Radiator Balancing

Joel M

I have a one pipe hot water system with risers going up to the radiators. The first radiator off the main is in an upstairs bedroom. It has globe valves on both the supply and return. I want to partially close these to get more heat to the last radiator which is on the first floor. This last radiator is in the living room and the room is always cool. I guess I am trying to balance the system. Is this a workable idea?

Brad White_9

I assume you have

a Monoflow system? One pipe main with supply and return branches coming of the very same main? Fair assumption.

Your approach is sound, that of balancing, but let's take this to another approachable level, shall we?

Ideally, the "globe" valves at the radiators are really stop valves, designed to be either fully open or fully closed. I would not use them for balancing.

In my old house system I had a Monoflow system but with plug cocks on the returns for balancing. It helped and as you said, throttle the first ones to serve the later ones.

Ever consider TRV's? Thermostatic radiator valves? Then the balancing is automatic based on need (temperature) not the whim of pressure drop.

More work, incredible benefit. Eminently workable.

Joel M

Yes Brad, the setup is as you described. I would like to have thermostatic radiator valves, but not being a plumber I would need to find someone to install them. Could I put them just on the 3 rooms that get more heat than they need or would all rooms need them? Thanks.

Ken_40

Brad nailed it.

The two valves are a tad unusual, since either one, if "throttled," would restrict flow enough to do what you desire. But, the double valves would allow removal of an emitter while the system is "active." Although that might be a stretch.

Simply throttling one of two isolation valves would restrict output by slowing flow, as you already suggest.

And yes, by reducing output of any rad does leave a tad higher water temp for downstream use and diversion, as you suspect. There are other strange "impacts" with MF-tee systems (called "one-pipe" [for some strange reason]) and "throttling." Among them: by restricting flow through any emitter, you reduce flow through the entire system. Admittedly, only a small impact if one merely chokes off one emitter and just a small amount at that, but one caveat we see in the MF-tee arena is this: "If you remove an emitter from the system, do NOT just cap off the two tees (regardless of whether they be two MF types, or a single MF-tee AND a "conventional" tee. ALWAYS install a full size pipe "bypass" where the former emiter was once. Meaning, the removal of an emitter also removes a small amount of total flow through the "trunk" - unless a bypass pipe is used (rather than two caps). The trunk line diameter is dertermined using "engineered" calculations; i.e., reducing the flow rate of the system (trunk AND emitters combined) was the trunk sizing criteria used. "Changing" that flow characteristic by capping the supply and return branches also impacts the entire basic design. One tweak; no problem. Two or three tweaks; might decrease flow rates to a point of inducing unacceptably high dT for the entire system.

There is a way around that WITHOUT closing any balance/service valves. Simply place a piece of cardboard or FG insulation over part of the emitter area. The chimney effect of all emitters is essential for full output. Reducing air flow accross most emitters reduces output by 50%!

I'd close one of the two valves a tad and see what happens. Once you set it at a point that the desired result is accomplished, LEAVE IT ALONE. If it responds poorly, you can always "choke" the chimney effect by denying air-flow as suggested above.

Let us know how it works out.

Joel M

Thanks Ken. I will try the valve first then if neccesary the insulation wrap. Thanks again guys. I will let you know how it turns out.

Plumb Bob

> I would

> like to have thermostatic radiator valves, but

> not being a plumber I would need to find someone

> to install them. Could I put them just on the 3

> rooms that get more heat than they need or would

> all rooms need them?

Yes, definitely. TRVs can be put in a few rooms, no problem.

Balancing with manual valves is not easy, because the heat output of a radiator is not strongly dependent on flow. In many situations you can cut flow to (say) 25% of its original value and still get over 90% of the output. A TRV will cut the flow as much as needed including all the way to zero (which DOES cut the heat output to zero).

Joel M

Yes , I know using the valves is not the most accurate method. The convectors they put in the two bedrooms of the converted attic of my cape house are too big for the square footage. I figure I can experiment a little with the valves this season and in the spring find a plumber to install the TRV's. Tough to find a plumber around here, they all seem to be doing new construction. I should have chosen another trade 30 years ago! Thanks Cricket.

Ken_40

Messing with what's there is

free. Buying and installing multiple TRV's would be costly. Costly as in around $100 each for the TRV's and the labor to install them cumulative. You could drop a fast thousand doing them all.

Try your method of tweaking a valve here and there fisrt. If you cannot live with the result, open your check book and look at he very top-left of this page. You'll see: "Find a Professional." Plug in your zip code and a few names of guys who know what they're doing should appear.

Joel M

Yes, that is my plan. I would rather put the grand twoards a indirect hot water tank so I will experiment with the valves. Thanks.

Brad White_9

And,

there is no need to install TRV's on all radiators, just the ones most prone to overheating and in rooms used less or which you like to have cooler. (Bedrooms not bathrooms as one idea.) But I agree with Ken, experimenting with manual valves is a good start to determine affect.