Flow measurment & balancing valves

Apprentice_3

Brad,
So am I correct in assuming that the circular slide rule takes the place of the manometer, and am I correct to assume that the two ports on the valve's outlet side are for the manometers hoses?

Perhaps a written walk-thru of the steps of balancing a system is what I need here?

Also, when there is no GPM specified, how do I know what flow rate is correct for the system I've just installed?

Sorry about all the questions! There's a lot more to this trade than just installing pipes! Unfortunately my mentors don't really see it that way, so I have to bother you guys :)

Apprentice_3

So gow does one measure Gallons Per Minute, Anyway?

I'm trying to teach myself about Gallons Per Minute, balancing flow in a heating system, etc. There are some questions the guys at work couldn't answer, maybe someone here can help?

- Say for example, you're installing a system in a commercial/industrial building where you're going by a highly-engineered drawing. The mechanical engineer has specified that your flow is to be set at "X" gallons per minute. I know that you use a Circuit Setter/Balancing Valve to set this, but how?
I DO have a hunch about this: The Victaulic curcuit-setting valve has two ports, one red and one blue, on the outlet side. I'm guessing that you install a manometer (with the manometer's blue hose on the valve's blue port, red hose on red port), and ajust the valve handle as per the manometer's reading until it agree's with the engineer's recommendation. This is just a shot in the dark. I've never held a manometer. OUr company just opens the balancing valve up all the way and hopes for the best, but I consider myself a (future)professional and I want to know how to do it right.

keeping that in mind I've got a few follow-up questions too.
- Are there other ways to balance the system? Other that the Victaulic circuit-setter type valve I mean.
- Say you're installing a residential system where there are no engineered specs, and you have to set the GPM and do the balancing yourself. What is the formula for finding the right GPM?
- What are the benefits of balancing a heating system?

Thanks! Sorry for the long post!

Apprentice_3

Anyone?

jp_2

balance?

what is true system balance?

getting the exact flow as determine on paper?

Or getting the required heat needed to make the occupants happy?

I think true balance is measuring the heat or temperature on the output, floor, radiator, etc then adjusting balance valves.

I'm thinking more of a house than an apartment complex here.

Brad White

Balance!

Firstly, it is great that you have the Victaulic (Tour and Andersson) type balancing valves. (Others of the type, Macon, Oventrop/Mepco, Armstrong, all good.)

What you have is a "variable orifice" balancing valve. Most of these have a "parabolic port/plug" (or similar term) which means that the moving of the plug into and out of the port orifice will yield a nearly linear flow response.

These valves in small sizes, say 1/2" to 2" size, have at least 4 turns open-to-closed (4 x 360 degrees = 1440 degrees), while the Macon types start at 10 turns (3600 degrees of turning). Larger sizes, 2-1/2" and up, have more turns, eight in the TA/Victaulic line.

(By contrast, a quarter-turn ball valve has 90 degrees open-to-closed operation, with the last 45 degrees doing nearly all the work. A little adjustment either way has a very wide flow response.)

The operating principle is very simple and you are on to it.

Every valve position at a given pressure drop has a corresponding flow.

Repeat:

Every valve position at a given pressure drop has a corresponding flow.

You simply measure the DP and note the valve position. A "wheel" or circular slide rule is available from Victaulic or Tour and Andersson (same valves last I checked; Victaulic imports them and offers them under both names, but you should verify this to your specifics).

There is also an on-line selection software program to assist.

What you need at least is an accurate pressure gauge with a needle adapter (basketball filler). I use a Dwyer digital gauge which ran me about $95 some years ago.

If you go all out, each valve manufacturer offers a digital gauge (not cheap) but it has software internally with all data for their valves and sometimes other manufacturers.

I for one am very glad you are seeking out this information. It is a shame to have nice balancing valves yet rely on guesswork otherwise to "balance" a system.

With today's high energy costs and low-temperature/high delta-T systems with low flow, water flow management is critical.

One place I no longer use these is on the discharges of circulators, especially those with variable speed. No point in measuring variable flow except once at start-up for full speed, but also, why drive with the brakes on? Balance the terminals and maybe significant branches.

As you know, the idea is to make each terminal and flow path have exactly the same pressure drop. Reverse-return piping is another subject but it also makes the adjustment range of the balancing valves very narrow, not a bad thing.

When you throttle a balancing valve to a branch or emitter you are imposing resistance (not adding it to the system but subtracting it from other more restrictive branches and the available pump head). Oh I am starting to ramble now...


My $0.02

Brad

Apprentice_3

JP,
you raise a few good points. Personally I would try and achieve the engineer's specified balance and ajust as necessary, based on tenants' satisfaction with their system's performance. Keep in mind I'm an aprentice though.
Is balancing more for maximum heat output/comfort, or more for maximum boiler efficiency?

Unknown

BV's

Simply put The numbers on the valves relate to its CV at that setting.

