# Another ruined heat exchanger.



## Brian Ayres (Sep 9, 2012)

Went out on a call for a leaking AO Smith HW 520 boiler today. 
The combustion chamber coil had a leak. I'm sure the heat exchanger is next to go. 

Any guesses on the cause?

Yup. Domestic return was plumbed back to the boiler instead of the storage tanks with a big ol Bell n Gosset 1/6hp pump. 
24 hour water flow through the boiler. 

It's a shame because the workmanship of the installation including the balanced manifold system for the 3-120 gallon storage tanks was excellent. 

Telling the customer that their factory warranty is void 3 months before the 5 year warranty is up sucks..

Most of my factory warranty calls are installation error.


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## OldSchool (Jan 30, 2010)

If it was me I would get them warranty ....
You owe your allegiance to your client not the manufacture


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## Gettinit (May 9, 2012)

Where was the leak? Are you hinting that the pump was over-sized?


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## Brian Ayres (Sep 9, 2012)

The pump was oversized AND , it should return from the building loop into the storage tanks, not run into the cold water supply to the boiler. Piped that way the copper coil will wear out years before it should. 

HW Boilers are longlived if done right. When I was in SC at AO Smith's plant they had just received an old HW boiler that had only just sprung a leak. I forget the age, but it was 50-60 years old? The owner of the boiler had called for parts and when it was figured out how old it was AO Smith traded him for a brand new boiler free of charge. They wanted to tear it apart to see if there was anything to learn from it. 

The tank is 4 years 11 months into it's 5 year warranty. The tank and heat exchanger still have a parts only warranty, but.... The replaced parts have to be shipped back to get inspected. Velocity erosion of the copper tubing wouldn't be covered due to the incorrectly piped return. 
If the parts aren't covered then combined with the costs for labor are close to the cost of a new boiler...

This is a crappy deal for the customer any way you cut it.


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## Brian Ayres (Sep 9, 2012)

Gettinit said:


> Where was the leak? Are you hinting that the pump was over-sized?


The domestic hot recirculating pump was a 1/6hp pump on a 3/4" return... Way oversized!

The leak is on the combustion chamber coil. It's a copper tube that is under the jacket around the combustion chamber. I haven't ever changed one, but I guess 6-8 hours labor?


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## Gettinit (May 9, 2012)

Call the manufacturer. They will have a time for how long it would take at the factory. Double it and it should be what it would take in the real world. I don't see how they will honor the warranty. It never ceases to amaze me what people do in the field.


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## Brian Ayres (Sep 9, 2012)

Yeah. I'm a warranty agent for AO Smith. It's why I was called out. I get the labor allowances all the time. They are NEVER close. Lol. 

I'll try calling AO Smith's local Mfg Rep tomorrow. They will sometimes help out when the Tech/Warranty Support can't. 

Honestly, the best backup warranty support for almost any product is the local manufacturer's rep. They often will go out of their way to protect the good name of the products the rep.


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## Catlin987987 (Nov 12, 2010)

Only if people read the instructions


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## OldSchool (Jan 30, 2010)

So you are saying the oversized pump wore out the tubing in the boiler ... 

Question ... Why didn't it wear out the copper that the pump was on???

You would think that the copper on the return would wear out first before the heat exchanger..


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## Brian Ayres (Sep 9, 2012)

OldSchool said:


> So you are saying the oversized pump wore out the tubing in the boiler ...
> 
> Question ... Why didn't it wear out the copper that the pump was on???
> 
> You would think that the copper on the return would wear out first before the heat exchanger..


They have had multiple leaks on the return line. Educating people on pump sizing for returns is a constant battle. It's a bigger is better mentality when just big enough is the right way to go for most returns.

The 3/4" return feeds into a 2" cold feed to the boiler, so velocity erosion isn't an issue on the 2".


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## MACPLUMB777 (Jun 18, 2008)

*YES I RAN INTO THIS MANY TIMES IN
L.A, CA. WHEN MY SHOP WAS DOING A. O. SMITH WORK,
IT'S LIKE THE PLUMBERS CAN READ ALL THE DIRECTIONS BUT MISS THAT
ONE ABOUT WHERE TO RUN THE RETURN LINE INTO,
I WAS UP PAST MIDNIGHT ON A FRIDAY NITE, 90 UNIT APT BUILDING TRYING TO SOLDER A BUNCH OF PINHOLE LEAKS IN THE HEAT EXCHANGER TO GET THEM THRU. THE WEEKEND FINALLY HAD
TO GIVE UP EVERY TIME WE REFILLED WITH WATER NEW LEAKS
SPRING OUT :whistling2:
*


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## OldSchool (Jan 30, 2010)

That's what I would have figured the return would have eroded long before the heat exchanger

That should have made the pump size an issue long before there was heat exchanger problems


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