Monoflo Heat System Question

R.N.

I purchased a two unit rental last year and immediately had the furnace replaced (it is in the basement). On the first floor, heat is provided by six radiators connected by single diverter tees to a copper tubing monoflo-design system. The first floor radiators do not seem to get very hot. (Heat for the second floor is provided by the same boiler but the second floor radiators are connected by regular tees to separate supply and return lines, and the second floor system seems to operate ok.)

The company that installed the furnace asked me to trace and label all the radiator risers to make their troubleshooting job easier. (I couldn't fault them for the request because the basement ceiling is a plumbing mess.) I have done that and found that as I follow the monoflo main in the direction of water flow, for the first three radiators the diverter valves are installed on the second riser (the return?) and for the last three the diverter valves are installed on the first riser (the supply?). The red band on each diverter valve is between the risers of the radiator it serves, so they are installed correctly, but three are installed on the return side of the radiator and three are installed on the supply side. Is this typical, and more importantly, could this be part of the problem?

I don't know if this helps, but when I bled the radiators recently, no air came out and the stream of water was not very strong at all. Thanks in advance, and sorry if I messed up any of the technical language!

Andy B.

Monoflo Heat System

R.N.

There are quite a few variables here. As Dan is so fond of saying---If you get water, it ain't an air problem.
Some additional information that you might provide is:
Are there 2 zones?
How is the water flow controlled---circulators and flo-checks or zone valves?
What type and size are the circulator(s)?
Are whatever is controlling the water flow new and operational?
Have any radiators been removed from the monoflo system and the tees just capped?
Your answers to these questions may point to your problem.
I'm sure I (and other readers) can think of more. If it weren't so late I might even check a book or two, but I'm done for tonight. Good luck--I'll check back.
Andy B.

R.N.

Andy, thanks for the reply. The furnace and all mechanicals attached to it (circulators, flow check valves, etc) are new, but they were attached to a 40+ year old system that was once one system and then divided into 2 circuits (and appears to have been modified several times). There are no capped off diverter tees. I don't know how well or poorly the system worked before the new furnace was installed. The company that installed the furnace is very reputable and is coming back to check it out, I was just curious why the diverter tees were installed in two different directions on the single loop. Thanks a lot for your interest!!!

Andy B.

Monoflo Heat System Question

R.N.
As I'm sure you know, diverter tees are designed to create a pressure differential between the supply and return to a heat emitter (radiator, etc.). The pressure differential is what causes the flow of water through the emitter. As long as the tee is in the right direction, depending on whether it is on the supply or return to the emitter, it will create the pressure drop. Usual placement is on the return side. If the emitter is below the main, sometimes 2 tess are used to counteract the effects of boyance. My questions were leading (I think you figured this) to perhaps a circulator with insufficient head.
I never meant to imply that your contractor was disreputable. Believe me,I feel for the guy. It really irratates me to see a system that has been butchered a little at a time and then some poor contractor who replaces the boiler is supposed to make everything OK.
I guess my interest was peaked because I saw a particularly bad job yesterday. They took out some cast iron radiators and installed copper finned tube baseboard that was "the same size" (read---"as long as" the radiator was!!) Then someone decided that the first floor monoflo system worked so well that it would be a good idea to run a pair of risers (in series loop) from some of the radiators up to the second floor and connect some more baseboard up there. Doesn't work. Lots of complaints. No action---until the landlord moved into the unit. Amazing!
If you get a chance, post your contractors solution for your problem. Always interested.
Andy B.