Two-pipe Counterflow-- boilerfeed pump question

Mad Dog

We steam psychos love this stuff. Mad Dog

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Mark Woll_2

Two-pipe Counter-flow; new boiler & feed pump, what the heck????

The job is a very large old stone house with two-pipe steam, but it's counterflow! Yes, two pipe. No end of main drips, the whole thing pitches back to the boiler, into a huge 6 inch header. Approximately 950 EDR connected load.

Question is how to properly plumb the new boiler I'm installing?

Original boiler was replaced in '87 by good hot water men, they installed a vastly oversized boiler and ran a boiler feed pump. That boiler ate its sections above the water line. However, no noise and good, but expensive heat. No insulation on mains at this point.

I have properly sized the new boiler, but I am wondering how to plumb the header drip/equalizer to account for all that condensate coming back into the boiler due to the counterfeed mains. With normal (non-counter-flow) piping, only a small amount of the near-piping condensate would go right into the boiler the rest would head downhill to the main end, but here it'll be a pretty good amount of condenstate I think coming all back to the boiler, so shouldn't it really go to the condensate receiving tank with all the rest of the return water to be properly fed with the pump? I'm thinking with the smaller boiler I'm putting in, there will be a flooding condition in the boiler as the mains condensate will bypass the boilerfeed pump system.

Let me know what you all think of this, here are some brainstorm solutions:

1. Install a F&T on the equalizer about 1-2 inches above the waterline, piped back to the receiver to divert any excess condensate (like what's used on a two boiler job).

2. Install drips on the mains near the beginning (the low point) into F&T traps.

3. Install a whole new header with the normal equalizer, take two vertical takeoffs and pipe up, over, then down to the retained old 6" header (it's pretty low to the floor 57 inches), the old equalizer now piped solely to a F&T to drip the old header.

Any suggestions would be very helpful. Thanks.

Unknown

I like #3

I'd do this, I think.

Noel

Mad Dog

Noel is the Man!

Exactly what I would do too! Mad Dog

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Mark Woll_2

Noel, Mad Dog, Thanks for the suggestion. A thought, however....if I pipe it the way you drew, then the mains' condensate still returns to the boiler directly, bypassing the boilerfeed system. This does not seem to solve the problem of excessive condensate return to the boiler leading to a flooded condition or an inappropriate raising of the waterline in an already tight headroom situation.

Unknown

OK

I see the confusion. There can't be flooding because the pump won't run until either A. You have a pump tank with a float in it to run the pump AND the water goes into the pump tank to trip the float....or B. You have a pump controlled by the boiler water level and the boiler needs water.

Neither would flood the boiler, because it isn't NEW water from the street in the mains, it is water that was already in the boiler. The water line at cold rest is the most water that there is in the system, ever. Unless you add new water while running, you won't have more than that in the boiler (flooding)

Said clearly, You won't flood the boiler with the condensate that came from the steam from the boiler without added water.

The tank won't pump water until water gets to the tank because the system won't be low until then.

Of course, flooding can come from other reasons, like steam in the returns holding radiator traps shut and filling radiators with condensate. The piping shown won't hurt or help that.

Noel

Mad Dog

YEAH!!!!!!!

that's what I wuz thinkin to. and if ya pipe a nice big header even a nice drop header and make nice dry steam, your boiler will not be losing so much water/condenstate...listen to Noel - he knows. Mad Dog

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Steamhead

One more thing to ask-

is that return pump really needed?

I'll bet that system originally had a Return Trap that failed, and someone decided to replace it with the latest mechanical return device.

But why did that Dead Man install a Return Trap in the first place? Because the dry return was a "B" dimension (see "The Lost Art of Steam Heating" for details), and the boiler pressure could not be controlled closely enough. Excess boiler pressure could cause water to back up in the dry return. The Return Trap prevented that.

But now we have Vaporstats. These very sensitive pressure switches can control a boiler's pressure down to the ounce. With this type of control, mechanical return pumps are not needed to overcome excess pressure. (Noel- think of your systems at Colby-Sawyer, the best-running Vapor systems in all of New Hampshire!)

