Heat Pumps: anyone have one/thought about it?

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Has anyone had an install done by octopus? they are quoting 1.5k for this:

• Includes £7500 off from the Boiler Upgrade Scheme
• Including VAT and boiler upgrade scheme discount
• Any necessary plumbing and electrical work
• Labour and workmanship
• Daikin compatible water cylinder
• Any necessary new radiators and upgrades
• Daikin heat pump expertly configured for your home

Ask them what flow temperature the system is designed for?

They have probably designed it for 50/55 and you'll need to ask them to design for 45 degrees max.

Also, not every heat pump puts out their rated output at the correct design temperature (-2 to -3). That's an important bit of data to obtain on what it can put out at 21 internal, -3 external and what the SCOP is.

 

[rangor gubbins]

I think most of us consider MCS a simple racket
Priority of 1) themselves, 2) the installers (the hand that feeds them), 3) the consumer

Certainly I see some solar installers saying MCS is a bit of a joke.
My suspicion is Octopus think the same considering how they now moving to not requiring MCS certification.
Octopus now moving to being an installer themselves means the would be under direction of MCS and I suspect they see how little benefit that is for consumers and installers really.

I've no idea if it's a bit of a scam or not, but our heat pump installers were MCS, did a detailed heat loss calc, showing differences running costs at different flow temps and also compared to other fuel sources. The predicted energy usage from the heat loss calc was pretty much spot on.

 

[Megahackerd]

I just had a quote for the current Daikin unit for a 2 bed mid-terrace of ~£2600

However they are launching the Cosy 6 unit in December so I'm waiting for that as it's supposed to be a lot cheaper (and much higher temp capability) so you may be approaching zero cost which Octopus themselves state is a possibility with some installations.

you are right on that. i am not in a hurry but the price seemed low in comparision to other quotes

 

[dirtychinchilla]

I've no idea if it's a bit of a scam or not, but our heat pump installers were MCS, did a detailed heat loss calc, showing differences running costs at different flow temps and also compared to other fuel sources. The predicted energy usage from the heat loss calc was pretty much spot on.

That's pretty impressive

 

[b0rn2sk8]

Worth a watch for all those wondering why heat pumps are not more of a thing here. Some interesting nuggets of information about certain countries in Europe banning gas and oil boilers as far back as 2013 and not all of them were Norway, Sweden for Finland with their cheap hydro power. Lots more banned them this year from new builds.

 

[theone8181]

Worth a watch for all those wondering why heat pumps are not more of a thing here. Some interesting nuggets of information about certain countries in Europe banning gas and oil boilers as far back as 2013 and not all of them were Norway, Sweden for Finland with their cheap hydro power. Lots more banned them this year from new builds.

Was confused there as the g was covered so wondered what kind of video was called 'asbusters'. Was disappointed .

 

[b0rn2sk8]

Was confused there as the g was covered so wondered what kind of video was called 'asbusters'. Was disappointed .

Haha, that’s an unfortunate youtub embedding issue, particularly when you put a pretty face on the thumbnail.

That said, the presenter is one of the best additions to the fully charged team in recent years and her credentials are legit.

I’d also prioritise watching anything Helen Czerski presents on the channel, great host with even better credentials.

 

[PermaChanged]

So we've been running just over a week now with the heat pump and to date I'm happy with its performance.

It's running a compensation curve to determine flow temps. they fluctuate based on the external temperatures so are kept nice and low currently - will see how it does when we hit a genuine cold spell.

My only gripe/thing to get to terms with are the hot water settings. The cylinder is well insulated, and uses a heat exchanger rather than a typical coil for more efficient heating of the water within, however choosing a temperature temperature at which we store water, and the temperature drop allowed before the heat pump kicks in to re-warm it is where I'm struggling.

The cooler we store the hot water, the more efficient the heat pump will operate, but then the quicker it'll drop to our "recharge" temperature and in turn the more frequently it will cycle. We're currently set at 52c, with an 8 degree allowed drop meaning our water can be as low as 44c before reheating - given my partner washes in scolding water she can essentially be using stored water only rather than a mix.

Heating up the cylinder to 52c the heat pump does get noisy, so I'm considering dropping that to 48c with a 5c temperature drop / 43c min temp before recharge to hopefully gain efficiency and lower the noise at the expense of more cycling - however storing at lower temperatures will mean the rate of heat loss is slower too right? There is a separate legionnaires cycle which uses the immersion heater, to bring temps up high enough every 2 weeks to kill legionella.

 

[gazref]

Wouldn't it be sensible to do a big heat once a day(overnight when energy is cheap) and got enough so it's good for most of the day?

 

[dirtychinchilla]

Heating up the cylinder to 52c the heat pump does get noisy, so I'm considering dropping that to 48c with a 5c temperature drop / 43c min temp before recharge to hopefully gain efficiency and lower the noise at the expense of more cycling - however storing at lower temperatures will mean the rate of heat loss is slower too right? There is a separate legionnaires cycle which uses the immersion heater, to bring temps up high enough every 2 weeks to kill legionella.

Yes, rate of heat loss would be lower. But if you have a heat exchanger, unless I'm misunderstanding something, why do you need to deal with legionella? You have a plate between your primary and secondary sides, so no real stored hot water.

 

[b0rn2sk8]

Yes, rate of heat loss would be lower. But if you have a heat exchanger, unless I'm misunderstanding something, why do you need to deal with legionella? You have a plate between your primary and secondary sides, so no real stored hot water.

