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Author Topic: System Planning Advice  (Read 2744 times)
Bikerzz
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« on: March 10, 2019, 06:31:34 PM »

Im busy renovating my 1967 detached property and this summer will be getting a few trades in (Im too busy and not that great at DIY so done the manual labour bits).
It will involve UFH (water) whole of downstairs along with a new kitchen (47m2 worth of kitchen) so have space for a cornered off utility type room where at the moment stand an old oil system boiler.

The plan is to run UFH off this oil burner for another year and replace with a ASHP next year and Solar PV on the roof once we saved up again for another year.  The house has the usual Hot Water Tank upstairs in airing cupboard and 2 cold water tanks in loft.  

The question is once we have a ASHP should the Hot Water Tank be next to where the ASHP will be (Kitchen Outside wall) as I see this on many peoples houses? Or Can it stay upstairs (I know it will need to be replaced with a modern Tank)?
Im hoping to run ASHP with UFH at very low temp (Sub 30c) to keep the COP high and then Solar PV to power ASHP and Immersum in the hot water tank.  

Im asking this now as we are doing kitchen designs and wondering if I should factor in some space for a Tank Downstairs?

Cheers
« Last Edit: March 10, 2019, 06:37:12 PM by Bikerzz » Logged

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titan
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« Reply #1 on: March 10, 2019, 07:46:24 PM »

First thing to do is calculate the heat losses from the building before considering a ASHP. As you say ideally you want to run the system at lowish temperatures this is just not possible if the heat losses are too great. Unless you have managed to get a lot of insulation into your house I think 30 deg flow temperature is unrealistic.
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Bikerzz
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« Reply #2 on: March 10, 2019, 07:51:51 PM »

Oki. We can ignore my comment of 30c.  Im just after advice of what space I need/may need to allocate for tank etc...
The whole house needs plumbing/Wiring and renovating hence going for UFH. Maybe I wont ASHP (Although I think I will), currently house has small rads with a boiler running water at 50-55c (its non adjustable and on its last legs).

I didnt think you could EVER run your UFH hotter than about 35c anyway?
Isnt your comment on ASHP irrelevant if UFH has a limited max temp anyway?
« Last Edit: March 10, 2019, 07:54:19 PM by Bikerzz » Logged

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rogeriko
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« Reply #3 on: March 10, 2019, 08:56:28 PM »

30 degrees is fine for underfloor heating, its just that you need a lot of it. Will an air source heat pump be able to supply in january/february without running continuously and costing a fortune. Insulate Insulate Insulate or you will have enormous electric bills.
Solar PV will not power an ASHP in the winter nor will it heat your DHW so forget about that.
Spend your money on external wall insulation.
« Last Edit: March 10, 2019, 08:59:28 PM by rogeriko » Logged

gnarly
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« Reply #4 on: March 10, 2019, 09:40:57 PM »

How many liters of oil do you get through in a year - that would give some idea of the size of heat pump needed.
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« Reply #5 on: March 11, 2019, 07:07:14 AM »

Bikerzz,

As others have suggested you need to calculate your current energy usage/ loss and the situation you will be in when you plan to install a ASHP.  You don't say how much of the work you are planning on having done is insulation related.

In my property the downstairs bathroom has always been the 'controlling' factor and I have always underestimated this space's energy demand. For instance yesterday the GSHP was pushing water out at 38oC as dictated by the bathroom whereas the Shower Room was only seeking 35oC and other rooms less than this.

It is next on the list for 'overhaul'.

Regards

Richard
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Bikerzz
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« Reply #6 on: March 11, 2019, 07:18:08 AM »

We used 2,900KWH a year on Electricity and Approx 1200 Litres of Oil so not terrible really for a 6 bed 240m2 detached house. Although I dont think its ever been above 19c as Im tight!

The insulation is:

Attic - Cold roof (Currently) 200mm in loft of rolled fiber (was only 100mm when moved in and going to 200mm hasnt made any noticeable difference) - Easy to upgrade if needed, although might do a loft conversion and put celotex in roof.

Walls are 50mm cavity which has been insulated, Fiber batts in extension and blown white fluff  in the older part.

Windows are Triple glazed.

