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Vac System Retrofit Doozy

Longtime reader, first time poster. I walked into a system that was recently installed that was acting up 10 ways from Sunday. I have been talking about this with every steam guy I know because it's just driving me crazy and I find myself second guessing myself. Be advised this one is long so get comfortable and proceed with caution.

1. Building is from 1923, old Herbert boiler abandoned. From pipe sizes believe it was originally a vacuum system but have no way to confirm.
2. At some point, someone installed two cast iron boilers on the other side of the building, creating a new boiler room and made the whole system gravity return. The building never heated right, everything was terrible, no big surprise. One of the boiler's sections cracked really badly, decision was made by the client to buy a new boiler.
3. A new cast iron boiler was installed which is slightly bigger than the older one that was still operating. The two were connected with a new common header.
4. A new vac pump system was installed next to the existing makeup feed tank and pumps. A chemical feed system was also installed.
5. Startup was done and immediately the problems started. The new boiler kept intermittently going off on low water and then flooding. The boilers started dumping into each other. The header is flooded. The feed pumps feed when they shouldn't. There is water stacking up absolutely everywhere and then eventually coming backing to the boiler and tanks and flooding everything.
6. It was recommended by someone to install some pressure differential valves in the feedwater piping to each boiler to prevent the siphoning issues so this was done.
7. All the traps throughout the building have been replaced or at least had new guts put in.
8. I'm told by the installers that it's something the startup people did when they set up the boiler controls.
9. So I get dragged over here because the startup folks are frustrated with the installers and vice versa.
10. The new common header was piped according to the project engineer's hand-drawn diagram and not according to the boiler install manual which is the steam in from boiler #1, steam in from boiler #2, steam out to building, pitched down toward drip leg on the end configuration. It's got a sidewise 90 off the one boiler takeoff to start, no swing joints, both boilers go into a common drop header with steam coming from both boilers on either end, the drip leg in the middle and three takeoffs out to the building which go to motorized zone valves in the middle. Hartford loop looks okay although the piping is 1/2" too small. The valves open fast and close fast which causes water to get sucked up into the header and even in from the feed tank.
11. There is no equalizing line. Not from the vac pump to the boilers, not to each of the zones, nada.
12. Vac pump is short cycling.
13. Boiler pressure is set to 5#.
14. I pull the strainers at the drip leg and off the vac, both are plugged. Not surprising since we've been blasting chemicals through piping from the 1920's. Once the strainer is clean, vac pump starts pulling a nice steady vacuum. Okay.
15. I'm told by the engineer that the boilers need to be at 4 or 5#, that they are happy there. I think that's insanely high for a vac system and I say so but I'm met with strong disagreement so I leave it alone for now.
16. I pull the fitting at the bottom of the header and water and mud come out. It's obviously in a deep vacuum. The little trap off the drip leg is going absolutely 100 mph trying to dump water.
17. I ask that the valve actuators be slowed down.
18. I recommend that an equalizing line be piped to each zone valve as per the manufacturer specs.
19. Nothing can be done about the header, it's too expensive to redo all the piping and the piping guy says there's nothing wrong with it so it's staying. I recommend a vacuum breaker just on the header.
20. I recommend motorized valves on the boiler feed pumps, blowdowns on the strainers so the mud can be cleaned out and a bigger trap off the drip. All of this is done.
21. Then I get a call that there is condensate stacked up all the way to the radiators in the zone farthest from the boiler room and also that the old boiler room flooded. What the funk.
22. I find the engineer draining gallons and gallons of water out of radiators. In the old boiler room, I find a condensate pump and tiny tank that apparently none of the installers knew was there which pushes water the 12' up and over the old abandoned Herbert boiler and back into the return line that runs all the way back to the new boiler room. It is, of course, open the atmosphere. Put my hand by the vent and it sucks my hand right to it. Alrighty then.
23. Pump guy comes out with a piping diagram from 1957 which shows condensation pumps on a vac system installation. Installers agree to change the piping.
24. I also find that the zone here is zoned yet again, to two separate areas. There is a section of the building that is not used that overheats horribly so the client wanted to be able to shut off steam to it to save on energy. I am not a fan of zone valves on a vacuum system period, I think simple is best but what's done is done. They're tied into new stats out in this very old, very brick and concrete building that talk to wireless sensors. Oh boy.
24. All is right with the world until it got to be 10 degrees here and no one noticed that the new combustion air in the boiler room was put a foot away from the return piping and left wide open. Once all the cracked piping was replaced, reports have since been good.
25. Then I get a call that I am getting uneven heat out in one of these "sub-zoned" areas. I'm assuming a sensor dropped signal or something but I'll know more tomorrow.