Measure the height between the top of the boiler's sight glass and the bottom of the lowest point of that dry return. You can allow a pound of pressure for every 30 inches of this height. I'll bet that system will run fine on 8 ounces or so. If this proves out, you can do away with the return pump. Just make sure to install a big vent on the dry return, to vent the air coming back from the radiators. Use at least one Gorton #2, which is also a good choice for venting the steam mains.

As for piping the new boiler- Noel and Mad Dog have it nailed. Be sure to insulate all that pipe!

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steve_6

piping

How long are the mains?? Are the mains 6" or just the header off the boiler? What brand of system is this? What type of steam traps are on the radiators, water seal or thermastatic? Did you find any vents on the radiators? Was there a pressurtrol or a vaporstat installed on the system?

Mark Woll_2

AHA!!! Of course it won't flood! You guys are right!! Steam, this is a very peculiar beast, seemingly never tamed; always ready to confound even smart, good hot water men!

Naturally, the condensate will return to the boiler, fairly quickly I hope and not trigger the boilerfeed pump's McDonnell 150. It should be ok, unless there's a big delay and the 150 calls for water. I have no idea how fast the mains condensate will return though I guess it could be calculated and the quantity measured.

I don't want to get rid of that beautiful 6 inch header, I'm thinking about installing a brand new header with the usual equalizer, then sending that steam to the old 6 inch and dripping that monster with a F&T. Any suggestions or diagrams for that piping?

For Steve's questions: System is circa 1929, Philadelphia, PA, Warren Webster, thermostatic traps on all radiators (5 mostly in the 3rd floor servant's area) and convectors (22 of them of various sizes all beautifully recessed with flush plastered fronts) seemingly absolutely top of the line stuff, no loops that I have seen, nor any wet returns discovered. Mains, 2 of them initially 3 inch, approx. 70 feet long, tapering. Previous guys in 1987 gutted old boiler and some of the return piping, may have indeed taken out a nice "cast-iron ham". No way to know.

Unknown

could you draw what you want to do (in paint)?

I'd be glad to help. You might be able to do away with the pump, as Steamhead said, too.

I've done that with success.

Noel

Mark Woll_2

Attached is a crude diagram, the little circle is the new 3 or 4 in header, the big is the existing 6 inch, the little box is an F&T. This one presumes retention of feed pump.

Mark Woll_2

Noel, see attached picture, the boiler is piped to a brand new, higher header, and dropped to the old 6 inch which is dripped into a F&T (the small box) and piped to the dry return. This presumes retention of the boiler feed pump. I guess I could directly pipe the new boiler to the old big header and use the old equalizer into the new boiler and possibly avoid using the pump.

Unknown

won't open

can you put it up as a .jpg file?

Mark Woll_2

Jpg diagram of proposed piping

Unknown

that'll work

That will work with or without the pump tank. The tank stays unless you use a L408A 1132 Vaporstat to keep the steam pressure below one PSI.

You don't have any fan coils or air handlers on this system, do you?

Noel

Mark Wollman

Noel, thanks greatly for the input--- no air handlers, no coils, just convectors and radiators, and 16 feet of 1960's installed baseboard (appears to be properly pitched with, imagine!! a thermostatic trap!). Incidentally, We're using Dan Holohan's 1.5 pickup factor to calculate the new boiler size, with all that metal, I suppose it'll be needed.

Also, the engineer interestingly suggested that we repipe all the mains to properly slope away, having never seen a counterflow two pipe (I hadn't either). Would love to have seen the original setup, though before the butcher job.

Unknown

best of luck to you.

On that old system, there is a certain steam pressure that is exactly the pressure that the system pipes turned out to work best at, the sweet spot. As you get near it, by starting above it and cranking it down, the cycle length will start to get nice and long. The steam will build slowly, much like at startup, and cut out on pressure. It will fall back very slowly, because at the sweet spot, there is no pressure (to speak of) to quickly drop off. It stays off quite a while. When it comes back on, it runs longer because of the cooling off without much change in pressure.

