Proverbial Can of worms (Help)

Jimfxstd

<span style="font-size:12pt">Comments appreciated!</span>

<span style="font-size:12pt">Simple over heating complaint opens up the <strong><span style="text-decoration:underline;">proverbial can of worms.</span></strong></span>

<span style="font-size:12pt">In the beginning; Service call taken from a homeowner complaining the “Garage” is over heating. Tech arrives to find a hydronic fan coil heating the garage with what he determined was a failed open zone valve. Simple (I wish), “Replace it”! </span>

<span style="font-size:12pt">Tech removed old & installs same new Honeywell 1043--- zone valve. Examining the fail one he notes an unusual failure, the ball disintegrated off the shaft & nowhere to be found. OK no big deal, they don’t build things like they used to “Right”!</span>

<span style="font-size:12pt">Tech gets the system back up & running & goes to test his repair and notes the zone valve is really straining to open in fact it won’t open fully with out a little help. He checks the power and source making sure the transformer is OK and not overloaded with to many zone valves applied, Wiring/power supply all good.</span>

<span style="font-size:12pt">Then he notes Wow this system is making a lot of noise, in fact it sounds like a faucet running!!! And when the zone valve is actuated closed the unit heater almost jumps off the hangers it bangs so bad!!!</span>

<span style="font-size:12pt">Tech calls me in the office and paints a picture and describes what he’s found. </span>

<span style="font-size:12pt">I directed him to install a differential bypass valve in front of the zone valve crossing its supply & return to dump the excessive velocity/flow etc. Now that unit runs well. Zone valve functions correctly & banging is for the most part gone.</span>

<span style="font-size:12pt">Here are the facts; Very Large older home totally rebuild with in the last 5 years as best we can ascertain. All new HVAC systems, 3 Atmospheric boilers with a net rating of 981,000btuh’s supplying 10 hot water coils in air handler/ A/C units “plus” about 100ft of HWBB in basement.</span>

<span style="font-size:12pt">Total hydronic coil rating plate capacity 1,100,000btuh’s + 50,000 for the HWBB.</span>

<span style="font-size:12pt">System piping configuration starting at the boilers. 3” return manifold across one side of the boilers with 1 ¼” returns (no pumps) feeds through the three boilers.  1 ¼” supplies up out of the boilers to a 3” supply manifold on the other side of the boilers. Supply main runs up to a 3” spiral troll with feed valve/expansion tank & auto air purger (This is good because the system pump comes next!). From the Spiral Trol to a set of pumps piped in parallel (one operating pump / one back up valved off). Pipes feeding the pumps are reduced down to 1 ½” (???) for about 3’-4’ on the inlet & outlet sides, both pumps.  Pumps are B&G series 80 1.5x1.5x8.25 3HP 1725 RPM. As far as I’ve researched they appear to produce about 80GPM at 80-100 feet of head!!!</span>

<span style="font-size:12pt">Discharge from the pumps increase back to 3” & through a 3DS-3s Triple duty valve and then out to the system. One set of 2 ½” mains feeds the 1st floor & another feeds the systems in the attic. The ends of the main supply and returns are connected with CB25 2” circuit setters. Each Air Handler has Honeywell zone valves on the supply and circuit setters on the return tying back into the large diameter supply & return mains. There is a large capacity indirect fired Phase III domestic hot water storage tank taken off the main after the triple duty valve pumped as a secondary loop. Boiler relief valves are 50lb relief valves (and weeping).</span>

<span style="font-size:12pt"> </span>

<span style="font-size:12pt"> </span>

<span style="font-size:12pt">Controlling the system is a Tekmar 264 capable of staging, alternating lead follow boiler operation, indoor-outdoor reset etc. Currently only wired to stage the boiler burners, switch the Domestic hot water operation & switch on the one & only system pump.</span>

<span style="font-size:12pt">The velocity noise through out the house. Further examination exposed all the zones bang loudly when cycling off. Can we “throttle the system down with the Triple duty valve & quiet the system with out harming heating output or stressing the series 80 pump? Would that create excessive noise at the Triple duty valve & transmit that velocity noise through out the home????</span>

<span style="font-size:12pt">Why this wasn’t the system designed with primary secondary pumping? To save the expense of additional pumps & devises?? </span>

<span style="font-size:12pt">Why such a high head pump contributing to the velocity noise? Doing some quick math system head should be that high & much better Hi Vol. Pumps available that what was installed (Better GPM at lower head).</span>

<span style="font-size:12pt">We’re assuming “Someone” designed this system and maybe an acceptable commercial application in a commercial setting? Not working well here.</span>What am I missing??? Input / suggestions appreciated.  Contemplating re-designing with primary secondary pumping loops. “BUT” I’d like to be confident it’s the correct recommendation and I’m just not understanding / appreciating this system as installed. Which may be salvageable.

