Big Four - Solar, Battery, heat pump and EV

[BullDog]

LOL! I have just tried twice and the web page crashed both times!

Ah, I had that too on my first attempt. There is a box on the RHS of another box that I'd overlooked and failed to fill in. Crashes the page according to a message that displays.

Other boxes missed bring up a different message telling you.

Nope. Not working. It seems.

Don't worry, it's us not you

This is unusual - refreshing the page may help. If it doesn't, these things usually clear themselves up reasonably quickly, so perhaps grab a cuppa.

[SMarkus]

There's a lot of misinformation about heat pumps, some of it on this thread. High temperature heat pumps will not be as economical to run as those that operate at a lower temperature, but the point here is that heat pumps should be run differently from a boiler. They are at their most efficient when running at a lower temperature (ours will be around 40C but goes up on colder days to maybe 45C) for longer periods so that they replace heat loss and maintain a stable temperature.

It is a myth that heat pumps do not work with radiators - we have radiators everywhere in our house and the heat pump works very well with them - we've had it for almost 5 years now, so have had most sorts of weather. It is true that undefloor heating is ideal for heat pumps as that lends itself to the lower for longer model, but radiators will also perform as long as they are appropriately sized - our radiators didn't need to increase in size as they were already large enough to cope.

When someone says that the house would not be warm enough unless heated at 70C - this is where you're using a boiler to heat the house from a colder temperature to a warmer one quickly. That is not how a heat pump should be used - heat it gradually to the correct temperature and keep it there. I'm very pleased with our energy and heating systems - they work very well in a house which is not your highly insulated, modern model.

Steve.

[DrFfybes]

The other issue related to lower flow temperature is that on the Y plan system that we have, the domestic hot water doesn't really get hot enough unless the boiler flow temperature is above 65 Celsius.

Same here - the main reason for our 65C flow is so the HWC gets up to legionella killing temp. However if you were going fully electric as in this thread you'd make more use of the immersion heater. Just don't get one of these unless you want to spend hours with a magnifying glass, the instruction leaflet, a laptop to watch youtube vids, and a Jumbo Geordie Bucket of swear words whilst you try and programme it.
https://www.toolstation.com/greenbrook- ... mer/p21162

Paul

[BullDog]

The other issue related to lower flow temperature is that on the Y plan system that we have, the domestic hot water doesn't really get hot enough unless the boiler flow temperature is above 65 Celsius.

Same here - the main reason for our 65C flow is so the HWC gets up to legionella killing temp. However if you were going fully electric as in this thread you'd make more use of the immersion heater. Just don't get one of these unless you want to spend hours with a magnifying glass, the instruction leaflet, a laptop to watch youtube vids, and a Jumbo Geordie Bucket of swear words whilst you try and programme it.
https://www.toolstation.com/greenbrook- ... mer/p21162

Paul

Thanks. Funny thing there. I came close to buying a timer for the immersion heater to heat the water on the Octopus overnight tariff in preference to using the gas. Especially in summer when the heating is off. But monitoring the gas used to heat the water demonstrated it wasn't worth bothering with.

[scotview]

I'm very pleased with our energy and heating systems - they work very well in a house which is not your highly insulated, modern model.

Steve.

Thanks for posting those interesting replies Steve, it's great to get feedback from actual users, thanks. To complete the picture of your setup could you maybe give feedback on you system for operating in say January, viz:
1 Do you heat all 5 bedrooms.
2 What temperature do you consider personally to be comfortable, 19, 20, 21 everyone is different.
3 Do you operate a zoned heating system and if so is there any heating inertia, I note it is a traditional wet system.
4 How effective is your solar in January.
5 Do you think a car with V2H feeding your home battery would be complimentary to your winter heating.
6 Do you have a backup system installed for power cuts.

Sorry for all the questions but they would give a more complete "worst case" for a winter month, thanks.

[Mike4]

6 Do you have a backup system installed for power cuts.

That's a good question for those of us living in the sticks.

