@johnmo I've downloaded it but it's just Windows and I'm on a Mac. So now I'm installing Windows 10 on Parallels.

Hi Andrew, I believe we may have chatted about Katie McCabe back in 2021. My handle is Crispspark on Grey arrows. I am working toward an ASHP and waiting for a survey report from Octopus. Lots of help from the forum members. 

@jancold Hi Jon, nice to hear from you. Small world! Let me know how you get on with your quote. We've had a quote of £4,200 from Octopus, which seems O.K.

Cheers, Andrew

@ash2020 Andrew, I have a 80M2 1926 three bed semi in East Devon on the coast and have had a quote from British Gas of £4100 and an Octopus one of £2300. However I have not heard back from Octopus since the survey so I'm not sure if they will stick by that quote. Worryingly BG put the heat loss at 3.46 my calculations using Heatpunk gave 4.9 and Octopus said 5.25 so I really want to see that report.

Posted by: @jancold

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BG 3.46 my calculations using Heatpunk gave 4.9 and Octopus said 5.25 so I really want to see that report.

All the sizes will put you at a 6kW heat pump. I would push octopus as they will most likely oversize the radiator based on bigger heat loss. That will drive down flow temp required considerably.

80m² and 5kW heat loss is pretty huge, have you done any heat loss mitigations or do you plan any?

@jancold That's interesting. I wonder why your Octopus quote is so much cheaper when ours is a 2 bed bungalow?

@johnmo Haven't done any heat loss calcs yet. Just investigating Heatpunk. We are going to install underfloor heating as we don't have the space for upsized rads so I'm wondering how to approach Octopus about that. The simplest (but the most wasteful) is to get them to do the whole job including bigger rads, then take the rads out as I do the UFH, maybe even one room at a time. We have a slight problem because there isn't any heating or hot water when we move in in September so to do the UFH first, then get the Heat Pump fitted will take a long time and get into the chilly season. Also I think they're unlikely to be happy about connecting up to someone else's manifolds and certifying it. It would be so much easier without this stupid MCS thing.

Posted by: @ash2020

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We are going to install underfloor heating

Hope you plan for plenty of insulation under the pipes. Otherwise the downward heat losses can be pretty big. General recommendation is 150mm PIR. 

Have you considered fan coils? More expensive than radiators, less faff than doing UFH correctly. Can do cooling in summer if you want it.

Posted by: @ash2020

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stupid MCS thing

I just didn't bother, we are a new build originally with gas boiler. As soon as house was signed off, I installed the ASHP. Cylinder was £1000 (210L slim line), 6kW Maxa heat pump £1300 from ebay, around £500 for stuff. So around £3k all in. When I bought the ASHP, Viessmann were selling a rebadged Maxa unit for around £4k.

@johnmo We have cavity insulation double glazing and loft is mostly well insulated, all except a walkway down the middle. Also the chimney stacks have been removed. Floating floors with no insulation.

Except the floor, sounds good, did the heat punk calc take all this into account?

@johnmo You couldn't do an unvented cylinder yourself though.

Posted by: @ash2020

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@johnmo You couldn't do an unvented cylinder yourself though.

I did the UVC course at a local college, so now qualified.