Weil Mclain wmb120

[Cpeters]

I'm replacing my cga4 with a Aquabalance wmb120. I have 2 taco 007 with built in check valves and have a question about the Primary/secondary connection. Where does it go? Is it necessary? I have 2 taco 007 on the boiler return, one per zone hooked up to a taco 2 zone controller. I have my air separator and expansion tank set on the supply side. Just not sure where this connection should go. It looks like it should go above the return pumps. Is it necessary for anything other than efficiency? Thanks in advance.

 

[Cpeters]

One more thing. This primary/secondary needs a separate circulating pump. And the connection between the supply and
return takes place before the hot returns to the boiler. It sounds similar to the HWH circulator pump which is useless in this case.
Just talking to myself.

 

[Sponsor]

 

[Dana]

Primary/secondary is necessary to keep from pumping the hell out of the water tube heat exchanger, and for maintaining a "reasonable" delta-T on the boiler that's not too big (stressing the boiler) or too low for efficiency, independent of how many zones are calling for heat.

Read the manual, particularly Section 17 (starts on p.37).

Look at Figure 48 on p.38.

For the WMB-120 they specify 1" plumbing on the primary loop, and either a Taco 0015, or a Grundfos UPS 15-58, or a B&G NRF 25 as the primary pump (or a much more efficient ECM drive pump with a comparable pump curve.) That would be pump #8 in the schematic diagram. With the 3-speed 0015e you'd be able to tweak it up or down if need be, but the Medium speed setting should just work.