Fitting my heat pump DIY

[Beelbeebub]

6 minutes ago, SteamyTea said:

Only if sized and used incorrectly.

Mine, from 1987, are fine.

If my house had twice the heat load, I could just charge them up to a higher temperature and for a bit longer.

 

Like a heat pump system, they are not used like gas or oil fired central heating.

 

If people can't get them to work, then they need to read up on them and stop blaming the technology.

The big issue is the units leak heat. The control is a bimetallic strip and a little metal flap. Even when closed shut a significant amount of heat leaks out.  Most of the occupants are out during the day, so the heat is not useful (though from a maintenance perspective it does help keep the properties drier) and when they come home at night and actually want heat there isn't enough left.  If they wind up the store temp it helps, but then they get even more wasted heat during the day.

 

We fitted some newer units, which are better insulated and use a fan to move the heat so leak less. 

 

The big issue with those units was the inflexibility. It was very difficult for the users to control them requiring diving into multiple setting menus rather than a simple "warmer/colder" setting.

[Beelbeebub]

At a higher level the issue is that E7 only makes sense from a cost perspective and it is all based on the idea of cheap rate night electricity.

 

Night rate electricity is only cheap because there is less demand for electricity at night.

 

If everyone switched to E7, demand would go up and it would no longer be cheaper*

 

From a carbon perspective, whilst electricity is now lower carbon (on average) than gas, storage heaters only have a COP of 1.

 

This means a nation using storage heaters will produce more carbon, and require more generating capacity, than a nation using heat pumps.

 

They aren't even that cheap, a typical unit will cost £600-£1,000 before fitting (and they are pigs to fit given the weight).  A 3 bed house might need at least 5. So you are looking at a minimum of £3k just for the most basic storage heaters.  Go for the better and bigger ones and you're at £5k. And all that assumes you don't need a rewire.

 

If you already have storage heaters, then sticking with them may be rational for now.  But as a technology for replacing other methods of heating, they are a dead end. 

 

*and with the uptake of electric cars and tariffs for charging them at night the demand for "off peak "electricity is growing.  E7 tariffs won't last forever.

Edited November 7, 2023 by Beelbeebub

[ProDave]

I do wonder if a storage heater might actually make more sense in a modern low energy house with good insulation and air tightness.

 

My own house heats up slowly and cools down slowly.  So an injection of heat overnight and it won't have cooled down much by the evening.  Some I believe do that charging a heavy insulated slab overnight.

 

But a heat pump is still way better.

 

I used to have storage heaters in my old 1930's semi.  Absolutely hopeless.  The house leaked heat so quickly that it really was of the type that needed constant heat input when you wanted it to be warm, and it barely had any left in the storage heater by the evening.  I did find an LPG gas fire was good for topping up the heat in the evening.

 

And I have lost count how many people I have had to explain how they worked. I turn up to a reported fault of "heaters not working" and when I get there, I see they are turned off at the wall.  "Oh i turned them on waited a couple of hours and they were still cold, so I turned them off again"  Bangs head against wall.

[Beelbeebub]

19 minutes ago, ProDave said:

And I have lost count how many people I have had to explain how they worked. I turn up to a reported fault of "heaters not working" and when I get there, I see they are turned off at the wall.  "Oh i turned them on waited a couple of hours and they were still cold, so I turned them off again"  Bangs head against wall.

^^^^ this, so much! 😁

[SteamyTea]

54 minutes ago, Beelbeebub said:

The big issue is the units leak heat.

They are designed to, that is how they work.

It is a bit like saying that UFH in a concrete slab 'leaks heat' when people are not there.

It is not very efficient to constantly raise and lower the building temperature during the day.

 

37 minutes ago, Beelbeebub said:

 

Night rate electricity is only cheap because there is less demand for electricity at night.

 

If everyone switched to E7, demand would go up and it would no longer be cheaper*

 

*and with the uptake of electric cars and tariffs for charging them at night the demand for "off peak "electricity is growing.  E7 tariffs won't last forever.

Industry and commerce still use a lot of power during the day, you can see the difference on the weekends/holiday weeks.

