Octopus heat pump

[greentangerine]

Dont forget hot water from a heat pump is not very hot. You would not be mixing any cold with it for a shower and it probably wouldnt melt the fat when your washing the dishes. Thats why they want a big tank.

It can be as hot as your HP can output.

My DHW is set to 55 which is plenty hot enough I have a 200l tank and that's also sufficient most of the time. I don't use the Legionella cycle but if I did, it'd take it to 60 or above.

The CH flow is 35 or below most of the time.

[Mart]

Hmm. My rads in my flat are quite big - they're all dual rads in fact - but they seem to have plastic pipes which are thinner than the metal fittings - is that microbore?
And I have a combi boiler here now, no hot water tank, so is that not suitable either?

Is this 6kW of electrical consumption, or 6kW of heat output?

How does one know if you need pipes and radiators changed to accommodate the different flow rates and temperatures of a heat pump vs a gas combi boiler?

6kW is heat output.

If you have an old system with big rads plumbed in 15/22mm then youre fine. New-build since the 90s with teeny rads plumbed in microbore and you'll need to rip out everything!

Hiya Dan, some news on the high temp HP. Good for me, as I have microbore, but possibly bad news for you.

This is a comment from the MSE website:

An update: Had the survey today. Took about 4 hours. Did all kinds of measurements and calculations and said we were fine for a heat pump and our original web quote was valid. We now need to sort out a installation date, estimated about 4 months away.
Note we have 10mm microbore and Octopus are happy to install with that in place. They have done their own research and since May have been ok with microbore (but not plastic pipes). Radiators are being replaced. 10.5kW heat pump calculated, big water cylinder and even offered to include the iboost i have in the system in the price. So far so good.

[dan_b]

Thanks Mart.
So I have plastic microbore. And no hot water tank. Guess I'll be on gas for a while yet.

[Andy]

Andy

Many thanks for confirming that it can be done, that has reaffirmed my belief that it was practical. I wouldn’t be going for an MSC certified system because there’s too many charlatan’s increasing the work needed in order to increase the cost to the homeowner and HM government haven’t got a clue so won’t be monitoring the average installation cost to police against sharp practice. I would prefer to understand the process and then design ny specific system and if I can DIY then I will but if not at least I can tell my plumber what I want instead of having to accept what they have to sell or worse what they know how to install- there’s already been some examples of that with solar systems and batteries that we’re all familiar with.

Thanks to everyone contributing- this is a very helpful thread.

Moxi

One thing I missed on my specs when doing the calculations was that despite my heat pump being badged as 12kW output, it only does 6kW into the hot water. It is a NIBE integrated cylinder so I guess the coil might not be big enough for more. That means that less than -10ºC OAT we do start to notice when the hot water is being heated. Baths are banned at that point!

This is the layout in mine. A simple valve guides the output to the central heating or DHW depending on the mode of the pump. My friend has a heatpump with an external cylinder (off the shelf big coils). So there must be an output for a valve on most heat pumps.