Advice on adding a pump to please

Hi, I’m a long term user of emonpi and for electricity monitoring so I know how well thought through all the OEM kit is.

I’m going through an application with Octopus for installing an 11kW Daikin and I wanted to see a step-by-step guide of installing emonHP heat meter. Found it at

Are all the installations in using the level3 emonHP?

Partly that question arises because Octopus have point blank refused to install an emonHP heat meter inline when they are installing the flow and return pipes. I don’t get this because it would be a 5 min job at that stage rather than a complete drain-down and reset if done afterwards and who knows they may want to void the waranty too!

I’m also getting a bit frustrated at their refusal to engage with adapting the MCS Ventilation ACH defaults for my renovated CategoryA house which risks running into the frequent oversizing issues discussed here - especially noting the broad thrust of this topic Measuring air change rates with CO2 sensors for heat pump heat loss calculation

Thanks for your thoughts and advice.

I would buy the kit and get some good biscuits/pizza for the plumbers on the install team. A lot can be done with a please and some free pizza Vs what will be officially listed on the paperwork.

Regarding the oversizing have you run your house through to see what size they recommend (requires recent EPC), also if you have a blower door test completed then they will be able to use the figures for heat loss (as opposed to their or mcs’s guess).

I would highly recommend getting the heat loss checked before (had the 9kw and had to have it swapped to the 8kw) as oversizing is a pain to prove and easy to avoid.

If you have any questions feel free to ask.

I Also had an octopus install and they did swap the pump for free but be aware Daikin only have 2 sizes, small (8kw) and BIG (16kW) anything between 8-16 is a software derated 16 and anything smaller than 8 is a software derated 8.

The 11 as the 9 will have sub optimal modulation but to be able to take advantage of the 8kW your heat loss at -3 needs to be less than 7kW to allow for defrosting. The the heat geek guestimater or heatpunk may give you an idea of the size you actually need.


Thanks for the reply Zak.

My EPC is A after refurb of the 1980s house, my area is 170 sq metres, the survey shows my MCS fabric heat loss as 5kW and my MCS ventilation heat loss as 4.5kW and this latter figure doesn’t feel accurate at all. But how to demonstrate it to the installer’s satisfaction?

I’d really like a HP that can modulate way down to the 350Watts I see for an 8kW Daikin on and run continuously rather than the 11kW Daikins that seem to have a minimum draw of about 950Watts. 350Watts is much easier to find continuously from my PV or batteries on milder days compared with finding 950Watts intermittently.

How did you demonstrate your oversizing?

Thanks again, David.

The 8kW unit is the one to get if you have a choice. Hopefully with 5kW of fabric heat loss you can have a much smaller ventilation loss and get by with the smaller unit.

With regards to air changes, the way to confirm this beyond doubt and guess work is to get a blower door test (as above), This would confirm your air loss and Octopus should clearly accept this.

In my case the survey missed the 600mm of loft insulation so the heat loss went from 7.3kW to 5.3kW (clearly less than the 9kW and 4kW minimum output of the bigger unit).