Space Heating Options

[Furnace]

  On 27/03/2023 at 08:02, Iceverge said:

Yikes, oil is certainly cheap. I didn't realise it was so much so now.

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Prices now back to pre-Russian Special Military Operation levels

[Gill]

  On 27/03/2023 at 00:05, Iceverge said:

 

A 300l UVC is a superb heat battery. We bank 10kWh every day from cheap overnight electricity. 

 

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Is that you're only water tank? For PV would you get a buffer tank ? 

 

I've crossed ESHP off the running list as I think it will work best with secondary heat supply such as stove. In the winter I don't think we want to be losing any internal heat for water heating purpose - we're economy 7 overnight water heating works well for us. 

[JohnMo]

  On 27/03/2023 at 15:35, Gone West said:

No because IIRC Grant recommend a minimum return temperature of 50C which I think is to prevent corrosion

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Oil boilers are pants really, you may as well go lpg or natural gas and get a proper modulating and condensing boiler or a heat pump.

[Iceverge]

  On 27/03/2023 at 19:32, Gill said:

n the winter I don't think we want to be losing any internal heat for water heating purpose - we're economy 7 overnight water heating works well for us. 

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It depends on how you look at it. If you are not using MVHR the heat due to ventilation will be lost anyway. With an ESHP you can forego the MVHR as you'll be recovering the energy into the DHW. 

 

In fact from an energy point of view I think they're probably better than MVHR in older leaky properties as they need a certain amount of infiltration to work correctly unlike MVHR which becomes a bit pointless in houses with high air changes. 

[SteamyTea]

  On 27/03/2023 at 20:53, Iceverge said:

In fact from an energy point of view I think they're probably better than MVHR in older leaky properties as they need a certain amount of infiltration to work correctly unlike MVHR which becomes a bit pointless in houses with high air changes. 

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As a general point, MVHR, or any extraction system, adds to the ventilation losses.

So if a house has an ACH figure of 4, and the MVHR/ESHP changed the air every hour, then the total losses are 5 ACH (or whatever the numbers are).

This don't matter much in the summer, but may well affect overall usage in the shoulder periods, like now (end of March).

 

[Gone West]

  On 27/03/2023 at 19:36, JohnMo said:

Oil boilers are pants really, you may as well go lpg or natural gas and get a proper modulating and condensing boiler or a heat pump.

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Work well with a thermal store if gas not available.

[joth]

  On 28/03/2023 at 06:24, SteamyTea said:

So if a house has an ACH figure of 4, and the MVHR/ESHP changed the air every hour, then the total losses are 5 ACH (or whatever the numbers are).

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You can't really just add those two figures together to get a meaningful result, as the airtightness test value is just a nominal value arrived at under test conditions (50Pa pressure difference) which may never actually happen or be massively exceeded in practice, depending on weather and building exposure. Whereas the MVHR flow rate is constant (for a given speed setting).

 

[Iceverge]

  On 28/03/2023 at 06:24, SteamyTea said:

if a house has an ACH figure of 4, and the MVHR/ESHP changed the air every hour, then the total losses are 5 ACH (or

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Doesn't the heat recovery aspect of an MVHR compensate for this somewhat? 

 

  On 28/03/2023 at 07:22, Gone West said:

Work well with a thermal store if gas not available.

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This crossed my mind . If I had an oil boiler this is what I'd choose. The 250l Maxipod TS I put in my parents house is working really well. All the benefits of an UVC ( on oil or gas) and no G3 requirement or expansion vessels etc.

Easily tied into a solid fuel boiler cooker in their case too. 

 

They're not much use with an ASHP unfortunately as they require ginormous volume to compensate for the lower temp. 

 

 

 

 

 

[joth]

  On 27/03/2023 at 19:32, Gill said:

For PV would you get a buffer tank ? 

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The idea being to heat the buffer from free PV? This is probably not worth it as PV is minimal at times you want heating on.

If you use the ASHP for cooling too, there maybe a better case for this.

 

 

[SteamyTea]

  On 28/03/2023 at 09:00, Iceverge said:

Doesn't the heat recovery aspect of an MVHR compensate for this somewhat? 

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Not really, for the reasons that @joth has said.

Why there should be a lot of effort to get uncontrolled air leakage reduced.

[Gone West]

  On 27/03/2023 at 19:36, JohnMo said:

Oil boilers are pants really

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I didn't think you could get modulating oil boilers but I've just been told by the heating chap about a fifteen stage modulating oil boiler. Every day is a school day.

 

https://sapphireboilers.co.uk/

 

 

[Gill]

  On 28/03/2023 at 09:00, joth said:

The idea being to heat the buffer from free PV? This is probably not worth it as PV is minimal at times you want heating on.

If you use the ASHP for cooling too, there maybe a better case for this.

 

 

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My thinking is thermal store gives us an alternative to battery which isn't currently cost effective. We're electric only with old storage heating hopefully soon to be phased out if A2A works out. 

 

My concern with ESHP is will it increase the draw of cold external air into the house from existing leaks? We're keen to seal up as much as is feasible (without going back to brick) to reduce space heating needs. We could potentially have a very minimal cost for water at least over the summer months using pv divert /eco 7. 

