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Patterson Kelley Mach 750

Grega Member Posts: 20
edited February 2020 in Radiant Heating
Recently had a 10 year old Mach boiler heat exchanger crack. So we did a like for like change as spaced by the customer. We had no prior history of the existing boiler which begged the question “why did it crack” ...on start up we kept getting Delta T too high, so Indicating we need more flow. Checked all strainers, air separator, valves etc.. found some small things but nothing major. Pulled pumps to make sure impellers ok and in tact. gas pressures are correct and even de rated boiler by 20% by changing inducer speed. The only information we did have is the PH reports of the 40/60 ethylene glycol which were all good. No make up water to this boiler it is closed glycol loop. Today we got a “high temp” alarm. I do have a water balance company coming to evaluate and give us a baseline to start with.

We have a 4 air handler with aqua coils that are 100% outside air. We also have in floor in concrete for perimeter heat through the whole building. I say perimeter because the in floor loops cover the entire building only 8’ in from outside walls. The center of the slab has no loops. And a lot of the piping is outside for the air handlers.

My experience with aluminum heat exchangers is that they are very touchy and heat up extremely fast. They don’t seem to want to work well with this kind of set up. Any thoughts ?

**** Forgot to mention that the boiler temp drops incredibly fast once boiler is shut down for any reason.


  • ScottSecor
    ScottSecor Member Posts: 565
    I may have missed it but what is your delta T? Is there any chance that the primary pump is undersized and this is the cause of your cracked heat exchanger? I would suggest getting the model data from the circulator pumps and making sure they are capable of delivering what you need.
    EBEBRATT-Ed Member Posts: 12,328
    Bringing the balancer in is the right thing to do. Hopefully you have some taps to measure flow at. If he uses a ultrasonic tester i would be very suspicious of the results.......they don't work good with glycol.

    I would talk with the PK rep. That's a lot of glycol which will inhibit the heat transfer