Problems with Will-burt 34170 timer

Has anyone had or familiar with problems concerning this will-burt timer, specifically the relay? My DF520 stoker was installed exactly 2 yrs ago. This past fall I noticed the relay chattering and not shutting down the stoker cleanly at the end of the timer cycle. My EFM dealer replaced the relay under warranty and things were fine for about 3 weeks and the new relay began doing the same thing. The stoker shuts down fine when being controlled by the thermostat the only problem is when it is being cycled by the timer.

Could this be a bad run of relays or should I be looking somewhere else (transformer, aquastat, etc) for a problem that may be effecting the relay?

Could be the signal to the relay, it may not drop off enough to release the contacts or bad connections somewhere.

Check all connections, grounds, etc....I think I have seen them put some type of capactiro and/or diodes? across the relay output terminals to prevent the chatter.? It's been a while since I dabble in electronics.

It's very rare that we send out a replacement relay. I would check for a loose neutral connection, not enough voltage to the relay and most importantly, and likely, an improperly matched heat anticipator setting on your thermostat.

To check this, you remove the thermostat from its base and you'll see the two screws that the tstat wire is hooked to. (Assuming you have a T87F tstat)

Put the probes of a miliamp meter tester on the screws, which will pull in the relay in the timer. (Assuming you have steam heat) The heat anticipator is set to whatever the reading says.

As a caution, some will measure this current at TT in an aquastat for a hot water system without removing one of the wires from T. This will probably burn out the heat anticipator.

Thanks guys. I checked all the connections and everything was secure. Stokerman, I put an ameter across the tstat terminal and got a reading of 12mA (the relay closed). Does this reading sound right?

I had a digital thermostat on with no anticpator adjustment. I do have a couple T87F's lying around and will install one tonight or tomorrow. Question on the anticipator setting, is the scale on the tstat in A's and should my setting be 0.12?

My system is one pipe steam.

12mA is .012. Did you let it run for 1 minute?

It ran for 1 minute last night and rechecked it this AM with the same result. Does 12mA sound low? I'm beginning to question the accuracy of my meter. I plan to check it again today with another meter.

My aquastat says "set anticipator to .02" printed right on it so that sounds about right. I would check to see if there is a burr on the timer wheel holding the switch partially open, it is an incredibly simple device really.

The common T87F tstat heat anticipator scale starts at 100 mA (.1) and goes up to 1.2A.

I believe Taco zone valves call for .7 and many applications call for .2, but the only way to know is with the amp meter.

The chattering seems to have stopped. I swapped out the digital tstat for a T87F. I got a 155mA reading across the terminals using a new meter, set the anticipator for 0.2 and the timer has been running well for 2 days. Thanks for all your help. This was the first time I stumbled across this forum. I plan to visit regularly. Keep up the great work.

efm has an area within this forum if you scroll down farther. If you have any efm questions, please visit there or call us. I don't always see all the posts in the Boiler section.