Parallel Flow & Counter Flow Piped Together?

Ironman

Look at replacing a boiler (300k output) on a one pipe system that has a piping arrangement that I'd never come across before: there are two mains that go left and right off the boiler for about 15 to 20 feet; then each one Tee's horizontally again. Going one way out of the Tee, the pipe slopes downward in parallel flow and loops around until it drops to the wet return. Going the other way out of the Tee, it's piped counterflow about 30 feet and originally supplied two rads and had a main vent. Now, two of the rads on one of the counterflow sides and one on the other side have been removed. the main vent has been removed. Originally, both sides had two rads. We intend on reconnecting these rads.



The system has been down for a year and the present owner is not able to know the long history of the system to tell if there were issues before the rads were removed. Heat pumps have been added which were heating the house for past 15 years.



My question is this: wouldn't this piping arrangement be subject to water hammer if we reconnect all the original rads? It seems to me that the condensate returning from the counterflow would be picked up by steam from the boiler at the Tee and slammed down the parallel flow main.



Again, one side of the counterflow is now capped at the run outs and dead and the other one only has the first rad connected near the main Tee so I can't determine if it had issues before.



My plans are to slope the pipes in question downward and vent them with dry returns on each. That would be included in my bid and eliminate the potential issues, but would not satisfy my curiosity.



What's the opinion of the experts? Has anyone come across this setup?

Steamhead

That setup will work

as long as there is not too much radiation for the pipe sizes involved... how big are the pipes, and how much radiation will be on each one?

Ironman

Pipe Sizes

It's 2.5 in coming into the bull of the Tee and going out the parallel flow side. I don't remember if was 1.5 or 2 in. on the counter flow side of the Tee. I think it was 2 in. and then reduced to 1.5 after the first run out. There will be about 38 sq. ft of radiation on the counter flow. The numbers are the same ( or close) on both sides.

Steamhead

Shouldn't be a problem

with that small amount of radiation. Vent the end of the counterflow properly and it'll work as the Dead Men intended.

Ironman

Oops

I only counted the rad that's presently connected.



Make that about 90 - 100 sq. feet on each counterflow.

Steamhead

You should

still be OK. 

Ironman

Thanks

Thanks, Frank.

Charlie from wmass

I have had to install drips

some times to catch the condesate for counterflow piped sections that were added after the dead men had left the building. Full size tees where the supply comes off the main are usually adequate for this. Can you tell if the pipes were added to the existing system or if they all went in at the same time?

Ironman

Piping

It's original.