Water backing up return

HVAC003

We are having a problem with water backing up thru a return to a Hoffman 4a vent located on a dry return. The boiler is a Weil-McLain EG series Steam boiler. We have removed, cleaned and inspected all return piping. Boiler is piped with equalizer as per manufacturers drawing. We have replaced pressuretrol and cleaned steam siphon connection. Pressuretrol is set at 1psi differential, .5 psi cut-in. Gauge on boiler functions and indicates corresponding pressures pressuretrol is set at. House is two story home. The system was originally a one pipe system with CI Radiators at some point (30+ yrs ago) The radiators on main floor were replaced with baseboard with piping added to dry returns. Hoffman 17c traps were installed on each lenghth of baseboard. CI radiators remain on second floor. Have replaced 2 traps on baseboard because steam was present in return. Have also skimmed boiler twice and added 1 can of Squick boiler cleaner. Boiler has been in around 5 years and seemed to run fine until about a month ago with a call that water was leaking out above mentioned vent and no heat in one room on main floor. My first concern is trying to stop water from backing up return any suggestions?

nicholas bonham-carter

Double check the pressure with a good low pressure gauge (0-3 psi). If the present gauge is on the same pigtail as the pressuretrol, and the pigtail is plugged, then your pressure may be too high, causing those symptoms.--NBC

Jamie Hall

The only way water can be backed into a dry return is too much pressure. So... double check, as NBC said.

The only other possibility is that there is a blockage in the return, trapping water -- but you'd notice the slow return, and a blockage is exceedingly rare, anyway.

Fred

Is the normal water level in the boiler where it should be? Do you have an auto water feeder? Any chance that has failed and is flooding the boiler?
Did anything change around the time this started happening? Any plumbing changes/repairs to the heating system?
Is the Hartford loop and all the wet returns still below the Normal water line?

HVAC003

have disassembled and cleaned pigtail, Water level in boiler is normal. Loop and wet returns are below water line and are piped up to equalizer 2" below water line.

HVAC003

Shouldn't equalizer prevent water backing up return?

HVAC003

This system has dry returns from radiation with radiator traps and dry returns from the ends of steam mains that drop down into a common return manifold below the water line. Would the pressure from the returns from the steam main push water up the returns from the radiation? there is no trap on the steam main return so that line would have pressure and the trapped returns have no pressure because of the radiator traps.

Jamie Hall

The equalizer doesn't prevent water backing up in the dry returns, since they are -- or should be -- at atmospheric pressure. However, remember that each pond of pressure will hold the condensate in the dry and wet returns 28 inches above the boiler water line. You have to have enough vertical there for whatever pressure you are actually running.

Fred

I think you are going to have to post some pictures so we can see what is going on. Was the Squick added to the boiler around the time this problem started? Does the water in the sight glass bounce a lot (more than 1/2 to 3/4") when the boiler is running? Are you 100% sure that one of the radiator traps has not failed open? It almost sounds to me that the radiator that doesn't heat may be passing steam through it and into the return. Are any of the returns from those radiators steam hot when the boiler is running?
Are you sure the return that has the flooding vent isn't plugged up with gunk, maybe at or below the water line causing condensate to back up?

HVAC003

All near return boiler piping has been removed, checked and is clear. I've come to to conclusion I need to install a F&T trap at the end of the Steam mains where they drip into the the wet return. Water level in boiler is normal when this problem happens. Water feeder is not in play have shut it off and tested.
Thanks for all the input