copper in 2 pipe steam

chris22

Just purchased a rather large house, Smith boiler 2 pipe steam. I was surprised to see the near pipe returns (estimate several feet) to be copper.  also I see one copper return from a radiator to have a short piece connecting it to the iron pipe.

I have read that copper is a no-no for steam (?) Should I change this? Local fuel people say its not necessary but I trust information here much more. What harm is the copper? Or is that it's soldered?



Another question, it has a gas burner and it runs a looong time to raise temps (we haven't moved in yet so we set back for days,..but going form 60 to 65 may take 4+ hours depending how cold outside. It DOES keep the temp up for a long time after it hits the goal and for a 4,500 square foot building keep at 60-65 this month cost around 400.00 which I didn't think was too bad esp with this cold previous month. But I wonder about how the mains work,..never had a 2 pipe before,..after it finally shuts down one of the mains sounds like it is sucking a lot of air and it does it for several minutes. Does that mean it is doing its job? The other main doesn't do this.

nicholas bonham-carter

Copper piping question

Copper piping on the supplies is considered to be a liability, mainly because of the effects of the greater expansion and contraction of copper versus steel. These forces can cause the soldered joints to yield, or can sometimes put enough force on the sections of the boiler to force them out of alignment.

On the wet returns, the temperature fluctuations are not so extreme, and there is only one point of connection to the boiler, so the non rusting qualities of copper are a plus.

With regard to the main sucking air, is this from a main vent somewhere on the return? Generally, on 2-pipe systems, the air is vented from one location, which may have had a vacuum check valve to enable the system to run at sub-atmospheric pressures in the days of coal-fired boilers. Opinion is now devided as to the benefits/disadvantages/strategies of running a modern gas-fired boiler in a vacuum, but some are trying it.

Whether vacuumized or not, the system at the start of firing after a period of activity must push out the air before the steam can arrive at the radiators. Large main vents on that central venting point let the air escape with no resistance (back-pressure 1-2 ounces). A good low pressure gauge of 0-3 psi will show you what is happening. The advantage of the sub-atmospheric system operation is less air to push out each time the boiler fires. For best results, the vacuum should be equally distributed throughout the system.

Some pictures of the boiler piping, and of the radiator supply/return/traps/etc would help to identify the system, and develop strategies for it's continuing economy, quietness, and comfort.--NBC

Jamie Hall

Copper -- it depends

The problem with copper is two fold: first, it expands much more than iron as it heats up.  Second, the soldered joints have no inherent give in them.  So...



Copper in the near boiler piping (the risers, header(s), equaliser, etc.) is a very poor idea; it expands so much more than the boiler that it puts a good deal of stress on things, and in time can damage the boiler or develop leaks at the joints.



However, although it is better to use iron elsewhere inn the system, copper can -- in my view, anyway -- be left in place if it is there, provided that it is hung or mounted in a way that it is free to expand.  Because it is expanding, it may be noisy.



I'd be more interested in the main which doesn't sound as though it is sucking air when it shuts down.  Does it have a main vent?  And, if so, is it working?  Or is your system setup with a single main vent and crossover traps -- and if so, are they working properly?

Pumpguy

Chemistry

I have heard operators and chemical sales people say that copper should not be used as it causes a chemical reaction to occur that is detrimental to the iron and steel components of the boiler and piping. 



I do not have enough chemistry savvy to understand or provide more details. but continue to wonder just how much validity there is to this?



Can anyone expand on the chemistry aspect of the use of copper piping, especially on the return side of a 2 pipe system?

ChrisJ

Same boat

I'm in the same boat as you Pumpguy.  However, my understanding is you will have a reaction between the copper and steel/iron but only very close together.   Meaning if you have a copper pipe screwed into an iron fitting and it is full of liquid there will be a reaction, but only in that fitting ie it won't travel through all of the piping.  So if you have a steel nipple screwed into the boiler with a cast iron or steel elbow or a tee screwed onto it and then a copper pipe screwed into that fitting, only the fitting will be attacked, not the boiler and how fast all depends on many things.  I believe a low PH speeds things up greatly.



As I said, this is only my understanding after asking many people and doing what reading I could on it.  I really don't know for sure.  In my opinion the main problem with copper carrying steam is expansion.  They do not hold much liquid there should not be much of a reaction if any. 



One thing is for sure, no matter what my opinion or anyone else's opinion is piping steam boilers and steam piping in iron and steel is always a safe bet.  I have some copper between 3 radiators and the runouts which I plan on removing just because of expansion noises.

Pumpguy

I had

a well respected chemical supplier tell me something about "copper ions attacking the boiler tubes", or something similar.  Had to remove some return lines done in copper as a result.  Fortunately we got paid to re-do this, but I'm still wondering how valid this really is.

Jamie Hall

In some situations

it is possible to get rather severe electrolytic corrosion as a result of having both copper and iron piping in electrical contact -- say through a threaded joint.  It appears that it is very uncommon, but if one really wanted to be very certain that the problem wouldn't happen, one would use dielectric unions to make the joint.



Which are a nuisance.



But one could search "dielectric union" here on the Wall and get some more thoughts on the subject.



I hate to be skeptical, but I very much doubt the theory of "copper ions" attacking the boiler tubing -- for two reasons.  First, the concentration of dissolved copper ions in the boiler water will be very low, unless the water is very acid (very low pH).  Second, if this really were a problem, the feed piping in most situations is also copper -- and the problem would be common.  I've not heard of someone suggesting that having the feed piping to a boiler be copper is a problem...

Pumpguy

Thanks Jamie

You have pretty much confirmed my thoughts on this matter.