Floors are Timber suspended (100mm celotex will go in with UFH)

Block and beam extension done in 1994, no insulation on top of beam - Will be putting 60mm minimum, some will get 100mm in. (Floors on different height currently)

According to the heat loss calculator you once pointed me too (MCS_heat_pump_calculator_v1_8) Heat loss is 14,700 watts for whole house, but that doesnt tie in with how much oil we are using currently (I guess they think the house is always kept at 21c or something daft).  I live in a conservation area so not sure I can get a heat pump (tho this sounds a mad rule, rather than burning oil), so still need to ring council planning.

Another calculator found online (Calculation-tool-for-design-of-low-temperature-domestic-heating-systems---V1.2) shows 10,050 Watts.

Cheers
« Last Edit: March 11, 2019, 07:36:10 AM by Bikerzz » Logged

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brackwell
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« Reply #7 on: March 11, 2019, 07:58:34 AM »

need a reality check perhaps?

1200L of oil is c 12,000 kwh/yr is it not.    This is in itself a reasonable amount for this size of property but where else is that amount of primary energy going to come from? definetly not from solar during the heating season!
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biff
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« Reply #8 on: March 11, 2019, 09:07:32 AM »

 Bikerzz, this is a good thread,
                It is the kind of thread that Navitron excels in. The members have lots of experience in heating and insulating and are glad to share it.
  I was going to suggest that the first thing that you do is install a 4kw ground mount PV array that will start paying for itself immediately. It will lighten the cost of the use of power tools and other extra running costs that crop up while refurbishing houses. But I noted that you live in a conservation area and getting that organised could be a load of hassle and then maybe you don,t have the room for a ground mount. The great thing about PV is that it starts paying back the moment you switch on. There is very little to go wrong and unlike a lot of other things it is good for 25 years so you can plan ahead.
     As for your refurbishment build. Take your pick and work to a plan but Insulate,,insulate and insulate again.
                                                       Biff
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titan
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« Reply #9 on: March 11, 2019, 09:32:01 AM »

Oki. We can ignore my comment of 30c.  Im just after advice of what space I need/may need to allocate for tank etc...
The whole house needs plumbing/Wiring and renovating hence going for UFH. Maybe I wont ASHP (Although I think I will), currently house has small rads with a boiler running water at 50-55c (its non adjustable and on its last legs).

I didnt think you could EVER run your UFH hotter than about 35c anyway?
Isnt your comment on ASHP irrelevant if UFH has a limited max temp anyway?

Depends what size tank you are considering. Something much bigger than standard cylinder to make the use of your PV, unvented means you can get rid of the loft tanks and you get mains pressure hot water. Size of heat pump required will also depend on the floor size and construction, tiles,wood ,carpet etc. You only mention downstairs are you having  other heating elsewhere will it run at the same temperature or will groundfloor UFH heat whole house.
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offthegridandy
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« Reply #10 on: March 11, 2019, 09:38:58 AM »

Hi Bikerzz.

Can't actually answer your question but if it was me I'd plan to put the new water cylinder down stairs close to the heat source/boiler. 2 reasons 1 the losses are less and the plumbing should be easier. 2 Any heat losses in the boiler cupboard/utility area will tend to rise and heat the habitable room above rather than the cold attic over the 1st floor.

As regards the mantra on insulation; all true but having invested in the insulation.  DO spend time very carefully sealing around all air gaps.  Watch out for trades cutting stuff  away to allow for pipe runs etc and ensure that all gaps and cracks are well sealed before closing up and plastering.  You will be amazed at how much heat can be lost through a small gap once the wind gets up and starts forcing its way around the cavity or up under the facias and soffit boards.

EG if you have access at the appropriate time.  Beam and block floors can be sealed by making a sand and cement slurry and brushing it in across the blocks.  The slurry will seal small gaps in the blocks reducing heat loss from below the insulation.  If using rigid foam insulation follow the manufacturers guidance on joint sealing.  Buy the proper foil backed tape and us it carefully on every butt joint.  The tape may seem dear but you are only doing the job once, so do it right.  You'll not get another chance.

Good luck.

