Rafiki

Only my second post here. Oak Frame SIP panel house now erected but a lot of construction work still to do including plumbing and heating systems. House is entirely off grid so no mains gas or electricity. We will have a large PV solar array on adjacent modern barn, with large battery storage. Thermal Store of 300 litres with inputs from Immersion ( which detailed calculations show will be sufficient for 8 months of the year), small LPG boiler and a wood burning back boiler. Outputs will be for DHW and UFH. The issue is with the wood burning back boiler which unfortunately is as far away from the TS as is possible- a full 17metres and on the same ground floor. It may be possible to move the TS to the 1st Floor, but house not desiigned for this, so weight may be an issue, in any case it would still be 17metres from the back boiler. From everything I have read back boliers are inherently dangerous due to boiling / explosion risks and reliance must not be placed on an electric circulating pump as it could breakdown. There will be an upstairs radiator / towel rail or two to act as a heat sink - but is that enough ? My suggested solution is to install a small ( maybe 100 litres) secondary HW tank upstairs very close above the log burner and have the log burner heat the water in that tank ( which would be open vented with a header tank in the loft) then pipe the water in that tank to the TS using an electric pump. That HW would in turn heat the TS via a heat exchanger (or directly). I realise that there would be some losses in the system and the pipe work from the secondary tank to the TS would need to be very highly insulated and relevant valves and stats would need to be incorporated to ensure that the secondary tank didn't inadvertantly cool the TS when the log burner not in use. Thoughts welcome? Andrew ( PS actually this is my daughters house and I'm not convinced that she and her husband or their plumber fully appreciate the dangers or complexity of their project)

I'm afraid not. In order to get PP the house had to be chalet style, officially a 1.3 storey house, so very little "loft" space. Planners wont allow a plethora of outbuildings either, other than an obligatory Bike store ! It 1.16 watts that raises 1 litre of water by 1 degree C. I know that intuitively it sounds wrong, but if you think of a kettle boiling 1 litre of water from 20 degrees that's 80 degrees increase or 93 watts on my calculation. So you could have a 93 watt element and wait an hour or an element 25 times more powerful ie 2.3Kw and wait 60/25 = approx two and a half minutes. My calculation may be slightly off, but it's definitely not 1.16 Kwh In any case my simplified formula comes out to the same KwH answer as you wrt raising 300 litres by 50 degrees

Yes bigger would have been better. It's actually my daughter's house and neither I nor the rest of the family got involved in planning the project early enough, partly because most were sceptical about ever getting PP for this house on a greenfield site with no services.

Everything I have read tells me that it takes 1.16 watts to heat 1 litre of water by one degree celsius . Therefore 300*1.16*50 = 17.4Kwh. But 4 people in the household will only use circa 140 litres. So the 17.4Kwh can be roughly halved. The Thermal Store is well insulated and loses only 1-3 degrees per day. The other factor is the heat of the cold water entering the house. Cold water in the mains varies between 12 and 20 degrees with the higher figures obviously being in the summer. The DHW will be heated by the immersion heater from April to September only. I am about to re-do my overall model and will increase the temperature from 50 degrees to 60 degrees in the summer. I also now have all the SAP calculations to double check my model. In particular I need to look at the winter month figures for space heating and DHW in total from the SAP's to compare with likely output from the log burner. The level of insulation etc for the house will be very high Yes a larger thermal store would have been better but no room inside, we were very restricted by planning permission constraints for this rural property.

Nearest electricity pylons are about 500 metres away. The cost of getting connected to the National Grid far exceeds the cost of a large PV array, large Lithium battery bank sufficient for 3 days and a generator. In the Summer months there will be enough electricity to heat the water by immersion, provide all house needs ( gas hob and kettle, via propane tanks) run an EV and have A/C if we wanted. In the Winter electricity generation is much lower and water heating ands UFH will be provided by a log burner. The diesel generator may have to operate 150 to 250 hours a year, primarily in the winter. We will do all the plumbing for a propane boiler as a back up but only buy and install it, if in the first winter it is neccessary. Central to the Heating and DHW is a Thermal Store of at least 300 litres which enables up to 4 means of heating the store and up to 3 means of using the heat therein - all houses should have one. We are fortunate in having large agricultural barns for installing PV and the cost of PV panels ha some down a lot.

Cheekmonkey. You seem to have got a good solution with you independent BC accepting that there was no supplier of Gigabit Services. We are in the same position. PP granted late last year. House is 100 metres from the road and there are NO services in the road ( No phone, no electric, no gas, no sewage). Nearest other houses are 800 metres away with phone lines (copper) and the nearest cabinet is a mile away ( not known if that has fibre). One other fibre supplier to villages a couple of miles away. We contacted them and they declined to quote. Trying to contact BT Openreach, but they will inevitably say "you're joking". Our independent BC is adamant we need to get 2 quotes, which is frankly impossible, so we may need to change horses. Are you able to send me the contact details for your independent BC. ( lordnelsonjones%gmail.com obviously replace the % with usual symbol)

First Post on here from a new member just introducing themselves. We are building an off grid house ( no services near enough to connect) on a family farm in North Bucks. Timber Frame supplied by Border Oak. Ground works "should" start next month after almost two years to get full PP.