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Author Topic: AHSP in Old House  (Read 6412 times)
NugentS
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« on: June 05, 2019, 06:49:20 PM »

Hi all,

Background

My parents live out in the country in an old house (1700's part of it anyway we think).
Its not got cavity walls
Glazing is a mix of double and secondary

Current heating is a mix of Storage Heater and Radiators
Current boiler is a Oil boiler, about 30 years old. There is no Gas available
House has an EPC of F29

Oil use us about 175 litres / month (85.00 pcm) average over the last 74 months or so. Obviously more in Winter and less in summer
Electricity is (from latest bill) 230 pcm (I need to look into what rate they are paying)

I would suggest that energy usage is fairly normal for an older couple with one fairly active
A couple of moderate TV's, Cooker, 1 fridge-freezer, 1 freezer, 1 Washing machine, dishwasher, microwave and a dryer plus other ancillary stuff). The freezer and fridge freezer relatively new and reasonably efficient.
Mother runs a small business arranging and printing chamber music so has a significant computer, a large printer (mostly in standby) and a 24*7 NAS device. Dad also has a small computer which is only turned on for email.
2 Storage Heaters
1 Aircon unit in a bedroom, not used that much since the room was better insulated
House is a large 4 bedroom detached house

They have solar panels - about 2.4kWp which do naff all in Winter due to trees, but the sun clears the trees in the summer so they work then
Radiators are elderly and haven't been flushed since forever - but the heating is reasonably effective but I think relies on the storage heaters to keep the core warm with the rads filling in.

They have dual rate electricity of some kind for the 2 storage heaters

Questions
The boiler is 30 years old, works well but they realise it can't last for ever and are thinking of changing it either for a new oil boiler or a shiny new ASHP (cos its the new, renewable apparently)

According to my reading, ASHP's work best with a well insulated house (F29) and underfloor heating (forget it) or large radiators (would need changing (10-13 of them)) so as a minimum they would need the HP installing and the rads changing.
Can this work in an old, not well insulated house? Or should they forget it and look at a new oil boiler.

One possible supplier turned up, (described by Mother as an "Oily Salesman") had a brief poke around and said 10K for an 8.5kW Monobloc by Mitsubishi. Subject to an actual survey and after a 2K deposit is taken (refundable if you don't go ahead). I am not saying he is wrong as I just don't know but I am betting the survey adds several grand for new rads, a new larger tank and other stuff. Their quote never even mentions RHI

Parents would like to reduce their bills and Dad loves the idea of getting money back of the Government through the RHI. They would also love to get rid of the oil tank

Is this sort of house suitable in general for an ASHP. Can it actually work the way the advertising says or should they just go with a replacement, more efficient oil burner?

Any advice welcome

Regards

Sean
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Westie
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« Reply #1 on: June 05, 2019, 08:38:37 PM »

Well, start with insulation, as much as you can possibly fit.

ASHP and GSHP produce large volumes of warm water which suits underfloor heating.   The problem with using those technologies in conjunction with a wet , rad based system is that the flow rates are low and your unable to get the rads hot enough.  This is even more of a problem if you have a wet system with the rads plumbed in microbore tubing which was 8 or 10mm diameter - which was the usual solution 30 yrs ago.   This is my problem.  One solution I've contemplated is a gas powered ASHP (Bulk LPG in my case).  This system produces water at around 70C which means the rads will get hot enough.  The product i've looked at is made by a company called Robur, its model no. is K18.  The cost is similar to the Mitsubishi ASHP you mentioned. 

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NugentS
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« Reply #2 on: June 05, 2019, 09:18:24 PM »

Is this a hybrid?
A combo of ASHP and Gas boiler?

[In this case - gas not available and I don't think they will want to swap an oil tank for a gas tank]

Sean
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A.L.
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« Reply #3 on: June 05, 2019, 11:10:00 PM »

hello,

According to my reading, ASHP's work best with a well insulated house (F29) and underfloor heating (forget it) or large radiators (would need changing (10-13 of them)) so as a minimum they would need the HP installing and the rads changing.
Can this work in an old, not well insulated house? Or should they forget it and look at a new oil boiler.

Yes it can work, the whole system just has to be designed to meet the heating demand of the house. Current heat input in the coldest months looks like averaging more than 150kWh/day with the worst days at twice that. An 8kW heat pump for 24hrs/day is 192kWh/day, so not big enough. When heat pump output rises above 14kW DNO's usually require you to use 3 phase electricity (s). Loft insulation will be required for RHI payments and should bring heat demand down by 20% if none at present. Mitsubishi do an 11kW ecodan which might just manage. Are the current radiators sized to provide 100% of heating demand, radiators at 40C give out about 1/3rd that of rads at 70C but this can be partly compensated by long (>16hr) runtimes. RHI may assume higher demand temperatures, and thus greater demand than your parents currently use.
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A.L.
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« Reply #4 on: June 05, 2019, 11:15:19 PM »

hello,

Is this a hybrid?
A combo of ASHP and Gas boiler?

