Galvanic action

Steve_45

If I'm using 1 1/4 Black Pipe out of my Bolier and am
building a manifold, do I gave to be concerned about
the four 1 1/4 copper male adapters that will thread
into the four iron tee's? If so what product could
I use? Also, if I simply use 1 1/4 copper instead of
1 1/4 Iron for the manifold(short distance on primary
loop of P/S, total 20 feet) will that change the gpm
thru the primary a great deal?(need 16 gpm thru primary
for the four zones)
Thanks,
Steve

clammy

die electric reaction

You could use steel pipe right to your pump flanges or you could use die electric unions npt female x sweat there avaible at most plumber supplies or you can get them at graingers good luck i use them all the time a worthy investment but not used by everybody have to keep costs down somewhere peace

hr

Copper to

steel or iron is not a problem. Keep in mind this is, or should be, a closed system. as such the O2 needed for corrosion will not be present, as it would at an open connection like a water heater.
It also has to do with the relative surface area also, the amount od copper to iron.

A brass nipple could also be used if you want another protection zone.

hot rod

hot rod

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Kal Row

agree - use Di-electric unions

not to expensive

http://www.plumbingsupply.com/leftright.html
about halfway down on the page

Mark Eatherton1

My experience with dielectric unions...

has been less than favorable. They generally cause more damage than they prevent due to leaking gaskets etc. If it is a concern, use a YELLOW brass nipple or adapter to isolate the disimilar metals.

In my 30 years of experience, I've taken some pretty old systems apart, and many of them had disimlar metals intact, and I've only seen strange inexplicable crystaline growth one time. And even it that case, the boiler was working fine and had not leaked in over 40 years of use.

Personally, I don't worry about it, but if I'm swimming upstream (against an engineer HO or persistent inspector) I'll use a YELLOW brass nipple.

ME

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Kal Row

always wondered about that

why is it that dielectric unions leak - but the round pumps gaskets don’t - and also why don’t they sell flanges with one side flat, and one side with a pump-side like circular channel for a pump type gasket – it seems like the best way to go instead of unions at all

joe_6

Dielectric

So Mark ,you do not use dielectric unions?Sure would save money not using them.I agree,i have sen old systems without them,no leaks at all. dielectrics leaking after few years.Some plumbers use them some dont.i cant make up my mind,think i will not use them for closed systems.Thanks.

mph

Brass unions

I have also given up on dielectric unions. Too many hardened gaskets that start leaking after a few years. I now use brass unions exclusively. No leaks; except on occasion when there is glycol in the system. A thin coat of pipe dope on the union faces takes care of that.

Jeff

Ken_8

Totally agree with ME

I have yet to see an application where dielectric fittings were needed or served any purpose. If however salt water is nearby or some other ion active element... That's a whole 'nother magilla.

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Steve_45

Thanks!

Thanks guys for your input. I feel alot better
about making my decision. Would someone help me out with
the second part of my question. Chart says 1 1/4 copper is only good for 14 gpm flow. My thinking is four zones, let's say an average of 25,000 btus on an average of 125 foot runs is 16 gpm(4x4gpm....3/4pipe) It's not like I can change my circulators since I already have four Taco 007's. The boiler has 1 1/4 in and out holes. I'm thinking go to the primary circulator with the 1 1/4 black pipe and then from the other side of the circulator use 1 1/2 copper for the primary loop. Then reduce back to the 1 1/4 just before entering the return on the boiler. The 1 1/4 Iron return then becomes the limiting factor giving me 17 gpm as the limit since the iron flow rate is 17gpm.

Mark Eatherton1

That is correct Billy...

I do NOT use dielectric unions. I won't even use them on a water heater. THe amount of corrosion that builds up inside the union from its own disimlar metal mixes is enough to cause it to clog in less than 5 years. I've got pictures floating around somewhere...

I've found that a disimilar metal mix does less damage than does the dielectric unions, and have even gone as far as proving it to a city to the point that they quit requiring its use.