Andy
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Bikerzz
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« Reply #11 on: March 11, 2019, 11:32:02 AM »

Thanks people

Yes 12kwh a year in oil does seem a lot, any idea what that would cost in Electricity from a ASHP? At a COP of 3 and 0.15p electricity isnt that only £600?

This is a 30 year home (Im only 31 and plan to live here till I retire), I have 0.75 acre so enough land space but more importantly a roof facing SW which should get me at least a 4kw array on.
Ok, will not be determined to go for ASHP. However I should leave enough space in utility for a thermal store with a Immersun off some PV.  For a 240m2 House how big unvented thermal store should I be looking at ? (4 bath rooms) but no children YET.........

The UFH is a good idea as radiators and plumbing have had it anyway and house needs redecorating and wiring, the Mrs also is happy for tiles around the whole house with only 1 room she would like engineered wood and living room she still wants carpet, but bar that tiles which is great.

I will just keep the oil boiler going as long as it does and when goes bang look into what could be more sensible, and get as much PV on the roof as is reasonable when I can afford.

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andrewellis
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« Reply #12 on: March 11, 2019, 01:53:17 PM »

Whatís the ground like? We had a ground source heat pump out in last year and Iím delighted with it.   We are in Scotland and the ASHP calculations didnít stack up as the COP drops off fast with the lower temperatures. You find most manufacturers wonít even provide the figures. A borehole might get round the whole conservation area issue. It cost more but our brine temperature didnít drop to zero until we hit -10 giving a fantastic cop through the year even on radiators. The best part is if you are staying, the cost of install/capitol all pays back over seven years from the RHI. An ASHP wouldnít do the same.
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Bikerzz
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« Reply #13 on: March 11, 2019, 01:56:21 PM »

Whatís the ground like? We had a ground source heat pump out in last year and Iím delighted with it.   We are in Scotland and the ASHP calculations didnít stack up as the COP drops off fast with the lower temperatures. You find most manufacturers wonít even provide the figures. A borehole might get round the whole conservation area issue. It cost more but our brine temperature didnít drop to zero until we hit -10 giving a fantastic cop through the year even on radiators. The best part is if you are staying, the cost of install/capitol all pays back over seven years from the RHI. An ASHP wouldnít do the same.

Thanks I ruled this out due to cost. Id have to have Bore holes although could have a few. Garden is on a slope not suitable for trenches really as alot if block paved. CV472YF is postcode (Warwickshire)
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Countrypaul
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« Reply #14 on: March 11, 2019, 02:48:39 PM »

Thanks people

Yes 12kwh a year in oil does seem a lot, any idea what that would cost in Electricity from a ASHP? At a COP of 3 and 0.15p electricity isnt that only £600?


12kwh a year would be great for any house, that woudl be 60p /year - unfortunately you mean 12MWh a year, and yes that works out at £600.

Our house is 225m2 and we have a 430L thermal store. Currently heated by immersion only, but will be putting in an ASHP this spring one other things are out the way. We already have 3.3KWp of solar panels, so will also be putting in a diverter to utilise more of the PV generation.  The immersion heaters were put in as a fail safe in case the ASHP were to develop a fault, meant we could keep the house warm all the time, as it worked out we have relised on them this winter. Total house heat load has been well below 4KW (6KW during E7 and 3KW during the day) even during the cold spell at the start of January, that compares with the calculations I had done coming in at just over 8KW (at -3C) so quite a bit better. Ground floor has 125m2 of UFH in a 60mm screed over 120mm celotex, upstairs has UFH for bathrooms only - about 15m2 total fitted from below using spreader plates with 22mm chipboard and then tiles.

Our thermal store in on the first floor for a couple of reasons - but mainly convenience and our plan to put a WBS in the lounge so we could have gravity feed to the TS in case of power failure. We are also in a conservation area and the ASHP will be about 20m from the TS plus 3m lower. The size of the TS was limited by the space available, otherwise I would have gone larger and taller.

If you can, I would keep the oil burner for use in case of emergencies, such as HP break down, very cold weather resulting in the ASHP not coping etc. You might also want to look at air to air heat pumps, I know a few threads on this forum have been about the subject and view them very positively mainly as a supplement that avoids or delays having to put the main heating on.
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