Boiler-Heat Pump Hybrids

[Beelbeebub]

4 hours ago, JamesPa said:

So I dont think the average will be 60%, more like 30% because most will inevitably be set up to be and actually used like boilers.

The 60% refers to time using HP rather than boiler.

 

The Gov report estimated carbon savings for *continuous hearing* to be 55% ie better than my quick calculation.

 

It is true that 2x a day heating causes those savings to drop drastically.

 

There is a really simple solution to that. 

 

Remove the heating timer (and provide an instruction leaflet explain why it's gone)

 

I've been removing timers from our boilers (we get simple wireless thermostats fitted) for ages simply because one of the biggest causes of "my heating isn't coming on" is always the timer being poorly set. Either the time has shifted due to summer/winter time. Or simply drifted or the schedule itself being badly set.

 

You could make removing the  (heating) timer part of the install, the boiler is going to be controlled by the new control box anyway. All the boiler has to do is turn on or off at either the DHW temp or the heating temp (or a single temp in a very dumb system)

 

 

 

[JamesPa]

3 hours ago, Beelbeebub said:

There is a really simple solution to that. 

 

Remove the heating timer (and provide an instruction leaflet explain why it's gone)

Agreed

 

But then some plumber will turn up (or there will be some flashy TV or Facebook ad) explaining how fitting Hive (or the like) will mean that they can control the heating remotely and save a fortune, and so they will buy Hive.  Perhaps less likely in a rental property, but in an owner-occupier situation the industry has done an absolutely fantastic job of selling us over-hyped 'smart' controllers of various which don't (and cant) save anything like as much as claimed whilst failing to sell us weather compensation for gas boilers which would and which would improve our comfort levels.  

 

I'm sorry for my cynicism!

Edited November 25 by JamesPa

[sharpener]

1 hour ago, JamesPa said:

there will be some flashy TV or Facebook ad) explaining how fitting Hive (or the like) will mean that they can control the heating remotely and save a fortune

 

I have been studying some music on youtube recently and getting increasingly annoyed by the masses of intrusive ads selling small electric heaters that claim to heat your house for fraction of the usual cost. Mostly they have some "magic" heating element based on ceramics or precious metals etc. We all know they are a physical impossibility but presumably they would not exist if ppl did not buy them. The level of technical education of the general public is truly shocking and some of the heating industry not a lot better.

So I fear @JamesPa is correct, and cannot see any justification for using public money to pursue the concept of hybrid systems in the UK environment. The scope for fiddling the results is so vast and the potential returns so poor.

 

While writing, I need a 13A adaptor linked to my wifi so I can switch off my Honeywell Evohome zone controller remotely. Is this thing from Shelley any good or do ppl recommend sthg else?

 

The controller has an annoying bug that after a power cut it does not come back on in the same state it went off. But I can use this to my advantage. If it is set to Away, then when I am planning to return if I turn it off remotely for 3 hours the standby battery will go flat and it will the come back in Normal mode so re-enabling the heating.

[SteamyTea]

17 minutes ago, sharpener said:

ads selling small electric heaters that claim to heat your house for fraction of the usual cost

I got one from The Range for £9.  It is just a 400W fan heater.

Works well, but a bit noisy, so sticking to my old fan heater as it is a lot quieter.

This last week, which was very varied in temperature, cloud cover, wind speed and rainfall, I heated my house with 20 kWh or finest electrons.

This may well be the first year I get to December without turning the storage heaters on.

[PhilT]

10 hours ago, SteamyTea said:

I got one from The Range for £9.  It is just a 400W fan heater.

Works well, but a bit noisy, so sticking to my old fan heater as it is a lot quieter.

This last week, which was very varied in temperature, cloud cover, wind speed and rainfall, I heated my house with 20 kWh or finest electrons.

This may well be the first year I get to December without turning the storage heaters on.

Have you ever had a go at working out the capex/running cost of pure electric, using storage/E7, vs. the capex/running cost of a heat pump installation? Could be an interesting comparison and possibly a surprisingly close contest in terms of payback/IRR?

Edited November 26 by PhilT

[SteamyTea]

37 minutes ago, PhilT said:

Have you ever had a go at working out the capex/running cost of pure electric, using storage/E7, vs. the capex/running cost of a heat pump installation

Yes, a few years back, and it is why I am still using resistance heating.

I started my energy monitoring over a decade ago, because I wanted to know if I would be better off on a flat rate as opposed to E7.

Why I am still on E7.

 

I have not run the numbers in the last few years, but doubt it has changed much.

