Steam Problem

Second question first...

(it's a lot easier) -- the cutout should be between 1.5 and 2.0 psi.  If you have the typical pressuretrol, set the front scale at a bit above 0.5.  The differential, which is added to the front scale, is probably set at 1 -- it's the white wheel inside the pressuretrol.



Lots of reasons why you might be getting steam at the condensate pump box, mostly having to do with either failed traps or a water seal somewhere which isn't sealing anymore.  It shouldn't happen.  But, to help further, we really need some photos or diagrams of how the boiler is piped, and how the mains and returns are set up, and how condensate gets to the condensate pump box.

Steam at condensate pump

You're right in figuring you have problems with your traps. The problem is, if your system is like most I've ever seen, you've got more than one failed, and trying to replace them piecemeal will end up costing more than you think, as one bad trap can ruin a brand new trap pretty quick by letting steam pressure jump from the supply to the return. Thermostatic radiator traps are fairly easy to check (by temperature drop), but you may also have end of main F & T traps which may have failed as well-which aren't as simple to diagnose. In any case, if you have steam at the pump, you need to stop it-the pump won't last long otherwise.

As for the pressure set-point,  it ultimately depends on your application. You didn't mention whether it was process or comfort heat, or whether you have a pressuretrol or vaporstat with either additive or subtractive differential-that will determine what the settings will be.

answers, comments, etc

You say the cast iron radatiators have only thermostatic valves.  No traps?  Are you sure there is not a thermostatic trap on the outlet?  If not, are they piped directly back into the return?  That should not be.  Maybe you meant that the radiators have only thermostatic traps?



Pressure drop between supply and return.  There should be no pressure on the return.  The return should be at atmospheric pressure.  That is why the condensate receiver is vented.  If all of the traps are working, you would not have steam at the receiver, or anywhere in your return piping.



Generall, F&T traps (float and thermstatic) can be repaired.  The cast iron bodies, while they may form a rusty film on the inside, generally will last 50-100 years.  The float, set, thermostatic element, etc., are another matter.  They are generally repairable.

This is a link to Hoffman Specialty page on type H F&T trap.  http://www.hoffmanspecialty.com/pdf/hs900/Hs900-h8.pdf

This ia a link to Hoffman Specialty page on type 17c Thermostatic trap.  http://www.hoffmanspecialty.com/pdf/hs900/HS900-17C.pdf

Thermostatic valve vs trap

A themostatic valve is on the inlet of the radiator.  It is adjustable, and it opens and closes the steam valve based on room temperature.  

A thermostatic trap is on the outlet of the radiator.  It closes with the presence of steam and does not allow the steam to pass through it.  When steam is not present, it allows for both air and condensation to pass.



Check out the links I posted for Hoffman products, it would give you an idea of what you're looking at.

Depends on the trap

Usually around 30 degrees F.

Here is a link to a page that may be helpful to you regarding steam traps.

http://www.bellgossett.com/Press/BG-lowsteam.asp

Manufacturer's Recommendations

You should refer to the manufacturer's recommendations before using any additives to your boiler.  Normal operation of cast iron steam boilers does not require any chemical additives unless you have abnormal and corrosive water conditions.



Did you get your traps fixed?