The ports are for reading differential pressure. Then you can calculate gpm.

Brad White

Hi Addam

Hey- if you think you are "just an apprentice", you will make a fine journeyman and master by the way you ask good questions. Keep it up! Don't apologize for asking. I am glad for the industry -and you- that you are.

The circular slide rule works WITH the manometer (more specifically, pressure gauge. "Manometer" is for measuring air pressure at least in my experience. Dwyer devices come to mind.).

If you do not have a GPM specified, find out what the BTU rating of the device is and at what temperature drop. See what the other known devices use and go from there. Triangluate information from knowns to find unknowns. If in doubt, ask the engineer.

Don't be afraid, we do not bite :P

(Some engineers can be imperious and condescending, but so can some cab drivers and lord knows, waiters in snooty restaurants.)

Say you have a length of fin-tube radiation, maybe 20 feet and 18 MBH. Typically but not always, this would be sized for a 20 degree drop. That works out to 10,000 BTUH per GPM, so 1.8 GPM would be ideal. In-duct reheat coils are sized as much at 40 degree temperature drops but could be anywhere between 20 and even 60 degrees.


Here is a walk-through, using what might not be the most current wheel, but is at least as "real" as I can make it.

Say you have an in-duct coil requiring 3.0 GPM. It has a 3/4" balancing valve (selected for FLOW, not necessarily line size). Valve is fully open, system is charged and pumps are operating.

Take an initial reading (Delta-P) across the valve. Say you have 24 PSIG entering and 20.8 PSIG leaving. This of course is 3.2 PSID (D for differential). That works out to 7.4 feet of head, fully open (valve position 4.0).

According to your wheel, that indicates 12.0 GPM, too much of course. Your target PD to get 3.0 GPM is going to increase which means you start turning the valve.

Practically speaking and to keep this discussion simple, most balancers I know do this by trial and error, turning the valve mid-way (position 2.0) and take a reading, see what the PD is and corresponding flow.

(The "correct" way, involves a little bit of math. Your target flow is 25% of your starting flow and PD with water varies by an exponent of 1.75, roughly the square but let's work with the trial and error method in the moment.)

Turn the valve to position 2.0 and take the second reading. Say you have 24 PSIG entering and 22.3 leaving pressure, a drop of 1.7 PSID of 3.93 feet. Your wheel says that you are just under 3.0 GPM at that valve position and differential pressure.

Sure, you can do the math way but every balancing technician I know does it this way. It is faster and besides, just because your calculations say something, what happens at your gauge is everything!

You can see the paradox in this: By turning the valve you would expect that the pressure drop increases (it does of course) but then immediately the flow rate drops and takes down the pressure drop with it, by the 1.75 exponent.

Not the last word, just a quick way to get the job done. I do not mean to teach shortcuts but in this case to get you started with the promise that you will learn the "right way" at some point.

For additional reference, I would seek out the AABC, NEBB or other recognized TAB organization for literature on certification, membership and means & methods. There are some good textbooks out there- I have one in my office but I am on vacation this week, otherwise I would give you the publisher and title.


Good Luck!

Brad

Brad White

rw

I like your answer better

Brad

Rich L.

Circular slide rule

Addam, you don't use a manometer, you need an accurate pressure guage with a needle adapter. The needle adapter looks something like the needle you'd use to inflate a basketball. After taking the pressure readings from both ports on the circut setter you use the pressure differential (Delta P) and size of the circuit setter with the circular slide rule and convert that pressure differential into GPM's. If I'm making it sound confusing I'm not trying to, it's really quite simple.

DON'T apologize for asking questions, It's how we all learn, and good for you for asking, you'll be a better tech for it!

Good luck, Rich L

Aidan (UK)

balancing act

All in here;

http://www.tahydronics.com/frameset_middle.asp?StructureNodeId=AA31E944-E0B7-4EF0-ABB4-55B5033631F2&SelectedMenuItemId=1AD9F3D9-4AD1-4D36-88B5-9C06388A1CAA&ArticleId=275C909C-8D6E-11D5-94BD-00D0B765C9A8&ArticleType=Link&Site=UK

Sorry about the length of that link.

I get involved in a lot of balacing. A drowned manometer is generally used, with fluorocarbon for low pressure differentials, mercury for high dPs. There are electronic dP meters, mercury isn't welcomed everywhere, but it remains the tool of choice for most commissioning technicians. Pressure gauges don't work on this application.

Apprentice_3

Starting to get it now.

I think I 've got the basic idea of it now: The two ports on the valve are for inlet and outlet pressure. Open valve all the way. Take a pressure reading at both ports and subtract to find pressure-differential. Use the slide rule to convert PD to GPM (this part, I'm sure, will be a bit clearer when/if I ever see the slide rule). Ajust valve to half-open and repeat. Ajust as necessary (this is the non-mathematical way of course, I'll start from here but I'll learn the math way as I get deeper into this topic).
I'm beginning to get the gist of it I think!
Thanks for your answers gentlemen. I'm extremely grateful for all your help and support.

