bypass on feed and return for gravity system

tim smith

If room will allow combustion and vent size and no water heater on flue. Now some of the mfrs are allowing unbalance flues, one to roof and one out wall. Tim

jim_43

bypass on feed and return on gravity system

Im installing a new boiler on old gravity feed system, locating the circ. on the feed.The supply house guy that did heat loss said I need a bypass from feed to return to prevent boiler shock, however he insists I dont need a check valve in between and primary secondary piping is not neccessary. I dont see how it will work, wont I just be pulling return water back into feed when circ comes on?

Dave_4

Wrong boiler!

Gravity systems cry out for condensing boilers. One reason is - they don't want or need bypass piping. Another is they pay for themselves in no time. Oil or gas. They make both ya know...

If you are locked into a bypass arrangement, and have already subrogated the heat load tasks to the supply house, you are somewhat compelled to let them also tell you how to pipe the boiler they have apparently chosen for you as well.

Make sure you get the heat load data in writing from them as well as a sketch as to exactly how they want you to pipe it.

That way, five years from now, when the customer's boiler goes south, you can show the heat loads and scehmatic drawing to the courts and tell them the truth,

"The supply house did all the heat-load math and near boiler piping; here it is your Honor."



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Mike T., Swampeast MO

A condensing/modulating boiler will give such increased efficiency with nearly any gravity system that it's a shame not to use one if gas is your fuel.

If you're using oil or for some reason won't use a mod-con, a thermostatic bypass valve type ESBE is the best way, but it costs significantly more than dropping a pipe size and inserting a globe valve.

Steamhead (in transit)

Or

a properly-sized primary-secondary piping hookup will work too.

BTW- we find that in many older homes, there's no good place to go thru the wall for the mod-con's intake and exhaust pipes that meets Code and manufacturer's specs. So it's back to the chimney-vent boiler.

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