Copper Pipes for Gas Boiler Steam Chest?

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coalkirk
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Post By: coalkirk » Mon. Apr. 11, 2016 8:34 pm

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For you guys who are in the heating/plumbing business, is it ok to use copper pipes for the steam chest on a gas fired steam boiler? I can't find a reference for it but something sticks in my head that it should be black iron for this purpose. I inspected this home today and found the boiler piped like this. Am I crazy?

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Post By: Rob R. » Mon. Apr. 11, 2016 9:05 pm

Copper is ok on the returns, but not on the steam side. The expansion/contraction from the steam cycles stresses the joints and they are likely to break at some point. With that said, some of them run a long time with copper.

Might be worth finding a manual for that boiler and see if it mentions anything about the piping material.

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Post By: franco b » Mon. Apr. 11, 2016 10:36 pm

Back in the 1960s copper was very cheap and I remember a friend telling me that some were using it on Long Island to pipe steam.

Copper does expand a lot more than iron or steel, but I think it expands very little more than the copper used in hot water systems at 200 degrees which is common.


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Post By: Rob R. » Tue. Apr. 12, 2016 5:10 am

The amount of expansion is part of the problem, the other is that you can't make swing joints with sweated fittings. On certain boilers the copper piping can put mechanical stress on the sections. With that said, if I inherited a system that was piped with copper and had been running a while without issues, I would just run it until something had to be addressed.

The use of copper rather than black iron isn't a code issue, and only a few boiler manuals actually say "do not use copper".

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Post By: blrman07 » Tue. Apr. 12, 2016 7:05 am

It's not the copper pipe per se but the solder holding the joints together.

Max temp for soldered copper joints in use on a boiler is 250F
Max pressure for soldered joints corresponds to the temp with is 15 psi.

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Post By: McGiever » Tue. Apr. 12, 2016 7:21 am

So, *coalkirk*, maybe another question would be, was it done with a lower temp lead solder or maybe it was a better, higher temp alloy solder? :?:


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Post By: coalkirk » Tue. Apr. 12, 2016 7:47 am

Boiler was 20 years old, no sign of a problem. Not sure how I could determine the solder. I pointed out the lack of a swing joint. Code doesn't require iron pipe. I downloaded several manufacturers installation manuals and none of them said do not use copper. So I guess the answer here is "it depends."

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Post By: blrman07 » Tue. Apr. 12, 2016 10:47 am

Unless your going to be running high pressure steam in excess of 15 psi I would say at this time there is no problem.

The melting point of the lowest solder is 360 F. 15 PSI steam corresponds to 250 F so I believe that it would be safe to operate.

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Post By: Berlin » Tue. Apr. 12, 2016 3:02 pm

I've seen and we have had to repair MANY steam boilers piped with copper near the boiler. The sweat joints do fail over time because of higher rates of expansion, although, it may be many many years before this happens. It is also my opinion - completely unresearched but supported by anecdotal evidence - that a lot of copper piping anywhere on a steam system leads to faster boiler rot-out; perhaps an interaction of the ample oxygen and copper with the cast iron...

Not against code, and may last for years without issue, but, good practice is all black iron on steam.

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Post By: jpete » Sun. Jun. 05, 2016 7:59 pm

The main reason I believe is just the conductivity of the copper. I guess eventually it will heat up but from cold, that steam is going to condense rather rapidly which would cause the boiler to run longer to reach setpoint. Everything I was taught says no copper on a steam system. That said, I've seen a bunch of them.

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