[SteamyTea]

  On 28/03/2023 at 23:47, Gill said:

My concern with ESHP is will it increase the draw of cold external air into the house from existing leaks? We're keen to seal up as much as is feasible (without going back to brick) to reduce space heating needs. We could potentially have a very minimal cost for water at least over the summer months using pv divert /eco 7. 

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I have been grappling with this problem for over a decade.

Even at our current inflated energy costs, I am still better off just using E7.

Yesterday, with just the smaller storage heater on, usual daily use and a go with the washing machine, I only used 9 kWh.  Come the summer I will be down to between 3 and 5 kW/day.

For me, it is just not worth putting in PV.

[ReedRichards]

  On 28/03/2023 at 23:47, Gill said:

My thinking is thermal store gives us an alternative to battery which isn't currently cost effective. We're electric only with old storage heating hopefully soon to be phased out if A2A works out. 

 

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The expensive thermal stores that use a phase change material instead of water describe themselves as heat batteries and that is an apt description.  The cheapest heat battery that you will find is a tank full of water and last time I looked it was much cheaper than an electrical battery in terms of cost per kWh stored.

[JohnMo]

  On 28/03/2023 at 23:47, Gill said:

concern with ESHP is will it increase the draw of cold external air into the house from existing leaks?

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Just let it draw and exhaust directly to outside, don't let it take house air.  Have an inlet and outlet in the outside wall. Your CoP will reduce in winter, but will still perform better than an immersion. In the summer it will draw warmer outside air and your CoP should be better. A quick look at a Dimplex Edel it has an operating range of -7 to +35.  Anything outside that range would be immersion, so you are not loosing anything.

[joth]

  On 28/03/2023 at 23:47, Gill said:

My thinking is thermal store gives us an alternative to battery which isn't currently cost effective. We're electric only with old storage heating hopefully soon to be phased out if A2A works out. 

 

My concern with ESHP is will it increase the draw of cold external air into the house from existing leaks? We're keen to seal up as much as is feasible (without going back to brick) to reduce space heating needs. We could potentially have a very minimal cost for water at least over the summer months using pv divert /eco 7. 

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Okay but the question I was addressing was about adding a buffer tank, not a thermal store. 

You've reverted to talking about eshp here so I presume the topic is DHW heating? In which case yes some way of heating it from PV (or overnight cheap rate) makes sense. 

A buffer is part of the heating circuit, not DHW, so a different topic but not relevant if you're going a2a.

 

[Gill]

  On 29/03/2023 at 08:02, joth said:

Okay but the question I was addressing was about adding a buffer tank, not a thermal store

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  On 29/03/2023 at 08:02, joth said:

A buffer is part of the heating circuit, not DHW, so a different topic but not relevant if you're going a2a.

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Thanks. I have very much manged to confuse buffer with thermal store. 😕

So any hot tank thank feeds off solar and then feeds your primary hot water supply vessel would be some form of thermal store?

 

  On 29/03/2023 at 04:09, SteamyTea said:

Come the summer I will be down to between 3 and 5 kW/day.

For me, it is just not worth putting in PV

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I would agree there. For us, makes more sense as we have much higher use.

 

  On 29/03/2023 at 06:42, ReedRichards said:

cheapest heat battery that you will find is a tank full of water and last time I looked it was much cheaper than an electrical battery in terms of cost per kWh stored

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My maths agrees. So regardless of what the primary mechanism for heating water is, I believe a second tank that heats from solar and feeds primary tank would allow diverting any unused solar. 

 

[Crofter]

@Gill what did you go for in the end? It sounds like we have very similar requirements- my house is all storage heaters, poorly insulated, with suspended floor and cold roof.

My current tariff (THTC) is set to be phased out and I really need to modernise the whole thing as the bills have become eyewatering...

[TonyT]

Get A2A run it off your night time tariff when it’s already cheap, and utilise the 400% efficient for of heating even more efficiently.

 

keep a couple of storage heaters in the far flung corners of the house controlled via smart plugs to bring them up to speed and a great hybrid solution 

[Gill]

  On 03/06/2023 at 03:45, Crofter said:

@Gill what did you go for in the end? It sounds like we have very similar requirements- my house is all storage heaters, poorly insulated, with suspended floor and cold roof.

My current tariff (THTC) is set to be phased out and I really need to modernise the whole thing as the bills have become eyewatering...

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We are getting quotes for A2A system in at the moment and solar / battery. (battery is very minimal investment return if any but I'm willing to go there as I prefer to have the flexibility to use what we generate) 

 

Was nightmare to get started with A2A as few companies around central belt Scotland and a lot that are commercial only. Getting there slowly so hope to have a system in by July latest. 

 

The immersion we want replaced with unvented cylinder with multiple immersions.

 

Solar should wipe out summer power use with divert to cylinder / battery.

 

Winter we're looking to buy cheap rate and battery store to reduce cost of flipping all heating from cheap rate.

 

Remains to be seen how this works out for us so we're keeping the storage heaters for the 1st winter. 

 

Happy to share the spec we went with. I have another thread that has some info on the quotes I've got so far here 

 

Edited June 3, 2023 by Gill