parallel or counter flow?

vinceM

Hello all.
Can someone confirm for me whether I have a parallel or counter flow system. The boiler is 40 years old so I assume the piping is also. Moved in to the house 2. 5 years ago. Slowly figuring out the heating issues. I was looking back to my earlier posts/answers ,I thought someone had answered this for me but I can't find it.
What is the key to knowing which type of system I have.
Thank you

KC_Jones

If the main is connected to the boiler and runs out, but doesn't have a pipe at the end that returns, that is counterflow. Also counterflow should have some kind of drip at the beginning of the main near the boiler. If at the end of your main it turns back towards the boiler with a smaller pipe, that is parallel flow.

vinceM

There are 3 mains. Each has a smaller diameter copper line connected by an elbow that drops down to the floor and returns to the boiler. There is no drip pipe at the boiler....
So it's a parallel system.
That does raise a few other questions for me though....
Thank you KC.

Fred

Sounds like a Parallel flow if those drips are at the end of each Main.and drop into a wet return (below the boiler water line all the way back to the boiler).

Dave in QCA

A parallel system is one in which the steam and the condensate in the bottom of the steam main are both running in the same direction, that is to say, they are running parallel to each other. Of course, the steam has to travel away from the boiler. If the mains slope down hill running away from the boiler, obviously, the condensate in the bottom of the main will run in the same direction.

JUGHNE

Just to clarify, you do have only one pipe connected to each rad?

My guess is that your piping is over 40 years, might not have been much new steam installed in the late 1970's. IMO

You are lucky to have copper wet returns, they may have been installed with the current boiler. Are they all above ground?
At the end of the steam mains before the copper drops down to the wet return you should have air vents, assuming you have one pipe steam.

vinceM

Yes. It's a one pipe system. The copper(wet) returns run along the periphery of the basement floor,above ground, back to the boiler. Yes, two weeks ago I replaced 2 out of three inadequate vents with #2 Gortons. It's a start. I need to replace the third. Then calculate the overall load to know if I need to supplement those new vents with more.
Is the distance that the returns travel back to the boiler a factor? Since the pipes run along the floor and there is no grade(slope) running back to the boiler, how does the condensate make its way back?

Fred

Those returns are always filled with water, up to the Normal water level of the boiler. Those pipes don't need any pitch. The laws of gravity cause the water level to equalize. The only factor the long wet returns have is, the longer the wet rturn, the more water there is in the system and the more wet return that needs to be flushed out from time to time (if you have valves or some access point to flush them).

vinceM

Understood.
Thank you Fred.
As a follow up, I understand that in a parallel flow system the MAIN(s) that come off of the header/riser should pitch(slope) AWAY from the boiler as they travel towards their terminus and a counterflow system(dry return) the MAIN should slope TOWARDS the boiler. In the case of my boiler there are 3 MAINS. 2 that come off the risers and 1 that Ts off of one of the two "original" Mains about 6ft away from the boiler. As I look at the ALL the pipes I see that in some places the pipes pitch AWAY and other TOWARDS the boiler. Again I assume the job is 40 years old so there probably is sagging in some places. Is there a technique with a line level that can be used to correct any discrepancies?

Jamie Hall

It's not unheard of for some sections of main to pitch one way, and some the other. What is essential, though, is that they all have a smooth slope to where the condensate can drip to the wet return. If the mains are insulated it can be a little difficult to measure the pitch, since the best way to do it is to place a good long level against the pipe and slide it along and make sure that the pipe is straight and pitches properly. Avoiding hangers and the like...

One can also stretch a string from one end to the other, say at the centre line of the pipe, and measure the pitch of that -- and at the same time, check that the string stays at the centre and that the pipe doesn't bow up or down.

There are other ways...

Fred

Typically, the main piping is from the original construction of the house, regardless of the age of the boiler. Yes, you can run a string taught along the top of the main to see if their are sags in the pipe. If you find a a sag, try to lift it with pipe hangers, being careful not to change the overall pitch in the wrong direction.
I assume the "Main" that has the Tee in it is actually a branch off to one side of the main ? It may be pitched back towards the main (looking like it is pitched towards the boiler) to let water run back to the main Main so that it can run parallel down the main to the wet return. That branch may well be counter flow, till it gets to the main Main, just like all the radiator run outs on a one pipe system where the condensate actually runs in a counter flow direction until it get back to the main.

nicholas bonham-carter

Good point Fred.
Many larger systems are like this.--NBC