 | Home > Off Topic > Air source heating. Any feedback? |
 
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508   
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This may become the issue in the UK as more and more people require the larger electrical supplies for ASHP's and Electric Car Charging.
The electrical supplier does not have capacity to give every house 100 Amps of electricity. Just because that is the fuse size. If all the houses on your road started drawing anything near to that, it would all start going pop in a very big way. The UK electrical suppliers have gone on record to say they are ready for this. I can't speak for the French one's! They may be ready, but whether our appetite for paying for this extra supply is as keen as their willingness to supply us remains to be seen  They won't be doing this for nothing and the end consumer will be the one who picks the bill up.
A little off topic, but if we go down the road of micro-generation and storage i.e. lots of PV Panels and big batteries to store our hard generated electricity, the consumer will not be taking their electricity from the grid and proportionaly the money which they earn from this electricity will go down or they will end up having to transmit this electricity if it is fed back in to the grid, and they won't make a penny in the current (no pun intended) set up in the UK. So it's not all smiles for the electrical supply companies. |
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4th Jan 2021 10:20pm |
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| lohr500 Member Since: 14 Sep 2014 Location: Skipton Posts: 1317 
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Big thanks to all who have contributed to this topic so far. Please keep the information flowing as it is helping me with the decision making process and with what questions to ask.
I'm now looking round for a local specialist so I can obtain a second quote for comparison. |
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5th Jan 2021 9:35am |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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Bear in mind that the installer needs to be MCS certified in order to qualify for the RHI grant
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5th Jan 2021 10:17am |
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| Intercept Member Since: 27 Feb 2017 Location: Suffolk Posts: 587 
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Watching with interest - thanks for the useful info. I'm currently running a Worcester Bosch oil combi driving full underfloor heating on all floors - installed 18 years ago. The water temperature in the floor tubes is ~55˚C so we're a good candidate for an ASHP driven system. I could set it to a lower temperature if it was on 24/7. However, we'd need to find a home for a big thermal store because the current combi means that a tank is currently not required. My brother is a heating engineer and prefers Grant so they'd be my first choice if/when we move to an all-electric heating solution.
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5th Jan 2021 11:55am |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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^^^^^
Intercept: How big a thermal store are you thinking? My 21kw ground source only has a 100Litre thermal buffer tank. I believe the big thermal stores are more relevant to biomass / log fired boilers that take a while to start generating significant heat. |
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5th Jan 2021 1:34pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508
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The size of thermal store will be dependant on the amount of hot water outlets you have and the recovery time between draining hot water off and bringing the water back to the desired temperature (bigger the external unit, the quicker this will happen)
If you are used to a combi boiler which has a theoretically limitless supply, this needs to be carefully thought about. We had a smaller hot water cylinder fitted when we had our boiler fitted and if I am brutally honest, we made a big mistake. It is usually fine for me and the wife showering but if we, or rather when we were able to have people to stay, shower after shower would soon drain the tank. It is a trade off between having enough water but not having an enormous tank where the water doesn’t turn over enough. Let me put it another way, if you and your partner enjoy deep baths, get a larger store!! |
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5th Jan 2021 2:28pm |
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| Intercept Member Since: 27 Feb 2017 Location: Suffolk Posts: 587
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For exactly reasons given by Rashers and looking at the Grant product list & prices I was thinking 300 litre minimum, maybe even 400. It'd be in a utility room on a concrete ground floor so there are no installation or mass loading issues. The maths looks pretty good - my EPC reports 10.3MWh (space) and 2.3MWh (water) per annum giving a £5.7K RHI payment over 7 years. A Grant 13KW ASHP and 400 litre tank is ~£7.7K plus installation and ancillaries. Assuming installation wouldn't exceed £2.3K that's only ~£1K more than an inevitable boiler replacement. With current electricity tariff and oil price I reckon this would reduce my fuel cost by 50%. I already have a 4KWp solar PV system (which will never pay off at current rates) so that could help run an immersion element during the summer. |
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5th Jan 2021 3:04pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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So by thermal store do you mean hot water tank?
Here's a pic of my ground source heat pump in situ. Heat pump on the left, buffer tank in the centre, 300L hot water tank on the right.  |
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5th Jan 2021 3:51pm |
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| Intercept Member Since: 27 Feb 2017 Location: Suffolk Posts: 587
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Apologies, yes. |
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5th Jan 2021 5:22pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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@intercept understand now
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If you're looking to replace the oil system anyway it makes perfect sense. |
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5th Jan 2021 5:25pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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Your solar array will power the heat pump in the summer rather than the immersion. That way, 1kw of solar energy will provide 4kw of heat into the hot water tank rather than just 1kw if its powering the immersion heater directly. You should only need the immersion for the weekly legionaires cycle to get the temp up over 60c. In the summer, our ground source only uses a few kwh a day to provide all of our hot water. |
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5th Jan 2021 5:28pm |
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| Rashers Member Since: 21 Jun 2015 Location: Norfolk Posts: 3508
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The perfect storm. Heat Pump and PV Solar. After the outlay it’s then free heating. Free is good
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5th Jan 2021 5:32pm |
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| camelman Member Since: 27 Feb 2013 Location: Peak District Posts: 3373
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It sounds like the ideal set up but, having done the maths, when the pv solar pv is producing most of it's power (summer days), you don't need the heat and there isn't realistically anyway of storing it
When you really need it (long winter nights and short days), the solar can only provide a fraction of what is needed. I looked into it but during the winter our heat pump uses upwards of 70kWh a day and you'd need a very large solar array and battery set up to support that |
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5th Jan 2021 5:53pm |
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| Intercept Member Since: 27 Feb 2017 Location: Suffolk Posts: 587
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I'm under no illusion about the actual cost - it's a long way from free and still needs annual servicing. Now, if the heat pump direction could be reversed in summer to cool the house using the PV electricity without causing condensation issues on the UFH pipes... Or maybe it'd be easier to add an inline aircon unit to the Heat Recovery Ventilation system...
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5th Jan 2021 6:33pm |
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