Octopus Heat Pumps

[drgannet]

Not an Octopus install, but I had a Vaillant Arotherm plus installed a year ago. It achieved a SCOP of 2.7 (SPFh4 will be a bit lower). With an electricity to gas price ratio of about 3 now, this is about parity with a 90% efficiency gas boiler in terms of running cost. There are efficiency gains to be had with how you run it; I experimented with some things last winter and will try a few more this winter. The house is a mixture of build including 100 year-old solid wall, 1980 cavity and 2000 cavity, based in Oxfordshire. We run radiators (replaced at time of install) and were perfectly warm all last winter.

The priority order for retrofit for energy efficiency should be:
1. Repair.
2. Insulation.
3. Easy energy efficiency measures e.g. tank stat, house stat, rad stats, etc.
4. Harder energy efficiency measures i.e.Clean heat e.g. heat pumps.
5. Other stuff e.g. PV, Energy storage.

The problem is people start at the wrong end because the technology is more interesting; Repair and insulation is really boring but will make the most difference to energy use and heating costs if starting from an average UK home.

[Kim]

It was happy with my house.  The hot water cylinder is going to be an issue for many, if they don't have a suitable cupboard or space for one.  Most newish small houses and flats have had combi boilers for years.

I kept my cylinder and conventional boiler when all my neighbours were getting them ripped out and replaced with combis.  Who's laughing now 

I always thought the move away from storing water locally was a bad one.

[Mr Larrington]

I saw someone on Twitter with a thread on their Octopodal HP install, they seem very pleased. It should be a 1 stop shop now as they bought a heat pump manufacturer recently. The database got our home correct and reckoned £3.5k, though they're not installing in the heathen lands yet.

They couldn't find my HPC which they said they needed to quote but everything else was there.
Unsurpizing if they're only hooked into the systems of the Shire

Couldn’t find mine either, but then I'm far from certain that such a thing exists in relation to Larrington Towers.

[Cudzoziemiec]

It thinks that our early Victorian semi with 1970s annex was built between 1900 and 1930. Does it actually have a database or just a random date generator?

[De Sisti]

Plumber also said combi boilers had a far shorter lifespan. 

Different plumbers with differing amounts of experience will probably have different opinions
of combi boilers. All of the ones who have serviced my boiler have not had a bad word to say
about combis.

[Kim]

Mine seems deeply sceptical about our landlord-issue boiler's use of an aluminimum heat exchanger, rather than (presumably) stainless steel.  I suppose it's a trade-off between efficiency vs how it's likely to die of corrosion, which probably depends on the amount of Canterbury Carbonate in the water.

You can probably have similar opinions about hot water storage tanks, though the modern approach of having the body of water on the heating loop, with a heat exchanger to heat fresh water on demand is probably an improvement on the traditional approach of storing umpty litres of limescale.

[Feanor]

You can have both.
A combi providing on demand hot water for some outlets, but an indirect storge cylinder heated from the primary loop on a zone of its own.

The stored water allows for filling baths fast, and for high flow showers which the combi can't do.
It could also provides a heat dump which can be used to dump spare PV voles into.

[ian]

We had a solar hot water heat exchanger at our last place. Worked well in summer on bright days. The other 50 weeks of the year were a tad more variable. We might have saved enough on gas bills to break even on the annual service.

All these solar and heat pump threads are a clear illustration of why there is no mass adoption, I’m sure at this point it’s probably less complicated to build and maintain your own personal nuclear reactor.

[Kim]

We had a solar hot water heat exchanger at our last place. Worked well in summer on bright days. The other 50 weeks of the year were a tad more variable. We might have saved enough on gas bills to break even on the annual service.

I believe the economics on solar hot water were (unless you have a swimming pool, or something else that could make use of a lot of lukewarm water) "makes sense if you can DIY the install, and the panels aren't occupying space better used for photovoltaics".  Might be a bit better with the price of gas rising.

OTOH dumping excess electrons into a hot water tank, while inherently inefficient, does let you cheat the temperature gradient.  And the hardware cost is approximately zero (if you've got a hot water tank it's silly not to have an immersion heater in it for times of need, so it's really just a case of the control logic).

