Laars minitherm bypass piping question

Joseph_4

Attached is a diagram from Laars with the pump located on the return which will pull hot water directly from the supply water into the return (through a bypass)

. This is on page 18 of one of their manuals and its purpose is to maintain proper flow through the heat exchanger of the boiler.

Ive attached a diagram with the pump on the supply side and Im curious if this will accomplish the same thing. ( if suction side of pump has higher pressure and return piping has lower pressure, id this water water go through the bypass route and straight through boiler as well

What do you say?

thanks Joe

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yellowdog

I say pipe it to manufacturers spec. Not the way you want to pipe it. The circ is on the return for a reason.

Joseph_4

The reason Im asking is because there is little space in the room and i wanted to pump away from the expansion tank. its not practical in the space on the return side

STEAM DOCTOR

Assuming this is a small residential system (hence the tight boiler room) don't worry about pumping away. And if it's a one zone system, or if you are zoning with zone valves, you can always put the expansion tank on the return. Don't let perfect be the enemy of good.

hot_rod

are you running a low temperature system, or looking to add boiler return protection?

What is the goal of the bypass?

EBEBRATT-Ed

Sometimes it is better to pump into a HX if it has a lot of pressure drop. You can still pump away from the expansion tank tee it in just above the pump.

Joseph_4

Its purpose is for boiler protection. to insure proper water flow through heat exchanger

Thanks

Joe

hot_rod

https://forum.heatinghelp.com/discussion/comment/1854973#Comment_1854973

what type of heat emitters do you have? Radiant floors, cast radiators are the systems that would need a protection valve. Copper fin tube, air handler, or panel radiators, usually do not need a protection loop, low mass systems.

I would use the part Laars suggests, the thermal union, or a thermal protection valve if you have a high mass systems.

mattmia2

doesn't laars want the bypass both for return protection and to keep enough flow through it because it is a water tube boiler?

hot_rod

They are not that restrictive of a HX, but being low mass, low water content, they want flow!

They do show the pump on either return or supply. Pump on return is noted as optional.

I would use a thermostatic bypass valve if you are taking the trouble to address an issue?

I don't know what year they started adding the low loss headers to the mini-therms?