2 year old boiler dry fired

Dannyt&c

After 2 years of heating nicely, One day last month the boiler chamber was full of water. The oil boiler was installed by the book according to the manufacturerer specs. and is sized correctly to the connected edr. It is a WM-psgo-4 with a 45 gal. superstor piped off the indirect taping and returns to the front section. A hydrolevel VXT feeds the system set at 2 min. and it comes equipped with a safgard 450 low water cut off. We installed "Steam Clean" to the system to balance the ph.  After the boiler dry fired, we found out the returns are a little slow to return the water. This is one of the few times we did not install a seconday low water cutoff. We checked the probe on the 450 and tested the control and found it does not shutoff the burner for about 40 seconds after its yellow lite is on. Checking this control on another boiler did the same thing. The boiler voids warranty because it dry fired. My question is why did it dry fire if the safgard control is working?

nicholas bonham-carter

40 seconds before cutoff

would 40 seconds of dry firing be long enough to toast a dry boiler?

my theory is: the boiler was suddenly and instantaneously emptied of its water, by a sudden freak over-pressure event, caused by a fauty pressuretrol. this forced almost all the water out, up into the returns; while the burner kept on firing for 40 seconds.

thank god my M-M LWCO cuts off the burner in an instant!--nbc

Dannyt&c

seconds to disaster

nbc, thanks for your reply. I agree with your theory and the replacement boiler does have a 2nd instantaneous safgard #550 lwco that has a manual lockout. We will find out if the boiler loses all the water again. If it locks out we will be looking at the primary lwco as the culprit. I have already found another previous installation with the 2nd lwco that has tripped into lock. If so I will hound Hyrdolevel about its primary. If the primary worked the 2nd should never have to trip correct? thanks. and make sure that M&M 67? lwco is clean on the inside.

Jamie Hall

Now you have my curiousity going...

a time delay on a LWCO?  I can see a time delay on an autofill, yes.  But on the LWCO?  I can see damping the LWCO, so it doesn't respond to very short (second or two) bounces, but a time delay I can't see.  Do all LWCOs have a delay?  Is it adjustable?



Mine is a McDonnel-Miller float type, and seems to be damped, but not delayed (and yes, it is purged regularly)(and yes, it does have a manual reset backup, set a little lower).  The autofill kicks in just above the cut off level...