Try it.

If you get too low, steam won't reach all of the radiators. If you get too high, the shorter cycles will come back. No harm done, though.

If your pickup number turns out too big, short cycles will result. If it is too small....HIGH fuel bills.

Noel

Mark Woll_2

Thanks

Mark Woll_2

photo of nearly completed big residential steam job

Here's a picture of the 70% done job. Weil-McClain LGB4. Brand new four inch drop headers to old 6 inch header which is dripped into an F&T. All new flanges, all new Anvil cast fittings (a fortune $$), etc. Used 95% American made fittings and valves which the guys at my supply house thought I was an jerk for insisting on.

Only reused parts were the McDonnel & Miller 150 pump controller which was disassembled and cleaned; and the boilerfeed pump and tank, also cleaned and inspected.

Threw away "master trap" above condensate receiver.

I added a second boilerfeed pump (I found a virtually new one on Ebay for cheap) to make the system true duplex. I engineered a duplexing pump electical panel which provides for alternating pump use and engages the dormant pump in case the primary fails.

I enclosed all the conrol wiring in a 12x12" NEMA 12 box attached the boiler jacket to neaten things up (not illustrated yet) and used nice conduit on the boiler jacket to run the wiring to the controls.

Added a Dwyer Magnahelic supersensitive pressure gauge (0-40 inches of water range which equals about, what? 2 psi at top of range) and vaporstat.

No pipe insulation yet in boilerroom, awaiting quotes.

Still, we ran it last night for first time. Heated the whole 6000 sf house, every radiator, preliminarily, on only 4-6 ounces of pressure! How can this be?

Steamhead

Try Again, Mark

the photo didn't attach.

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Mark Woll_2

another try with photo

photo should be attached

Unknown

How can this be?

Engineering. The mains are usually sized to only lose 2 ounces per HUNDRED feet of pipe.

They done good!

The sweet spot is just barely above the pressure that heats the last radiator all of the way across. Once there, the run cycles will be quite long, and the off cycles will be pretty long, too. There isn't pounds and pounds of steam pressure cooling and collapsing like crazy to bring the boiler right back on. Since the load is constant, and being met below this high pressure, the pressure will jump right back up quickly, and off it goes again on steam pressure.

The high pressure short cycle.

The sweet spot that you have found makes longer cycles, makes fuel costs lower, and is kinder to the chimney liner.

Nice piping job!

Noel

Mad Dog

Way to go Mark....very nice job

I love your nice blowoff drains ...a serviceman's dream....Mad Dog

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Mark Woll_2

thanks

Thanks guys, not too many people appreciate a piping job, and judging by what we've all seen out I wish a lot more guys had the guts or discipline to do stuff the right way rather than the quick way. Time of course is really the issue and I'm not sure how to solve that one.

Electrics is another thing I've been spending a lot of time on for this project, and I'll post up some pictures of that shortly. I've been using hinged NEMA 12 (UL rated industrial enclosure) boxes usually in approx. 12x12 sizes mounted on the jacket and installing 2X14 wiring block terminals therein to really neaten up the stuff. Certainly not essential but I like the look of fine industrial equipment.

The addition of the 2nd boilerfeed pump caused me to think long and hard about how to duplex (alternate) two pumps. How would you guys build from scratch an electric circuit that would alternately run each pump every other time to equalize wear, and also provide for complete backup, i.e., the dormant pump will operate in the event the initial pump fails?..... and without buying an expensive dedicated Hoffman pump alternator????

Well I came up with the perfect solution....stay tuned.. Mark

Mark Woll_2

Completed system photos

Guys the boiler which generated this thread is now completed except for the insulation. Pictures for those who are interested. Thanks for all your input and help. Works fine, noiseless, too.

Steamhead

Looking Good

aren't those drop headers great?

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