no, this an example of the gas absorption cycle rather than the vapour compression cycle. COPs around 2 wrt to energy in the natural gas used to power it
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rogeriko
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« Reply #5 on: June 05, 2019, 11:16:44 PM »

An ASHP will not work in your situation, you will be freezing cold in the winter and wishing you had not wasted your money. Buy a new condensing oil boiler and everyone will be happy. The RHI now is not worth bothering with.
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Countrypaul
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« Reply #6 on: June 05, 2019, 11:36:27 PM »

As has been mentioned recently on another thread, you may also want to look at a hybrid system.   You should be able to get some figures for degree days for the location, then relate than to the proportion of heat required giving a fairly good approximation to the heat load required. This might be easier than trying to have heat load calculation done based on Uvalues for the walls, ceilings, floors etc. and likely to be more accurate.

If you ignore the RHI and the extra restrictions that imposes, you might find that using an ASHP will cover the majority of autumn and spring as well as milder periods during winter. The oil boiler should be able to handle the more severe weather during winter. Having 3 sources of heat (storage heaters) means that even if one such as the ASHP or oil boiler were to fail should mean that the house won't get absolutely freezing but may be colder than prefered until the failure can be remidied. As your parents get older this may be more important.

Around 2000L of oil per year doesn't actually sound that much given the description of the property. Can you tell how much electricity is used for heating presumably E7 or similar, as that might be a significant amount that can also be reduced by using the heat pump.
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todthedog
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« Reply #7 on: June 06, 2019, 06:36:39 AM »

Rogeriko +1

As much insulation as you can manage. We have a 70's bungalow with modern'ish condensing oil boiler. We went through the same thoughts but decided against, that the cost and disruption, new underfloor or at least oversized rads, and no guarantee of being warm in winter. If it ain't broke don't fix it. From personal experience we swapped an old oil boiler for a modern one and saw our oil consumption half!  Different house some years back.
At one point in time we had an lpg boiler modern supplying rads and hot water pre going green in France, it would have been cheaper burning notes as fuel.

Could they get a grant for new boiler in Wales continual cold calls offering this ?
Like Mart we have a ashp air/air in the lounge kitchen combined with PV which I hope will provide heating for most of the year we don't like hot bedrooms.
Good luck


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brackwell
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« Reply #8 on: June 06, 2019, 07:05:04 AM »

Rogeriko + 1

There is no chance of RHI as the cost to comply with the qualifications would be huge.

I suspect your parents are of that age where they should be seeking a more modern cosy place nearer to civilisation and support that we need in really old age.  Of course they will not move but for me it highlights all the future problems stacking up.  People need to think about the end game earlier and not leave it till it is to late.
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gnarly
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« Reply #9 on: June 06, 2019, 09:02:29 AM »

For a hybrid system with an average ASHP (maybe 5-8kW), surely you could still get RHI at a reasonable rate with the existing rads.  For this output power the rads won't need to be oversized and they will still get good SPF as the flow temp won't need to be that hot.

The only cost is an additional heat meter (temperature sensors and flow meter)

Somehow there does need to be a solution for this kind of house - there are plenty of them around!

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brackwell
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« Reply #10 on: June 06, 2019, 09:17:11 AM »

Sell them to someone who has the money to knock them down and start again.

Everything in life we throw out and replace after a few yrs with more modern up to date tech but when it comes to houses our attitude changes. Remember these houses would be prohibited to be built today.
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NugentS
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« Reply #11 on: June 06, 2019, 09:33:24 AM »

The move conversation just isn't worth it. They have been in the house for the last 50+ years and have no intention of moving

Sean
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NugentS
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« Reply #12 on: June 06, 2019, 09:36:03 AM »

The last bill (estimated) was for 3 months
1420 Units of unrestricted
3468 Units of E7

Ouch

Also they appear to be paying 11.94 / 16.97 per unit as they don't know what switching means - needless to say that will be fixed shortly. Just not sure what with.

Sean
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brackwell
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« Reply #13 on: June 06, 2019, 11:24:08 AM »

Those power consumptions do not look unreasonable but as you say need to shop around for prices.

I would suspect that they may have not have done enough to reduce drafts and air leakage (of hot air).  Visit when it is strong winds and put your hand around windows and doors looking for draughts.  Any unused chimneys need to be blocked up to prevent draughts -this is a huge 24/7 heat loss. How much insulation have they actually got in the loft -thier definition may not be up to date -if non or little they maybe able to get a grant for it.
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GarethC
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« Reply #14 on: June 06, 2019, 11:34:00 AM »

How about a few air conditioners, supported by existing heating system if really really cold? No RHI, but far cheaper and easier to buy and install, higher COPs, more controllability. Selfish aspect to asking this question as I'm considering doing this.
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