DuncanL

Not much has been provided by way of detail on the controls front for the new system. A Madoka (Daikin control panel) is about all that's been specified. At the moment, the conservatory has a digital programmable stat, which can trigger the boiler and open the conservatory-specific UFH diverter valve, as well as activating the pump for this circuit.

Thanks all, good thoughts on possibly using the existing 22mm pipes for water heating, and also easier than I'd envisaged to temporarily disconnect, and then reconnect (after heat pump install) the conservatory underfloor heating. If possible, the easiest option for me would of course be for it all to be sorted as part of the install, which it seems would require the MCS heat loss calculations to be sensible where the conservatory is concerned (i.e. not insisting that the heat pump be sized to fully heat an unused conservatory in the depths of winter)!

What's included: Cosy 10 heat pump Daikin 300 litre hot water cylinder Volumiser One new radiator (basic k2 600*700 unit replacing a marginally smaller radiator) Controls Plumbing and electrical components, as required Labour The install appears quite simple to me - the heat pump will be located on the outside of the house wall where the gas boiler currently is, which is about 1.5 m away from the electric meter. The pipes between the gas boiler and the cylinder (in the upstairs airing cupboard) are 22mm, so I understand need replacing with 28mm - I think this would probably be the most awkward bit. Cost-wise, I was assuming the something along the lines of the following: Heat pump: £4.5k Cylinder: £2k Controls: £1k Volumiser: £500 Pipes, valves, lagging, anti-freeze, filters, etc: £500 Labour: 10 days total at £350 per day: £3500 TOTAL: £12k (so not a million miles away from the £12.8k Octopus has worked out) Any other quotes, indicated prices, etc that I've seen have been much, much higher than Octopus, but maybe I should look harder?

@Beelbeebub I like your thinking! It might be slightly more complex, in that the conservatory is a separate zone with programmable thermostat and control valve... I definitely need to retain the ability to NOT heat the conservatory whilst the rest of the house is heated (i.e. through winter). Could be a last resort if we can't come up with an official approach that satisfies MCS requirements.

Good point, I wasn't clear on price! It's £5.3k for me to pay, so total "cost" is £12.8k with £7.5k from the heat pump grant.

Primarily for environmental reasons, I'd like to switch our 2009 built detached house from a mains gas boiler to air-source heat pump. Octopus has quoted £5.3k for a fully installed system including their Cosy 10 ASHP, and have completed a survey, calculating 9 kW heat loss at -2.4 degC ambient temperature. We built a conservatory a few years ago, but kept the existing patio doors, etc, so the conservatory is thermally separate from the rest of the house. We added a new, separate zone to our existing ground floor underfloor (wet) heating for the conservatory, and we heat the conservatory a little during mild spring/autumn days, but don't heat it over winter - this would be environmentally and financially costly as the conservatory is quite large and obviously has high heat loss! The survey report from Octopus doesn't include the conservatory in the heat loss calcs, but they've now said that MCS requires them to include the conservatory due to the underfloor heating connection, and that they would need to specify a heat pump capable of heating the entire house AND conservatory for 99.6% of the year (i.e. all through winter). I've pointed out that heating a standard conservatory all through winter would be silly. I've also pointed out that if we were to fit a 12-14 kW heat pump (based on these MCS requirement calculations), it would probably run terribly (very inefficient) when only heating the house through most of spring and autumn (i.e. milder weather). Octopus has stated that the only way to satisfy MCS requirements would be to permanently disconnect the conservatory underfloor heating as part of the install. Is this really the case? Has anyone else experienced a similar situation (e.g. a radiator in the conservatory), and did you find a solution that satisfied MCS without fitting a heat pump that's too powerful for actual heating requirements? I've suggested Octopus sets the target temperature for the conservatory to be 5 degC, but they've said MCS requires a minimum of 16 degC for conservatories. Please let me know if any further information would be helpful! Thanks for any advice! In case it's relevant, smart meter readings over this winter show our highest gas use over any 24 hour period is 100 kWh (noting that we haven't had any super-cold days this winter). Dividing by 24 shows average heating power over this period is 4.2 kW (assuming close to 100% efficiency from the gas boiler). If we assume that on a very cold day, we might need 6 kW of continuous heating (instead of the 4.2 kW we've seen so far this winter), and that an "X kW" heat pump can only deliver about 70% of X kW at an ambient temperature of -5 degC (if I understand correctly, nominal power rating is typically based on an ambient of +7 degC), then it looks like an 8 kW heat pump would be about right for us. I can't find much data on the Cosy 10, and how well it modulates down to lower power levels, but it's clear that from the Octopus offerings (Cosy 6, Cosy 10), that the Cosy 6 wouldn't be sufficient.