What are the considerations for balancing a split loop?

ralman · September 2006

1.25" iron supply pipe for a monoflow system. The pipe splits and follows the perimeter of the L-shaped house. 120' to the right side, 53' to the left side. The current valves used for balancing are probably 50 years old. They have Welsbach stamped into the housing and nobody ever heard of them. I would like to change over now before trouble starts in the middle of winter. Since the valves are used to add head to the circuit, can the pipe be reduced to a smaller diameter so I can install a 1" B&G Thermoflo balancer?

Brad White_126 · September 2006

Is there a problem with it now, Ross?

"If it is not broken, don't fix it", is my first principle. (As if I do not ignore it just for fun, mind you!

What is the imperitive to balance the legs?

Depending on the number of fittings and assuming the flows are proportional to each branch pipe size, you ought only need a balancing device in the smaller, shorter, less fitting-intensive branch.

Not sure what you mean by, "the valves are used to add heat to the circuit". Typically all that balancing valves do are to equalize the pressure drops in disparate branches; essentially they remove any incentive for too much flow to take the "shortcut" and force flow to the longer branch. Artificial resistance.

What is your assumed flow rate or approximate heating load in each branch and at what temperature drop? Until I know that, I would not make any changes or decisions.

My first course of action would be to, if possible, balance flows at each radiator runout. Once the terminals are balanced, no need to balance the mains. TRV's on the terminals will do the same thing once the system is warmed up.

My $0.02

Brad

Ken_40 · September 2006

Take a look at

the "logic" of the two circuits. If one seems to be mainly "sleeping areas," and the other: "mostly living areas," you may want to do the obvious, e.g., remove the two balancing cocks and install two zone valves?

I would not rule out keeping what you already have however. Since the system is sealed, corrosion should be minimal. We use a cheap temperature "gun" to see what the dT is across each circuit and balance the temps to "balanced." With today's fuel costs being what they are, you may want to tweak or zone the system to more accurately control each leg.

Whattaya think?

ralman · September 2006

It doesn't leak while I watch it, but I 'm not sure

There is evidence that water has leaked at some point. I really think they are not the right valve for the job and I am trying to figure my options before something happens.

The flow rates through the baseboard branches are affected by the position of these valves. The "heat" you refer to is "head" as in feet of head pressure.

With both valves fully open not all downfeed baseboards will get flow through them. Both loops must be throttled to get flow throughout the entire system.

I can't find any written material that covers splitting a loop. So, I was wondering if a smaller pipe diameter than 1.25" could be used at the end of each loop. This would give me the option to use thermoflo balancing valves. I would think that a 1" balancing device will be cheaper than 1.25" devices. If it will accomplish the same purpose I would like to use the smaller valves and save the expense for other repairs.

ralman · September 2006

Delta tee

I have tried checking the delta tee. I have the loops as balanced as I can get it for now. I am planning some changes that will upset the balance. It was very difficult to balance by the delta t method. I was thinking the thermoflo circuit balancers might work better and more accurately for me. I can't find written information on splitting loops so I wondered if it was acceptable to use smaller diameters at the end of the 1.25" loop.

What are the considerations for balancing a split loop?

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