Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

raypak hydronic malfunctioning controls

I have a Raypak copper-fined tube boiler used in a circulated hot water heating system (baseboard hydronic).  This fall it began to make a noise, a descending in pitch, increasing in volume "shriek" that was finally observed to coincide with the "high fire" stage of the two stage gas valve.  The shriek was significantly reduced by adjusting the two manual controls (stage to 160 and high limit to 180).  However, coincidental to the shriek was quite a bit of water hammer.  After paying several companies to take a look at it, this still remains unresolved.  I have observed that when the boiler receives a call to heat the water in the boiler (an internal call, as none of the three zone thermostats are calling at that particular time) the water quickly exceeds the high limit setting; in fact, the boiler kicks on when the boiler temperature gauges reads 185 or 190 (which should be the cut off) and continues to burn until the fast response temperature sensor control board registers excessive heat (yellow bulb) which indicates water temperature exceeding 240 degrees (thus boiling the water, making all kinds of drumming noise, and causing air that needs to be released and new water drawn in).

Question: does anyone know what is calling for the heat (at such an inappropriately high temperature) and what component to check for failure?  I have a small meter, and checked the fast response temperature leads, and got a "2" on my scale, which from reading someone else's questions I assume means the probe is functioning).  Thanks in advance for any advice!


  • Raypak

    Those harmonic sounds are typical of a boiler with a copper heat exchanger (HX), i.e. Raypak and Laars.

    It seems that the HX complains when there's not enough flow to pick up all the heat.  Check your pump(s) to make sure you have proper flow.  You may also have to service your HX to make sure it's clean.

    Search The Wall - there are plenty of other threads from people with the same problem.  Here's one:


    I would also call Raypak technical services and ask them.

    As far as the boiler firing when there's no call for heat, that's not right unless there's a tankless coil.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
  • Tim McElwain
    Tim McElwain Member Posts: 4,554
    Do you get domestic

    hot water from the boiler? The noise you are hearing is the water flashing to steam inside the finned copper. That type boiler has to be very careful with that condition as it can dmage the boiler. I suggest getting in touch with Raypak. Go to www.raypak.com
This discussion has been closed.