Balancing Valves

Pwall

Hello Everyone,
I'm trying to get a handle on when you would use a balancing valve, why you would use one and how you would select and adjust it.
I don't have a specific problem I'm trying to solve I'm just trying to wrap my head around all the different aspects of a hydronic system. I have watched several of the Caleffi videos (thanks for those Hot Rod) read a bunch of stuff (couple of Dan's books) and it just seems balancing valves get over looked or assumptions are made about experience and knowledge.
Heres my example. I have a 100 feet of 3/4 pipe in a loop, for whatever reason I'm not happy with it.
So I decide to split it right down the middle and do a split loop with each loop being 50 feet. This type of setup should balance itself naturally since everything is equal.
In my mind if I change this to say a 70-30 split the natural tendency of the water is going to go through the short loop since it is the path of least resistance. Ideally I would throw on a balancing valve or some other restriction on the short loop which to the water will make the loop look longer therefore help force more water down the physically longer loop.
Am I understanding the purpose here of the balancing valve?
It's also a way to step down the GPM flowing through one area and in the example above it would send it down the other path. If you had a valve on both loops you could restrict the flow down to something like 3gpm per loop or set one to 2 gpm and the other to 4gpm depending on your needs.
How do you decide this is the valve for me? Do you select it based on the GPM you are trying to achieve? The Caleffi Circuit Setter comes to mind with it's handy gauge on the body. Use a valve where your ideal GPM falls somewhere in the middle of the valve specs so you can wiggle one way or the other if needed.
Measuring and adjusting seems like everyone wants you grab some expensive gauge set but in one of the Caleffi videos they mention a simple pressure gauge with a needle probe will suffice if you don't mind a little spray from the ports moving from one to the other.
You just have to find the differential compare it to the provided chart and adjust up or down to get the GPM you want.
Does all that make sense? Still fuzzy on the selection process.

RPK

You seem to have a pretty good handle on the concept. In my experience most balancing valves end up being line-sized. Basically, you select a valve that can handle your desired flow without creating excessive pressure drop. You don’t necessarily need an expensive rig to measure flow and set a balancing valve. You do need a way to accurately measure the pressure drop across the valve. A single pressure gauge with the appropriate range (not too large or you won’t have good resolution) and the necessary fittings would suffice. Using the same pressure gauge to measure high and low pressure individually is preferable to using two separate guages.

hot_rod

The first thing you need to know is the desired flow rate in the various branches or loops.

Correct you are, balancing assure the correct amount of flow, heat output to various piping circuits. Comfort, energy efficiency, proper flow velocity are some of the goals.

How accurate of a flow do you need or want? More expensive balance valves have fine thread stems for more accurate balancing.

I've seen videos online of neanderthal balancing methods by crimping down the tube with a channelocks (not recommended).

Some valves like the Quicksetter have the gauge built in, other types need a gauge or delta P meter to read and adjust accurately. That is what this PT ports are used for.

Basic balance valves are often a ball type, like B&G circuit setters, etc, usually the most affordable choice. Globe valves or design specific balance valves have a better flow path and are best for accurate, flow friendly balance, more $$.

Good, better, best would maybe be a basic ball, globe valve, engineered balance valve.

If both branches are always flowing, no zone valves, a manual valve would be fine.

When you have multiple zones with zone valves, for example, a pressure independent balance valve will assure exact flow under changing flow conditions. You buy this type with a specific gpm cartridge built in, no adjusting in the field. PIBV with delta P circulators are an ideal balance method.

You can also balance by temperature, either with gauges or your bare hands depends on how accurete you want/ need to get.

Pwall

The desired flow rate would be dependent on what kind of output you was looking for?
Say you had all 3/4 fin tube and manufactures all give charts for 1-4gpm with the sweet spot being around 3gpm. If you placed a balancing valve on the end of that part of the loop you could regulate the flow to be 3gpm through the valve. The problem I can imagine is that at the start of the loop your flow would be higher depending on the distance between the start and end of the loop due to resistance along the way. Or am I seeing that wrong in my brain?
Is it better to balance at the start or at the end or really is there no difference?

I was under the impression ball valves are frowned upon for balancing because of the turbulence it generates along with gate valves.

hot_rod

The fin tube size and length would be matched to the heat load of the space it is intended to heat.

So if you had a room with a 10,000 BTU/ hr load and the fin tube you selected had an output of 500 BTU/ ft at a determined temperature and flow and ∆T you need 20' of fin tube and a flow rate of 1 gpm.

You should really always start with the heat load, and build everything to it, heat emitter, pipe and fittings, valves and circulator. The balance valve is the fine tuning mechanism, or to correct mis-matched loops like you have. It's rare to see an engineered design that doesn't include balance devices. Most quality hydronic manifolds include balance function for adjusting loop output.

What ever goes in one end of the loop will come out the other, flow wise:) If 3 gpm goes in one end, it will come out the other. Unless you have a large leak along the road. So the balance valve can go on either end.

What will change is the temperature, if you supply 180, design for a 20∆, 160° comes out the other end at design conditions.

Correct again with a ball valve as a balance device, not ideal but workable under these low flow conditions. Certainly better then pinching the tube. It's the entry level $$ choice, plenty of Buick and Mercedes balance valves available.

Avoid oversizing a valve, for example a balance valve with a 12 gpm max installed on a circuit choked down to a 1 gpm flow, not so good as the valve will be closed way down.

You will also discover fine tuning a ball valve is tricky at that low flow, the first 80% of close off, not much change, but the last 20% a tiny movement makes a big effect, hard to be super accurate.

I think the ball style B&G CircuitSetter has been around since the 1960, probably millions, & similar styles in other brands in use. It is perhaps the most common balance valve you will come across.

Caleffi goal was to make that style of valve more user friendly. Teach an old dog new tricks, hence the added flow indicator, temperature gauge option, and choice of connections, insulation jacket as well as low lead versions, check valved versions.

If you have read Idronics 8, you see that balancing can be a very deep subject.