So here are my questions because I have gotten so many different opinions on this, my brain hurts. I have been told by the project engineer that me asking for an equalizing line is stupid, he fought me tooth and nail on it. He's installed ten of these systems before he says, no equalizing line and they all work perfectly. He also thinks my hesitation about zoning is foolish. You should be able to control each zone with wireless stats no problem, doesn't matter if the system is vacuum or not. This has not been my experience but okay. Then the piping guy tells me that he's never in his life heard of putting in swing joints in the header for a cast iron boiler and see above comment about how he feels like there's no issue with the header. Have I lost my marbles? Have you guys seen vac systems out there with no equalizing lines that don't have issues? When you have the choice do you zone or not zone? Will I go to heating hell if I sneak in there and crank the boiler pressure down to a pound or so?

This post is ridiculously long already so I didn't include photos but I do have them if anyone wants them. Thanks so much in advance for reading and for any comments or opinions you may have.

Comments

  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    Seeing you don't need gravity to get the condensate back (vac pump) I would think zoning would work ok. Yes I would be sure the valves are sized correctly (don't line size) and have slow actuators.

    Should have swing joints but I have seen plenty without them. probably a lost cause

    Not getting what you are thinking with "equalizers" for zone valves and vac pump.

    I have yet to see "wireless" anything work reliably
  • OldschoolboilerOldschoolboiler Posts: 4Member
    Thanks Ed. I think the zoning will work okay now with the actuators adjusted it’s just not my preference thus why I’m curious what people think about zoning a vacuum system when you have the choice. For the equalizing lines to the zone valves this was based on the vac pump manufacturer’s recommendations. How would you pipe it?
  • AMservicesAMservices Posts: 420Member
    I would tell them that if the system isn't piped the way the people that manufacturers the equipment want it piped ( you know? The people that tested all this equipment and know how to get the best performance and most efficiency from their products. The people that print these installation manuals so the people looking to install their equipment will know how to price the job and they don't have to re invent the wheel.
    If the piping isn't done how the manufacturer wants it done, DONT BOTHER ME!

    And you need a vacuum equalizer one large two pipe steam systems.
    It's purpose is to prevent the vacuum level becoming deeper on the supply side.
    Deeper vacuum = lower pressure.... high pressure goes to low pressure, always.
    If a zone is filled with steam and the valve at the start of the supply closes, a vacuum will form very quickly and cause steam and condensate to move in directions it's not supposed to.
    All kinds of strange things will happen.
    You can't save a person from there own stupidity.
    I hope for the people that need that heating system you can make it right for them.

    And let's see some pic's

  • OldschoolboilerOldschoolboiler Posts: 4Member
    Strange things is the name of this game for sure. And I know I had boiler water being sucked into the header when the valves opened because all of the sudden the boiler would go off on low water and then the trap off the drip would be going crazy trying to dump it.

    Here are some pics:






    Here's the little pump down in the "old" boiler room:


    And here is the weird sidewise elbow takeoff:





  • SteamheadSteamhead Posts: 13,114Member
    They welded the header. And it doesn't look like the risers to the header are tall enough.