I get power cuts lasting anything from minutes to many hours randomly, but perhaps once a month on average. I have the feeling that the power supply failing while a heat pump is running might do it no good at all.

[funduffer]

So I started this thread, so I will make a few more points based on some of the comments:

1. Octopus base their online heat pump quotes on your home's EPC rating, prior to any proper survey. Ours was out of date (level E) and the first quote based on this was £6250 (incl govt grant). I had the EPC re-done to reflect the improvements we have made in the last 8 years. It is now level B, and the heat pump quote is now £2768. Obviously it may change a bit when they come and do a proper room by room heat loss survey.

2. Because the house is well insulated, we run our gas combi boiler at 55C flow temperature for the radiators. If we need to heat the house quickly if it is cold and we have been away, we use the air con unit in the living room until the gas heating catches up. At 55C, this gives me confidence I can run an ASHP system at a lowish flow temp with a reasonable COP. I have a couple of radiators to replace with bigger ones, but otherwise I am good to go.

3. Surely an ASHP with weather compensation will adjust the flow temperature to run efficiently based on the outdoor temperature? Thus, for most winter days (circa 5C-8C) in the UK, it will run efficiently, and only on the very coldest days will it need to run hotter, and less efficiently. I haven't selected an ASHP yet, but this is what I am expecting to find.

4. For hot water I currently run my combi boiler at 50C, which is absolutely fine. With the ASHP, I will need a new tank, and I understand I can still use 50C, but the pump will run occasional legionella cycles to prevent this bug appearing in the water.

FD

[DrFfybes]

So I started this thread, so I will make a few more points based on some of the comments:

4. For hot water I currently run my combi boiler at 50C, which is absolutely fine. With the ASHP, I will need a new tank, and I understand I can still use 50C, but the pump will run occasional legionella cycles to prevent this bug appearing in the water.

FD

This all looks very good for you. One point switching from the combi to a 'tank', whilst I'm sure you realise this it is effectively is a water store with a radiator in the bottom to heat it.

Your Hot Water Cylinder (HWC) will also come with an electric immersion heating element which can be adjusted to (say) 65C and can be operated on a timer. You might actually find this better than heating the water from the heat pump. Like Gilongo I compared using the gas boiler or the electric immersion for Hot Water and found the costs pretty much even when using half price electricity, however this was in summer so included the gas boiler getting the (insulated) pipework up to temp first. Running it with or immediately before/after the rads come on removes the 'warmup' cost.

Other considerations are - the tank will not quite get to the same temp as the boiler flow, perhaps 3-5C less depending on the duration, and as it warms up the rate of heating slows as it nears the temp in the heating coil. The heating coil from the boiler/ASHP is at the bottom of the cyl, so heats the whole thing. The immersion heater is often only reaches 3/4 the way down so perhaps heats 80% of the tank, although Mike will tell me this is no longer the case and the one we replaced was the wrong one for the tank .

With 'on demand' comi boiler water, you are always getting it as the set temp. But with a HWC then do a bit of washing up or have a shower and the hot water comes from the top of the HWC and cold is drawn into the bottom. Over time this will mix and cool the water in there so an evening shower can need an afternoon heat top up.

As always, trial, error (aka a tepid shower) and experience will get your most efficient setting

[9873210]

With 'on demand' comi boiler water, you are always getting it as the set temp. But with a HWC then do a bit of washing up or have a shower and the hot water comes from the top of the HWC and cold is drawn into the bottom. Over time this will mix and cool the water in there so an evening shower can need an afternoon heat top up.

As always, trial, error (aka a tepid shower) and experience will get your most efficient setting

Sometimes you need to look at and adjust or replace the shower mixing valve.

Ideally the mixer has thermostatic control and will use up to 100% hot water if needed to maintain the desired shower temperature and will mix in enough cold to prevent over temperature that could cause scalding. These can deal with variable supply temperature.

