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Author Topic: Nervous about ASHP  (Read 5902 times)
pdf27
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« Reply #15 on: June 08, 2018, 02:52:12 PM »

A couple of additional comments:
  • RHI companies jack the price up something awful - that same heat pump can be bought for £4,500 inc. VAT and because it is a monobloc unit installation is almost a DIY job (you need an electrician to do the connection, the plumbing is DIYable if you're confident). The remaining ~£5k is for the paperwork to enable you to claim the RHI plus a little bit of plumbing and wiring.
  • As per the Mitsubishi website, the claimed COP is with the water being supplied to the house at 35°C. That absolutely kills the radiator power output - assuming your water is currently flowing through them at 70°C then you need to quadruple the radiator size to give the same level of heat. They're right in that it's pretty easy to do (a DIY job if you're reasonably confident or have access to YouTube - I did two recently), but if you don't do it the COP will fall of a cliff.
  • The fact that they're suggesting an 11kW unit but a 20kW stove isn't keeping the house warm rings all sorts of alarm bells for me - heat is heat no matter where it comes from, and an undersized ASHP is likely to prove horribly expensive to remedy. The RHI is supposed to guarantee that the heat pump can be the sole source of heat - so I'm wondering if they're sizing it based on the heat losses after insulation is fitted and not saying so. They may be assuming it is left on 24/7 rather than firing up as needed - that would let a smaller unit keep the house warm, but the total heat used would be rather larger than if you just left the house to cool down during the day while you were out and heated it again just before you got home.
  • The forum mantra is "insulation, insulation, insulation" - at the very least get yourself down to the nearest DIY shed and pick up a load of rolls of loft insulation and get them in ASAP. It'll make your life a lot more comfortable in both summer and winter, and if you don't have any insulation at present start making a sizeable dent in your heating bills.
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A.L.
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« Reply #16 on: June 08, 2018, 03:17:12 PM »

hello again,

- your presumably rural location, total lack of loft insulation and potentially high carbon savings from a non mains gas fuel at the moment could make you a valuable customer under the energy company obligation to the extent that you could possibly get loft & cavity wall insulation (and possibly other things) free!

- contact the Energy Saving trust on 0300 123 1234 for an unbiased assessment of your situation.
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Speltzer
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« Reply #17 on: June 08, 2018, 03:24:47 PM »

Many thanks for everyone's input. A.L I'll give them a call thanks.
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Countrypaul
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« Reply #18 on: June 08, 2018, 06:37:57 PM »

Can you clarify what the issue is with the current heating system as you say after using it over winter you need to upgrade? Is the sytem not putting out sufficient heat, or is it too much hassle to live with? Your comment about wanting to flick a switch rather than carry buckets of coal makes me wonder whether the hassle is the primary reason for changing as opposed to the actual heat output.
If the hassle factor is the main issue, then some of the advice given may benefit from revision. It would also be worth explaining how you actually use the coal fired stove currently as that can give an insight into other features. For example, if you ran the stove full bore for an hour in the morning and just left it ticking over in the evening. Does the stove heat the radiators directly or does it heat a large tank that is used to heat the radiators?  Are you in most of the day, or out to work office hours or shifts?  Where does the stove get its air supply from? Some can take the air directly from outside, others require that there is a large vent in the room to allow (cold) air in.
Be aware that if you insulate well and also seal all draughts and leaks there is a possibility you may run into other problems as the house may not ventilate enough on its own. If you therefore put double glazed windows in you may need to heave trickle vents in the windows just to provide ventilation.
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Speltzer
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« Reply #19 on: June 08, 2018, 06:52:51 PM »

Hi Countrypaul. All good questions...

- issue with the fire is both that it is inconvenient but also that it cannot heat more than two or three radiators at any given time effectively - as well as the lounge that it's in (there is no radiator in there). We can activate or deactivate its feeding of the radiators, but there is no way to stop it from heating the water in the hot water tank - even if we don't want any hot water! So there's quite a bit of wastage there.

- I am in most of the day because I work from home and would need to keep the fire fully stocked throughout the day to keep temperature up for more than say an hour.

- There is an open vent in the lounge wall because of the fire - one that we can't close.

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desperate
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« Reply #20 on: June 08, 2018, 09:41:33 PM »


  • The fact that they're suggesting an 11kW unit but a 20kW stove isn't keeping the house warm rings all sorts of alarm bells for me - heat is heat no matter where it comes from, and an undersized ASHP is likely to prove horribly expensive to remedy.
Spot on,

this company say that your heating load is 8.5kW but your 20kW stove wont heat the house!! there is something fundamentally wrong here. TBH for a solid wall house of that size 8.5kW heat load sound pretty low to me.

Go nuts with insulation and draught proofing, keep your present heating system and see how you get on this coming winter, buy a couple of extra jumpers and save your self a shedload of money. Then if you need to upgrade the heating system you will truly know where you stand.

Desp
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still a crazy old duffer!
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« Reply #21 on: June 08, 2018, 09:49:19 PM »

Speltzer,

You are in a difficult situation, one not entirely dissimilar to the one we found ourselves in when we moved in to our current property.