    You can't fix stupid.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
    https://heatinghelp.com/find-a-contractor/detail/all-steamed-up-inc
  • adambnycadambnyc Posts: 258Member
    @Steamhead always learning and had quick question. The main risers look really short. I don’t see an equalizer coming off the header. It looks like you’d get a lot of wet steam, and a lot of boiler water getting pushed straight up into the header and out into the system. are systems this large usually piped without a equalizer coming off the header? Maybe some other way to return the wet steam that I’ve never seen?
  • AMservicesAMservices Posts: 420Member
    @Oldschoolboiler "The new common header was piped according to the project engineer's hand-drawn diagram and not according to the boiler install manual"
    Was it formalized in crayola crayon on construction paper? Would have made it easier for the other people involved
  • AMservicesAMservices Posts: 420Member
    When there's a pumped return, a equalizer piped off the header, is not really doing the job it does in a gravity return. It acts more as s drip. And it does look like it's there.
    The risers had plenty of room to be taller. The boilers should of had their own drop headers and then dropped into a common drop header, with a drip back to the condensate receiver tank and the supplies to the system.
    That how I would have colored it.
  • PumpguyPumpguy Posts: 379Member
    I wasn't able to digest your whole post, but from what I've gleaned, a big problem here is induced vacuum due to steam condensing in the headers.

    You really do need equalizer lines. @AMservices post describes perfectly the reason why. And if you have steam zone valves, there should be an equalizer line just downstream of each zone valve.

    The attached file shows the piping arrangement. You can use either a dropped check valve or thermostatic radiator trap in the cooling leg. The purpose for dropping the check valve is to trap some water and provide a water sealed check valve seat.

    With a separate boiler feed pump set that is vented to atmosphere, there should be positive closing valves on the boiler feed pumps' discharge. A simple swing check valve won't do.

    What appears to be happening is steam is condensing in the header which causes an induced vacuum to occur. With the boiler now under a vacuum, atmospheric pressure pushes water out of the boiler feed tank, through the pumps, and into the boiler and headers, causing the flooded problem you describe.

    A positive closing valve on the discharge of the boiler feed pump will prevent this. This positive closing valve should be wired to open only when the boiler feed pump is running.

    This is a problem I have run into several times before. I have heard stories where equipment representatives have tried to explain these problems to the consulting engineers, only to be told "I DON'T CARE ABOUT YOUR EXPERTISE, THIS IS WHAT I WANT!" So then the poor facility operator and their own steamfitters have to deal with the problem later down the road.
    Specializing in vacuum pumps for steam heating systems, especially older Nash Jennings units. We build new ones too!



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  • BobCBobC Posts: 4,970Member
    edited January 2018
    Anybody that does not follow a manufactures instructions without good reason is a moron. I wonder where that engineer bought his license?

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,914Member
    Boiler header doesn't look like 24".

    The sideways elbow is fine

    The boiler risers are 5" ips

    We all know nobody is going to screw that together
  • OldschoolboilerOldschoolboiler Posts: 4Member
    You don't think that sidewise elbow is going to cause a trap? I've seen it happen before, it's not terrible but they had plenty of room to pipe it right. I disagree about not screwing the header together. I was brought up that you were always supposed to do that with cast iron, all the jobs I've put together have them. There's actually an install company we joke about here in my area- you can always tell they did the install because the headers are all welded together the same way. Whenever we get a call for a cracked sectional, the first thing we look for is their signature header.
  • LanceLance Posts: 138Member
    If I may be so bold. Because their way didn't work they are right? Disbelief of truth is a psychiatric issue often affirmed by a lack of money to fix or accept the errors. The measure of a person is not in the problems we make, but how we fix them. In my career, I found all complicated things must be right before all will work right. Three possible causes, low budget, low bidder, or lack of ability. Anything else would get too personal. Boiler is the heart, the pipes are the body. Can't have one without the other.
    Anyway I look at this, it is a huge challenge to make it right.
  • AMservicesAMservices Posts: 420Member
    Maybe it would be cheep To cut in expansion couplings.
    You know they gonna end up with a crack section if they're running the pressure at 5PSI.
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