Older mixing valves do many different things. Often, they don't measure temperature but volume, and simply limit the ratio of hot to cold. These do not deal well with variable supply temperature. You need less hot if the supply is at 70C than 55C. Usually there is an adjustment behind the face plate.

N.B. Scalding can be an issue you need to consider before you tweak this, in many cases you need to consider scalding if you don't tweak this.

[SMarkus]

Thanks for posting those interesting replies Steve, it's great to get feedback from actual users, thanks. To complete the picture of your setup could you maybe give feedback on you system for operating in say January, viz:
1 Do you heat all 5 bedrooms.
2 What temperature do you consider personally to be comfortable, 19, 20, 21 everyone is different.
3 Do you operate a zoned heating system and if so is there any heating inertia, I note it is a traditional wet system.
4 How effective is your solar in January.
5 Do you think a car with V2H feeding your home battery would be complimentary to your winter heating.
6 Do you have a backup system installed for power cuts.

Sorry for all the questions but they would give a more complete "worst case" for a winter month, thanks.

1. No, very rarely, even when we have the kids at home (and they're not kids!). It is a zoned heating system - since we got the batteries, I've found it more efficient to simply heat the zones we want heated all the time, rather than timing them on and off as we used to. The pump is sized to heat the whole house though and to be honest is probably over-sized for what we use it for.
2. Comfortable temperature would be around 20-21C - I don't find the need to wear a jumper around the house, although obviously my wife does!
3. Solar is not effective in January. It starts to become more effective from early March and from mid-March on a good sunny day it is very helpful. From April, given sunshine, we could be grid-independent, if we don't need much heating.
4. I'm not sure about a car with V2H - it'll be interesting to see how that develops - the Tesla M3 has a 74kWh battery which would keep us going for over 2 days, but not sure I'd want to relinquish that much control.
6. (sorry, numbering went wrong somewhere) - no backup system for power cuts - we've got a wood burner - we live very close to a town centre and on the very rare occasions we have power cuts, they don't last long. It is possible to set the battery inverter up to provide a backup power supply though, if you wanted to.

[funduffer]

Thanks for posting those interesting replies Steve, it's great to get feedback from actual users, thanks. To complete the picture of your setup could you maybe give feedback on you system for operating in say January, viz:
1 Do you heat all 5 bedrooms.
2 What temperature do you consider personally to be comfortable, 19, 20, 21 everyone is different.
3 Do you operate a zoned heating system and if so is there any heating inertia, I note it is a traditional wet system.
4 How effective is your solar in January.
5 Do you think a car with V2H feeding your home battery would be complimentary to your winter heating.
6 Do you have a backup system installed for power cuts.

Sorry for all the questions but they would give a more complete "worst case" for a winter month, thanks.

1. No, very rarely, even when we have the kids at home (and they're not kids!). It is a zoned heating system - since we got the batteries, I've found it more efficient to simply heat the zones we want heated all the time, rather than timing them on and off as we used to. The pump is sized to heat the whole house though and to be honest is probably over-sized for what we use it for.
2. Comfortable temperature would be around 20-21C - I don't find the need to wear a jumper around the house, although obviously my wife does!
3. Solar is not effective in January. It starts to become more effective from early March and from mid-March on a good sunny day it is very helpful. From April, given sunshine, we could be grid-independent, if we don't need much heating.
4. I'm not sure about a car with V2H - it'll be interesting to see how that develops - the Tesla M3 has a 74kWh battery which would keep us going for over 2 days, but not sure I'd want to relinquish that much control.
6. (sorry, numbering went wrong somewhere) - no backup system for power cuts - we've got a wood burner - we live very close to a town centre and on the very rare occasions we have power cuts, they don't last long. It is possible to set the battery inverter up to provide a backup power supply though, if you wanted to.

Thanks for this really useful feedback.

I think a zoned system sounds really good. We have a couple of rooms we would not want to heat all the time.

