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Amtrol indirect descailing

I have a customer who has a top coil boiler mate....I know finned copper. A competing company installed it 10 years ago. I got called for a no hot water. 

I get there, boiler is set if 175F and the circulator is running. Domestic Water is less than 100F. 

Supply and return to the indirect are less than 5 degrees different. 

I drained the indirect, cranked the boiler up to 220 and proceeded to try and shock the coil multiple times. No dice, got some red stuff out of the drain but no performance difference. 

Customer has what he calls "red clay" and has a whole house water filter which clogs monthly. No softener.....

What would you use to descale this thing? I've got some Hercules Sizzle in the van, but I don't want to own this. I talked to some other guys at the supply house and they said they use Sizzle in water heaters. 

I really hate boiler mates...they are quite popular around here, but I've never seen one this new perform so poorly. 

Serving Northern Maine HVAC & Controls. I burn wood, it smells good!


  • HomerJSmith
    HomerJSmith Member Posts: 2,406
    edited July 2022
    I never liked Boiler-Mates because of the heat exchanger and high pressure loss.
    Supply and return to the indirect are less than 5 degrees different.
    indicates to me a problem in the HX. The boiler sys water quality may be problematic. But of course, a build up of minerals on the domestic water side of the HX can mitigate heat transfer. 1mm of build up can reduce heat transfer by about 12% as I recall.
    I think I would be reluctant to use Sizzle on the domestic side and use vinegar at 4% acetic acid. Depending on the build up, repeated treatments may be necessary and it takes time for the treatment to work.
  • mattmia2
    mattmia2 Member Posts: 9,469
    Is there a warranty still in effect on the tank you need to be careful not to void?

    Does the coil come out of the tank? I'd remove the coil and soak it in citric acid and see what rinses off if it does.

    It is possible whatever is in this water has coated or clogged the boiler side too.
  • hot_rod
    hot_rod Member Posts: 21,878
    Removing the coil and soaking in the correct mix of Sizzle would be one method. It takes a lot less Sizzle, compared to filling the tank and adding Sizzle.

    May want to have a new gasket on hand if you remove the coil. 10 years without descaling is a long time if he has high mineral water. The hotter you run those coils the faster they scale up.

    At some point they may do some treatment to their water?  If they have hard water, a softener in the cold feed to the tank is an option.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Larry Weingarten
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    I added 1 gallon of sizzle to a 5gal pail and 3 gallons hot water. Pumped that into the empty boiler mate through the drain. I dumped another 4 gallons of hot water (had on hand before draining the indirect) to clean my hoses and pump. I turned on the boiler and ran it up to temp. Slowly adding cold water through the dip tube. I let it build pressure and never opened the hot valve. So there was air in the top of the tank. 

    I let it come to temp and listened. After about 30 min. I turned off the boiler and drained the tank with gravity. Filled, drained, 3 more times with cold water. 

    Tested the final rinse with Ph strips and it was 7. Same as the cold water. 

    So I opened the hot tap and let the air out, tested Ph again and ran about 20 gallons through it down the drain, just to be safe. 

    I now have a 20 degree drop across the coil. Only thing that came out the garden hose drain was a bunch of fizz and clowdy water. No solids at all. 

    They have a softener, but it is in a well house and the salt turns into a brick so I'm told. This is shoehorned into the smallest space possible behind a wall with shelves on it. Homeowner removed the shelves and opened up a piece of pegboard for me to even see the boiler mate......to each their own. 

    I suggested a new softener on at least the cold going to the boiler mate as well. 
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • GGross
    GGross Member Posts: 974
    In my experience using a good solar salt helps to eliminate salt bridging. Suggesting a new softener implies the existing one doesn't work, if its not able to regen with the salt bridge a new unit will run into the same problem. It is possible that the media is no good any more, if it has been installed less than 20 years and the media is done I would start over as something is not right. What is the hardness of the water before and after the softener?