[Kim]

All these solar and heat pump threads are a clear illustration of why there is no mass adoption, I’m sure at this point it’s probably less complicated to build and maintain your own personal nuclear reactor.

It's new (in the sense that its decades old technology widely in use around the world) and not the way things are usually done here, which means you're not only having to do the maths, but you're fighting all the niche supplier problems and government subsidy problems, as well as the usual tradespeople problems.  Octopus are having a stab at reducing that inertia.

If the internet had been mainstream in the 60s and 70s I'm sure there would have been similar threads about that newfangled 'central heating' and the relative merits of complicated timers vs giving a convenient tweenager a thick ear for not filling the coal scuttle.

[FifeingEejit]

Eigg's had solar heating and photovoltaic since not long after the landlord was kicked out.

Also the heating was done by importing used flourescent lighting tubes so each panel costs about a quid to make.

Iirc there's 1 or 2 wind generators on their private grid, the only down side is the rationing but then that just reduces tumble drier use and increases imports of washing line and drying horses.

Sent from my IV2201 using Tapatalk

[Wowbagger]

We had a solar hot water heat exchanger at our last place. Worked well in summer on bright days. The other 50 weeks of the year were a tad more variable. We might have saved enough on gas bills to break even on the annual service.

I believe the economics on solar hot water were (unless you have a swimming pool, or something else that could make use of a lot of lukewarm water) "makes sense if you can DIY the install, and the panels aren't occupying space better used for photovoltaics".  Might be a bit better with the price of gas rising.

OTOH dumping excess electrons into a hot water tank, while inherently inefficient, does let you cheat the temperature gradient.  And the hardware cost is approximately zero (if you've got a hot water tank it's silly not to have an immersion heater in it for times of need, so it's really just a case of the control logic).

Our water tank has been heated by the sun for about 17 years. From February to October we have useful solar-heated water. The first winter we had it, I took part in the SEG 75 mile ride on a frosty, sunny early February day. I arrived home and had a warm shower (it was tolerable, but would have been better about 5°C higher) despite the fact that the air temperature hardly crept above freezing all day.

We also have an immersion heater in that tank, but we haven't turned that on for 6 months. Thi summer, teh tank has been ridiculously hot. The drawback is that we can no longer fill our washing machine from it. Washing up and the upstairs shower, and other hot water, are what it supplies. This summer, I've been mostly having very cool showers. We've taken to doing more hand washing up and using the dishwasher as an extension of the draining board.

I have absolutely no idea how economical it has been. When we paid for it, you could still get 6% on a high street building society instant access account. We also have to use a water softener because our water is very hard and the panel would be liable to fur up. That's not prohibitively expensive.

[Kim]

MIL's system did an excellent job of producing hot water, even in winter.  I doubt it ever paid for itself, given their failure to make good use of the hot water (they had an electric shower fed from cold, not the pre-heated supply, because plumbing is hard, and of course appliances became cold-feed over the life of the system). It was also a complicated east/west split system, with pressurised antifreeze rather than the now preferred drain-down approach.  It also used a bit of mains electricity (couple of ~30W circulating pumps and a controller).

Poor financial decisions run in the family, thobut.

[rogerzilla]

Not an Octopus install, but I had a Vaillant Arotherm plus installed a year ago. It achieved a SCOP of 2.7 (SPFh4 will be a bit lower). With an electricity to gas price ratio of about 3 now, this is about parity with a 90% efficiency gas boiler in terms of running cost. There are efficiency gains to be had with how you run it; I experimented with some things last winter and will try a few more this winter. The house is a mixture of build including 100 year-old solid wall, 1980 cavity and 2000 cavity, based in Oxfordshire. We run radiators (replaced at time of install) and were perfectly warm all last winter.

The priority order for retrofit for energy efficiency should be:
1. Repair.
2. Insulation.
3. Easy energy efficiency measures e.g. tank stat, house stat, rad stats, etc.
4. Harder energy efficiency measures i.e.Clean heat e.g. heat pumps.
5. Other stuff e.g. PV, Energy storage.

The problem is people start at the wrong end because the technology is more interesting; Repair and insulation is really boring but will make the most difference to energy use and heating costs if starting from an average UK home.

Who is your energy supplier?  I'm paying almost exactly 4x more per kWh for leccy than gas, which shifts the balance a lot.  And do you use any top-up heating or resistance heating for water?

