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.