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Author Topic: RHI - is it worth me applying for it still ?  (Read 4640 times)
nickhlx
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« on: July 10, 2016, 03:13:50 PM »

We moved into this (large) house and have done a lot of things to it. Now fully double-glazed, lots more insulation, both in the loft space and also some external walls Celotex'd on the inside, LED bulbs throughout, and also draughtproofed where possible. When we moved in, the EPC was a "D", so must be better now.  We have also installed Solar PV, and have an ageing oil boiler with rads for central heating and topping up the DHW cylinders      (primarily heated with surplus PV via the excellent Intelligent Immersion I3 controller).

So, now looking to further save on regular outgoings and was considering heating the property with a more environmentally friendly system, e.g. either air source or ground source heat pump, or pellet boiler.  We are on clay with a very high water table from approx 6 " to zero inches (water on surface of ground after prolonged rain) which I guess might affect the choice of ground source heat pump as a source of heat. I work from home and am on site most of the time, so e.g. loading up a pellet boiler would be no problem.  Also keen to install systems that do not rely on a mains supply or can run off batteries for a short time as we are prone to mains outages, usually short, (which also knocks out the Solar PV, sadly)

Also not sure with the ongoing changes to the RHI, both recent and imminent, what will be the path to greatest savings, and would welcome any guidance.

Thanks

Nick

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System:   7.5 kWp, 2 x SamilPower 4500 Inverters, Orientated at 145 degrees, 43 degrees slope.
               DHW - Two 200L cylinders heated via Intelligent Immersion I3 proportional diverter and fitted
               with Willis (external) immersion heaters
marshman
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« Reply #1 on: July 10, 2016, 06:03:38 PM »

Hi Nick,

I can only speak with experience about RHI for GSHPs. It would have been better financially speaking to sort out the heating and RHI first before all of the energy saving measures. The reason is that the scheme takes the deemed heat requirement from the EPC as a basis for the calculations for the payment. In my case the deemed heat requirement stated on the EPC was just over 34,000 kWh per year. I had a 10kW GSHP installed, then improved the insulation etc. The system went "live" early December 2015 and since then has used 1900kWh of electric - mild winter I know - but you can see the massive discrepancy! and I've just fitted triple glazed windows so expecting next year to be even less.

Having said that I would say it is still worth looking at. Remember if going for a GSHP you need quite a large area for the ground loops - though wet clay is ideal. I've got 1200m of ground piping split over 4 loops. This is oversized as half of it is sitting in shingle which is probably the other extreme to wet clay. The system is not cheap either but has the advantage of being virtually zero maintenance. We also suffer from the occasional power cut, more than usual this last winter season and the GSHP will happily run off of my 5kVA standby generator, just don't boil the kettle at the same time!

You need to do some initial investigations starting with a new EPC to find out the deemed heat requirement, the bigger the better in RHI terms!. Then do you own calculations as to the actual heat requirement. From there you can look at the various options - biomass/pellet boilers, GSHP or ASHP etc and do the math to see if it is worth it. Remember that to claim RHI the installation must be MCS registered/certified which adds to the cost. It maybe that you ignore it and just install a system that suits your needs best.

Roger
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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
nickhlx
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« Reply #2 on: July 10, 2016, 07:42:14 PM »

Thanks for the info on your system..  Not sure what we use for heating other than we use about 4000 litres last year  (is that around 40,000 kWh ?) The house is long and thin so not the best shape for heating efficiency. We also have a large log burner which uses around a 1000 Kgs of kiln dried logs over a winter, but only heats a couple of rooms and no water. I am about to install another small log burner in the kitchen / breakfast room to save having to put the heating on for the room that is used most each day, and both those are independent of electricity if / when we get power cuts..

Fortunately we have a large back garden ( about 3/4 acre) and trenches would be relatively easy to dig pipes into - Or borehole(s) could be dug which sounds like less earth moving / might be less expensive ?

Anyway - more research to be done, and thanks again for your input,

Nick
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System:   7.5 kWp, 2 x SamilPower 4500 Inverters, Orientated at 145 degrees, 43 degrees slope.
               DHW - Two 200L cylinders heated via Intelligent Immersion I3 proportional diverter and fitted
               with Willis (external) immersion heaters
marshman
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« Reply #3 on: July 10, 2016, 08:27:41 PM »

Thanks for the info on your system..  Not sure what we use for heating other than we use about 4000 litres last year  (is that around 40,000 kWh ?) The house is long and thin so not the best shape for heating efficiency. We also have a large log burner which uses around a 1000 Kgs of kiln dried logs over a winter, but only heats a couple of rooms and no water. I am about to install another small log burner in the kitchen / breakfast room to save having to put the heating on for the room that is used most each day, and both those are independent of electricity if / when we get power cuts..

Fortunately we have a large back garden ( about 3/4 acre) and trenches would be relatively easy to dig pipes into - Or borehole(s) could be dug which sounds like less earth moving / might be less expensive ?

Anyway - more research to be done, and thanks again for your input,

Nick


As far as I know boreholes are not cheaper than trenched pipes. I was told about 10k per hole (obviously a bit less if you have several). Don't forget you need access to the rear garden for some big machinery to put the pipes in, either a trenching machine, which is the idea,l or a big digger!

Doesn't sound like your house would suit a heatpump to be honest. They like energy efficient (well insulated)  houses and running at low output temperatures. They will produce the goods at higher output temperatures but the efficiency suffers.

