compression tank surging at start up

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So this past summer I got ambitious and removed the nine cast iron radiators in my two story house and took them to a powder coater for sandblasting and powdercoating. They are 1920s Corto design and look beautiful after removing 5-6 coats of paint. Reinstallation went well with no leaks.

The only change I made to the system involves the old Trane steam control valves on the radiator inlets(the original system was a Trane low pressure steam system, now converted to hot water) which I opened to their maximum opening after seeing how restrictive they were at the midpoint where they had previously been set. I think they were designed to throttle very low flows of steam.

I have a Burnham non condensing125,000 B hot water boiler about ten years old with a cylindrical(non bladder) expansion tank with a BG Airtrol fitting, plumbed to the top(outlet) of the boiler. The circulator pumps away from the boiler.

The boiler has always started up quietly, and only a very slight flow sound at the expansion tank at shutdown. When I started it up this fall, there were a lot of flow sounds (surging?)into or out of the expansion tank that persisted for about 15-20 seconds, then subsided. I have bled the air out of the radiators, as well as 3 convectors that are not as pretty as the radiators. I also drained the expansion tank and refilled it. Once it is up and running, all the radiators heat up uniformly. If I close the ball valve to the expansion tank, it starts up quietly.

Any ideas why It is noisy now? Does it need to go through a number of start up shut down cycles ? It really hasn't run much yet this season. Thank you for any advice offered.

Peter Ferguson

La Crosse, WI

Paul48

Relevant Info

http://www.heatinghelp.com/forum-thread/128385/expansion-tank-non-bladder-type-problem  Do the convectors have air vents on them? Are you running the system at the proper pressure? Are you pumping away from the expansion tank(you said boiler)? In a newly converted system, a non-bladder type expansion tank would not have been my choice( my opinion).

nicholas bonham-carter

Noisy expansion tank

These noises from the tank must result from some restriction in the system, such as the trane valves, which as you say were designed with a very small flow of steam in mind. If you have to remove them in order to have a normal hot water flow, then please offer them for sale on the sale department here. Those people who have trane systems may need those valves.--NBC