Gravity Return vs Condensate Pump?

elfie

have an old low pressure steam system that now includes a condensate return pump



originally it appears to have been a gravity return with a hartford loop.  unclear why system was converted - maybe it occurred when it was switched from coal to oil.



are their advantages in switching back to a gravity return?

Jamie Hall

Yup

There sure are.  Gravity works every time, and doesn't need repair.



However, you need to figure out why the system was converted in the first place.  It is very likely that it was a knucklehead.  However, it is also possible that some other change was made (by a knucklehead) which forced the addition of the pump.



Check you pressure; nothing over 2 psi -- and if it is two pipe vapor, over 12 ounces.



Check you boiler water level.  Any loop seals or wet returns get dried out by lowering the water line with a new boiler?



Is this one pipe or two?  If two, check all the traps.



And get back to us with what you find!

gerry gill

if the condensate tank is placed

by the boiler, its really dumb..if water could make it back to the condensate tank, it could make it back to the boiler by gravity..that said, perhaps there is a use for a condensate tank if you have a remote part of a building that because of the pitch of the steam main the condensate has to be pumped back up to an over head return, or another instance would be if radiation sat so low as to require it to drain into a condensate tank..otherwise we usually remove them and restore the wet returns.

elfie

pic of condensate pump to be removed possibly

i think the problem with coverting back to a gravity return is the issue of venting some of the return lines that know depend on condensate tank vent



another issue is the circled area in pic below where water appears to be accumulating in the underground return pipe which slopes down toward circled area.



wouldnt this accumulation of water prevent air venting?  and why would it be piped to go slightly upward before connecting to the receiver? why would there be a pipe design here that would seem to be blocking air flow?  the pipe coming down also shares condensate flow to this accumulation area (bias toward receiver)

furnacefigher15

Is this for

A 2 pipe system?

elfie

gravity vs condensate pump

yes, it's a 2 pipe trapless radiator system (low pressure)

Jamie Hall

The venting

problem can, and should, be fixed by adding main vents to the ends of the steam mains.  They should be there anyway.



That little odd bit of pipe... who knows?  But keep in mind that so long as it is all below the water line of the boiler, the water doesn't care -- it will go through it anyway.  As you note, air won't -- but that won't matter if you have venting on your steam mains.

elfie

vents at end of main (low pressure)

its a low pressure system and i guess it would be better to have air vents at end of mains vs a f&t trap.



the water blockage that appears to exist neat condensate pump may be an issue for air venting purposes



does it much matter if air venting occurs at end of mains vs the vent pipe on condensate receiver for a low pressure system?



one complexity may be the existence of an over sized boiler (so air venting at end of main vs relying on condensate receiver vent may make sense?)



thanks

Jamie Hall

main vents

Oh yes.  Good venting at the ends of your steam mains will help in a lot of ways!



That said, some really low pressure systems -- vapour systems -- had dry returns, and used crossover traps at the ends of the steam mains.  These were typical radiator traps -- but usually the larger 3/4 inch size, which were mounted above the steam main.  Inlet from the steam main and outlet to the dry return.  With those systems all the venting was concentrated where the dry returns drop down at the boiler -- often with one of a variety of fancy contraptions at that location.  But even those can be satisfactorily handled, if the crossover traps have been removed, with main vents at the ends of the steam mains.



Then all you need is a way to get condensate back to the boiler from all the low points in the mains or dry returns if you have them -- and chances are that that is setup just fine, as the condensate is getting back to the condensate pump now.



So... in my view you would add main vents on the steam mains, take out the whole condensate tank and pump nonsense and connect the wet returns which were going to the tank directly to the boiler, through a Hartford loop.  No other traps -- f&t or otherwise -- needed.



But keep the pressure down!  If it really is a low pressure system -- or a vapor system -- you may want to invest in a vaporstat for better control, but 1.5 psi should be your cutout, or less if you can (the system I superintend cuts out at 6 ounces!).