The big advantage of resistance heating is that repair/replacement is very cheap. Only had to change the DHW element, but as the cylinder was leaking, I changed that as well, but that was after 33 years of daily usage, cost less than £300 (got the cylinder of @Nickfromwaless mate Trevor).

One of the problems I have is that I live in a warm part of the country.  I am only have the heating on for 8 to ten weeks a year, with a bit of fan heater usage when needed.  The other problem is that my usage is low, generally less than 15 kWh/day in the depth of winter, which sometimes drops below 8°C down here.

The biggest problem is that I never meant to be in this place for 20 years, was only a temporary move while I retrained as a teacher, then back to Hertfordshire.  Well that is what I told my then girlfriend.

When I move next time, I shall invest all my cash in RE, insulation and airtightness, and an EV.

[Beelbeebub]

Resistanc e heating is the cheapest capital expenditure system.

 

And right now it's lower carbon than gas boilers

 

The only problem is electricity is bloody expensive compared to gas (at least in the UK)

 

If we had fusion or whatever magic "too cheap to meter" electricity generation system then we'd all be using resistance heaters. The French, with their nuclear fleet, were pretty big into it.

 

But for now HPs are the way forward, mainly because they drastically reduce the amount of renewable generation we need to build out

[JohnMo]

20 minutes ago, Beelbeebub said:

Resistance heating

 

And right now it's lower carbon than gas boilers

The generation emissions factor (2024) for grid electricity is 0.20705 kg CO2e per kWh. (source: https://www.itpenergised.com/new-2024-uk-grid-emissions-factors/#:~:text=This lag is standard and,CO2e per kWh.)

 

A gas boiler Co2 emissions according to Energy Saving Trust, work out at 0.225kg CO₂ per kWh. So lower for resistive heating, but not by much - 0.02 kg CO2e. So if you are doing resistive heating for great environment credits, not sure there is much in it. The only way a heat pump is better is because you have a 3 or 4:1 output ratio compared to input. 

[PhilT]

23 minutes ago, Beelbeebub said:

Resistanc e heating is the cheapest capital expenditure system.

 

And right now it's lower carbon than gas boilers

 

The only problem is electricity is bloody expensive compared to gas (at least in the UK)

 

If we had fusion or whatever magic "too cheap to meter" electricity generation system then we'd all be using resistance heaters. The French, with their nuclear fleet, were pretty big into it.

 

But for now HPs are the way forward, mainly because they drastically reduce the amount of renewable generation we need to build out

Mostly agree although gas power efficiency is abysmal (25% for non CCGT) and getting worse as gas turbines have to keep stopping and starting more and more with fluctuating renewables https://www.statista.com/statistics/548943/thermal-efficiency-gas-turbine-stations-uk/#:~:text=Thermal efficiency of combined cycle,in the UK 2010-2022&text=The thermal efficiency of combined,gas was converted to electricity.

[JamesPa]

18 hours ago, sharpener said:

Is this thing from Shelley any good or do ppl recommend sthg else?

I have one of Shelleys 16A relays to switch on and off the charger for my EV.  It looks and feels like quality and it works a treat.  Obviously the product you are looking at is a different one, but if my experience of Shelley is anything to go by I would give it a try.

[JohnMo]

30 minutes ago, PhilT said:

CCGT

Their efficiency comes mostly from, the free steam they generate from the flue gas, and this takes awhile to stabilise and be usable in the steam turbine. So a CCGT, if started and stops frequently is only as good as and CCGT.

 

Note: CCGT, is Combined Cycle Gas Turbine. A gas turbine, with a free power turbine in the gas stream diving a generator. In addition steam is made from the heat in the exhaust gas, which in turn drives a Steam turbine to give additional input kW driving force for the generator.

[SteamyTea]

36 minutes ago, JohnMo said:

only as good as and CCGT.

Do you mean OCGT there (open cycle gas turbine).

[SimC]

In theory it could be possible to add an ASHP in parallel with an existing boiler, but both would need to have their own pumps in the correct part of the circuit, and each have a non-return valve to prevent reverse flow through the non-running unit, and the existing plumbing would have to support the required flow rate through the ASHP, and the water teatment used would have to suit both. So quite a lot of dependencies.

 

My 8mm microbore to most of the rads will probably not allow the required flow rate for an ASHP, and I have no idea what water treatment would be required to suit both devices.

 

Thinking about inserting a plate heat exchanger, but then the issue becomes the ASHP does not engage with sufficient volume of water for de-frost cycles etc.

