primary secondary help!

nathan

apartment bldg boiler replacement.
5 boilers. 2 cast iron. 3 munchkins.
3" main from and to apts. we pump away.there are 2 pairs of
3x2 t's. 1st pair for munckins(cold return water)2nd pair for cast iron. bulls of first munchkin t's look to ceiling(so dirt wont fall down in to loop). bulls of second cast iron t's look down at floor (so first pair is 180 degrees opposed to second pair).all boilers have swing checks to prevent reverse flow in idle boiler.
problem is..2 munchkins firing fine.pipes for 3rd idle munch cold. good. but pipes for cast iron are very warm their temp gauge is showing about 100 degrees.the cast iron has not been gas piped nor wired yet???????????????????

nathan

primary secondary help!

ps space between t's is 5" and 6" between 1st pair and the 2nd pair

Floyd

Can you..

post some pics????
It would be very helpful and make troublrshooting this thing much easier.

nathan

primary secondary help!

here is sketch photos later

nathan

pics

Eric

Working?

It looks from your schematic that you have 2 primary loops and one secondary. I assume your secondary flow is always greater than either of the boiler loops.

I redid schematic with some flow arrows. see attachment

The munk will always see the colder return because they are first in line to pull out of return.

The cast will pull from return after the munks and have a warmer return.

check for air on the third munk if its cold and its pump is on.

Note that your boiler pumps are in parallel and not decoupled.

The total Primary flow will increase as you stage boilers but the indv. to each boiler will decrease because they are in parallel