Roger
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3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
nickhlx
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« Reply #4 on: July 11, 2016, 12:46:52 AM »

Hi Roger,

Thanks again for the input - I did wonder whether a heat pump would be appropriate, as even if it quarters the price per kWh of electricity, electricity is still more than 4 times the price of oil (at the moment !) 

I will continue with the research though..

Nick
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System:   7.5 kWp, 2 x SamilPower 4500 Inverters, Orientated at 145 degrees, 43 degrees slope.
               DHW - Two 200L cylinders heated via Intelligent Immersion I3 proportional diverter and fitted
               with Willis (external) immersion heaters
Mikel
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« Reply #5 on: July 12, 2016, 09:56:07 AM »

Nick,

It would probably be possible to put in an efficient GSHP system for your house but it would be a high upfront capital expense. We have done it for our house, which was EPC D rated when we moved in. You would be looking at totally re-lanscaping your garden and uprating your radiators (think in terms of changing single rads to doubles and doubles to triples and big rads for bathrooms). You should think of the RHI as a means of recovering some of the capital. The RHI intention, on average, is to level the costs compared to oil installation over a seven near period. With your deemed heat requirement, you might do better.

Sorts of questions to ask yourself are:

How long do I intend to live here?
How concerned am I about environmental impact?
How much capital do I want to spend to reduce recurrent costs?
What is my view on how energy costs are going to change over a longer term?

For the latter, we put our system in when heating oil was 60p per litre. It is now about half that!

Mike
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monstermonster
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« Reply #6 on: July 13, 2016, 08:17:32 AM »

I think heat pumps are better suited for new builds or complete rennovations where the insulation has been maxed out to the extreme. Our 2500m2 1900 farmhouse is EPC D banded after good levels of insulation. Although we have a one acre plot a ground loop system was not enough. Bore holes looked the best option so long as the ground is geologically suited BUT cost is stupidly high at several 1,000's per hole and several holes would have been required.

Although heat pumps were a very attractive option I just wasn't convinced as to their performance in older properties. I heard too many horror stories and met too many installers that clearly did not know what they are doing.

In the end we went for a log gasification boiler and to be honest despite it working reasonably ok I wish I hadn't done it. Upfront cost was high in effect, wood has doubled in price, oil has more than halved, good installers are as rare as hens teeth, it's a complete ball ache feeding a boiler every day, not being able to go away for more than two days.

To be honest be very careful in going the alternative heating route. Better to spend the money on reasonable insulation first and go from there. Do not be swayed by any RHI payment; treat RHI as the cherry on the cake. Make sure all quotations are fully broken down, check the prices especially the labour element. A lot of installers have inflated their installations costs because they know the customer is getting RHI payments.


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Eco Angus Orligno 200 40KW. 3000l Akvaterm. Laddomat. Termoventiler CC. 10xSharp NU180 PV 1.8KWp. Immersun. Very tried patience.
nickhlx
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« Reply #7 on: July 13, 2016, 09:52:09 AM »

Thanks guys - From all the comments and looking into it in more detail, I am going to give it a miss, stick to more conventional space heating, keep on improving the insulation and  hope the boiler keeps going for longer than expected. 

Nick
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System:   7.5 kWp, 2 x SamilPower 4500 Inverters, Orientated at 145 degrees, 43 degrees slope.
               DHW - Two 200L cylinders heated via Intelligent Immersion I3 proportional diverter and fitted
               with Willis (external) immersion heaters
chasfromnorfolk
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« Reply #8 on: July 13, 2016, 11:19:18 AM »

Thanks guys - From all the comments and looking into it in more detail, I am going to give it a miss, stick to more conventional space heating, keep on improving the insulation and  hope the boiler keeps going for longer than expected. 

Nick

It may be the current 'late entry' terms aren't as favourable as I got early on, but do consider a wood pellet boiler - ours is effient and easy, the cost of pellets reasonably stable and you won't need to replace the rads.

Chas
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nickhlx
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« Reply #9 on: July 13, 2016, 11:33:35 AM »

Hi,

Thanks for confirming that - I saw one of those the other day and was impressed by the machine -  this one had some sort of "screw" feeder from a hopper (they possibly all do) and seemed to be an efficient clean burn.

Quite expensive though !

Nick
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System:   7.5 kWp, 2 x SamilPower 4500 Inverters, Orientated at 145 degrees, 43 degrees slope.
               DHW - Two 200L cylinders heated via Intelligent Immersion I3 proportional diverter and fitted
               with Willis (external) immersion heaters
dhaslam
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« Reply #10 on: July 13, 2016, 11:48:05 AM »

Wet ground is  a good source of heat and  you could use a  few  deep holes  dug out with a  digger  that are just big enough to take  150 metres of  pipe  coiled.    About one hole for each 3kW of output and the output would be from the lower end of each coil in parallel.   The pipes would need to be connected to  28mm  pex pipe to bring the heat into  the heat pump.   As a DIY project, without RHI you could use a low cost or SH heat pump   to work alongside the oil boiler.   In spring and autumn you might be able to  use  the heat pump with  a good portion  of input from PV but in winter off peak electricity would be needed to minimize cost.  With the present low oil price it might be a little difficult to have a net  saving  in the short term  but  that depends on how cheaply you could get the work done.  Oil is likely to rise in price again when or if the  Middle East oil producing countries  are stable enough to  moderate production.     A system for RHI would probably cost four or five times more  so it needs a much larger outlay even if the difference is recovered over a long period.

The present low oil price unstable because  the price doesn't  allow a profit  on many shale oil sources and export volume of conventional oil is increased to maintain income.
 
http://www.nytimes.com/interactive/2016/business/energy-environment/oil-price-supply-demand-imblance.html  
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DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
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