S86 ignition module problem

delta T

We cleaned and serviced a boiler for a condo building this summer and I am running into some weirdness with one of the ignition modules.

The set up is as follows:
Two gas operators piped in series (24v), two intermittent pilots, one pilot operator (also 24 v).
Each ignition module controls one of the operators so that both pilots must prove for the main burner to come on.
Hot boiler with an outdoor temp shutdown, standard aquastat, zone valves in each unit.

We pulled all the burners, cleaned the boiler and thoroughly cleaned the burners. The two existing ignition modules were getting pretty old, so as a preventative measure we replaced the ignition modules, completely re-did the wiring as it was a crazy rats nest, installed new pilot assemblies, new pilot tubing. Set the combustion correctly, fired it up and it worked great for about a month. One of the ignition modules threw a six flash error code 'Internal Error'. Called Honeywell and they said replace the unit. We did that, and it worked just fine for another 3 weeks, and then locked out again. Did some math and found the existing 40 VA trasformer was close to its capacity at about 38 VA, so we replaced it with a 75 VA. Worked just fine for another 3 weeks, and now it is throwing the same error.

I don't think I got two dud controls in a row.

Any thoughts appreciated.

JUGHNE

Would each module have the same polarity connections observed from the single 24 V supply? WAG

delta T

Yes both fed from the same xfrm with polarity the same.

Tim McElwain

Some pictures would help, not sure I can picture what you have as to controls and how they are connected. Do you know how to diagnose the electronics on those modules?

furnacefigher15

I would look at the valves VA draw. The s86 controls cant handle very much VA load, if a valve is sticking, then it may be over loading the control.

delta T

Spent a good hour on tech support with honeywell yesterday checking and re checking wiring, connections, voltages etc. No one there could definitively say what the problem was, however, I had connected both s86 modules to the pilot valve in parallel. (pv and mv/pv contact from both controls connected to the single pilot operator. Seems like the only likely candidate, though tech support was still not sure that that would cause that error given that they are fed from the same xfmer on the same polarity. So now I have only one module controlling the pilot operator, with the PV lead on the other control capped and no cross connection on the common MV/PV terminal. Hoping that is it, does seem like the only likely candidate, though the extreme intermittent nature of the lockout is still a little confusing to me. Electrical weirdness where the boiler fires at the exact time there happens to be a fluctuation in the main voltage maybe?

@furnacefigher15 I did check the amp draw on the gas operators and the pilot operator and they were all within 5% of the rating label. I did notice that the total VA was awfully close to maxing out the existing 40 VA Xfmr, so we swapped it out for a 75 VA. Runs MUCH cooler now. Checked against the honeywell manual, and everything are within the operating range of the

@Tim McElwain I will load some pics later tonight of before and after the work, and a wiring diagram of how it was and how it is now after talking with tech support.