 

The Daikin hybrid schematic does not indicate where any pumps are located to generate flow, so they could be in series, meaning the non-running pump will restrict the whole system flow rate.

[Beelbeebub]

25 minutes ago, SimC said:

In theory it could be possible to add an ASHP in parallel with an existing boiler, but both would need to have their own pumps in the correct part of the circuit, and each have a non-return valve to prevent reverse flow through the non-running unit, and the existing plumbing would have to support the required flow rate through the ASHP, and the water teatment used would have to suit both. So quite a lot of dependencies.

 

My 8mm microbore to most of the rads will probably not allow the required flow rate for an ASHP, and I have no idea what water treatment would be required to suit both devices.

 

Thinking about inserting a plate heat exchanger, but then the issue becomes the ASHP does not engage with sufficient volume of water for de-frost cycles etc.

 

The Daikin hybrid schematic does not indicate where any pumps are located to generate flow, so they could be in series, meaning the non-running pump will restrict the whole system flow rate.

Grant have a schematic in one of their manuals for a hybrid.

 

It's a pretty simple tee into the flow and return with NRVs to stop back flow (as you mentioned)

 

The HP has a pump fitted already. In the case of the grant units, it's pretty powerful. With a 12 or 10m head (depending on model) vs the usual 6m or even 5m max heads in most normal pumps, so there is some. Leeway for extra pressure to drive the higher flows. But yes, flow might be an issue in some cases where microbore or just plain crappy plumbing is involved. Micro bore has been used successfully with HPs. A common way for MB to be plumbed was via a 22mm manifold in the floor/ceiling and only MB drops/risers to to individual rads. This means the MB only has to support the flow required to each radiator and an 8mm microbore can provide 750w typically with a HP. 10mm is 1kw

 

With the advent of antifreeze valves you no longer need to use glycol and can get away with regular water plus some inhibitor/biocide (basically compatible with boilers).

[Dillsue]

53 minutes ago, Beelbeebub said:

Grant have a schematic in one of their manuals for a hybrid.

 

It's a pretty simple tee into the flow and return with NRVs to stop back flow (as you mentioned)

 

The HP has a pump fitted already. In the case of the grant units, it's pretty powerful. With a 12 or 10m head (depending on model) vs the usual 6m or even 5m max heads in most normal pumps, so there is some. Leeway for extra pressure to drive the higher flows. But yes, flow might be an issue in some cases where microbore or just plain crappy plumbing is involved. Micro bore has been used successfully with HPs. A common way for MB to be plumbed was via a 22mm manifold in the floor/ceiling and only MB drops/risers to to individual rads. This means the MB only has to support the flow required to each radiator and an 8mm microbore can provide 750w typically with a HP. 10mm is 1kw

 

With the advent of antifreeze valves you no longer need to use glycol and can get away with regular water plus some inhibitor/biocide (basically compatible with boilers).

Nice positive take on a hybrid system and music to my ears.

 

Planning on adding a HP next year alongside an LPG boiler and WBS. We select between the boiler or the WBS with 2 port zone valves rather than NRVs so will tie in the HP with another one.

[JohnMo]

3 hours ago, SteamyTea said:

Do you mean OCGT there (open cycle gas turbine).

I did, it must have auto corrected 

[SteamyTea]

8 hours ago, JohnMo said:

auto corrected 

Over the last few months I have noticed that my autofill/autocorrect, on both the phone and PC, are putting in random words and phrases.

Is it Google and Microsoft playing about with AI.

[JamesPa]

5 hours ago, SteamyTea said:

Over the last few months I have noticed that my autofill/autocorrect, on both the phone and PC, are putting in random words and phrases.

Is it Google and Microsoft playing about with AI.

Probably

 

The next step is that Elon Musk will be 'autocorrecting' so that it says what he wants you to say.  

[Beelbeebub]

21 hours ago, Dillsue said:

Nice positive take on a hybrid system and music to my ears.

 

Planning on adding a HP next year alongside an LPG boiler and WBS. We select between the boiler or the WBS with 2 port zone valves rather than NRVs so will tie in the HP with another one.

Grant seem to have a fair bit of experience with hybrid systems - you can (I think) still order an oil/HP hybrid unit from them but they also make some sort of advance interface box/buffer to link two separate units together.

[sharpener]

On 26/11/2024 at 16:25, JamesPa said:

I have one of Shelleys 16A relays to switch on and off the charger for my EV.  It looks and feels like quality and it works a treat.  Obviously the product you are looking at is a different one, but if my experience of Shelley is anything to go by I would give it a try.

