old moniflow main

tuk869

whats up guys I'm a heating contractor, first time on the wall and also a big fan of Dans.

I have a little problem but I think I have a clue on what wrong, but just wanted to check with some of the best to see if i'm right. I have a two story apartment building that I just replaced the boilers in after some hack destroyed the so called new heating system he put in about two years ago. I have been taking care off the complex for ten years but I turned down the boiler job when I found out what they were going to do, I was dumb because guess what I'm the dummy that got stuck fixing all the guys screw ups. The building has a 4 inch supply and return with branches of 1 1/2 that turn into a single venture tee piping system that feeds four apartments at a time front to back with 60 year old convectors. For the past two years we have been getting complaints that the last four apartments at the end of the building are not getting much heat so after a little crawling threw the two hundred foot crawl space I found that the last contractor installed a 0013 helper circulator to try and push the heat around. But guess what, it still doesn't work and as I looked further I found that the last boiler installer left 60 feet of both the supply and return 4 inch mains that used to feed other building until he separated it and the last 1 1/2 moniflow main ties in about 60 feet before he just cut the pipes and left all of that extra piping, is anyone thinking what I am? any answers.

billtwocase

did he

cap off the ends, or tie it back in? If it's no longer a monoflo loop, the "helper" circ will do nothing, I feel

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Mike Kusiak_2

End of main

Did he cap the ends of the supply and return mains or did he tie them together at the ends? I wold think that it would not work at all if they were tied together, since there would be a "short circuit" across the last monoflow loop and therefore no deltaP. Where is the "helper" pump connected?



Your system sounds exactly like the monoflo system I maintain in a 100 unit apt complex.Heat in the building at the end of the loop is always a problem.

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Mike Kusiak_2

Dead stubs

So there is 60 feet of "cold" main past the last monoflo loop. Is the main still 4" at that point?



In my system, the main gradually reduces in size from 5" until it becomes the last monoflo loop at the end at 1.5".

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Charlie from wmass

can you sketch what the

piping looks like? What makes to water travel up the 1 1/2" laterals?

Mike Kusiak_2

Dead end

Seems to me that with the mains capped 60 feet from the last takeoff you might have a reservior of cold water sitting in the dead ends, mixing with the heated water. The last loop never really gets full temp water.



I would think the best solution would be to cut the mains right after the last monoflo loop and cap them there. If that would be difficult, then drilling into the mains just past the last loop and installing a bypass valve so you could get at least some flow of hot water past the last takeoff.



The takeoffs from my mains are all plain tees. Monoflo fittings are only used in the sub loops to the convectors.

Mike Kusiak_2

Ladder System

Charlie, think of it piped as a ladder system with the rails the supply and return, and each monoflo loop rungs on the ladder. The supply and return mains have a delta P across them forcing flow the monoflo loops forming the rungs. Think of it as a parallel flow system. Its only monoflo in the individual subloops

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Mike Kusiak_2

Pump wont help

Don't think flow is the problem. You just don't have hot enough water at the takeoff for the last loop.

Mike Kusiak_2

Banging my head

Definitely true, these systems can be a headache. I have three of them, each with 36 apartments in a total of 15 buildings. Mains are almost 400' long, so getting heat to the last building is a problem. Had to increase the pumping with series connected pumps to even out the heating. Right now maintaining 72-74 degrees even at the ends, but it was a lot of work!



Where is your building located?