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Designing ASHP system using the Freedom toolkit spreadsheet

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(@hughf)
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Hi everyone, just checking into this thread as I'm a new lurker... I'm Hugh, an embedded software & electronics engineer by day (mostly in the offshore industry - not very renewable, I know) and machinist/plumber/electrician/welder/fabricator/wood basher/digger driver/farm boy by night.

Currently renovating and upgrading my Wife's post war end of terrace in rural somerset, and designing/specifying a new central heating system based around an ASHP, using the Freedom toolkit spreadsheet.

Hoping to hang out and chat with likeminded DIY'ers and talk all things heat pump/plumbing.

 

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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cathodeRay
(@cathoderay)
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@hughf - Welcome, others more august will also welcome you soon as well.

Be aware the Freedom toolkit spreadsheet is not perfect. It is good, and was put together by @grahamh, a regular here, but it does contain some dodgy data for some heat pumps (unlock/unhide it to see the hidden data), and like all spreadsheets that need a lot of manual data entry, it is very easy to have typos creep in. You have to do sanity checks on results to spot these typos eg total heat loss doesn't make sense, then probably one of more data entry items is wrong. The rad selection table assumes you are adding to existing rads, and also only uses a basic watts per square metre calculation to determine output, which is an approximation, a 500 x 1000 rad has a different output to a 1000 x 500 rad, and there are also small differences between brands. The rad selection table also, if I remember right, assumes a fixed delta t of 30, and so the rad sizing tables assume a flow of 55 degrees (delta t 55/45/20), so you might end up with too small rads if you use a lower flow temp.

PS the rad table also doesn't include K3/treble convector rads, which are often needed (to avoid colossal rads) in ASHP heating systems.

 

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@hughf)
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Posted by: @cathoderay

@hughf - Welcome, others more august will also welcome you soon as well.

Be aware the Freedom toolkit spreadsheet is not perfect. It is good, and was put together by @grahamh, a regular here, but it does contain some dodgy data for some heat pumps (unlock/unhide it to see the hidden data), and like all spreadsheets that need a lot of manual data entry, it is very easy to have typos creep in. You have to do sanity checks on results to spot these typos eg total heat loss doesn't make sense, then probably one of more data entry items is wrong. The rad selection table assumes you are adding to existing rads, and also only uses a basic watts per square metre calculation to determine output, which is an approximation, a 500 x 1000 rad has a different output to a 1000 x 500 rad, and there are also small differences between brands. The rad selection table also, if I remember right, assumes a fixed delta t of 30, and so the rad sizing tables assume a flow of 55 degrees (delta t 55/45/20), so you might end up with too small rads if you use a lower flow temp.

 

I've got some real-world data from our smart meter and our current boiler rating plate which is a good start. We have an 11kW gas fired back boiler (baxi bermuda), which when run at the current settings, seems to keep the house warm in the depths of winter with the current flow temp of 55 (measured with a clamp on k-type thermocouple). I'm designing for a flow temp of 45 deg at -3.4 outside, but didn't realise that the rad sizing chart didn't take into account the value entered for floe temp. I thought it odd that the oversize/undersize values didn't change with flow temp. Luckily I'm upgrading from type 11 rads is nearly all rooms, so a jump to type 22s is more than enough to cover the required heat loss of about 7kW.

I don't have access to a proper version of office, relying on LibreOffice instead - can that unlock/unhide the data?

As you've probably guessed, this will be a non BUS self install (provided someone will sell me a heat pump)... Anyway, that's probably enough thread drift for now. I'll take this discussion over to the ASHP section.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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cathodeRay
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Posted by: @hughf

I don't have access to a proper version of office, relying on LibreOffice instead - can that unlock/unhide the data?

Yes (its what I use). You need to do some hackery to the spreadsheet (google is your friend) and then open it in LO Calc, select all the cells in the worksheet you want to view, click Format > Columns > Show. 

Posted by: @hughf

I thought it odd that the oversize/undersize values didn't change with flow temp.

Now you know why they don't! Well spotted, that's the sort of sanity check that helps us to spot these things.

 

Midea 14kW (for now...) ASHP heating both building and DHW


   
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Mars
 Mars
(@editor)
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@hughf, welcome to the forums and look forward to hearing how your system comes along and which ASHP you chose. I’ve created a dedicated thread for you, so please continue to share updates here.

