zone valves and check valves

Campo

I am working on a 2-pipe, air vent steam system which heats a business/appartment building. System has zone motorized zone valves. Pressure set at 0.5 psi. All condensate returns go into wet return indevidually. However, there are check valves on each branch of the wet return. In know before the hartford loop and equalizer, these were used to prevent the back flow of condensate. My question is if they are still necessary.

With the zone valves installed, how can the condensate water be put back into the boiler and not work its way up into the mains? At the end of the cycle, I know that the "A" dimention and the remaining steam pressure a the ends of the mains are needed to put the condensate back in the boiler. But, if the zone valve is closed at this point, all the is left is the A dimention (which is only 17" on this system). Does this make the check valve necessary? Should I be "maintaining" or cleaning it out?

Thanks for your help,

Campo

Ken_8

Remove the swing-check guts...

And see what happens. At half a pound, you are where you should be for a vapor system. The water's backing up into the returns.

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