Two Joined Single Loop Hammering Question

ECSmith

Disclaimer - I am a homeowner who is NOT a plumber, so I apologize in advance for any lack of knowledge/terminology.

I bought an old house (1888)  1 1/2 years ago.  It has a steam system.  With major construction going on in half the house, the boiler has been updated (from 250K BTU to 500K BTU - old system was said to be inadequate for size of house plus was old and cracked).

My question is around the return.  There are two loops that come out of the boiler, loop 1 does one side of the house, loop 2 does the other side of the house (they go out away from each other).  The two loops meet again at a T, then one pipe goes to the return/Hartford loop.  The question is should they really meet in a T before the return, or should each loop individually meet below water level before the Hartford loop.  Here is why I ask...

When the new boiler was put in, it heats up quick because it is more powerful, but can create sever hammering (sounds like pipes about to burst).  I am no plumber, but I think the reason is clear.  The bottom line is unless the two loops are in perfect balance (meaning the steam from each loop meet at the T before the return at exactly the same time), it causes great hammering and water to collect in the pipes (you can hear water sloshing around, back and forth).

What I have noticed is as the boiler heats up and the steam starts to flow through the two loops, if loop 2 completes it's "lap" before loop 1, when it gets to the T, besides going down the return, it starts to go backward up loop 1.  When that steam meets the steam coming down loop 1, they collide, create great hammering and you can hear the instant build up of water in the pipes unsure of where to go (the pitch in the pipes is there, but very small).

Now if you work on all the radiators on each side to try and perfect when loop 1 and loop 2 meet at the T, it certainly reduces the opportunity for one loop to go backward up the other loop and thus reduces the hammering tremendously.  But this means that both loops need to be in perfect balance, all the time (i.e. telling everyone in the family not to touch the vent settings on any radiators).

So that is why I am thinking that this issue could be avoided by getting rid of the T and have loop 1 and loop 2 meet at the floor level, below the water level in the Hartford loop.  This way, you would not need to ensure both loops are perfectly balanced to reduce hammering.

Is my logic correct?  Any other considerations?  I think my logic makes sense, but I want to confirm before I suggest the change to my plumber.  Thanks for any help!

nicholas bonham-carter

Return problems

Yes, the returns should always drop below waterline height before they connect.

I hope the plumber measured the radiators, and calculated their EDR before sizing the new boiler, as a boiler which too big, or too small will not be as quiet, or comfortable, or economical as one which has been correctly chosen.

Make sure the main venting is very generous, and the radiator venting is as small as possible to start with. I am guessing you probably have half the number of rads as I have, and I have a total of 18 gorton #2's on 6 dry returns. The air escapes from then at a back-pressure of 2 ounces, and they are silent in operation, which tells me they are working right.

Order some of the books from the shop here, and you will find it easier to follow the principles of your system, diagnose any problems, and even help others with their systems (so addictively fascinating are the principles of steam heat!).--NBC