New boiler problems

airhead

I was sent to evaluate a system in a newly constructed building. The load on the system consists of 2 rooftop AHU's & indirect DHW. The system uses the condensate recievers to vent the air. The pressure is set to 5psi hi fire then 8psi lo fire. There are vacuum breakers at the boiler and each AHU. The problem is that it surges very wildly and on startup {morning warmup} the water level drops faster than the makeup pumps can refill system. It has been treated and been skimmed. It is my feeling that 1 the pressure is set too high 2 there should be #76 vents at AHU'S 3 that there is still contaminents in the water. The problem is that the ENGINEERS wont allow me to change anything. Any suggestions on how to approach this. I am just a tech trying to do the right thing. THANKS for any suggestions. Checked near boiler piping is ok

Gary Fereday

Brainstorm here!

Is the steam side of the system insulated? Is the steam side of the system graded to carry off the condensate. i.e. traps at low points. ( does the water overfill the boiler after warm up ?) (excess condensate from the surges most likely does this). When the ENGINEERS are not looking set the steam pressure lower and see if that stops the surging. Yes Skimming could be causeing this, sometimes skimming a boiler is needed more than just once or twice on a new start up. Air in the system not vented but pushed to the condensate recievers is ok! If the system is graded and drains properly. a big trap of standing water in a low or trapped place in the system (either condensate or Steam) could be the cause. Like I said "just brainstorming"
bigugh

Gary Fereday

Are there traps on the outlets of the AHU's?

And do they work ? they could be full of debrie's from a new start up and need to be cleared.

Don_4

Suggestion

Had a simmilar problem with a multi boiler installation. Engineer had "overtreated" boilers. Send them for coffee and drain half of the water from the boilers and refill with fresh.

GaryDidier

Steam problems

Ed,
I had the same problem with a high pressure steam system at a dry cleaners.It turned out (after nearly pulling out what was left of my hair) the customer was over treating the water with anti scaling agents. Once we adjusted the treatments and reskimmed the boiler all problems dissapeared.
Gary from Granville

[Deleted User]

My 2 cents

in the order of your questions.

1. The pressure may or may not be too high. Don't know the pressure drop across the AHU Coils.
2. No to the 76's. The vacuum breakers are the correct application. They will keep the coils from collapsing in case of a vacuum on the system. I can only assume that the system has properly sized and installed F&T Traps w/ discharge that drains properly back to the tank.
3. Concur w/ Gary. Sounds like a PH problem. PH should be between 7.5 & 10.5. Anything higher is like trying to boil dish water. Someone should have a PH Test Kit.

Good luck.