Steam heat with Dunham vacuum pump

RonK

I have a large old house built in 1929 with steam heat.  This winter the boiler has begun to leak and I need to add water once or twice a day.  The boiler is probably 50 or 60 years old, so it is time to replace it.  It has a two pipe system and the condensate return line looks relatively small.  Near the condensate return tank there

is a very old-looking, very noisy pump that says on the ID plate “Dunham

Differential Pump - manufactured for exclusive use with Dunham Difr~enshal~vacm

Heating System– A fixed differential in pressure, a variable degree of vacuum.”  The pump has 2 gauges on it: the gauge on the left says “vacuum” and doesn’t move, it always reads zero even when the pump is running.  The other gauge reads ~15-20 when it comes on to return the condensate to the boiler. 



I have gotten 3 estimates to replace the boiler.  One estimate proposes “Sterling feeder

pumps with receivers and Dual vacuum pump with receiver”.  The other two estimates list only “condensate tank and pump” and they say that the system doesn’t need a vacuum pump, but I’m not sure they really understand this old complicated system.  Except for the water leak, the system works fine and all of the radiators get hot. 



So my question is, if I replace the boiler, does the new

system really need a vacuum pump as part of it to work right?

BRIANJ

Look in the Library on this site

Do a search of "Dunham Vacum" on this site and it will list "Old Steam Systems". The Dunham Vapor Vacum system is explained in detail as to what it needs to work. This will not only help you understand your system more thoroughly but also you may be able to determine what's wrong with it now. Probably the boiler does need replacing but maybe the parts only need some maintenance.



Take a look and good luck

crash2009

25 Steps

I found an interesting article that you might be able to relate to.  It explains why the vacuum pump is likely not working, how one thing leads to another and eventually to the demise of the boiler.  http://www.heatinghelp.com/article/357/Vacuum-Steam-Systems/251/The-25-steps-in-the-repair-of-a-vacuum-steam-system



Here is some info on rebuilding this geat old system.  http://www.heatinghelp.com/forum-thread/104173/Need-help-understanding-Dunham-system

Steamhead

This might be

a Dunham Differential model "DH" system. Here's a link to an old thread regarding such a system in Huntsville, Alabama. The postings are scrambled since it was imported from an earlier incarnation of The Wall:



http://www.heatinghelp.com/forum-thread/104173/Need-help-understanding-Dunham-system



And here is a set of scans from an old Dunham Handbook describing the DH. See if this is what you have:



http://www.heatinghelp.com/article/163/Older-Steam-Heating-Systems/1299/Dunham-Differential-System



This system needs vacuum to operate. If the pump is not working, it can probably be rebuilt. And make sure all your traps are working properly!