My EFM 520 highboy with a steam setup has the honeywell timer pictured below. The timer/control was installed in 1974 and I personally have repaired it several times. A problem that I have had several times is the contacts sticking and the stoker not shutting off even though none of the inputs are calling for the unit to run. It can get warm in the house very quickly...fortunately I was home when this happened. I used to file the original points but they eventually wore out. My most recent fix which lasted about 7 years, was to remove the electrical contact points from an old pump switch and solder them on the plate and copper "arms" in the relay (pictured as the black box on the lower right of the image). Worked well and I could make the same repair (for now I have just filed them smooth and they are working okay but will only last so long), but after 37 years I am thinking about replacing the entire unit. I have also repaired the timer side of the unit, but that has worked flawlessly since, this was a mechanical not an electrical repair. Is a direct replacement available as I understand this unit is no longer available? I believe that inputs from the aquastat and steam pressure switch as well at the T-stat also run into this control unit.
EFM recommends the use of a Will-burt No. 34170 timer for steam applications. It includes a transformer and relay to allow the use of a 24v thermostat. The down side is the cost of the Will-burt timer, the last time I looked a new one blew a big hole in $400. If you want the boiler to maintain a minimum temperature, you will also need to purchase a L4006A aquastat.
Depending on your budget for this project, you may want to consider a used or refurbished L8124A aquastat, and an Intermatic C8865 timer. The L8124 can maintain the boiler temperature and allow the use of a tankless coil for hot water; it also has a high limit control that will come in handy if your timer or pressuretrol ever malfunctions.
Do you have a low water cutoff installed on the Highboy?
Thanks for the input, I believe I will nurse this along and look for NOS replacement. There is not a low water cutoff installed on the boiler. All of the other controls are from the original install in 1952.
I think the only low water shutoff is me! I've been looking at this for 40+ years, sometimes without the covers on and I'm almost certain that it doesn't have anything beyond an immersion aquastat that looks like this:
So the low water cutoff would be a device that would override the relay in the event of a failure like I experienced where the stoker kept running and enough steam escaped through the vents and/or relief valve?
Thanks to all who responded. I had an old, but barely used, honeywell S400 timer on hand and a local EFM dealer installed a new ARGO 822II relay in conjunction with that timer. Normally I do all my work myself, and if I had used an exact replacement I certainly would have been comfortable doing that. Actually I did find a rebuilt Honeywell R183B for $300, but the fix I did was about half that.
Everything is working well. I will plan on installing a low water cutoff next spring. In addition, on recommendation of the service person, I cleaned the pigtail etc. to which the pressuretrol/pressure guage is attached, something I had never done. Might save a bit of coal if the system was pressurized but the t-stat was still calling for heat. Also set the pressure to 1 1/2 lb cut outwith a 1/2 lb differential from 2 lb cutout and 1 lb differential.
Good you were able to get things resolved. S-400's look to be pretty solid timers, I have 2 of them on hand, one will be put into service on my Axeman-Anderson I'm installing here now, other will be a spare.
BTW, maybe you haven't seen this posting of member wanting old timer/relays to repair or for cores: