Weil-McLain Tankless Coil.... you know the rest...

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Old 01-12-18, 05:48 PM
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Weil-McLain Tankless Coil.... you know the rest...

Hi Gang,

Advanced DIY'er here. Lately been studying up on my W-M boiler, model P-SGO-4 Series 3, installed in March, 2001,

It's attached to an Aero brand (now Bradford-White) 30 gallon AST-30 model coil-less water tank.

The hot water for years has been 140+ degrees. Lately I've been trying to lower it. I've discovered the watts 70-A tempering (mixing) valve is seized. I've also learned the rebuild kit might not be worth it, and was told to buy a new unit, which I did. I shall install it shortly, along with a new electric thermostat for the water tank.

My question comes from what I've learned on this DIY voyage of discovery. The question is about this controversial water coil. Attached is a picture. It has been in service since 2001. I'm in the northern NYC suburbs, and our municipal water's not too hard.

Regardless I think the coil could use an inspection. Ergo, I'd like to remove and inspect it. I think I'll need a new gasket for that. If removed can I clean it? Can it be sand blasted with a gentle media? I've read about an acid treatment. How long would that take?

Should I buy a new one? I'm having trouble finding an exact match. The model numbers on the rectangular mounting plate are model "35S29" and "590-921-660." It has a rectangular mounting plate with 8 bolt holes, an inlet and outlet hole, and a sensor hole.

So, any info appreciated.

Thanks folks...

-Bill
 
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Old 01-12-18, 08:20 PM
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I'm not the pro here....

You can't see much by pulling out the tankless heating coil. The part that causes the problem is the inside of the coil. The minerals buildup inside and reduce the flow thru it.

The guys will be by to offer further info.
 
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Old 01-12-18, 08:46 PM
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Thanks for the help. I just looked up acid cleaning and learned that the innards need to cleaned. I'm looking into installing 3/4" purge valves, and using a pump I have to pump CLR fluid through the coil. Should be interesting.
 
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Old 01-13-18, 04:49 AM
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I worked in the heating field for about 40 years. My best recommendation would be 2 fold; #1, If you are going to pull the coil out of the boiler, and that would yield you the best results, take the coil to a car/truck radiator shop and have them clean both the inside and outside coil surfices. Your boiler looks like steam from the pictures and if that is the case internal and external cleaning is required. They can also give their estimation of the coil's condition and life expectancy. Make or buy a new gasket . #2, If you do not want to remove the coil, cleaning with an "acid" may be required. I can not comment on how well CLR will work since I have never used it. One last Item, if you are going to remove the coil and that may be your best fix, start now spraying the nuts and studs with a penetrating oil or similar product to allow for easy removal of the nuts. (you don't want to break off any studs. Spray many times over a long period of time to allow the stuff to work.
 
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Old 01-13-18, 01:24 PM
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I can't comment on CLR either but from watching the guys do coil cleanings...... it will be almost completely ineffective as they use acids for cleaning.

Also, probably best to wait until heat is no longer needed before taking the boiler out of service.
 
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Old 01-14-18, 04:13 AM
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coil cleaning

To clean the inside of the domestic coil, you will need to use something very strong and acids will serve that purpose. I said that rad shops can do this type of work. We always took our coils to a rad shop that specialized in large earth moving equipment rad repair since many of the coils we serviced were very large and sometimes 8-12 feet long. Since acids are dangerous to use, we always contracted this to companies that specialize in coil cleaning and not our own people.
 
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