DanHolohan

It could possibly be this:

http://www.heatinghelp.com/article/11/Hot-Tech-Tips/139/Banging-Zone-Valves



And if it is, know that you're the first. :-)



Others?

Jimfxstd

On the right track

Absolutely! That's one of the causes. I had that same noise in my house (along with many customers) and it drove me Crazy in the past. One of those zone valve manufactures (a double return spring manufacture) recognized that problem too and has developed a clutch assembly on top of the zone valve motor to slow the valve closing speed down. Some jobs it helps others it doesn't. The "Solution" I've found is to relieve the energy of the water in motion. Doesn't matter where the zone valves are positioned (supply or return) the water is traveling at "X" amount of feet per second equally through out the system. Another thought, If the valve slams closed and the water comes to an abrupt stop on the inlet side (bang) what does the water on the outlet side do?? That's right, it stops & snaps back real quick too! (Bang)! And if the water is hot enough just think could the sudden low pressure/Vacuum cause the hot water to flash to steam for a Mili second, collapse & bang back???? Sound like water hammer in a steam pipe(What if!). Back to the solution! A differential bypass in parallel with the zone valve will "relieve" that velocity & energy by opening & allowing the water to gracefully slow down & then will close when the energy is gone. The bigger picture (this can of worms system) is this systems design as far as I can see. With out doing the math this system sound like a faucet running, grossly over pumped! The water must be traveling at a tremendous rate (Feet per second). I did a quick calc. with my trusty old System Syzer Calculator and found the gallons per minute is close but the existing pump head is through the roof verses what it should be. My Tech called the manufactures rep regarding the "Triple Duty" valve and asked What the #$!! is this and what does it do? Third hand the response was Oh, that device regulates the flow & you set it by running the system and setting by the circulator motor amp draw (????). Common sense tells me if we "Throttle (Choke off) the water flow at this valve hence we create "MORE" velocity noise from the water molecules forcing their way through a restricted opening. And as we all know sound LOVES traveling through pipes!! That's no good.

This is not a factory, it's a "BIG" home. Could this design possible work quietly as is OR should we re-design it using principle's we've been taught over the years of primary / secondary pumping?? Would be nice to have a variable speed pump driven by the correct Tekmar + a large differential pressure bypass to dump excessive energy / pressure when most zones are closed.

Comment's & idea's appreciated.

DanHolohan

I would try

removing the pump's impeller and running it on just the shaft key. It's so oversized that wold probably do the trick. :-)



A properly sized pump with a relatively flat curve would also work.



Anyone else have any thoughts?

Constantin

What does the customer want to pay for?

This system seems to have many improvement opportunities, the question is: what does the customer want to put on the table to fix it?



First, I'd see if the customer is willing tpay for a diagnostic of flow needs vs. actual supply. My guess is that the system is completely over-pumped. In fact, this customer should consider applying for the local electric heating rate considering the amount of heat that the pumps are putting into the water.



Once you've used something like Siggy's program to determine the flow needs of each zone on a design day, you can go about figuring out the best way to deliver the required amount of BTUs to each zone. One nifty thing you can do is to pair zones which have similar head characteristics, then put a &Delta-P variable speed circulator in front of them. Add zones to the pump until you hit the GPM capacity wall at whatever head you have on your hands on a design day. That will save the customer a great deal of cash on the pumping and solve the banging zone valves also.



Next, I'd take a look at the near boiler piping. It looks like the three boilers are not set up with individual circulators, which is a great way to create ghost flow. That is, all the water in the main runs through each boiler and since they look to be atmospheric units, they'll vent all that out - either into the boiler (hot in there?) or up the flue. Either way, an individual circulator for each boiler on a primary-secondary header seems like a better idea. Chances are, all three boilers are not needed anyway, I'll wager that this house has way too much heating capacity vs. heat loss. So, how big is it?



But it all comes down to what the customer wants to live with vs. pay for. To me, self-destructing components, etc. are not a something I'd tolerate, but every customer has different preferences.

