What pump between boiler and heat exchanger?

[SillyBilly]

I am moving my 30kw domestic boiler to an outbuilding where there is a new biomass boiler. I plan to run two independent systems via two separate heat exchangers placed where the boiler was. They are unlikely to be run at the same time. The original mostly 28 and 22mm copper internal central pipework and pump will be retained.
I had expected to use 2 new 11/2" screw Grundfos Alphas or similar circulation pumps. The two heat exchangers are Nordic Tor BA-32-30 and BA-32-50 which have flow rating of 12m3/h which is way over the usual perhaps 3 or 4 m3/h.
What pump should I use?

 

[ShaunCorbs]

Why not put the boiler into the biomass buffer ?

 

[SillyBilly]

Why not put the boiler into the biomass buffer ?

That is 2000 litres!

 

[John.g]

I am moving my 30kw domestic boiler to an outbuilding where there is a new biomass boiler. I plan to run two independent systems via two separate heat exchangers placed where the boiler was. They are unlikely to be run at the same time. The original mostly 28 and 22mm copper internal central pipework and pump will be retained.
I had expected to use 2 new 11/2" screw Grundfos Alphas or similar circulation pumps. The two heat exchangers are Nordic Tor BA-32-30 and BA-32-50 which have flow rating of 12m3/h which is way over the usual perhaps 3 or 4 m3/h.
What pump should I use?

So, you will be using the original circ pump/piping to circulate through one side of the PLHEX(s) and the new pump(s) to circulate (primary side) through the other side?.
If the secondary side (central heating) is circulating at a present say 1.72m3/hr to give a dT of 15C then its unlikely that you require a secondary flowrate much higher than this so 6M 45W Alphas should be fine but email Nordic with what you think your secondary (central heating) flow/return temps are and expected heat output of say 30kW?, and give them the biomass cylinder storage temperature, (flow temp into the primary side of the PHEX) and they will calculate the (primary) flowrate (and return temperature) required.
Also ask them the expected pressure losses through the PHEX(s).

What is the existing pump make/model/head?

Who/how were these PHEXs specified and under what primary/secondary conditions?.

 

[SillyBilly]

So, you will be using the original circ pump/piping to circulate through one side of the PLHEX(s) and the new pump(s) to circulate (primary side) through the other side?.
If the secondary side (central heating) is circulating at a present say 1.72m3/hr to give a dT of 15C then its unlikely that you require a secondary flowrate much higher than this so 6M 45W Alphas should be fine but email Nordic with what you think your secondary (central heating) flow/return temps are and expected heat output of say 30kW?, and give them the biomass cylinder storage temperature, (flow temp into the primary side of the PHEX) and they will calculate the (primary) flowrate (and return temperature) required.
Also ask them the expected pressure losses through the PHEX(s).

What is the existing pump make/model/head?

Who/how were these PHEXs specified and under what primary/secondary conditions?.

Thanks for response.
Yes I will.
I will contact Nordic direct as the ebay seller just has a ebay business link. My current in-house pump is a 3-speed Grundfos Super Selectric UPS15-60 130. Few rads just fan convectors and finrads and dhw cylinder, The PHEXs were specified by Nordic