Central Heating design help please

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Hello all. I am renovating an old country house and adjoining annexe and am having a crack at the central heating system. We have had a biomass boiler installed with associated thermal store in the outbuilding which has been heating a standard radiator system in the annexe for the past year no problem. (It actually is pumped to a tank in tank (ACV 240) which then goes to the central heating).

I am now designing the system for the main house which is altogether more complicated.

The start, however, is simple enough. We have a larger tank-in-tank (ACV 300) and hot water from the boilers will be pumped to this via 28mm copper before feeding the various systems in the main house (initially via 28mm copper, and then stepping down to 22mm and finally 15mm). The house will be split into 5 zones. Half of the ground floor (c. 100 sqm) will be underfloor heating, the other half cast iron (CI) radiators (4 column). The first floor will be mainly CI radiators with wet underfloor in the bathroom & 2 en suites. Then there will be the top floor which will be CI radiators. The tank has a number of connections making it ideally suited to running a combined system (or so the manufacturer tells me) – enough for a flow/return for the UFH zones and another flow/return for radiator zones. Each zone will have a 2-port valve controlling it with independent programmers & thermostats. The UFH zones will each have separate pumps/manifolds/controls/etc. I will also be installing a Fernox TF1 to the main radiator loop.

Given the size of the system (ground floor = 7 CI rads, 93 litres, 1st floor = 10 CI rads, 123 litres, top floor = 5 CI rads, 70 litres), layout (big rooms – the biggest is 9m x 5m - and over 3 floors) I obviously want to keep resistance in the pipework to a minimum. However, given the location of the tank and where pipes can be practically run there is going to be a fair few bends to work with. For anyone curious, the tank will be on the 1st floor rather than the ground floor to minimise pipework as much as practicable.

Anyway, here are my questions:

1 – would it be beneficial to have a separate pump for each ‘radiator’ zone or will one pump suffice, T-ing off the 3 circuits as necessary? Note that the flow/returns for each have to ‘join’ to get back to the tank.
2 – Sizing pumps seems to be behind a lot of questions on this site and I don’t yet have a solution to determining the size for mine. If they were independent zones I would be tempted to use the Grundfos Alpha range (15-50 for the small zone, 15-60’s for the larger zones). But if I use 1 pump what size would I need to go up to?

I am very open to any suggestions on this and hope that I’m posting it in the right place. And apologies for those who say that I should get a professional in – if I could find one I can trust I would! The guys who put the system in the smaller property for me left me with luke warm radiators, 2 leaking valves, leaking SR fittings, no filter, and to cap it all a 4” nail though the main flow pipe! That 35mm copper aint cheap…
 
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If you post the heat output of each radiator zone then it's possible to at least make a start on the pump sizing.

I prefer the pump per zone approach, but sometimes it all comes down to cost, large pumps...large money.
 
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Here are the rough outputs for the radiator zones:

Ground floor = 37,000 BTU = 10.8kW
First Floor = 36,000 BTU = 10.5kW
Second Floor = 30,000 BTU = 8.7kW
 
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If you post the heat output of each radiator zone then it's possible to at least make a start on the pump sizing.

I prefer the pump per zone approach, but sometimes it all comes down to cost, large pumps...large money.

Can I make one of my Tuppacentres please? :mrgreen:
 

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