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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(@jezzaf)
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@hughf Hi.. just read your comment and the last line caught my attention and if I understand you correctly  .. so many years ago I did a self install of a Trianco Active Air Heatpump .... it was a rebadged  chinese made machine anyway the compressor failed I can't now remember if it was in warranty or just out. The point was that as I was not an "approved installer" the manufacturer "Trianco" would not even talk to me or assist in any way.  Ended up scrapping the unit and now happy with air to air. But moving to G2 listed Farmhouse in Somerset in two weeks so its  full circle for me back to oil 🙂        


   
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(@hughf)
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Posted by: @editor

@hughf, welcome to the forums and look forward to hearing how your system comes along and which ASHP you chose. I’ve created a dedicated thread for you, so please continue to share updates here.

Thanks for creating this thread for me Mars, appreciated...

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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(@hughf)
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As per the thread title really, and following on from my introduction post - I've been designing a new CH system for my Wife's 1946 end of terrace in rural somerset. We have 300mm loft insulation, blown cavity walls, relatively recent DG (due to be replaced with Uw 0.9 units this year) and we currently heat with a 35yr old Baxi Bermuda. Typically using 17MWh of Gas/year for CH and DHW and looking to upgrade from the current system that is on borrowed time.

I can't see the merit in installing a new gas combi, only to find in 2035 that we can't find a replacement when that fails. Plus, it would be nice to ditch the gas finally so I don't have to bother a gas safe engineer and try and ninja a 28mm gas through the house to the new boiler location.

Attached are my latest workings using the Freedom toolkit. At the moment I'm torn between a Midea (concerned by the fact they might not sell me one), a Cool Energy CE-iVT9 (concerned by the efficiency using r410 vs r32 - I don't know enough about the finer points of refrigerants to assess this), and an LG Therma V (because the controller looks excellent, I like the look of the AI weather comp mode, and they're cheap as chips)

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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cathodeRay
(@cathoderay)
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@editor - not sure where to post this here seems as good as any other place, as this thread is about using spreadsheet calculators. FWIW, this is my modified OFGEM rad sizing calculator, based on delta t conversion factors so you get a more accurate (!) result. It currently contains data for a typical hypothetical old leaky 3 bedroom house, which can be edited to suit. It also allows you to add more rads if the contained list does not meet your needs (get the delta t 50 value from manufacturer's data). I set it up and use it in LibreOffice Calc, but but should work in anything that can open xlsx files. 

It goes without saying, use is entirely at user's risk, if you turn your house into a freezer of a frying pan using the calculator, it is your responsibility, not mine. But, in the right hands, it might be of use to some people, if only as an independent sanity check.

@hughf - I think various people have been borrowing other people's calculator spreadsheets and modifying them over the years - just as I have done with the OFGEM calculator. If the spreadsheet is available online, that is what will happen (and it is basically a good thing, openness and transparency and not to mention error checking etc). Freedom made their calculator available online, ie put in the public domain, so, as I see it, it is available to all. I suspect many installers also send property/quote specific copies to their customers, again increasing general circulation.  

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@hughf)
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@cathoderay I agree, this stuff should be out in the open and available (I write/use open source software as part of my job - don't have time for closed source stuff)... Thanks for your radiator sizing sheet, I'll have a play with that.

It's really odd that Midea won't sell to end users, even if no warranty was offered. I'd be happy to buy one if they knocked some coin off for warranty voiding - I'll void it anyway as I'm not installing it with a LLH or a Plate - ain't got the space for that, I'll just use the overly long loops of 28mm...

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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cathodeRay
(@cathoderay)
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Posted by: @hughf

I'm not installing it with a LLH or a Plate

You may have seen the discussion on these, both in the thread I started about my installation, and elsewhere. One interesting point is that Freedom changed their requirement for these, from being and absolutely essential component (bye bye warranty if not used etc) to, in their latest installation manual, it being shown as a component, but the warranty voiding aspect if not used has been removed.

I still have my PHE in place, and am still on the fence about it, pros (keeps rad circuit crud away from primary ASHP circuit) and cons (extra expense, losses and something else to go wrong).  

Midea 14kW (for now...) ASHP heating both building and DHW


   
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(@hughf)
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  1. @cathoderay I’ve read your thread completely, I’d bin that plate off at the first opportunity, can’t see the point of it at all. 

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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