On the backup power, a battery like a myenergi libbi has the facility to power a backup circuit in the home. My idea is to have it power a couple of plug sockets near the meter. If there is a power cut, power can be diverted to these and used to run a small (500W) electric heater, a light, the TV and maybe a microwave. With a 10kWh battery this would last a few hours and cover most power cuts, but obviously not after a huge storm as we have seen in some areas recently. I live in a city so maybe this is less likely anyway.

I agree with the comments on solar, but currently I receive 12p/kWh for my exported solar, and it would cost only 7.5p/kWh to charge the battery off-peak. So I would only use solar to charge the battery if these cost rates changed around!

My EV won't do V2H, and like you, if I did have it, I am not sure I would want to give up this much control!

FD

[scrumpyjack]

I have all of those now, but the Heat Pump is for the pool heating – still use our oil boiler for heating and hot water.

I had a major upgrade of our PV etc system in January. We had installed a 3.8kw PV system in 2011 so that still gets the highest rate of FIT.
We added another PV array (6kw), plus 20kWh battery storage and a backup system that automatically kicks in when the mains electricity fails. It has already kicked in 3 times and works very well. In addition there is an automatic switch so that surplus electricity is pushed into the hot water tank immersion heater. All the kit is Solaredge.

We are on the EON Next Drive tariff so the rate is 9.5p from midnight to 7am. The Solaredge system is programmed to top up the battery at the cheap rate in the winter months. (Current rate for that tariff is 8.5p but ours is fixed until Nov)

I have been surprised how much the PV system produces in the winter months.

I usually leave the EV set to charge at 2kWh so it picks up surplus power in the day.

The effect on our electricity bills has been dramatic. We use virtually no day time mains power and less and less night time as we get more sun.

Overall our FIT receipts will be a lot more than our mains electricity cost.

In the summer solar output should easily cover our swimming pool heat pump needs as well, so we will no longer use the oil boiler for that.

We also have a large wood burner (12kWh) and unlimited own firewood – that’s lovely in winter!

Bottom line, our new system was expensive (33k) but it works very well, provides protection against the frequent mains failures we get, and in the longer term is probably just about cost justified. Anyway it is quite a satisfying boy’s toy!

[scotview]

– still use our oil boiler for heating and hot water.

plus 20kWh battery storage and a backup system that automatically kicks in when the mains electricity fails. It has already kicked in 3 times and works very well.

Great feedback, thanks. Does your backup supply run your oil boiler electrics seamlessly in a power cut, thanks.

[scrumpyjack]

– still use our oil boiler for heating and hot water.

plus 20kWh battery storage and a backup system that automatically kicks in when the mains electricity fails. It has already kicked in 3 times and works very well.

Great feedback, thanks. Does your backup supply run your oil boiler electrics seamlessly in a power cut, thanks.

The backup unit kicks in within about a minute and then all the mains electrics in the house are running off the battery. So yes the boiler carries on.
You can set a reserve level so the system won't run down the batteries completely to ensure there's something left to cover a power cut.

[9873210]

I think a zoned system sounds really good. We have a couple of rooms we would not want to heat all the time.

Zoned systems sound good but are mostly a symptom of inadequate insulation. In a properly built house the R-value for the exterior walls will be about an order of magnitude higher than interior walls. It's hard to get much of a temperature difference between rooms unless they are leaking like a sieve.

[SMarkus]

Zoned systems sound good but are mostly a symptom of inadequate insulation. In a properly built house the R-value for the exterior walls will be about an order of magnitude higher than interior walls. It's hard to get much of a temperature difference between rooms unless they are leaking like a sieve.

I think it's the other way round - our internal walls are all brick i.e. properly built (I suppose you might have meant to 'modern standards' i.e. plasterboard) but that does mean that we keep most of the bedrooms and the attic at much lower temperatures than the rest of the house. Very little leakage through the walls - most of our heat loss is from ground floor up to the stairs and landing, but with doors closed that's minimal.

