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Superstor low delta-t problem

I have a problem with two instatations that I could use some advice with.

Both systems had the same boilers 140M, both with a superstor indirect(one 80 and the other 119), both with in floor radiant, one has hydroair. Both systems, years after install when I was out performing yearly maintenance found that when in DHW mode there is at the most a 10° delta-t and the boilers are cycling. Everything was working perfectly for years. I just had to replace one of the boilers because it had a Leak in the heat exchanger and replaced the 140M with a ELP-199, and have been trying to figure out what is going on with the DHW delta-t. Then this week I went to replace the blower on the other install that was having the DHW delta-t issue and discovered that boiler also has a leak in the heat exchanger. Both boilers have a Taco 0011 for the DHW pump, one location I know has a water softener and I'm not sure about the other location. also both locations run perfectly fine when they are in heating mode. HTP suggested to shock the superstor heat exchanger in case there is any buildup on the heat exchangers. they told me that the elite plus should have a taco 2400/45 instead of the 0011 but the 0011 should still work, just not get maximum input into the tank. I have not been able to return to try shocking the heat exchanger yet. Besides that i have not received any advice from HTP. Any advice would be appreciated.


  • kcopp
    kcopp Member Posts: 4,010
    sounds like....

    good advice.... the finned coil can "lime" up. Even on City water.... Shocking it will get that crap off of it and get the heat transfer back. Have you ever tried this method before?  You can make a wand out of 3/8" copper, drill some 10-15 holes in it and attach it to a hose thread adapter. Pull the aquastat out and let her rip.
  • ColoradoDave
    ColoradoDave Member Posts: 54
    Cleaning DHW coils

    We've often used (Phosphoric acid?) Ice maker cleaning acid bought at our local supply store.  It's marked as safe for use on ice makers and such.

    Heat the tank up.... drain it down until the water level is just a few inches below the coil (use a hose on the drain to make a liquid level ... 1/4" full is a good guesstimate for superstore)... and pour in a half gallon of the acid.  Let it soak for 30 mins then flush it with water.  We usually install a ball valve and a boiler drain on the hot water out (depends on the water heater)... but the T&P could be pulled temporarily as well.

    The Amtrol WH7's (BLUE BULLET) tend to lime/scale up alot in some installations with hard water... and it's worked very well for them.  Never had to do it on a SuperStor though.
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