Your milage may very depending on use...

ME

ME

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Mark Eatherton1

The limits about which you speak

are based on the need to sweep air back to the removal/recovery system through vertical down flow pipes, and avoiding continuous exposure to velocities that can generate objectional noises. Primarily its a noise issue, and with it being in the mechanical room, I don't think it will be a big deal, especialy if you pay attention to the need to ream your pipes to full bore.

I also see an error in your math. If your branch loads are 25K butH, and your delta T is 20, the flow through the branches are only 2.5 GPM each for a total of 10 GPM for the whole.

Then there is the time diversity factor. How often are all four loads going to be running at 100%?

It's good to see you thinking in this direction, but I fear you're overthinking the situation. Just because there are 1-1/4" holes on the boiler doesn't limit the flow to an
1-1/4" pipe size. If you change the delta T to say 30 degrees, the whole shebang changes.

Got drawings?

The best example I can think of as it pertains to running pipes outside of the recommended velocities happens every day in your own house. The 3/4" water service coming into the house should be limited to 4 gpm, but its obviously not, and I haven't seen my own service jumping off the wall due to excess velocities.

I personally think the case is overstated and has been for quite some time. I've force the issue before and didn't suffer.

Quoting form the ASHRAE 1989 Fundamentals handbook, "Piping noise. Closed loop hydronic system piping is generally sized below certain arbitrary upper limits, such as velocity limits of 4 f.p.s. for 2" pipe and under, and a pressure drop limit of 4 feet of head per 100 foot pipe length for piping over 2". Velocties in excess of 4 f.p.s. can be used in piping of larger sizes. This limitation is generally accepted, although it is based on relatively inconclusive experience with noise in piping. Water velocity noise is NOT caused by water velocity, but is caused by free air, sharp pressure drops, turbulence and or a combination of all of these which in turn cause cavitation or flashing of water into steam. Therefore, higher velocities may be used if proper precautions are taken to eliminate air and turbulence" End quote.

Earlier in this same section, it is stated "Erosion in piping systems is caused by water bubbles, sand or other solid matter impinging on the inner surface of the pipe. Generally, at velocity of 100 f.p.s. erosion is not significant as long as there is no cavitation"

It goes on to speak to slurry systems where high velocity should be avoided.

So, based on this, if you do a good job of air elimination, avoid sharp turns and such, your 1-1/4" pipe is capable of carrying about 400 GPM...:-)

Go with 1-1/4" on your near boiler piping and sleep well my friend:-)


ME

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Steve_45

Mark I can't thank you enough for your complete and thorough
answer. I guess this is way the wall is so great, people like you taking the time to help. Yes I'll sleep alot better
believe it or not. I'm really looking forward to doing this
job. I'm retired and need to keep busy.(Our house two story
with daughter and grandkids upstairs. Don't want to screw up) About the flow rate of the loops. I know that the 25000btu's would need 2.5 gpm, the literature says 2.5 gpm
BUT do the circulators know that the loops only need 2.5
gpm. I'm assumming, since these 007's do not have any type
of control, they will pump at the max. Should I be putting
some type of throttling valves in each loop to limit the flow to 2.5 for best results?

Mark Eatherton

Choke'm back podnah...

You're correct. They have NO idear how many gpm you need.

But they really don't care either:-) If you let them do whatever they want to do, the delta T will be less than you thought, but the btus will still be there. To avoid possible noise issues, I'd throw a balance cock into te mix.

ME

Steve_45

Thanks again Mark! And to all the guys for their help with the galvanic part of my question. I'll post some pictures when it finally gets done. It may take awhile. Been doing all my homework first, left over habit I think :-)
Steve

Larry Weingarten

just a mention of water heaters...

Hello Mark: For water heaters, I've found that coming out of the tank with a lined steel nipple and then using a copper flex gives a true dielectric and puts distance between the dissimilar metals. Yellow brass doesn't work well around here as white tubes grow inside. Our water can be pretty impolite.