[csearle]

It's hard to get much of a temperature difference between rooms unless they are leaking like a sieve.

My rooms have huge temperature differences between them when I heat one rather than another. This is the case because they don't leak like a sieve but retain their heat.

Chris
PS Could it be that you were referring to a room's external walls whilst I am thinking of inter-room walls?

[9873210]

It's hard to get much of a temperature difference between rooms unless they are leaking like a sieve.

My rooms have huge temperature differences between them when I heat one rather than another. This is the case because they don't leak like a sieve but retain their heat.

Chris
PS Could it be that you were referring to a room's external walls whilst I am thinking of inter-room walls?

It's the PS. It's the exterior walls leaking like a sieve that enable a temperature difference between rooms.

If the outside walls were perfectly insulated, then after a while the entire interior would reach a uniform temperature (and you turn off the heater or you bake). In practice the outside walls can be pretty well insulated, an order of magnitude better than an interior wall is reasonable. Making reasonable assumptions about the geometry that means the temperature difference between rooms is an order of magnitude less than the temperature difference between the rooms you want to heat and the outside. So outside at 0C, rooms you want to heat at 20C, shut off rooms 18C.

If the outside walls are only as well insulated as interior walls you have outside at 9C, rooms you are heating at 20C and shut off rooms at 10C.

So why not insulate interior walls? It requires the walls to be thicker, with multiple layers and lots of detail work.* If you're starting from scratch (either a new build or a retrofit of an uninsulated building) it's far easier and cheaper to put double the insulation on the outside than to try to insulate every interior wall. It also makes the house much more livable; it's a win-win-win in almost all cases. If you shut down a large proportion of the house then perhaps zoned heating and insulating interior walls makes sense, but that's not how most houses are used. Few people want to be restricted to less than half the house or have to grab a parka to visit the loo.

* It's not just insulation, there's also air sealing and moisture control. A single leaf brick wall or 2x3 stud wall works fine for an interior wall with the same environment on both sides. You also have to consider things like interior doors, if you insulate interior walls you need to upgrade the doors and weather strip every door, possibly including closet doors if you go mad and don't want to heat the closet.

[88V8]

My rooms have huge temperature differences between them when I heat one rather than another. This is the case because they don't leak like a sieve but retain their heat.

If you shut down a large proportion of the house then perhaps zoned heating and insulating interior walls makes sense, but that's not how most houses are used. Few people want to be restricted to less than half the house or have to grab a parka to visit the loo....

But.... when designing a wet system if one wants different temps in different rooms, and one sizes the rads accordingly, it works, even without internal wall insulation. Provided of course that one keeps the doors shut.
Or at least, it did in our 1920 house with its brick internal walls and single room stat in the hall.

After all, one wouldn't heat the bedrooms or the hall to the same temp as the bathroom for example.
And given that the rate of external heat loss increases with internal temperature, it pays to heat each room according to need.

V8

[BullDog]

If you shut down a large proportion of the house then perhaps zoned heating and insulating interior walls makes sense, but that's not how most houses are used. Few people want to be restricted to less than half the house or have to grab a parka to visit the loo....

But.... when designing a wet system if one wants different temps in different rooms, and one sizes the rads accordingly, it works, even without internal wall insulation. Provided of course that one keeps the doors shut.
Or at least, it did in our 1920 house with its brick internal walls and single room stat in the hall.

After all, one wouldn't heat the bedrooms or the hall to the same temp as the bathroom for example.
And given that the rate of external heat loss increases with internal temperature, it pays to heat each room according to need.

V8

Quite. Then there's the fact our heating system doesn't get the rooms warm enough in cold weather if the water temperature is set much below 70 Celsius. Well, it is because the system was reasonably well designed in the first place. With the radiators sized asuming a 70 Celsius water temperature. I am guessing there's tons of houses like ours out there where a complete system reinstallation would be in order to run at a lower circulating temperature.