Hi guys

I've been lurking on these forums several months and have learned a lot from you guys.

I tried doing a couple searches and can't seem to figure out the right answer.

We're replacing our boilers in our hydronic heat loop with Lochinvar Crest condensing boilers. Lochinvar provides piping diagrams for primary variable flow or a primary/secondary arrangement. But which is the recommended setup??

I can't seem to figure what the best/recommended setup is. Doing research, primary/secondary was invented to prevent cold water shock to old school boilers, however with a condensing boiler you want the coldest water coming in to help condense and be more efficient.

Please help. I have talked with 2 vendors in our area, one said he wouldn't do anything besides primary/secondary setup since that's all they've done in the past with these boilers. They other said primary variable flow is fine since.

A little background, we're moving our chilled water and condensed water to variable flow as well. We'll be moving hot water loop to variable flow as well. If we do primary/secondary setup, the boiler loop will be constant but the building loop will be variable flow.

Thank you,