What will make a difference is our nuclear fleet shutting down, they are designed to run, basically unmodulated, 24/7.  This is where storage is going to be needed.

Nuclear is currently churning out about 4.25 GW, so multiply by 7, ~30 GWh needs to be replaced to cover its contribution for night storage.

This does not have to be stored chemically, it can be stored thermally, which is what happens now.

The price differential is another issue and has nothing to do with the technical ability to store and deliver energy.

It is of course, better to use heat pumps.

I had my smart meter repaired today (was the communication hub not working, shall see how long it lasts this time), the man who fixed it said he had a Daikin ASHP, but then said he had hot water on demand, as in instantaneous heating.  Seems odd, but he did not seem to know much about the workings of a heat pump and said the old line that 'they only work in well insulated houses', then commented that it would not work in my house as my windows were wooden.

34 minutes ago, ProDave said:

I used to have storage heaters in my old 1930's semi.  Absolutely hopeless.  The house leaked heat so quickly that it really was of the type that needed constant heat input when you wanted it to be warm, and it barely had any left in the storage heater by the evening. 

Bet I could have got them working, may have needed an increase in capacity.

35 minutes ago, ProDave said:

Bangs head against wall.

Exactly.  My old lodger, who may have had a stroke and seemed a bit slow, was actually very clever, struggled to understand that the hot water only heated up at night (I never told her about the upper heater), so if she drained the hot water cylinder, there was none left for when I got home from work smelling of cooking fat.

I eventually got her to use less when I showed her my water bill of £2000 for the year and compared it to the previous year of £400.

 

If we, as a nation, do start to use ToU tariffs, there are going to be a lot of people with huge bills.

[Beelbeebub]

6 minutes ago, SteamyTea said:

They are designed to, that is how they work.

It is a bit like saying that UFH in a concrete slab 'leaks heat' when people are not there.

It is not very efficient to constantly raise and lower the building temperature during the day.

 

"That's not a bug, guv. That's a feature!" 😁

 

I don't buy that. 

Imagine being told that you can't shut your heatpump off even if you're plenty warm enough.

 

There is nothing engineered about the heat leak, it's just the poor seal. Some units leak more than others because the metal flap fits better on some units.

 

The newer units are designed to keep heat in better, with more insulation and a fan powered design that leaks less heat. If heat leaking was a deliberate feature what would they be going to great lengths to eliminate it?

 

you are absolutely right that we don't necessarily need to store excess electricity as electricity (or rather chemical potential). Thermal storage makes a good deal of sense.

 

but even then heatpumps are a better option as you still get to store more heat than you consume. Even at high temps like 65, the COP can be greater than 1.  The only time direct electric would be useful would be for really transient use, so if the time of use tariffs were minute by minute or even faster.

 

In that scenario the spin up time of a heat pump might be too long but flicking an immersion heater on for 60nsefonds to take advantage of a brief drop in price might be possible.

 

 

[TonyT]

6 hours ago, Beelbeebub said:

Simplicity is about the only thing storage heaters have going for them. Everything else about them sucks.

 

I look after a few properties with them and nobody likes them. Expensive to run, hot in the mornings, cold in the evenings and god help you and your back if you have to change one.

your meant to strip the bricks out to remove the heater.

 

how is 7.5p a kWh expensive?  It’s the same  price as my gas?

 

if people can’t figure out storage heaters, basic gas central heating systems they have no chance running a heat pump.

 

 

[SteamyTea]

1 hour ago, Beelbeebub said:

There is nothing engineered about the heat leak, it's just the poor seal.

Except there is a power difference between the flap being closed, partially open and fully open, as well as the power loss though the casing.

When the units are charging up at night, the output flap automatically closes.  If the unit is blasting out heat first thing, then it is faulty, get it fixed.

During the day, there are incidental heat gains most of the time.  If the output control, even on old heaters like mine, is set correctly, then it tracks the inside temperature nicely, i.e. as the room natural warms, the heater is loosing energy, but not in a linear fashion, it follows Newton's Law of Cooling.  This keeps everything in equilibrium.  There is, therefore, no need to adjust for the evening.

