I’ll ask my professional network for advice. As an aside, how accurate is the assumption that you need a 100-120kW unit?

I hope its pretty accurate as has been done by M&E consultants and checked by my architect to ensure it includes the (limited) insulation upgrades that we can do.

Space heating has been calculated as 75kW and domestic hot water at 50kW (seems high?), hence the M&E consultant are suggesting adjusting down for plant sizing.  So, 100kW total load - but the Clade units are 60kW, hence 2x is 120kW.

Hope that makes sense?

Firstly by being “suggested” what does this mean? 

has a full heatloss survey been carrie don’t determine what load is required?

by periodic is this a lived in house or is this something for the trust for eg. 

intermittent heat maybe required if so and needs a different way to look at it.

is there hot water to include?

what is the flow temperature and what emitters are being used, 100kw of emitters is somewhat staggering.

you would need to provide more information for me to be able to start having ideas.

the main fact is you keep mentioning cost, to do something this size and get it right will be expensive and the right units will be expensive. Getting something like this wrong will be catastrophic, 

@damon Sorry, you may get two replies (as one is awaiting moderation).

Yes, heat loss survey done by M&E consultants plus checked by architect for the limited efficiency gains.

75Kw space heating, 50kW of hot water (the latter being staggering to me).

The house is being restored having being empty for many years - old oil boiler not working and insufficient radiators so unable to do an actual test of the old heating system

There are around 49 radiators scheduled - mostly large four column cast iron.  We originally started with a lower flow temperature but the size of the radiators were too large for the rooms - as being listed we have quite some constraints.  As such, its currently specced with up to 80 degrees C (Clade units) but the M&E consultants are re-doing the work to see if they can get down to 70.  There is no real option to make the radiators much bigger in many of the rooms.

Yes, this will be a main residence, occupied all year around.  However, about 1/3 of the floor space will have limited use (i.e. family holidays etc).

Cost of course is an issue, we recognise that this will not be cheap but the cost for the larger commercial units seems much more expensive than smaller ones.  In simple terms if I took, say 8x16kW units (we cannot do this due to planning) they are currently coming at more than half the cost of 2x60kW units - which does not seem very logical?

Thanks

Posted by: @greenlover75

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I hope its pretty accurate as has been done by M&E consultants and checked by my architect to ensure it includes the (limited) insulation upgrades that we can do.

Space heating has been calculated as 75kW and domestic hot water at 50kW (seems high?), hence the M&E consultant are suggesting adjusting down for plant sizing.  So, 100kW total load - but the Clade units are 60kW, hence 2x is 120kW.

 

120kW seems enormous, whats the floor area of the property?

I dont understand why DHW needs to increase because the property is listed.  50kW allows you to heat a total of 25cu m of water through 40 degrees C every day.  What do you plan to use such a vast amount of hot water for? 

Do your M&E consultants have a scooby what they are talking about or is this a non-domestic situation?

Running a heat pump at 70C is nuts, why not use fancoils?

@jamespa Agreed - the hot water seems very high - hence in design they are suggesting 25kW.  Still seems very high to me!  We will end up with around 6 bedrooms & 5 bathrooms, but most of the time only two bathrooms will be regularly used.

The floor area of the house is around 680 sqm, but it has quite high ceilings, solid wall (albeit thick) and single glazed (with lots of windows).  Its Grade I so we are very restricted on secondary glazing - the only system allowed looks like not able to pay off.

We have managed to get permission for insulation between the first and second floors which will help for the low occupancy periods as we can keep the top floor "cold" but at peak (i.e. Christmas when all of the family there) this does not help the peak load.

@jamespa Sorry, also should say, of course the 70 is the peak temp, they will obviously run at much lower temperatures the rest of the year.  The problem is the house being Grade I its very heat inefficient

Posted by: @greenlover75

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@jamespa Agreed - the hot water seems very high - hence in design they are suggesting 25kW.  Still seems very high to me!  We will end up with around 6 bedrooms & 5 bathrooms, but most of the time only two bathrooms will be regularly used.

Its not 'very high' its completely ridiculous.  25kW is still enough to heat 12cu m of water every day, I repeat, what are you gong to use this vast amount of water for?  DHW use has nothing at all to do with the construction of the building!  Are you running a hotel?

Posted by: @greenlover75

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@jamespa Sorry, also should say, of course the 70 is the peak temp, they will obviously run at much lower temperatures the rest of the year.  The problem is the house being Grade I its very heat inefficient

Thank goodness for small mercies.  Its still nuts unless there is absolutely no alternative.  Have you got the heat loss calculations?  What about fancoils?

Im sorry to be blunt but, if the suggestion you need 25kW for water is serious, I wouldn't trust these jokers as far as I can throw them, unless you have a very large family or this is not for domestic use.  Its just so far out as to be laughable, if it weren't so important!

The first issue you have is the dated m&e consultants. Everything is copy and paste and old school workings. 

you need someone who deals with design and specification of heatpumps.

the additional hot water load onto there is crazy, some redundancy could be made into the heat source to accomadate for usuage in colder weather to compensate but something like a large fresh water cylinder would be ideal. 

With the high flow temps unless

yoor using co pumps the performance wouldn’t be there and would cost loads, a hybrid may seem a better option to pick up on your bi valent point.

i would advise using someone who designs and installs this stuff. 

your going to end up with a generic design that won’t be suited to your houses needs  

@greenlover75 please feel free to continue asking questions. Would you like me to connect with suitable, reputable installers? If yes, I can do that tomorrow if you’d like.

@editor Thanks - that would ideal if you could.  As I said, we originally wanted to use isoenergy who had a very long track record in installing such systems in large old houses.  So, some recommendations of similar companies would be ideal.  We have obviously tried to do this as professionally as possible by installing very professional M&E engineers so we are disappointed with some of the reactions here - which implies we may have used the wrong people.  However, isoenergy, even prior to heat loss were sugegestign 80kW, so the fact we are now at 100kW did not seem to be so wrong?