Steve Whitbeck

pump

Looks like a good place to install a variable speed pump. I would use one that you can preset a certain ft of head.

Another solution would be three way bypassing zone valves.

You need to change the pumps though. That much water flow has to be causing erosion in the piping due to excess velosity.

Big Ed_4

Garage Zone

I would think the problem is solved with the bypass unless there is other issues ... That small garage zone loop should have been piped separately from the massive main system ...

Mark Eatherton

If a little pump does a little good, then....

a LOT of pump will do a lot of destruction...



In your post, you said the one and only pump, but I see two pumps with no check valves.



If these pumps are not being operated at the same time, much of the pumps capacity is spinning in a vicious circle. The only way to know for sure wood be to observe the non operating pump while the other one is running. If the impeller shaft of the OFF pump is moving, you've got a problem, other than the fact that these pumps are grossly oversized.



My recommendation would be to undertake a complete design/re-engineering study, and install a variable speed circulator that can meet the needs of the system.



You should also check the boiler sizing to make sure you are not driving any other tacks with sledge hammers...



As for the zone valves, once you address the oversized pump situations, the banging should subside. If not, time to start looking for valves installed backwards.



Typical over engineered, under designed residential system.



ME

Jimfxstd

Headed in the right direction

Looks like the reality is a re-design using as much of the system piping as possible. I like the idea of isolating the boilers with pumps, flow checks etc. and making the system a big loop. Will need some help-consulting sizing the pump replacement (recommendations appreciated), want to it right the 2nd go around. I like the variable speed pump application, don't think the existing Tekmar 264 will manage a variable speed pump (a shame).

On another note this system design incorporates a "Triple Duty Valve" right after the pump. What is the purpose of this device other than throttling??

Many thanks!

Mark Eatherton

Stop, check, and choke...

http://www.bellgossett.com/productPages/Parts-Triple-Duty-Valves.asp



Like driving with one foot on the gas and one foot on the brake pedal... And there is NO backing down the highway :-)



ME

Jimfxstd

That makes sense!!

OK, so instead of putting in the correct pump, over size the pump & choke it!!! Sounds like a great way to spend additional money (un necessarily!)

This system has 2 sets 2.5" copper of mains (supply & return). One for the 1st floor & one for the 2nd floor. Construed as a ladder system with the air handlers "T"ed appropriately with 1" branches. I'm leaning towards the following solution.

A)Figure the "Correct" pump base on load & existing pipe sizes(assumed much lower head with appropriate GPM)(Variable speed if available).

B)Correct piping to main circulator pumps from 1.5" to full size.

C)Remove the triple duty valve and add it to my mooring anchor.

D)Remove circuit setters from ends of mains.

E)Install 1" differential by pass valves in parallel with zone valves at air handlers and remove circuit setters.

F)Install pumps, & flow checks on 3 boilers.

G) Cross connect supply & return main @ boilers to establish a main "Loop" past the boilers instead of 100% through the boilers at all times.

H)Add a Tekmar variable speed pump controller.

**I'm sure there will be additional items Incorporated into the design as we move forwards.

Mark Eatherton

Stock up on sawzall blades....

I suspect that if they oversized the pump stations, they most probably oversized the piping system as well. Figure on some means of air elimination higher up in the system than normal, and at a minimum the ability to force purge the FCU's



Good luck



ME

Jimfxstd

Air elimination

Do you think we should anticipate air problems??? They did put a large capacity spirol trol air eliminator just before the main circ.pump. I was pleasantly surprised to see that piped in correctly. See the Pic's below. We could certainly give some thought to an auto air eliminator up high some where in the system. The only reservation I have is installing another serviceable component remotely if not necessary.

Mark Eatherton

A good clean initial purge is key...

to a trouble free system. With lines sizes of 2-1/2" and 3", it is going to be tough if not impossible to perform a forced power purge on the system. Systems like this typically are bottom filled, and manually top purged or vented. If there is anywhere on an upper floor where air can accumulate, it will, and it could cease flow.



Water, and similarly air, are like my ex brother in law. Wet (except for air) lazy, and stupid. You MUST tell it what YOU want it to do, because if you leave it up to the fluid, it will do what IT wants to do, and that probably doesn't match what you had in mind.



Just think like air when looking at the system. The Rol-air-trol works great once you establish good flow, but really has no value in initial fill and purge.



ME