Two-pipe with vent

Jeremy Scott

I have an old steam building that has had many changes to it, and not all were consistent...All of the radiators are two-pipe with both the supply and return connections at the bottom. Each radiator also has an air vent. This looks like an old gravity, wet return system. Many of the radiators were retrofit with Honeywell electronic valves and remote 24v thermostats. they installed traps but left the vents. the boiler was recently replaced and a new condensate pump with two main traps was installed...some radiators had TRVs installed in the vents...even found a one-pipe radiator in a small room...

My plan is to replace all of the steam valves with new TRVs, replace all of the traps, install traps on the radiators that don't have them and remove the traps at the condensate receiver. Question is what to do with the vents in the radiators. With the traps are they needed?

Sad thing is almost every radiator has an electric heater plugged in next to it...
thanks,
Jeremy

Brad White_203

Oy Vey

What a mess it sounds like. Seems whomever cobbled that together over time to no end benefit, despite good intentions.

The best system of what you describe (my neighbor has one, an old Victorian), is a two pipe vapor system which has each radiator return running express down to below the waterline into, of course, a wet return.

Each radiator has a vent for that reason, whereas a normal "trapped" two pipe system uses the traps as air vents.

Maybe if that sounds like what was or could have been originally, that might give you a picture of the end result? If dry returns, yes, traps. Sounds like a redesign.

For what it is worth, I have seen a couple of churches with such a hybrid system which work, well, "OK" but what grace I am not sure.

Jeremy Scott

Thanks Brad!

You think this is a mess...wait till my next topic describing the rest of the system of the building I told you about with the thermal chimneys...