Boiler. Primary/Secondary---yes, or no?

[Doug. G.]

I'm replacing an ancient gravity boiler with a Weil-McLain Aqua Balance wall hung condensing boiler.Existing system is 2 1/2" supply and return mains feeding 1" supply and returns to each of 6 cast iron radiators ln 1200 sq. ft. house.---WM piping instructions show need for primary/secondary piping.---I've found so much disagreement on the Internet on the need for P/S ( not to mention the extra install cost and complexity ). In the absence of compelling reasons for P/S, I'm inclined to go with the simplicity of a single multi speed circulator.--- After looking at my particular situation, I'd appreciate some knowledgable opinions,--- P/S, yes or no!

 

[Scott D (CA)]

Try asking your question at the following:
https://forum.heatinghelp.com/

 

[Sponsor]

 

[Flat_Twin]

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[Dana]

The pumping head of the heat exchangers in the Aqua Balance are about 10-100x that of a gravity feed boiler, and it's likely that the system's flow requirements to achieve reasonable room-to-room temperature balance and a reasonable overall delta-T will be quite a bit different from the 4-15 gpm min - max specified for the heat exchanger on that boiler.

You may be able to pump direct, but you'll have to do some math to prove that the system delivers less than a 40F temperature drop at a pumping rate within the min-max pumping rate. It's probably do-able, but you'll need to pick the pump carefully. A smart pump may make that task a little bit easier, but you'll still have to estimate the pumping head of boiler + system to pick that pump.