UFH/ASHP manifold pumps needed?

[Dunc]

I hope someone can enlighten me on the need or otherwise for pumps in a wet UFH system with ASHP.

Does each manifold require a pump? Is this in addition to or instead of the ASHP's own circultion pump? If in addition, how is this set up in the @JohnMo style using just flow/return temps to contorl the heat delivery with no thermostats to put a call on each manifold pump? If not, what parameters do I need to check to make sure the ASHP pump is up to the task.

 

If specifics are useful: I have 1 manifold on each of GF and FF (lets keep any discussion of need for upstairs heating for another thread!). GF is 10 port supplying circuits of 40-100m lenght. FF is 6 port supplying circuits of 23-78m length. ASHP 6kW Mitsubishi.

 

thanks.

[crispy_wafer]

I cant add too much, but in the first instance i'd ask, does the HP have a pump built in, if it does, then does it have enough grunt to supply the needed litres per minute for the install.

Edited Wednesday at 10:40 by crispy_wafer

[JohnMo]

You really need to get built-in circulation pump performance curve (in install manual).

 

Calculate your system pressure drop. So flow and return piping the longest UFH loop pressure drop.

 

Calculate your flow required.

 

Read system pressure drop on pump performance curve and validate if your pump puts out enough flow.

 

Advantage - purchase choices.

Route all pipes from ASHP to manifolds in 28mm, so very low pressure drop.

High kvs diverter valve. Look at a kvs of 10 or over. Then valve will be invisible hydraulically.

 

If your pump still doesn't flow enough install a second pump on the return from UFH only (not cylinder side) run at a set speed to get the flows you need to see at the UFH manifolds.