15M pump required, one large Vs 2 small in series?

[Michael Groves]

5 Storey Victorian house, Boiler in the basement. It's actually 13.5M, (I measured it exactly) so 15M being the closest.

 

[Chuck]

5 Storey Victorian house, Boiler in the basement. It's actually 13.5M, (I measured it exactly) so 15M being the closest.

If you are talking about a circulation pump, it doesn't need to have a head of 13.5m, which is what you seem to be thinking. This is because the inlet pressure is 13.5m and the outlet pressure is the sum of the pump-inlet plus pump-working pressures. So you only need enough head to overcome the impedance of the pipework, which should be sized to work with a standard 6m pump.

 

[Michael Groves]

If you are talking about a circulation pump, it doesn't need to have a head of 13.5m, which is what you seem to be thinking. This is because the inlet pressure is 13.5m and the outlet pressure is the sum of the pump-inlet plus pump-working pressures. So you only need enough head to overcome the impedance of the pipework, which should be sized to work with a standard 6m pump.

Yes it's a circulation pump, in a sealed system. Will have Worchester Bosch 40CDi Classic with a Robo kit. I get your point if it were open vent, or am I missing the point?

 

[ShaunCorbs]

Yes it's a circulation pump, in a sealed system. Will have Worchester Bosch 40CDi Classic with a Robo kit. I get your point if it were open vent, or am I missing the point?

unvented cylinder?

 

[Michael Groves]

unvented cylinder?

Yes

 

[ShaunCorbs]

Yes

i would say your shy on your heat loss calcs

unvented cylinders require 15-20kw on there own

 

[Michael Groves]

i would say your shy on your heat loss calcs

unvented cylinders require 15-20kw on there own

Cylinder is 20kW, Radiators are 17kW.

 

[Michael Groves]

If you are talking about a circulation pump, it doesn't need to have a head of 13.5m, which is what you seem to be thinking. This is because the inlet pressure is 13.5m and the outlet pressure is the sum of the pump-inlet plus pump-working pressures. So you only need enough head to overcome the impedance of the pipework, which should be sized to work with a standard 6m pump.

I thought it was building height, clearly I am VERY wrong, Grundfos Technical support also confirmed building height.

Here's a link I found, good explanation. I need to reconsider
How to size a Circulator Pump. Taco pump curves.

 

[ShaunCorbs]

Cylinder is 20kW, Radiators are 17kW.

how many rads? seams low only 8 2kw rads

you done a room to room heat loss? and not just measured the existing rads?

 

[Chuck]

Yes it's a circulation pump, in a sealed system. Will have Worchester Bosch 40CDi Classic with a Robo kit. I get your point if it were open vent, or am I missing the point?

Makes no difference to the conclusion whether the system is vented or unvented. You would only need a 15m head if you were trying to pump water from, say, a borehole in the basement to an open tank in the roof.

If this is not obvious to you then you should subcontract the design of the system to someone who knows what they are doing. (No offense intended!)