Now if you have a heat load of say 30 kWh/day, and your storage heater only has an effective capacity of 20 kWh, then you will have problems, but that is incorrect sizing, not useless technology.

 

If people cannot get storage heaters sized correctly, and learn how to operate them, there is little hope that heat pumps are going to be successful.  They are much harder to set up.

 

But as I have said, a heat pump is a better option, but there is going to be a steep learning curve, so steep that most people will fall off it unfortunately.

  

3 minutes ago, TonyT said:

if people can’t figure out storage heaters, basic gas central heating systems they have no chance running a heat pump.

Cross post, same sentiment.

Edited November 7, 2023 by SteamyTea

[Lofty718]

11 hours ago, sharpener said:

 

For anyone else looking this is the best I have been able to find, in a 700/2 controller manual online. VR71 pinout.pdf

 

Seems to have suffered a bit in translation, @Lofty718can you confirm that the demand inputs R6, R7, R8 are for external contacts that need to be closed for heat demand (as it would be for a conventional boiler)?

 

R7/8 9/10 and 11/12 are for electronic mixing valves/pump mixing groups

 

R6 is I beleive a switched live that can turn a pump on and off.

 

I have two pumps wired into the VR71 on my system R6 and I can't remember which other one so I'd assume R5

[ProDave]

10 hours ago, SteamyTea said:

If people cannot get storage heaters sized correctly, and learn how to operate them, there is little hope that heat pumps are going to be successful.  They are much harder to set up.

The only bit that needs knowledge is the initial setting up and comissioning, getting flow temperatures and flow rates right.  After that is all done you just leave it to get on with things, you never need to tinker with it.  Just like any other central heating.  In the heating season I never touch any controls and the house is always the correct temperature.

 

That is a far cry from storage heaters when you need to look at the weather forecast each evening and see that it is going to cool down tomorrow so you need to increase the input control to put more charge into the heaters tonight to be ready for that.

[Beelbeebub]

10 hours ago, TonyT said:

your meant to strip the bricks out to remove the heater.

Yeah, but you still have to hump 100kg or so of bricks up/down stairs (in my case up to 5 flights).

 

Plus, if you are unlucky enough to have one of the asbestos models, dismantling and disposing of them is a whole other level of bother.

10 hours ago, TonyT said:

how is 7.5p a kWh expensive?  It’s the same  price as my gas?

Dunno about your area, but here (midlands) I'm getting gas around 6.5pkwh and the tenants seem to be around 9pkwh for their off peak. 

 

10 hours ago, TonyT said:

 

if people can’t figure out storage heaters, basic gas central heating systems they have no chance running a heat pump.

A fair point and, in my experience, the average level of knowledge regarding heating is really poor regardless of the heating system.  With gas systems invert often get call outs "no heating" and it's because they are trying to hear outside the timer hearing periods.  In one case the old lady complained of her hearing nitncoming on, or coming on when she didn't want it. When I went to look at the thermostat I couldn't find it and she looked blankly when I asked where it was.  When I described it she thought for a minute, then rummaged around in the kitchen drawer by the oven. 

 

That said, people expect their hearing system to at least get warm when they want and the idea of storing it at night then using it later really seems to throw a lot of people.

[Beelbeebub]

10 hours ago, SteamyTea said:

When the units are charging up at night, the output flap automatically closes.  If the unit is blasting out heat first thing, then it is faulty, get it fixed.

Even with new control units fitted tenants still complain of poor marching between heat output and demand. 

 

You cannot argue that storage heating is a nicer heating system to use Vs gas boilers.

 

Only a lunatic would take out a gas boiler and replace with storage heaters. 

 

There are some limited situations where they might make sense but for the majority a well set up HP will provide a better end result.

 

And from a high level perspective of national policy heatpumps make the problem of generating all that extra electricity tonreplqce direct gas much easier than storage heaters would.

[ProDave]

I always feel it is a shame we are all so poor that we even have to consider storage heating as a way of getting it a bit cheaper than real time electric heating.

[sharpener]

18 hours ago, sharpener said:

Seems to have suffered a bit in translation, @Lofty718can you confirm that the demand inputs R6, R7, R8 are for external contacts that need to be closed for heat demand (as it would be for a conventional boiler)?