[Wowbagger]

MIL's system did an excellent job of producing hot water, even in winter.  I doubt it ever paid for itself, given their failure to make good use of the hot water (they had an electric shower fed from cold, not the pre-heated supply, because plumbing is hard, and of course appliances became cold-feed over the life of the system). It was also a complicated east/west split system, with pressurised antifreeze rather than the now preferred drain-down approach.  It also used a bit of mains electricity (couple of ~30W circulating pumps and a controller).

Poor financial decisions run in the family, thobut.

We had a hot feed into our cold feed machine until a massive water leak meant an insurance-financed re-engineering of the extension's plumbing and we no longer had a hot fill. We had to make sure that we put the sheets etc in first in the summer, because the water temperature was often >60°C. It never bothered us that we rinsed in warm water, because in the peak 6 months of the year we had an almost inexhaustible supply. That was the annoying bit as of course the washing machine's heating element would make up any shortfall in temperature, so that the winter months would still produce something.

But I discovered months after the panel was fitted that from about the second week in November next door's chimney cast a shadow over the PV cell that powered the 12v pump from about 2pm, and given the SW facing nature of our panel, that deprived us of what would have been the most effective hour or so of the day.

[Cudzoziemiec]

Eigg's had solar heating and photovoltaic since not long after the landlord was kicked out.

Also the heating was done by importing used flourescent lighting tubes so each panel costs about a quid to make.

Iirc there's 1 or 2 wind generators on their private grid, the only down side is the rationing but then that just reduces tumble drier use and increases imports of washing line and drying horses.

Sent from my IV2201 using Tapatalk

Are the drying horses of Eigg similar to Shetland ponies?



IGMC

[ian]

All these solar and heat pump threads are a clear illustration of why there is no mass adoption, I’m sure at this point it’s probably less complicated to build and maintain your own personal nuclear reactor.

It's new (in the sense that its decades old technology widely in use around the world) and not the way things are usually done here, which means you're not only having to do the maths, but you're fighting all the niche supplier problems and government subsidy problems, as well as the usual tradespeople problems.  Octopus are having a stab at reducing that inertia.

If the internet had been mainstream in the 60s and 70s I'm sure there would have been similar threads about that newfangled 'central heating' and the relative merits of complicated timers vs giving a convenient tweenager a thick ear for not filling the coal scuttle.

I get the early adopter sentiment, but really at the moment, that's what it is, far from the mainstream. I have the resources to do such a project, but honestly, the time and inclination I lack. Our last place was a new build that came with the solar heat exchanger, so there was no pain (that said, it needed regular maintenance and cleaning and judging from the neighbours, we were fairly unique in keeping the panels clean and serviced).

If our ancient gas boiler blew up tomorrow, I'm pretty sure we'd just get a replacement.

[Wowbagger]

I've just been out to buy some more softener salt. Price today: £51.89. The last time I bought some was 9th September last year. £39.89. 30% price increase.

[drgannet]

Not an Octopus install, but I had a Vaillant Arotherm plus installed a year ago. It achieved a SCOP of 2.7 (SPFh4 will be a bit lower). With an electricity to gas price ratio of about 3 now, this is about parity with a 90% efficiency gas boiler in terms of running cost. There are efficiency gains to be had with how you run it; I experimented with some things last winter and will try a few more this winter. The house is a mixture of build including 100 year-old solid wall, 1980 cavity and 2000 cavity, based in Oxfordshire. We run radiators (replaced at time of install) and were perfectly warm all last winter.

The priority order for retrofit for energy efficiency should be:
1. Repair.
2. Insulation.
3. Easy energy efficiency measures e.g. tank stat, house stat, rad stats, etc.
4. Harder energy efficiency measures i.e.Clean heat e.g. heat pumps.
5. Other stuff e.g. PV, Energy storage.

The problem is people start at the wrong end because the technology is more interesting; Repair and insulation is really boring but will make the most difference to energy use and heating costs if starting from an average UK home.

Who is your energy supplier?  I'm paying almost exactly 4x more per kWh for leccy than gas, which shifts the balance a lot.  And do you use any top-up heating or resistance heating for water?

Octopus.

