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high temp / high pressure

markos Member Posts: 1
Having a little trouble with my friends baseboard gas fired system...  It keeps going over temp/ pressure... it normally is sitting high around 18psi/160 degrees..

then goes real high 200+ and almost 30psi   and blows off...   then it is quiet   for a little while ... and again.. this can happen 5 + times a day.....   

I replaced the expansion tank, supply valbe and relief valve... same exact issue

what do you think??   ( I need a new line of work?  :)   )


  • don_9
    don_9 Member Posts: 395

    The fact that the temp of the water is rising along with the pressure point me too a faulty aquastat for what ever reason.

    I'm surprise that you are not getting alot of noise issue as well.

    The only other thing i could think of at this time that will make the pressure rise but not the temps would be if the unit had a leaky tankless coil. 

    I hear the city is hiring.
  • Lance
    Lance Member Posts: 242

    When you installed the new tank did you pressureize it to matching pressure before putting it on the system? 12-PSI. Is it big enough? They come in different sizes. Extrol 30 should be more than good enough. 12 psi should be enough to start with unless you are over 3 stories high. Sometimes new products can be defective. I once had a tank that had correct pressure, correct size, but the bladder was glued to the pipe opening and could not receive water to allow for expansion. Turns out there was a slew of them after I was told that was impossible. Another tank fixed the problem. It is hard enough to figure out problems, it's worse when you are betrayed by defects.

    PS. Pressure will climb faster than temps normally without expansion. That is the key. Water will not condense. the quickest way to test for a leak is to eliminate all air, and as a few drops leave the pressure will plummet to zero fast indicating a leak or lack of an air cushion.

    Pascal's law.

  • Steve_210
    Steve_210 Member Posts: 625
    air seperator

    do you have an air seperator on the system. this could be an air proublem
  • Tim McElwain
    Tim McElwain Member Posts: 4,556
    edited February 2010
    What is the

    gas valve on this boiler? Make, model and serial number so I can identify if it is a valve that has had a problem with not always shutting off.

    The fact that temperature and pressure are rising goes beyond PRV, expansion tank, tankless coil leak or high head pump on the return all of which can cause a rise in pressure. Something on the control side is amiss perhaps?
  • Steve_210
    Steve_210 Member Posts: 625
    air question

    Tim i have a similar proublem. the relief valve pops maybe twice a week.

    would air not cause the tempeture to rise
This discussion has been closed.