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Author Topic: One year in... some GSHP numbers  (Read 22275 times)
gnarly
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« Reply #60 on: December 24, 2017, 12:11:49 PM »

Thanks... thatís very interesting, thatís about 33% duty cycle for both of you.  Of course you do want some headroom to accommodate warming house up from cold, or being able to turn off the heat pump for the evening peak if we ever get demand pricing...
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titan
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« Reply #61 on: December 24, 2017, 02:03:51 PM »

Thanks for all the data davec/titan.  What % of the time do these gshp systems run on the very coldest days?  (And do you feel warm enough? - appreciate it is a bit subjective and depends how you have the thermostat set).  Iím asking because I wonder if, in general, the heat pumps themselves are a bit oversized for 24hr operation on the coldest days and in fact you could get away with something smaller. (As long as you have the right approach with leaving it on continuously and not trying to heat up house from cold when you are in it!)

The gshp should be sized for the maximum heating load certainly not oversized. The coldest here so far (2013)  was -12 C for almost a week  and that week it used 130 kWh which at 2.5kW load is around 6.8 hours  per 24 hours  but that was exceptional, last week with a couple of -6 C nights  it  used 60kWh for the week. The  house is always a constant temperature. I don't have the DHW 305 ltr cylinder as part of the normally on system just heat it as required which works fine, the tank is never cold and is up to 55 C in around 20 min, I think it saves unnecessary heating and standing losses but others will probably disagree or have different lifestyles.
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davec
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« Reply #62 on: December 26, 2017, 09:31:56 AM »

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... being able to turn off the heat pump for the evening peak if we ever get demand pricing...

We never turn the actual HP off but its internal controller does offer 'raise' and 'lower' timers for the compensation curve that we've set so the thing 'prefers' to run in the E10 low-rate times; there's also a standard CH programmer that runs the demand pumps to match occupancy and lifestyle. The rest is left to the exterior temp sensor plus thermal inertia.

DaveC.
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linesrg
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« Reply #63 on: December 26, 2017, 11:57:11 AM »

Good Morning All,

As I've noted elsewhere the heat pump here operates 24/7 and modulates the output dependent on return temperature and the external air temperature.

This holiday period is the first time the four family members have been in the house and us all dependent on the heat pump for domestic hot water (the electric shower having been removed in summer). SWMBO wasn't terribly happy with their not being enough hot water for her bath at the end of the evening on Xmas Eve.

Yesterday evening saw us needing water for the two boys and myself having a shower, SWMBO having a bath and needing water for washing up those things that didn't go in the dishwasher. As the process was started sufficiently early in the evening the system coped (just). It did involve selecting the highest hot water temperature i.e. 58 degrees C to make it work and thus the heat pump/ immersion heater functions were operating every 30 minutes (for 30 minutes at a time) to achieve this.

This is the same situation if we are in the flat in Aberdeen to a degree except there of course the boiler can be 'forced' to focus on heating the hot water only rather than the operator being limited to only 30 minute bursts of water heating.

Regards

Richard
« Last Edit: December 27, 2017, 07:07:41 AM by linesrg » Logged

1.28kW on a Lorentz ETATRACK1000 + 1.44kW/ SB3000TL-21 (FIT), 1.28kW/ SB1700 (ROO/FIT). CTC GSi12 heat pump/Ecosol/Flowbox 8010e/Gledhill ASL0085 EHS/3off Navitron 4720AL Solar ET & Immersun T1060/T1070/T1090. 3.375kW/ SMA SB3600TL-21 and a Sunny Island 4.4M-12 c/w 15.2kWh battery and a Renault Zoe.
marshman
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« Reply #64 on: December 12, 2018, 07:51:15 PM »

Year 3 numbers!

GSHP now been up and running for 3 full years.

Year 1:  2330kWh
Year 2:  1599kWh
Year 3:  1468kWh

Figures are for Heating and DHW. Heating roughly from end of October through to end of April.  DHW in the "summer" is via PV diverter. If there is not enough sun then Heatpump is called into action to heat the water (not needed this year until end of October).

Year 3 lowest yet even after the "beast from the east". My wife has now retired so we are both home all day everyday, but she is quite happy (at the moment!).  Still working on insulation and draught proofing (mainly to stop the colder north easterly winds penetrating). Year 4 is off to a promising start - already 25% lower consumption than last year and it was turned on a week earlier.

Ground loops currently sitting around 11 deg C.  Last year they never went below 8 deg C.


Details: House:c1700's farmhouse, detached 240 sq m, exposed position. 10kW Thermia GSHP with 4 x 300m ground loops [50% of which are in shingle] driving UFH throughout. DHW - conventional vented system with 300 ltr storage tank.  System runs 24/7 regulated only by external temp sensor. House has MHRV system (needs it as it is now getting quite airtight!). Log Burner in the lounge (external air feed).