Mike Dunn

balancing valves

Any suggestions on where to purchase the needle valve, pressure guages and slide rule?

Weezbo

As an apprentice you might find what i have to say somewhat

different.*~/:)

first off even though you are an apprentice as classified by some nebulous bunch, always remember You are what God wants you to be and he is expecting you to do your best at whatever you do and he has given you certain blessings to be able to do whatever it is that is asked of you.

Your here right? Your conscious right? so, where ever you are there you are in other words,

"I am Here ,Now."

how do you know what the drawings say are correct? unless you think it through you dont. you are only trusting that whatever you are following is correct...there fore before you set about balancing circuits you really should pay attention when it is done the first time. keep an open mind dont ask any questions and focus....

The next thing is you need to understand what you are working on,...some gizmoes need specific flow rates through them , often the same thing that applies to setting the circuits at these gizmoes is the exact same principal that pertains to branch or main take offs.

Each Size of pipe uses different circuit setters and each supports a range of flow rates...as doest the piping...

when the pipes are designed to carry a certain flow rate maximum, you can look at that check ,the type of circ you have and its flow rates,...match the requirements at max for the equipment in the field and then determine what kind of flow rates is actually required, in a way it is like reverse engineering something,...then once you have all the individual components in the system put together(added up at that flow) you then get what the specific BTU requirements are at each and then think at what temp does this need to operate ... ok ,so now you have :the pipe size, the temp requirements,.... the flow rates :through the cirulators , pipe, equipment,

you are ready to adjust the G.P.M.'s at the circulators right? Wrong... not if you are still doing the best job that you were doing when you first looked at the drawing...

Here is why,...you need to know the advantage or disadvantage in the piping, arrangement, sizing, temp requirements and lowest flow rates that all these components can still deliver the necessary BTU's to the station in the field.

Right about here, Now.

is where you want to start..
before ever even freaking with a circuit setter...

lets flip the page to the electrical side of the shop drawings for a moment,..

Here you need your electrician hat ▒
~:)

What kind of electrical drives do the circuits have? Each circulator has some means of turning it off and on How many H.P. are they? a H.P is about 800 W just for a SWAG,some circulators are chosen for different reasons so you have to add the info that you have of these circulators to see what type of flow these pieces operate in economically. Some of these may have variable speed drives or they may have duplicates of themselves to pick up the slack if one takes a dive...sometimes Not,...sometimes the system is so huge that i think engineers get "Pump habby" and put way way too many circulators in the system ...sorry,...i digress...

thing is now you have an idea of the range of the equipment ,

those Gert circs might be like ten time bigger than they need to be buh then again you wouldn't KNOW THAT unless you burnt all this time checking these things out.

the reason you want to know this is because if you blast the living Heck out of equipment with a fire engine hose at 2oo G.P.M. somethings gotta give sometime...that means that the electrical components in order to do the job for which they were selected need to be able to slow down or speed up within the ranges that the circulator will confront during its life time. Without Letting the Smoke out

i bet you never thought that a circuit setter could fornicate up the electrical system:) or eat the impellers off the circulators...

how are we doing so far? is what i am saying easy enough to understand? is it helping?
i got to post or i may time out..i type like a frog.

ok well, that made it *~/:)

The things that apply to large systems basically apply to smaller more modest residential arrangements.

in commercial apps there are lots of parts and pieces the same basic idea applies though, use equipment to do the work and design them with the idea of them having a bit of "Longentivity" to them and the system. you want the piping and pieces to last a while... if you have a chance take up a class by Caleffi on some of their new radiant headers...Taco Load Match is also a very top notch program to burn some daylight with...Really smart money is Siggy's classes , books, programs and trade journal contributions to the advancement of residential hydronics...

This next thought that i have for you is quite a ways over the top buh if you design the heating system and think things through sizing the piping little bit large here and there use variable speed variable voltage or some of the new circs sized for operating within predetermined ranges i think you will have new tools and flow meters...that are far more efficient than circuit setters.

on some older systems that are way over pumped you can buy different motors to bring them into "Reality" the reason i like variable speed variable voltage is because you can dial the flow rates down in some cases real slow:)i understand that there are so many fun things to study in this Work, i would want you to have more than 'crank it down two clicks to the right. ok she's balanced' to go forward "With"...

Brad White

Any supply house

should have what you need, except the slide rule. The slide rule is available through the manufacturer and your supply house could order it for you, just that they probably do not stock them. Maybe they do!

The slide rules are specific to each manufacturer, so calibrated are the valves.

The fancier and more expensive balancing computers are available through the manufacturers but are recommended only if you are a TAB contractor to justify the use and cost.

If to check your own work, a NIST traceable gauge, well protected, will be worth it. A gauge tree with petcocks is easy enough to make up yourself.