vacuum return changed to gravity commercial

maria union hvac tech

hey guys can you help a girl out,im probably the only comerical/industrial hvac tech in north america that is a woman or at least that i know of and i need help from the dead men.im starting a couple of steam boilers,different locations,but both commerical,the engineers on the job took out vacuum return systems and put in boiler feed tanks/pumps to start.we know that the piping in vacuum return systems were sized smaller,now my condensate is 80-100 degree f in the tank,we know that it needs to be between 160-185degrees now that we are a newly gravity return system,ok so i have to raise the pressure in the boiler to force condensate back quicker as to loose the the sensible heat as to not through cold water into the boiler.we know what this can cause....other than that, they took scotch marine boilers(big steam chests)and put in packeged boilers(smaller steam chests),the velocity of steam in high fire(power burners)suckes the water right out the of the boiler,now i know the bioiler manufacturers nowadays use the near boiler piping as part of the boiler and all sizing ok,any suggestions and how i can make this work,im running 5psi,when 2 needed,did edr calculations,and still getting cold condensate back.can anyone help maria

Steamhead (in transit)

Some of those old vac pumps

were added to existing systems. If this is the case, and there aren't any "lifts" (places where vacuum raises returning condensate to a higher elevation) then gravity return should be fine.

If the vac pump was added to lift the condensate, use a transfer pump instead to do the lifting. This is covered in chapter 12 of "The Lost Art of Steam Heating".

The water leaving the boiler on high fire can have several causes, here are some big ones: 1- improper near-boiler piping, 2- water dirty or too high in the glass, 3- boiler is over-fired.

The lower temperature of condensate in the tank probably isn't much of an issue, unless that cold water is pumped straight into the boiler instead of the equalizing piping (BELOW the waterline) which will temper it. I hope they didn't install a large trap in the return line approaching the feed tank. That's a major no-no.

BTW, scotch-marine boilers don't have big steam chests. Most other older steel and cast-iron ones do.

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