Octopus heat pump

[Stinsy]

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?

Plastic microbore is worse than copper (inside diameter is even thinner). You’ll need a tank.

[Moxi]

Nowty Towers can be run in this arrangement with both DHW tank and heating in parallel. But the problem is the lower temp in the rads will bring down the temp in the hot water tank to a tepid temp and not workable for DHW.

So why is the government and the plumbing and heating industry saying "have a heat pump"? if a heat pump can only do one thing or the other ? Theres something missing in my knowledge here and its bugging me - but surely we are not being asked by HM government to buy two heat pumps one for DHW and another for CH. What is the KW rating for your DIY system Nowty ?

Moxi

A lot of combi-boilers can't do both at the same time anyway either... Surely the answer is to use zone valves to hot up the DHW as much as you want first, then close it off and run the CH instead?
It's how my gas system works. (When I went to work it got the water hot enough to shave before switching over to heating the house. It didn't cool the DHW because the coil in the tank can heat water above it, but not cool that water!)

That’s the system I was expecting to see being offered but I am starting to get an idea of the missing info I think. I’m guessing that what Nowty is alluding to and the bit I’ve not previously considered is that unlike our combi boiler the heat from the HP is already around twenty degrees cooler so by the time it’s got back to the HWC to reheat it’s got a larger delta t and therefore the HWC has to give up more of its heat which the HP can only replace at a rate presumably slower that the radiators are radiating ?

If this is the case then it’s much less of an issue than I thought as we primarily want DHW and on the occasion where we use the CH it’s not likely to coincide with DHW use. For people with a variable tariff it’s also an option to pop on the immersion ? I’m not looking for perfection in a system I need flexibility to make use of what I have so in my case it’s looking like a big HWC that’s got enough connections to fit energy input sources that I have now or buy later.

Moxi

[Andy]

So why is the government and the plumbing and heating industry saying "have a heat pump"? if a heat pump can only do one thing or the other ? Theres something missing in my knowledge here and its bugging me - but surely we are not being asked by HM government to buy two heat pumps one for DHW and another for CH. What is the KW rating for your DIY system Nowty ?

Moxi

They can do both just not at the same time. But whilst doing the DHW cylinder the radiators are either slowly losing temperature or if you have a buffer tank then that can still be pumping round the circuit also losing heat. Once the DHW temp is fulfilled then the heat pump ramps up a bit harder to recover the heat lost in the radiator circuit. Mine also will cycle 30 minutes about between heating and DHW (user configurable). In practise I don't really notice the slight temperature drop in the house unless it is super windy and cold. I also get round it a little by ramping the cylinder up during the day when we are out of the house. With a mixer the cylinder then goes further in the evening.

[chris_n]

A heat pump is most efficient at low temperatures, this is why it is important to have oversize radiators, pipework etc. When a heat pump is called on to heat domestic hot water it uses zone valves to divert the output to the tank heat exchanger. When this happens the efficiency reduces as the target temperature is higher. When the water has finished heating the zone valve(s) change position and the target temperature is lowered. This is exactly the same as a condensing gas system boiler which runs at a lower temperature when heating to allow the condensing to take place thus improving efficiency.
A heat pump is purely a heat source same as a boiler, how you use the output determines the efficiency.

[richbee]

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?

Dan, I signed up on Octopus site to be contacted when they get this far North. I expect that to be a couple of years and hopefully they'll be doing larger units by then?

It's good to see a company actively getting into and on with it.

I've just done the same on the Octopus website; Especially with the new £7.5k government assistance - has to be worth a look.
It says you need 2m x 1m x 1m space for the hot water tank - that sounds enormous!

[Stinsy]

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?

Dan, I signed up on Octopus site to be contacted when they get this far North. I expect that to be a couple of years and hopefully they'll be doing larger units by then?

It's good to see a company actively getting into and on with it.

I've just done the same on the Octopus website; Especially with the new £7.5k government assistance - has to be worth a look.
It says you need 2m x 1m x 1m space for the hot water tank - that sounds enormous!

I think to qualify for the grant the tank has to be a minimum of 300L.

[Joeboy]

Dan, I signed up on Octopus site to be contacted when they get this far North. I expect that to be a couple of years and hopefully they'll be doing larger units by then?

It's good to see a company actively getting into and on with it.

I've just done the same on the Octopus website; Especially with the new £7.5k government assistance - has to be worth a look.
It says you need 2m x 1m x 1m space for the hot water tank - that sounds enormous!

I think to qualify for the grant the tank has to be a minimum of 300L.

Straight away I'm switched off by that. Can shove their grant up their collective. I'll decide on my water tank, not some donkey far far away..

Maybe that's just me though.

[Stinsy]

I've just done the same on the Octopus website; Especially with the new £7.5k government assistance - has to be worth a look.
It says you need 2m x 1m x 1m space for the hot water tank - that sounds enormous!

I think to qualify for the grant the tank has to be a minimum of 300L.

Straight away I'm switched off by that. Can shove their grant up their collective. I'll decide on my water tank, not some donkey far far away..

Maybe that's just me though.

There is a whole load of needless complexity that a heat pump installation is required to have in order to qualify for the grant.

[Joeboy]

I think to qualify for the grant the tank has to be a minimum of 300L.

Straight away I'm switched off by that. Can shove their grant up their collective. I'll decide on my water tank, not some donkey far far away..

Maybe that's just me though.

There is a whole load of needless complexity that a heat pump installation is required to have in order to qualify for the grant.

This is visceral for me. I Don't like being told what to do and as for a part of a home system (aye, my home) being decided by someone else.... oh deary deary me.

[Stinsy]

Straight away I'm switched off by that. Can shove their grant up their collective. I'll decide on my water tank, not some donkey far far away..

Maybe that's just me though.

There is a whole load of needless complexity that a heat pump installation is required to have in order to qualify for the grant.

This is visceral for me. I Don't like being told what to do and as for a part of a home system (aye, my home) being decided by someone else.... oh deary deary me.

You can easily plumb in this:
https://www.theheatpumpwarehouse.co.uk/ ... troller=NO

or this:

https://www.ebay.co.uk/itm/276019808137

Yourself!