Still need thermal by-pass?

Paul Pollets

If your control does not include a boiler return sensor,and the ability to regulate the boiler temperature above dewpoint, then yes, you need a bypass.

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amhwrite_3

Still need a thermal by-pass?

I'm in the process of redoing the mainfold on a boiler of a converted gravity to forced circulation system. It's a two pipe, direct return, with rads. The trunk lines are 2", 1-1/2", 1-1/4", 1". Another guy replaced the boiler 3-years ago and didn't install a thermal by-pass, and the pump is on the return side. I also have to re-configure the air-eliminator and compression tank. Because of the tight area, it would be easier for me to install a primary loop between the supply and return with a circulator. Then make the existing system a secondary loop with a secondary circulator pumping away, taken off of tees spaced within 12" on the primary loop, as outlined in Dan's primary/secondary pumping book. Another reason for using this configuration is that the present owner is planning to eventually remodel the entire house on a room by room-basis over time. He is considering adding radiant heat as he goes. On the new manifold, I can make the primary loop to accomidate new future secondary loops for radiant heat as it is added. My question is do I stll need the thermal by-pass if I use primary / secondary in this case? Could all of my gpm take the "service road" through the secondary loop, and no hot water blend to get the water up to temp at the boiler until it returns hot from the secondary loop? Is using primary/secondary a good idea under these circumstances? Any suggestions, I have to start the job next week!