 

Does it just have an integral web server which you can see via your wifi, or does the signal also go through the Shelley servers as well? Am trying to minimise my use of such things though of course have to use the Vaillant servers for their app. Have not had any big problems with this but many ppl report significant outages and incompatibilities.

How is yr install going @JamesPa?

[JamesPa]

20 hours ago, sharpener said:

Does it just have an integral web server which you can see via your wifi,

Exactly that.  Also works a dream with HA.

 

20 hours ago, sharpener said:

How is yr install going @JamesPa?

So far so good.  Dhw done and system is working on the immersion, no heating today, switch over early tomorrow.  Literally a one man 'team' on the install.  Only 3 rads to touch which helps of course (I did the majority myself a year ago) and electric feed to breaker was also pre-installed.

 

Someone close by has theirs done last week by a different company, they were without heating for 4 days However they had a lot more rads changed, the installation looks good so I think they are happy.  Interestingly this one had 'designed-in' under sizing with backup heater to make up the difference.

Edited November 28 by JamesPa

[Beelbeebub]

17 hours ago, JamesPa said:

Someone close by has theirs done last week by a different company, they were without heating for 4 days However they had a lot more rads changed, the installation looks good so I think they are happy.  Interestingly this one had 'designed-in' under sizing with backup heater to make up the difference.

In one sense that's a hybrid system, just with a slightly larger HP and a smaller (and cheaper to install) secondary heat source.

[JamesPa]

2 hours ago, Beelbeebub said:

In one sense that's a hybrid system, just with a slightly larger HP and a smaller (and cheaper to install) secondary heat source.

Yes it is indeed, but of course the secondary heat source is guaranteed to be more expensive to run than the heat pump, so there is no incentive to use it unless absolutely necessary, and the control is fully integrated to guarantee that.  Perhaps this is the only form of hybrid that should receive any public subsidy.

 

On second thoughts, silly me, it doesn't satisfy what I suspect is the industry objective for hybrids, namely to perpetuate the use of fossil fuels.  Or am I being cynical?

Edited November 29 by JamesPa

[Beelbeebub]

14 minutes ago, JamesPa said:

Yes it is indeed, but of course the secondary heat source is guaranteed to be more expensive to run than the heat pump, so there is no incentive to use it unless absolutely necessary, and the control is fully integrated to guarantee that.  Perhaps this is the only form of hybrid that should receive any public subsidy.

 

On second thoughts, silly me, it doesn't satisfy the industry objective for hybrids, namely to perpetuate the use of fossil fuels.  Or am I being cynical?

You make a point and badly done "fig leaf" hybrid installs probably won't help much.

 

On the other hand, fear of spending more is a big issue for HPs.

 

A cheap bolt on unit that effectively guarantees not to cost more than gas, has minimal disruption to the existing install. (eg no new cylinder, no massive replumb) has some potential.

 

Clearly there will be some homes that cannot use a HP because the heat load is so large and/or the emitter are too small.

 

But most homes in the UK aren't in that situation.

 

Most people have upgraded the house with insulation, even if just loft insulation. Most people have double glazed windows. And crucially alot of radiators and pipe work was oversized for the 70C boiler flows.

 

I've been encouraging some of my tenants to experiment by turning the flow temps down over the cold snap.

 

One property, stone walled, steel framed window with some secondary glazing, semi with microbore pipes and P+ rads has been kept warm (OK as warm as before, 17C, the guy is trying to save money) with a 40C flow temp.  Which surprised me alot.

 

Another victorian ground floor corner flat with single glazed windows can hit 20C with 45C flows. That one has got some pretty big rads because it used to be famously cold so we chucked some massive k2 rads throughout.

 

My point is both those places could probably manage with HPs and be cheaper.

 

But they have combis (so hot water would cost a lot to fit and take up space) and I don't want to spend a bunch of money and the tenants complain it costs more to heat.

 

If I could fit a box on the outside and a control box on thi inside for a grand or so after grant I think I would try that 

 

[JohnMo]

18 minutes ago, JamesPa said:

and the control is fully integrated to guarantee that

So would just about every hydrid install. The boiler works be switched via the heat pump. Just about every heat pump has hybrid mode built in.

 

Having an immersion heating your CH system, based on current 2024 CO2 grid emissions, is no better or worse than a gas boiler. In fact if you include the real output of Drax and other green wash, you are possibly better generating heat locally via the boiler.

 

Hydrogen is coming anyway, there is so much wasted potential with wind, which could be utilised instead of turning the blades away from the wind, to keep bigger plant online, leave them powered and generate hydrogen.