Architect

Sailor_Paul

Looking for some advice from a very experienced steam heat plumber or engineer to solve current problem.   We are working in an old10 story loft building with a large Weil Mclain steam boiler that supplies heat to all of the builidng.   We have created a new space in what had formerly been a partially excavated cellar and set up a new heating system.   The old heating system has a gravity fed return loop for condensate and our new system has a steam take off and condensate return line that ties back to the main lines in such a manner as to work wthin the gravity parameters.   However, we are finding that the condensate line is backed up with water to a degree which prevents our steam coils from getting steam.   It has been suggested that we add a condesate pump to enable our system's coils to get steam off the base building.  The idea would be to then collect the condemsate within a dedicated tank and sump pump system isloated to our system which would then pump the condensate back into the base building condensate return line somewhere above the point where the line is backed up.   I am looking for an independent opinion on the complexity of doing this but it seems to me a fine idea as long as we add back the condensate well above the point that the base building's line might fill and be sure to have a proper check valve / back flow preventer at the condensate pump.   Does this seem reasonable?   We are also checking on the pressure of the base building boiler to see if it might be a bit too high but that is another story.   Any thoughts from an old time steam guru would be greatly appreciated.

Dave in QCA

A little hard to follow....

It is hard to follow from your descriptions, but I think I get it, perhaps.

Some very pertinent question that would affect operation. 

Is the boiler level at the same floor level as the new space?

Is the boiler currently all gravity return?

Is it 2 pipe, with a vented return, or 1 pipe?

What is the pressure?

What is the elevation of the new equipment you installed. relative to the boiler?

New system, I am guessing you mean a new air handler with a steam coil?

Can you take some pictures and post them please.  There are a lot of knowledgeable contributors here, and quite a few of the best steam pros in the country too.  If we can't solve it on-line, maybe one of the pros can come out and help you out.  Where are you located?

Steamhead

What Dave said

and, another option is to run your coils with hot water from the bottom of the steam boiler. This would avoid moving the coils higher.



Here's a much smaller job where we did the same thing to run an indirect water heater.

Sailor_Paul

Answers to steam issue

The old system is a (1) pipe system.  

The old system is all gravity return - no pumps.

The old boiler is relatively on the same level of the new space we created but the water level is below the level of oursteam  take off supply to feed our new steam coil - air handler system.   Also, the condensate returns back into the existing system into one of the exiting legs of the condensate return of the main system (above the boiler).   I would say that the water level of the boiler is probably about - 16 - 20 inches below the trap on our new system.  

The equipment we installed (air handler with steam coil) is meant to serve only our space and our equipment is well above the existing boiler of the building as our equipment is mounted up high near the ceiling of the basement, whereas the boiler sits down on the floor of the basement.

This project is in NYC NY - I will be back at the site tomorrow and see if I can get some pictures that might help.  Thanks for responding.

Dave in QCA

Not seeing the piping arrangement....

The trap on the return of your new coil at first glance, makes no sense.   Is there a vent?

Your elevations sound right, but the max pressure of the boiler needs to be low.  The piping setup for this coile is going to require a different approach than normal, will require venting, and a gravity return, which probably means no trap.  Of course, if you have an atmospheric pressure dry return, that changes everything, but it is highly unlikely on a one pipe system.

Also, do you have any information on the coil?   Hopefully, the inlet is near the top and the outlet is at the bottom, or bottom side so that all condensate drains by gravity.

nicholas bonham-carter

high pressure not just "another story"

that system pressure may be key to your problem, as excessive pressure could cause the returning water to stack up in the returns. i would suggest that you get a good low-pressure gauge from gaugestore.com, [0-2 psi, and put it on with a 16 ounce vaporstat]. i suspect that your boiler may have a staged firing burner [or should have], so that with a second vaporstat, you could use high fire, up to 6 ounces, and then switch to low fire. if the temperature, and building heat-loss then begin lowering the pressure, the burner will go back on high. remember that the returns can rise 1.75 inches for each ounce of pressure in the boiler-keep it down.

these low pressures will save lots of money; however the main venting is key, key, key!!! the low pressure gauge will show you the back-pressure of inadequate venting during the initial burn as air is escaping. you should aim to get the air out without going over 4 ounces.

don't mess around with pumps where none were originally, just return the system back to its state of operation when first installed.--nbc