The plate heat exchanger heats the tank of hot water which is directly connected to the taps.

The other way round would mean the tank is a heat store and not a hot water tank.

 

[dirtychinchilla]

I'd be curious if that was recommended or selected. Thermal storage could eliminate stored hot water and give instantaneous hot water, which would eliminate the need for the purge, meaning the whole system could run at a lower temperature in the long term.

 

[robj20]

What's the average flow temp for heatpumps.
For comparison my gas boiler was happy sat at 25c flow this morning to maintain 18.5c in the house.

 

[b0rn2sk8]

They will flow as low as they can go to maintain the temperature. They fuel source is almost irrelevant on that point if you are using weather compensation.

Clearly if the unit can’t modulate it’s output low enough for the heat loss of the property then it will cycle.

 

[jpaul]

yes - can you see/hear if boiler was modulating, or, cycling

so should we infer it is a modulated output down at 20C , say, outside of evening slot ... will the boiler report modulation level ?

I'm thinking of some of the opentherm plots I'd mentioned earlier via

eg.

Spoiler: plot

 

[rangor gubbins]

So we've been running just over a week now with the heat pump and to date I'm happy with its performance.

It's running a compensation curve to determine flow temps. they fluctuate based on the external temperatures so are kept nice and low currently - will see how it does when we hit a genuine cold spell.

My only gripe/thing to get to terms with are the hot water settings. The cylinder is well insulated, and uses a heat exchanger rather than a typical coil for more efficient heating of the water within, however choosing a temperature temperature at which we store water, and the temperature drop allowed before the heat pump kicks in to re-warm it is where I'm struggling.

The cooler we store the hot water, the more efficient the heat pump will operate, but then the quicker it'll drop to our "recharge" temperature and in turn the more frequently it will cycle. We're currently set at 52c, with an 8 degree allowed drop meaning our water can be as low as 44c before reheating - given my partner washes in scolding water she can essentially be using stored water only rather than a mix.

Heating up the cylinder to 52c the heat pump does get noisy, so I'm considering dropping that to 48c with a 5c temperature drop / 43c min temp before recharge to hopefully gain efficiency and lower the noise at the expense of more cycling - however storing at lower temperatures will mean the rate of heat loss is slower too right? There is a separate legionnaires cycle which uses the immersion heater, to bring temps up high enough every 2 weeks to kill legionella.

What size is your hot water tank? Ours is 250 l and I wish we'd opted for even larger.
My missus also loves scolding hot showers.
When we first had the system installed in 2018\19 we used to sometimes run out of hot water because we'd be showering in the morning at the same time the system was also trying to heat up the house. This resulted in too much demand at the same time on the heat pump, too many defrost cycles and high electricity usage.
So now the heating comes on earlier (5am), and we changed the time ratio between heating and water to favour hot water (IIRC, 45 minutes hot water and 15 minutes for heating).
Our hot water is heated to 50 and the low threshold is 46. However, you've reminded me to check it and I may drop it a degree or two.
We turned our legionnaires cycle to every 4 weeks, and then when we got a solar diverter into the hot water tank I turned the legionnaires cycle off completely as the tank regularly rises to 60 degrees anyway

 

[PermaChanged]

We've got a 300l cylinder, we had originally asked for a 210l but I'm super thankful that, by luck rather than judgement, we ended up with the larger one.

I've dropped storage temps to 50c with a 7c drop pre recharge - will see how we get on with that.

The water is allowed to cycle 24/7, with individual room thermostats dictating heating - set back temps of 18c and living temps of 21.5c at the moment, I think current flow temps are around 30c based on the weather compensation.

 

[rangor gubbins]

We've got a 300l cylinder, we had originally asked for a 210l but I'm super thankful that, by luck rather than judgement, we ended up with the larger one.

I've dropped storage temps to 50c with a 7c drop pre recharge - will see how we get on with that.

The water is allowed to cycle 24/7, with individual room thermostats dictating heating - set back temps of 18c and living temps of 21.5c at the moment, I think current flow temps are around 30c based on the weather compensation.

Sounds good to me. We have similar except our bedrooms are set to 17-18 degrees and bathroom, kitchen, sitting room to 22-23 (my wife likes it cosy warm).

 

[rangor gubbins]

We've got a 300l cylinder, we had originally asked for a 210l but I'm super thankful that, by luck rather than judgement, we ended up with the larger one.

I've dropped storage temps to 50c with a 7c drop pre recharge - will see how we get on with that.

The water is allowed to cycle 24/7, with individual room thermostats dictating heating - set back temps of 18c and living temps of 21.5c at the moment, I think current flow temps are around 30c based on the weather compensation.

Wish we'd put in a 300 l tank. The installers suggested a 200, we opted for 250.

 

[PAz]

From Octopus:

Daiken 950kw heatpump
250l cylinder
7 rads upstairs including pipework

£14,880
after the BUS payment £7380

Install target is April/May.

I am replacing an oil driven warm air system hence the pipework. Downstairs is UFH (which I've prepped already).

What I find frustrating with Octopus is they won't give me any indication of where pipes will run / where rads will go etc but want me to sign up ASAP. Local installers are coming in around £15k before BUS so pricing is similar and I get to work with them on the design. Plus install lead time is around 10 weeks.