We had a single oil burner Stanley range in the kitchen which required a window to be left open as it was not eternally air fed and which didn't really provide heat to all the radiators fitted due to the pipework starting off as 22mm then down to 15mm and then 8mm all of which severely restricted the flow.

Whilst you may not be overly enthusiastic about the prospect of lugging coal around it may pay to find out whether your current system is performing as it should be. Better piping/ pumping/ controls may transform it?

Like you it was clear the house need work doing on the insulation front, the draught front and also the heating front. Now while not everybody on the forum will agree with our decision we too decided, after the first winter, there was no way we were going to tolerate the 'status quo' for the following heating season. After much research and advice we went down the route of an LPG condensing, weather compensated boiler and a major re-piping of the radiator system (the latter alone would have improved the original system to be honest as where 30" walls required to be 'penetrated' they were). We went the LPG route as it was more able to deal with a wide range of heat outputs as we improved the house insulation values as against an oil fired boiler which is less flexible.

Having changed the heating system we then set about ripping out the old lath and plaster upstairs one room at a time and refurbishing using large amounts of Celotex and fibreglass. We've replaced the sealed units in the Velux windows and new glazing goes into each room we refurbish. We went slightly over the top on the last occasion with two triple glazed window units and a triple glazed front door.

We still have some way to go but our energy consumption is way down on what it was. Money for larger scale projects isn't really available at the moment but I do intend putting another 100mm of fibreglass in the roof space before the next heating season.

Regards

Richard
« Last Edit: June 09, 2018, 08:57:04 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.
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« Reply #22 on: June 09, 2018, 07:44:06 AM »

A 20kw boiler should be more than enough if the house is adequately insulated and the boiler is running correctly. We heat a 150m2 house at 800 ft with a 21kw unit which burns wood only. There is underfloor wet system covering approx 40% of the ground floor but since installation 3 years ago the rads have never been turned on and the combination of the WBS,UFH and the thermal store keep the whole house at 20 deg plus. The stove is lit for about 12 hours each day in winter and occasionally in summer.

The reason this works and our combined electricity bill and wood cost is less than £600pa is the INSULATION and DRAUGHT PROOFING. We do have oil back up and have used less than 500 litres over the past 4 years.

Regen
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« Reply #23 on: June 09, 2018, 08:23:34 AM »

You can combine the ashp with another backup heat, eg. Oil.  That completely avoids any risk of the ashp not coping.  (As a general point ashp’s aren’t great when below zero as they get into a freeze/defrost cycle, and there is typically an auxiliary electric resistance heater).  Ashp would be on when the external temperature is above a ‘bivalent point’ and the oil will be on when it is colder.  It also means you get the best efficiency out of the ashp, the oil boiler will cycle less (a good thing) and you will also use much less oil.
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Speltzer
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« Reply #24 on: June 09, 2018, 11:47:31 AM »

Thanks for your responses everyone. Even if the multi-fuel stove were able to heat the house, I still wouldn't want to make a fire every time I want the heating on.

I also understand that insulation will improve the efficiency of any heating system. I'll get around to that but I need to decide on a heating system either way and I need to do it in the next month.

Having read the responses here, I'll go with bulk oil since that is tried and tested and has a better output.
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brackwell
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« Reply #25 on: June 09, 2018, 11:52:10 AM »

Do not forget to block up the chimney and the obligatory air vent.
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Speltzer
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« Reply #26 on: June 09, 2018, 11:58:51 AM »

We'll be keeping the fire, so think will still need them.
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brackwell
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« Reply #27 on: June 09, 2018, 12:28:15 PM »

Well i can understand that but if this is an occasional fire remember it is quite likely more heat is being lost than gained from the fire. Amazing thought that?  Anyway best of look with the change.
Ken
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Speltzer
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« Reply #28 on: June 09, 2018, 02:12:48 PM »

Yeah, I know whatever we put in place won't be the ideal. Not really looking for ideal though - just didn't want to install an ASHP and have a cold house and astronomical elec bills.
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billi
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« Reply #29 on: June 09, 2018, 09:02:52 PM »

Quote
Currently our house is fully fitted with radiators and a hot water tank but they are powered by a 20kW multifuel stove in the lounge. After trying it this winter, we need to upgrade!

Hi

I guess the woodstove is not delivering 20 kW  

Do you have  a thermal store ?  how much liters ?  , i guess  i would leave the big  AS heatpump idea out for 10000 GBP  for now ,  maybe  take that monney and  fit solar pannels or PV , for double the RHI  payment  of 20 pennce for solar thermal
or just forget about RHI  

10000 GBP buys me 8-10 kW PV  including a little ashp  that feeds the buffer tank (if you have one )  that can deliver   about  3500 kwh in winter  and plus heatpump then Cop3  brings you  to about 10000 kWh in winter  for heating  and  s!te loads of surplus in summer   , so  brings  your electricity bill down  and hot water for free during summer

I mean   just install something that does not costs running it
Anyway    as all others said,   think about insulation , it has a huge inpact

Billi
« Last Edit: June 10, 2018, 08:21:43 AM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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