Piping arrangement on hot water boiler

HomePro

I saw a boiler today that had piping and a valve installed between the supply and return pipes. The valve was half closed. See picture. Can someone tell me the purpose of the arrangement
. Thanks in advance for your help.

Danny Scully

It appears to be a bypass of sorts. When older gravity systems are converted to forced circulation, the returning water temperature can be quite low. To protect the boiler, a bypass is installed to temper the returning water.

Gman66

Looks like a bypass circuit. Can't tell where the circulator is so can't say if it is a System Bypass or a Boiler Bypass. If the circulator is tucked away behind the boiler on the return you have a System Bypass which would raise the return temps seen by the boiler. If the circulator is near where the camera is on either the supply or return you have a Boiler Bypass which lowers the supply temps to the emitters below what is directly exiting the boiler (perhaps for a radiant emitter?).

Ironman

It's a bypass to prevent the boiler from being cold shocked during warm up.

HomePro

Thanks very much for all the quick replies. It is a newer boiler on an older hot water system with radiators and big diameter steel piping. So it appears to be a system bypass drawing hot water from the supply side to the return side to prevent cold water shock to the boiler?

Here is another picture. The bypass valve is at the top of
the picture.

STEVEusaPA

You better do something with that expansion tank. That's way too much weight hanging off of that boiler.
That's also the cheapest, laziest, and worst way for boiler protection, but it probably works fine . If you have some k-type style clamp on attachments for an electric meter you could check the return temps

Danny Scully

Hey now @STEVEusaPA, nothing wrong with this simplicity of the bypass! Expansion tank support is a must though...

hot_rod

STEVEusaPA said:

You better do something with that expansion tank. That's way too much weight hanging off of that boiler.
That's also the cheapest, laziest, and worst way for boiler protection, but it probably works fine . If you have some k-type style clamp on attachments for an electric meter you could check the return temps

And yet another system pumping at the PONPC?

j a_2

I think it's a boiler bypass intstalled,,,Manufactures require them because on high capacity systems the returning water may constantly be below the condensing temp of approx. 140 deg....Boiler and vent will rot out very prematurely.....The bypass don't look all that correct...Observe boiler temp and see what's going on there...Send back some more info.....You may not want to hear this but whoever piped that boiler has issues....Primary secondary piping would also have been a good idea in lieu of a boiler bypass. Jmo

HomePro

Thanks very much for all the input.