My heat pump is too big, what should I do?

marko · 2024-01-28T10:53:14.462Z

Rob-G:

I did explain to Octopus that the boiler I had installed had weather compensation and had been running for 12 months between 27.5 - 42.4’ish depending on weather and that produced comfortable temps throughout the house

Iny my experience the junior monkeys don’t know why that is relevant and the middle management monkeys are too arrogant to take more of anything other than what they’re telling the junior monkeys to do.

All cookies to be the same size made using the same cookie cutter etc.

Top brass actually understand heat losses and heat pumps but they’ll only be involved very rarely / after you’ve escalated through the problematic middle management layer.

KnightPhoenix · 2024-01-28T23:34:11.187Z

If you have a full heat loss survey from a independent installer / heat geek you can question it with Octopus.

They are reluctant to take an end users word for it as soon many people complain without looking into it fully or after they have a 24°c lounge and wonder why it is costing a fortune to run.

If you are concerned you can ask them to check the heat loss survey and they can re run the figures but personally going with a heat geek heat loss survey (that will cost but be very accurate) and a solution to the problem (what size pump / radiators you need is far better and more efficient.

If you have not yet had the install you can look for a heat geek install if you have one local, it will cost more but they design for lower floor temperatures so it will be cheaper to run. Alternatively get octopus to do the cheaper install and budget to have work done before hand (upgrade all radiators and pipework yourself or via a plumber) or have a heat geek come and review after then ask octopus to correct issues.

Much easier to spend a few quid up front and get it installed right first time though.

Had the 9 and have changed to the 8 and had 5 radiators replaced again to soft out my install but they did do it all for free to fix it and hand made it right.

Gary · 2024-01-29T11:45:28.225Z

Thanks. I will probably get a second quote through the Heat Geek website.
Interestingly their on line quote assumes a heat loss of 5.3kW which is much closer to my gas energy usage. They suggest a Vaillant aroTHERM plus 5kW would be adequate.

I do find it odd that they want to charge £1771 to guarantee the installed performance though.
Without this, and if I can keep my existing cylinder, they would be a very similar price to Octopus.

My main concern with Octopus is if they over size the heat pump. Radiators would be an easy fix compared with having to change out the heat pump and all the stress that would entail.

KnightPhoenix · 2024-01-29T12:19:04.346Z

The Guarantee charge is there as if your original installer makes a mess and the system does not perform as expected (and they cannot correct it) Heat Geek will pay one of their other installers to visit you and correct any issues with the installation. If you want that level of assurance it will be a good install then it is probably worth while.

Depending on the Cylinder you have Octopus may allow it to stay but again they want to do things by the book, so if it is a bit small, vented or any way out of scope they may want you to have the recommended size.

Regarding swapping the heat pump, you have it backwards. For the Daikin at least swapping from the 09-16 to the 04-08 was about 4 hours work all outside the house (except config on the MMI). The replacement for out oversized EDLA09DA3V3 showed up at 13:30 and the new EDLA08E2V3 was installed and running by 17:00, configuration took about 20 mins as I have all the PV Diversion to re enable. They just un-wired and disconnected the plumbing on the outdoor unit then re installed the new unit. The main controllers indoors and all the plumbing and wiring inside stayed the same.

With the radiator swaps as some need to go smaller I am expecting to have to do a bit of filling and fixing but that is not exactly difficult but more work than I had to do for the pump swap.

markocoheat · 2024-01-29T12:38:43.097Z

There is also the option to contract directly with a heat geek installer.

Buy form “Heat Geek” including the £1800 “insurance policy” against anything going wrong and Heat Geek needing to pay for the work to rectify.
Decide that if the installer is a “Heat Geek” anyway then you’re happy to rely purely on the installer with no separate “insurance policy” to rectify. They’ll then be a similar price to Octopus by the sounds of it.

You may find the installers less inclined to go with (2) because I think they won’t be able to buy the equipment on credit in quite the same wasy as they get to do with (1).

The “5kW” Vaillant is more like a 6 kW unit when operated with flow temperaures below 55C at design condition. Similarly the “7kW” becomes almost 9 kW.

No point buying the “3.5 kW” unit. That’s just a 5 kW with a software limit and has the same minimum output as the 5 kW unit.

matt-drummer · 2024-02-20T19:02:19.550Z

My heat pump was replaced today.

I want to say a big thank you to Octopus Energy Services.

The guys that came today were fantastic, no fuss, no judgement, just did their job and did it very well.

The heat pump was swapped in only a few hours with no fuss whatsoever.

The new heat pump is working really well and I couldn’t be happier.

I can make all sorts of arguments about they should have got it right in the first place but I really have no complaints, they put it right and that is all that matters.

Again, thanks to OEM too, I would never have known or be able to show what was going on without their fantastic monitoring system.

