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hydronic system at 100psi?

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  • hydronic system at 100psi?

    Guys, I've been working on this building w/ a system that includes 2 hot water , 2 pumps, and 40 vav boxes heating a 100k sq ft building. The mechanical engineer speckt it out to run at 100 psi. I've got make up water piped in and its right at 80 lbs and change. The suction side of the pumps are at 80 and the discharge is at 100-105. I've never worked on or put together a system w/ so much pressure. I don't understand why so much pressure? The flow control on the boxes are at 1 gpm and 2 gpm dpending on how big the unit is. It a four story building(tree floors above ground level and a basement) W/ the boiller in the basement and the air handler is on the roof. There is a small 1 1/4 3-way control valve on the roof by before the airhandler. The pumps and boilers and relief valve on everything are rated to 125 and 150 psi. If I were to change it I'd recommend a prv valve at the make water rp valve w/ it set to 45lbs. That would give me aprox 20 lbs on the roof( elevation change) and theat would be suficient. I'm not sure how all the componemts of the system will react at 100 psi for an extended period. Any thoughts?

  • #2
    thats 2 hot water boilers. start up temp is 145 and cut off is 165. The first thing we noticed is the pressue built up pretty fast vbecause no one checked the expansion tank pre-charged pressure it was only set to 15 lbs.


    • #3
      Is there even a pressure regulator (fill valve) with backflow on the feed line that conforms to what the boiler's specs call for? I too have never heard of any boiler running at such pressures, even for that many zones and that much square footage. The fact that the expansion tank was pressurized to 15 PSI, which by the way is the usual pressure for most hydronic systems, tells me something is wrong, and if pressure is too high it is creating a potentially seriously hazardous condition. Get somebody who knows what they're doing before you lose your skin or destroy the place.


      • #4
        There isn't a backflow device on the building water supply nor pressure regulator. There is a 1" rp backflow device on the make-up water but no prv valve. It wasn't specked out on the plans, and I brought it up to my boss. He hasn't worked on very many systems like this. Probably not as many as I have, and I've only done half a dozen or so. I brought it to the attention of the mechanical engineer also. I said" all we have to do is move the water. And there are two pumps for that." But who am I to question a man who went to college for 4 years and has a degree. I told him 20 to 30 lbs was more than enough and there should be a rp 3" RP on the hole building supply along w/ a prv valve ( there is right at 80psi + or - 5 lbs on the building. There should also be a prv on the make up water supply to the boiler system. Both boilers are 750k btu. I'm no its not right but how do I go about getting the wheels in motion to correct it? Tell the governor. WE had a boiler inspection last week and he didn't say a word. I wasn't there or I'd have asked him.


        • #5
          Okay, before somebody there gets killed, scan and post some of these specifications. If you do not have a scanner then please type word for word some of these numbers and "speckifications" you are quoting.

          Every HVAC product ever sold in the United States has a manufacturers phone number included with their literature. It is in the manufacturers best interest that their products be properly and safely installed. Call them.

          None of this looks legitimate to me, but if it is and you have less than ten installs between you and your company owner you need to hire a competent person to supervise the both of you and I think your States Attourney General should be made aware of the competence level of your outfit.

          This is the edited part; please post your units manufacturer, model number, and serial number so that an accurate determination of what you really have might be made.

          [ 11-29-2005, 08:38 AM: Message edited by: plumber ]
          Work hard, Play hard, Sleep easy.


          • #6
            No Regulator or fast fill valve???

            This is partly why the pressure is so great. You are supplying the boiler with straight city water pressure. The boiler is spec'd fora a certain feed pressure, usually 15 to 20PSI, though I have seen some units including the smaller wall mount units run up to 25 and 30PSI. But NEVER the pressures you are quoting.

            The guy you say who spec'd all this out, degree or not, needed to be called out on this one, and not only would I question him I would call him an incompetent, inept schmuck too....and to his face as well. He probably knows just enough about boilers and hydronic systems to be dangerous, degree or no degree. This system is not safe and is a ticking time bomb waiting to cause a disaster. Get experienced help.


            • #7
              On a second note, just last night I got called out to a no-heat call. When I arrived at the gentleman's residence, I could not believe what I was looking at. He had a smaller residential boiler feeding fin tube baseboard, and the no heat on the downstairs loop was being caused by a bad Taco power head that was'nt opening. But on further examination, I noticed the following...

              No Backflow on the feed water line or ANYWHERE on the entire system including the main water supply. No regulator as well, just a very old pressure regulating fill valve which was not set properly, and not able to set due to extreme age (system is over 30 years old) and allowing only 8 PSI. The expansion tank had long ago failed and was filled with water and installed horizontally off a male adaptor. Auto-vents leaking. The pump was grinding and the bearings shot. And for the grand finale.....NO high temp limit at all controlling the valve, no secondary aquastat, and the boiler was running at over 220 degrees. Oh, and NO combustion air intake at all, anywhere, not even a hole cut in the wall, and there's a 50Gal. water heater in the boiler room too. The thermocouple had'nt been changed in a decade and was a wonder it even still sent a current to the gas valve at all. The burn chamber was filled with dirt and dust.

              The guy had'nt had his boiler serviced in over 10 years, and whoever did it last time was an incompetent idiot to let it just pass like that. The original installation looked as if a 6 year old did it as the manifold was a mess with lines running poppycocked and at odd angles.

              This is what happens when people without experience install and service boilers. This guy had just been extremely lucky nothing really bad ever happened, and I have to go back today to finish getting the unit at least safe.



              • #8
                Too bad you didn't grab a photo of that installation, then we could all get a good laugh....or gasp in fear for the homeowner's life.

                To me an oil fired boiler or water heater is one piece of equipment that you definitely want a service contract on. Most that I know of include an annual inspection and cleaning which in istself usually just about pays for the contract, that balance is cheap insurance for that evening when the oil pump quits of whatever. You just call and (with my contract anyways) all parts and labor are included, can't beat it.


                • #9
                  I'll see if I can get my hands on some of the specs and yes I have a scanner. If this system is so dangerous how did it pass the boiler inspector?
                  I would agree its out of the ordinary, but like I asked before where does it say what the operating parameters should be for a system such as this. Like plumber said in a different thread there isn't a licensing for boiler installers nor a test for the same. I would like to take a class or course of classes and learn the dynamics and engineering for such systems as I've been a part of. I would not willingly install a system that could really hurt someone especially if I possessed the greater light.


                  • #10
                    All you have to do is write down the brand and model and serial number of the unit you are working on. It requires a flashlight a pencil and a piece of paper.

                    Again, the manufacturer of this unit will be more than happy to help answer some of your questions. They will not want their good name sullied by bad installation procedures.
                    Work hard, Play hard, Sleep easy.


                    • #11
                      better use a plate heat exchanger and 80 pipe and 250 rated valves but why 4 stories?


                      • #12
                        In addition to what plumber has already posted about phone support, most manufacturer's will send out a rep to meet you in the field when you have questions.

                        "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                        I never lost a cent on the jobs I didn't get!


                        • #13
                          Re: hydronic system at 100psi?

                          how is the t/p valve not opening all of the time, or were you that ignorant that you switched it out for a higher rated unit. reading your questions you are either an apprentice or a poor journeyman. get controll and read the instructions. heres a thought that shiney metal plate on the boiler is caled a rating plate read it. by the way call the inspection office and talk to the manager, your inspector is blind
                          how is it that so many answers are in the instructions