 

7 hours ago, Lofty718 said:

R7/8 9/10 and 11/12 are for electronic mixing valves/pump mixing groups

 

R6 is I beleive a switched live that can turn a pump on and off.

 

I have two pumps wired into the VR71 on my system R6 and I can't remember which other one so I'd assume R5

 

Sorry, my mistake, I meant the demand inputs S6, S7, S8, it's not entirely clear from the text if these are contacts and circuit closed for heat or the opposite.

[sharpener]

18 hours ago, sharpener said:

Seems to have suffered a bit in translation, @Lofty718can you confirm that the demand inputs R6, R7, R8 are for external contacts that need to be closed for heat demand (as it would be for a conventional boiler)?

 

7 hours ago, Lofty718 said:

R7/8 9/10 and 11/12 are for electronic mixing valves/pump mixing groups

 

R6 is I beleive a switched live that can turn a pump on and off.

 

I have two pumps wired into the VR71 on my system R6 and I can't remember which other one so I'd assume R5

 

Sorry, my mistake, I meant the demand inputs S6, S7, S8, it's not entirely clear from the text if these are contacts and circuit closed for heat or the opposite.

[sharpener]

18 hours ago, sharpener said:

Seems to have suffered a bit in translation, @Lofty718can you confirm that the demand inputs R6, R7, R8 are for external contacts that need to be closed for heat demand (as it would be for a conventional boiler)?

 

7 hours ago, Lofty718 said:

R7/8 9/10 and 11/12 are for electronic mixing valves/pump mixing groups

 

R6 is I beleive a switched live that can turn a pump on and off.

 

I have two pumps wired into the VR71 on my system R6 and I can't remember which other one so I'd assume R5

 

Sorry, my mistake, I meant the demand inputs S6, S7, S8, it's not entirely clear from the text if these are contacts and circuit closed for heat or the opposite.

[sharpener]

  

19 hours ago, sharpener said:

Seems to have suffered a bit in translation, @Lofty718can you confirm that the demand inputs R6, R7, R8 are for external contacts that need to be closed for heat demand (as it would be for a conventional boiler)?

 

7 hours ago, Lofty718 said:

R7/8 9/10 and 11/12 are for electronic mixing valves/pump mixing groups

 

R6 is I beleive a switched live that can turn a pump on and off.

 

I have two pumps wired into the VR71 on my system R6 and I can't remember which other one so I'd assume R5

 

Sorry, my mistake, I meant the demand inputs S6, S7, S8, can you confirm if these are contacts closed for heat or the opposite, it's not entirely clear from the wording

 

The text for S6 says "DEM1 External heating switch-off for heating circuit 1" and the footnote says "Closing the "DEM" contact ends the heating demand for the relevant heating circuit" which is the opposite way round for the usual (S-plan) boiler controls.

 

In my case S6 will be the radiator circuit, I will anyway have to add a relay to get a voltage-free contact, so that can be either way round.

 

S7 will be the UFH, the signal from the manifold location will be the OR function of all the four thermostat call contacts which at present calls the boiler so I would need to invert the sense of that with another relay.

 

S8 will be the call for the thermal store, that is an external timeswitch with changeover contacts so can be either at no penalty.

 

Edited November 8, 2023 by sharpener

[SteamyTea]

8 hours ago, Beelbeebub said:

 

Only a lunatic would take out a gas boiler and replace with storage heaters

Well yes, that would be silly, unless you are a landlord.

 

8 hours ago, Beelbeebub said:

You cannot argue that storage heating is a nicer heating system to use Vs gas boilers

Works well for me, and so far it has been maintenance free.

No difference in the 'feel' of the heat when I have it on.

8 hours ago, ProDave said:

I always feel it is a shame we are all so poor that we even have to consider storage heating as a way of getting it a bit cheaper than real time electric heating.

When the price war was on between the power companies, there was little in it.

But we found out what was happening and E7 is not a bad option for people off the gas grid, especially in smaller houses.

Down here there are thousands of places without natural gas (I am one), we also have a weak local electrical distribution in some areas, so has been a nicer engineering fit than the old, non inverter heat pumps.