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.
gnarly
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« Reply #65 on: December 13, 2018, 08:02:50 AM »

That's really interesting, thank you for posting.

Working back from a guessed COP of 4.3 say - which would make the electricity draw about 10kW/4.3 => 2.3kW
So 1468kWh / 2.3kW => 638 "full load equivalent" hours, which doesn't seem that much. (GSHP's can be designed for around 2000 FLEQ hours per year)

Do you think you could have got away with a much smaller pump and smaller ground array?  Even 5kW would have been on for only 1276 hours!  Given that you have an additional heatsource the power could be even lower as it doesn't need to cover the total load.

Makes me wonder if more people could install smaller heat pumps (using them in conjunction with some existing heat source like your log burner). 
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marshman
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« Reply #66 on: December 13, 2018, 09:38:16 AM »

Yes we could have got away with a smaller pump BUT we wanted the RHI payment so the calculations said we needed a 10kW to cope with demand (our EPC stated over 30kWh p.a. for heating and 3kWh for hot water!).  Having said that it is nice to have a unit that can produce huge quantities of DHW when everyone is at home having showers etc.

The ground loops were a tricky issue. We are right on the edge of a shingle bank and no one knew how the loops would perform in shingle. So the installer was insistent on going over the top on loop length to make sure it would be OK and we didn't have any space issues. In the event the pipes ran out into an area of nice blue clay which sit below the water table most of the year, so they are very good. Also because he could get a large trenching machine in the extra cost was minimal. )Took 1 1/2 days to lay 1200m of pipework.  In a way I am pleased that we have such large loops as it keeps the temperature up throughout the season. In the middle of the "beast from the east" last year (late in the heating season) the incoming water temp was 8 deg C and it was -6 deg C out side. If we hadn't seen the news we would have been unaware that it was cold out! I assume the net result is that the heatpump is always running at a fairly high COP. In those conditions an ASHP efficiency would drop off, just when you need it the most.

The RHI will pay for the system in around 4 years. Even without the RHI I would still have installed something similar. As others have said it is so cheap to run (about £225 p.a. in electric for heat and DHW) and beats having to chop up wood and light the fire every day which we did for many years, in fact I wish we had done it years ago.

Roger

p.s. just checked on the heatpump and in 3 years it has run for 2029 hours for heating = 676 hours per year, so you "guess" seems correct.
« Last Edit: December 13, 2018, 09:41:20 AM by marshman » Logged

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.
davec
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« Reply #67 on: December 23, 2018, 08:08:47 PM »

And, six years in....

Year1, Dec-2012/3 was:-
Quote
Total import 8361kWh (3412 high-rate, 4949 low). GSHP heating accounts for about 50% of this (4420); DHW about 10% (Immersion 650 plus heat-pump 216); the remaining 40% is cooking, light, appliances, kettle....

Year2, Dec-2013/4 was:-
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Total import 7845kWh (3226 high-rate, 4619 low). GSHP heating accounts for about 50% of this (3725); DHW about 10% (Immersion 636 plus heat-pump 144); the remaining 40% is cooking, light, appliances, kettle....

Year3 Dec-2014/5 was:-
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Total import 7862kWh (3324 high-rate, 4538 low). GSHP heating accounts for about 50% of this (4221); DHW about 6% (Immersion 343 plus heat-pump 128); the remainder is cooking, light, appliances, kettle, MineCraft....

Year4 Dec-2015/6 was:-
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Total import 8841kWh (3871 high-rate, 4970 low). GSHP accounts for about 50% (4504); DHW about 7% (Immersion 563 + heat-pump 97); remainder much as before.... So, Y4 numbers up on Y3 but not massively out of kilter given that the kids are staying up longer nowadays, leaving lights on and doors open...

Quote
Year5 Dec-2016/7 was:-
Total import 8678kWh (3824 high-rate, 4854 low). GSHP accounts for about 50% (4633); DHW about 8% (Immersion 512 + heat-pump 170); remainder much as before.... So, Y5 numbers fairly flat with Y4; slightly more DHW could be because of constantly showering daughter...

Year6 Dec-2017/ was:-
Total import 7792kWh (3259 high-rate, 4533 low). GSHP accounts for about 55% (4280); DHW about 5% (Immersion 71 + heat-pump 286); remainder much as before.... So, a bit more in line with Y2/3 so maybe Y4/5 was a relatively 'cauld-yin'. Different DHW numbers: I changed the program so the heat pump does more of the lift from what the solar thermal gives us and the immersion just gives an occasional kick over 60degC to ward off the L-word. Numbers seem to indicate COP > 1, even when heat pump is boosting to 55degC.

DaveC.
« Last Edit: December 24, 2018, 09:46:45 AM by davec » Logged
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