No, there was no need for any space heating top-up. The heat pump supplies plenty of heat, it is just a question of the efficiency; increasing the flow temperature can increase heat delivered, but the efficiency decreases. The SCOP I quoted was for space heating only.

I selected this heat pump because it uses R290 as the refrigerant (propane, which has a GWP of 3, although you hope never to lose it to atmosphere of course). This means the heat pump can supply water at a flow temperature of up to 75 C, so you can pasteurise without needing an imersion heater. Mind you, at a flow temperature of 75 the COP is only 1.2 (but still better than an imersion heater at 1.0). For hot water I installed a solar thermal system 12 years ago, and this has provided about 75% of annual hot water needs (family of 5 for most of that time, although we are down to 2 now). The heat pump does most of the hot water in deepest winter, but virtually nothing in spring, summer and autumn (it has done about 10 kWh of water heating since March).

[Joe.B]

Question for those who have already made the switch from gas to ASHP: Did you require in increase to the diameter of your central heating/hot water pipework?

We currently have an open vented system with a 120L HW tank and a Y-Plan system layout. 22mm copper from the boiler to the 3 way diverter, then 22mm copper to the upper and lower radiator manifolds which then reduce to either 8mm or 10mm copper.

Given that I am currently renovating the living room, hall & landing I have the perfect opportunity to replace some of this micro-bore with bigger diameter copper in preparation for a future conversion to ASHP.  For belt and braces future proofing I’m thinking of replacing the 22mm supply to the lower radiators with 28mm, reducing to 22mm after teeing off to the first 2 radiators. The final supply to each rad will be 15mm but I’ll keep the 15mm runs as short as possible.  That will provide improved flow to every lower radiator except the dining room, currently on 10mm copper. I’ve got no intention of upgrading that to 15mm as it will involve destroying the tiled floor I laid only 5 years ago.

I strongly suspect that when the time comes to have a ASHP installed the main run from the ASHP to the tank and 3 way will need upgrading to 28mm. That won’t be too much of a hassle.  As for the upstairs radiators, in the 10 years we’ve been in the house 3 of them have remained shut off and unrequired so I’ll probably just replace the pipe runs to the other 2.

[drgannet]

Question for those who have already made the switch from gas to ASHP: Did you require in increase to the diameter of your central heating/hot water pipework?

No. Stayed with existing 15mm throughout, after the initial 22mm from the buffer tank to 'manifold' (= 22/15/15 T!).

We had one rad (end of downstairs circuit) that was piped in 10mm copper from the previous rad, laid in concrete floor. The installer recommended upgrading to 15mm, which they did by dropping from the upper floor circuit.

[Kim]

I can't imagine that you'd ever regret replacing microbore with 15mm if a perfect opportunity to do so presents itself.  That stuff is a work of Stan.

[Joe.B]

I can't imagine that you'd ever regret replacing microbore with 15mm if a perfect opportunity to do so presents itself.  That stuff is a work of Stan.

Up to the point that I started to take a more serious interest in heat pumps I'd always been quite happy using 10mm. We have quite soft water so scaling has never been an issue.

[Joe.B]

Question for those who have already made the switch from gas to ASHP: Did you require in increase to the diameter of your central heating/hot water pipework?

No. Stayed with existing 15mm throughout, after the initial 22mm from the buffer tank to 'manifold' (= 22/15/15 T!).

We had one rad (end of downstairs circuit) that was piped in 10mm copper from the previous rad, laid in concrete floor. The installer recommended upgrading to 15mm, which they did by dropping from the upper floor circuit.

Interesting that you didn't need any 28mm runs.  Given the size of our house and the additional insulation I've been busy installing over the last couple of years I suspect that 22mm would suffice for us too.  However, I figure that if I fit 28mm rather than 22mm in a couple of years time when we move to a ASHP we'll avoid have to rip up the floors that I'm about to lay if the installer specifies 28mil.

I'm considering replacing our current tank with a Mixergy tank. When we eventually make the switch to a ASHP we should be able to avoid fitting a buffer tank as the Mixergy uses plate exchanger to interface with the heat pump.

[LittleWheelsandBig]

Is there an issue with reduced water velocity (= heat transfer) when using larger diameter pipework? Velocity is inversely proportional with cross-sectional area and all that.