How do you set a Differential Bypass Valve

Unknown

A H/B PD valve is a great valve. I use them all the time, all I do to set them is, when all the zones are calling for heat, it doesn`t bypass, when only one zone calls, it does. I find usually the grey cap(your adjustment) is backed-off all the way anyway. And yes, downstream of the pump, at the end of the header is fine.

Jeff_89

Our new home has radiant floor heating. When one, of the five zones are operating (note Zoned by pumps ,not valves) There is a lot of noise (velocity noise) When more than one zone is on, it is fine. There is a Pressure differetial bypass between the supply and return header down stream of all the zones, past the last zone pump. My father in law is a retired pipefitter, and said this valve may be the source of my problem. However, we both dont know how you adjust it the corret way. The valve says Braukmann on the side and its model is a D146M it is 3/4" NPT.
Also is this valve in the wrong location, my father in-law also mentioned it should have been installled upstream of all the zones, directly after the priming/charge pump??

Could Someone please help.

Jeff

Timco

As I was taught, a diff bypass is for when you have zone valves, and one large circ. If one ZV is open, the circ is oversized, as it is sized to be able to run all zones when all ZVs are open, and the bypass eliminates the velocity sound. Having individual circs, your circs should be seperatly sized for each zone, and a bypass not needed. What are the settings on the bypass? Does it have two ports on the side? May just be a circuit setter.

Tim

Brad White_148

I have the very same valve

The D146, same size.

Any DP bypass valve has the inlet side on the supply side (downstream of the circulator), the higher pressure side. The discharge of the DP bypass valve can go to the return header or a return line common to the system or back to the suction header at the pumps.

First order of business is minimizing excess flow, down to your actual needs. Lower pump speeds if possible, balancing valves and so on.

Personally, I favor "rat-racing" the pumps especially if the boiler is a condensing one. If the valve opens to the return of a condensing boiler it can quench condensing by raising the boiler temperature.

With a conventional boiler, to the boiler return is fine; it helps protect it from shock and flue gas condensation.

If I gather your setup correctly, it seems to be piped across the headers from suction of pump to return header? Not much delta-P if that is the case. It is not doing much then.

To set up the valve properly, it is easier to describe and operate if you are using TRV's or other valves. With multiple parallel circulators, you have to choose one, your main zone if you have one. I cannot think right now how I would pipe this up with multiple circulators in parallel.

With control valves, to set it up, figure what your minimum load is, say one or two valves open and calling. Turn the valve towards open until you feel or see flow in the DP valve indicator. As other valves open, this DP flow should stop. The gauge of performance absent other criteria would be noise.

My $0.02

Brad

Unknown

Brad,

Hard to figure-out, there must be a circulator "pushing into the header" don`t you think? Then off the header, it sounds like there are individual loop circs?

Brad White_148

That is a possibility, Dave

Had not occurred that it might not be pumping away. If it was pumping into a header, the bypass could work a little, but I am not sure where the bypassed water would go...

I would have to see a photo or a diagram- good call though, Dave. It is all in words so far and we all see different things!

Jeff_89

Follow up to questions

Just got back from eating dinner and seen the your responses. To answer some of what I read so far. Yes, there is a charge pump/pime pump feeding the supply header. The Zone pumps are in parrallel arangment through wirsbo truflow manifolds that have (I Believe) flow balancers for each loop. The Pressure Differential valve is at the end of supply header. Before this Charge/prime pump there is a Sensor that feeds back to a motorized 4 way valve. My father-in-law says it is for mixing water temperatures. hope this helps more. If this system seems like a stupid design let me know.

Jeff

Jeff_89

Just got back from eating dinner and seen the your responses. To answer some of what I read so far. Yes, there is a charge pump/pime pump feeding the supply header. The Zone pumps are in parrallel arangment through wirsbo truflow manifolds that have (I Believe) flow balancers for each loop. The Pressure Differential valve is at the end of supply header. Before this Charge/prime pump there is a Sensor that feeds back to a motorized 4 way valve. My father-in-law says it is for mixing water temperatures. hope this helps more. If this system seems like a stupid design let me know.

Jeff

Unknown

True Brad,

But if he is "pumping" into this header with "loop" circs coming off-it, and the D146 is at the end of this header, the return from the valve would just go into the other (return) header. This D146 would be after the (what he calls) the "priming-pump", and before the loop pumps, viza-vee the end of the header. If I understand correctly.

Unknown

That`s right Jeff,

That is exactly what that senser does, it feeds back temp. info to your 4 way valve, to keep the header at the design temp. I`m not too familiar with truflow manifolds, but that seems to me, like a "strange-way" of doing-it. Maybe the guy got paid "by-the-pump" on that job.

Jeff_89

Dave,

Is that charge pump after the four way mixing valve even nessassary. Why cant the zone pumps do the job themselves. Why is there a charge pump in the first place. It seems to me that this charge pump is just adding more harm than good. Adding extra velocity or Delta P when just on zone pump kicks on. (i.e. two pumps in series). Both my father-in-law and I have been jumping back in forth between the computer and utility room all evening, and have come to the conclusion that if the charge pump were eliminated, we could also eliminate the D/P valve. The zone pumps would just draw down straem of the tempering/mixing valve, The Boiler pump feeds a coil tank and the four way valve. Do you think this pump and valve could get tossed??? P.S. We adjusted the DP Valve as you said it made a small difference. it is less loud, but it still wistles a little.

Thanks

Jeff

Unknown

Jeff the........

"charge-pump" as you call it, creates constant circulation in this loop back to your 4 way. You need this so whatever zone pump "calls", the floor will get the design temperature. In turn if any of the other zones "calls" they will also get the same temp. This temp. is all in the calculation that would have originally been done on your system. Removing this pump will throw everything out-of-wack, so I wouldn`t. But maybe try this, if the "charge pump" is pushing into the manifold, maybe it`s pushing too hard (and the configuration of the D146 is what`s giving you the noise), try removing this valve, and piping back up using just a ball valve, then you will be able to better adjust your velocity noise. Please keep us posted as to your results!