Random no flame, yet always flames after reset

SchenleySeven

My old but regularly serviced Columbia steam boiler with Beckett RF will attempt to start up when heat called for, but randomly not flame. When I tap the reset button, it always fires up. This happens 1-2 times weekly, with no pattern I can figure out.



Thoughts are to replace the Cad flame detector, and if the problem remains, replace the Honeywell control. Both are at least 27 years old; the transformer was replaced six years ago. N & F done a month ago.



Other ideas? Thanks.

Abracadabra

old mechanical relay flameguard?

Had a similar situation with a powerflame burner with an old style honeywell flameguard. Replaced the flameguard because the mechanical relay was flaky.  A tap would get it going sometimes. Honeywell no longer makes it with the mechanical relay.  The replacement is a rm7800 series which is all solid-state.

Jamie Hall

You're probably

on the right track, considering the age of the units -- but don't overlook the possibility of excessive draught, which can pull the flame right off the burner.  I've seen it.  Check the barometric for working right -- or it there isn't one, check the draught to see if you need one.



Couldn't help noticing your pressure settings -- you might be happier with a smaller differential (maybe even as low as 1).

SchenleySeven

Beckett RF and draught

I read here that the Beckett RF can be touchy about wind across the chimney and draught issues like you say, that can cause no flame or a flame out after fire. I checked my Steinen at least 30 y.o. barometric damper so see that it is missing the screw and nut to adjust it, and probably has been for many years. The last annual service shows a breech draft of 4 and an overfire draft of 3.So I buy a 21st century damper!



JH, thanks for your advice on the differential pressure. I know the cut in should be as low as is functional, but the diff was set by who knows who, and i haven't learned what changing it does. What does a lower diff do?



Here is a pic of the old girl:

Jamie Hall

I'll be very happy

if it turns out to be the barometric damper!  But they are such simple things, one tends to ignore them in the dark back there!



The differential, on a pressuretrol, adds to the cutin setting to give you the cutout pressure.  There's a dial inside which controls it.  A smaller differential will give a lower cutout pressure -- in this case, if you set it at 1, a cutout of about 1.5 psi.  Changing it thus will make a small -- a surprisingly small -- but significant change in the cycle timing of the burner towards the end of a steaming cycle (say coming out of a setback, for instance) when the system does build pressure (I'm assuming here that your venting is at least reasonable, and the boiler not too oversized!).  What lowering the pressure will do, however, that is significant is that the various vents and traps will be much less stressed and the whole system should work better.