Air Separator + Tank in Primary or Secondary loop?

[DrS1]

I am getting more serious about pulling the trigger on my combi boiler conversion. The boiler I am looking at requires a primary/secondary setup and comes with an integrated pump for the primary (Looking at WBRCNG140W) Current boiler has a single loop, so I need to reconfigure things.

Looking online for examples, I have seen where the air separator/expansion tank is plumbed on the primary, and others where it is plumbed into the secondary loop. Menards sells an integrator panel that has it in the primary (https://www.menards.com/main/plumbi...use-boilers/hsps150ht-htp/p-1444433736282.htm), but the installation diagram for the boiler shows it plumbed into the secondary loop right before the circulator pump.

Any thoughts on what is better? What are the considerations?

As always, folks on this forum have been really helpful. Thank you for being here!

 

[Fitter30]

Have to know what your heating devices are. Radiators, radiate tubing or fan coils. Can't pick a pump without knowing want u have.

 

[Sponsor]

 

[DrS1]

Have to know what your heating devices are. Radiators, radiate tubing or fan coils. Can't pick a pump without knowing want u have.

Single zone, about 130 ft of fin tube baseboard radiation.

 

[Fitter30]

3/4" or 1" total feet of pipe

 

[DrS1]

3/4" or 1" total feet of pipe

It is 3/4" pipe. Approx 180' of pipe including fin tube (130' of actual fin tube) There are a few places that have out and back returns in them so fin tube + bare 3/4" return.