.3kw 200litres a day from 25c to 55c should take 6.99kw On the face of it, it does seem low. But. DHW below about 30°C is of little use, and above 40°C it too hot. As I use just the top part of the cylinder, there is only around 60 lt heated. As that is about 50°C, that is only 15 to 20 °C uplift. 60 [kg] x 17.5 [°C] x 4.2 [SHC] = 4.41 MJ = 1.225 kWh. So pretty close. Link to comment Share on other sites More sharing options...
Gasgavalar Posted November 11, 2022 Share Posted November 11, 2022 Reading all thieve threads, people are working out the cost of the electric of using the immersion. I thought the use of the immersion was only to complement the thermodynamic panel operation, or is it that this really isn’t as good as they say? Link to comment Share on other sites More sharing options...
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