Like my title states, I recently started a new job as a maintenance mechanic for a school district. I have 8 years of HVAC experience, but have not worked with heating systems in 5 years. For the past 5 years I've been working with large centrifugal chiller plants and building automation, but now brought in to a position where I was asked to modernize a school system with their automation system and get their plants up running. In my short time of being here I've been thrown immediately in to solving issues with a big steam boiler that has been constantly over heating a very old building within our organization. Like I said it's been some time since I've worked on any sort of Hydronic or Steam system, primarily in residential applications so I have a good idea of the theory and operation of a heating system, but from what my foreman tells me about the operation of this system, is completely foreign to me. I'll add in that my foreman does not come from an HVAC background, but knows the quirks and nuances of our buildings...but that doesn't necessarily mean it's correct.
1. Our steam boiler is controlled through a BMS system, when the sensor in this building calls for heat, 2 Johnson Controls Actuators wired in tandem open and close the Steam Isolation Valve and send steam to the radiators. One of the issues we were having is that it was constantly sending steam through the building due to the isolation valve not seating. I found the actuators that controlled the valve were not wired properly at all and corrected that. What was happening was the Master/Slave dampers were not wired to work as such, only relying on the master damper to open and close the valve. now wired properly and adjusting the standing voltage it now is configured that it is using motorized power to keep the valve shut and prevent steam from passing through. We are still getting high temps in this building, my foreman believes there is still steam weeping through but I don't think so and for 2 reasons. 1 the radiators have been ice cold since correcting the issue, based on trend analysis the boiler has not been called for heat the past 36 hours since correcting the issue.
2. The other issue and this opens up another question because it's where I'm not certain in my theories. The temperature sensor for this building is mounted on the wall of the Chimney, it will always read high because of the flue gas temps radiating through that wall. Which brings me to that other question, even when the building is not calling for heat, the boiler will run every 5-10 minutes to build up pressure in the vessel, then trips on pressuretrol due to the steam isolation valve being closed since the controller is not calling for heat...since this is a PLC controlled system it may be different, but based on the operations and theory I know from residential steam, the boiler isn't going to turn on and create steam unless the thermostat calls for it to. My foreman says this is normal this is what the boiler does it will always generate steam pressure, it's questionable to me but since the boiler is firing all the time creating 5-6PSI of pressure, it is constantly sending flue gasses up in to the chimney, thus giving a false reading to the PLC temperature sensor saying the heat in the building is x amount of degrees. With everything I'm telling you at the moment, my foreman still thinks that steam is passing through the isolation valve, despite all the radiators being ice cold...but I'm confident these high temp readings we're getting are due to the sensor being mounted on the same wall in front of the Chimney.
Since correcting the issue with the Actuator on the valve, looking at a trend analysis of the boiler it has been doing it's thing of running for a few minutes and tripping on pressure, but not running for prolonged periods of time which would be from a true call for heat. I'm also keeping in mind finding the politically correct way to address this issue with my foreman, because while he may understand the nuances of the building and how to combat them, his theories seem off and I think there's a way we can permanently fix both issues I mentioned.
For further info, this sensor is on the 2nd floor the building, and the first floor of the building being cold has always been an issue from what they tell me (which makes sense as heat rises). This is also a 15 PSI boiler with a 7275 SqFt. Rating. Thank you in advance for all the help.