I am glad I got there in the end.

ajdunlop · 2024-02-21T10:59:31.736Z

@matt-drummer it will be interesting to compare the unit’s performance and behaviour. It isn’t often that multiple heat pumps can be compared against the exact same heating system.

HydroSam · 2024-02-21T15:03:13.413Z

Second that. Really good outcome. It’ll be good to see the difference on your and @KnightPhoenix systems after a couple of months (if winter sticks around)

I might go the same route (just not in a position to go back to the previous installer unfortunately). Can I replace a monobloc myself I wonder?

matt-drummer · 2024-02-21T19:38:51.147Z

The difference the correct heat pump makes!

It’s performing pretty well on it’s first day here. A bit of a hiccup in the middle of the day but otherwise really good.

image1144×1109 140 KB

scanfer · 2024-02-21T21:21:56.636Z

Great news. One less 9kW beast in the competition too!

matt-drummer · 2024-02-21T21:33:45.211Z

HydroSam:

Second that. Really good outcome. It’ll be good to see the difference on your and @KnightPhoenix systems after a couple of months (if winter sticks around)

I might go the same route (just not in a position to go back to the previous installer unfortunately). Can I replace a monobloc myself I wonder?

Daikin for Daikin was an easy swap.

Do you have the MMI Sam?

The plumbing is really easy, the flow and return on the 8kW are laid out slightly differently from the 9kW but if you have flexi pipes then its no trouble if you can solder and if not compression fittings.

The electrics on mine were easy. it was only the removal of the BUH supply and a minor change to a breaker for the booster (immersion)

If you can understand the wiring diagram or have a friendly electrician then I see no issues.

The only other thing is ensuring the new heat pump is installed level.

It’s four or five hours with a bit of chatting included.

That is the good thing with heat pumps, the initial installation is painful but changing one is easier than a gas boiler. I think it is a competent DIYers dream.

HydroSam · 2024-02-22T13:58:28.364Z

Hi Matt

No MMI here, I’m on the generation before that, but I wouldn’t have any hesitation wiring one up, I had to lend tools to the sparky who did mine .

The problem is I can’t access the grant as far as I know, so it’s £3500+ I think for the unit. At an estimated saving of £100-£150 a year through better SCOP (I have solar+battery so only pay 10-15p per unit on average through the winter) it doesn’t stack up. What I need is a clause in the grant that says if your heat pump is ‘faulty’ you can access the grant.

jtrent · 2024-03-04T08:36:36.482Z

Havent been on the forum for a while - glad to hear you ended up sorting it

matt-drummer · 2024-03-04T08:50:27.775Z

Thank you Jordan.

Geert_Bellens · 2024-03-05T09:59:59.825Z

To return to the unclear information from Daikin regarding the minimum consumption of 950 Watt.
I now see in their documentation that they present the COP positively at part load, but at 12°C they do increase the output spectacularly to 5.3 kW to have a decent COP.

EDLA09_COP partload Daikin941×311 45.4 KB

Not realistic at all.
At T_outdoor 12°C you should have ± 3kW heat output which gives a COP between 3.1 and 2.9 depending on the pump.

TrystanLea · 2024-03-05T20:37:49.185Z

Congrats @matt-drummer you must be really happy with the performance of the new unit! this is looking great! your running at a much lower flow temp and more consistently and a substantial improvement in COP by the looks of it!

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matt-drummer · 2024-03-05T20:47:07.089Z

Thanks Trystan,

It is going quite well, really good when it is cold with minimal defrosting.

I am struggling a bit when it is warmer to find settings that work. Daikin’s initial phase of the heating cycle is quite aggressive in terms of flow rate, I can restrict it like I did with the 9kW but that causes other problems.

I just get more heat than the radiators can handle at really low flow temperatures.

But all in all, a huge improvement, it uses half the electricity and I don’t have to open doors and windows.

TrystanLea · 2024-03-05T20:58:30.951Z

Really impressive difference! really interesting to see such a night and day change, your low temp rads are really coming into their own as well, well done

matt-drummer · 2024-03-05T21:04:34.523Z

I did say all along that I had the wrong heat pump.

There isn’t really any denying it.

I hope the people I upset at Octopus notice, at least Octopus and Daikin are starting to get some better performance and aren’t languishing at the bottom of the COP table.

It doesn’t really matter but I am happy that they can be made to work relatively well.

TrystanLea · 2024-03-05T21:13:02.222Z

It’s interesting comparing the weeks before the switch to the last few weeks:

Before COP 4.09, Outside temp 8.7C, Flow temp when running 34.7C, Room temp: 21.8C (very patchy).

image1015×884 201 KB

After COP 4.73, Outside temp: 6.2C, Flow temp when running: 29.C, Room temp: 20.2C

image1017×893 196 KB

Carnot efficiency appears to be generally higher with this unit, periods of ~55% of carnot vs 50%, very nice!