Boiler not firing (Happy Thanksgiving!)

EdTheHeaterMan

109A_5 said:

EdTheHeaterMan said:

109A_5 said:

Can you manually open the Damper and then disconnect the damper cable to the L8148E and jumper B1 to R ?
Does the boiler fire up with a call for heat ?

You can connect B1 to B on the Aquastat switch as indicated on the photo above.
Then the L8148 can be used automatically for the rest of the life of the control.

It appears that this control will have 9 lives as long as @matt9090 has a soldering iron

Won't going to B instead of R bypass the High Limit Controller switch depending on which wiring diagram you believe? OK for a test but not good for normal running.

Yep. I noticed that at the last minute and made a change on my post.

I wonder if you know why the fuse blows on that L8148 control when you plug in a vent damper the first time?

matt9090

Ok so i jumped the center connectors on the damper molex plug on the board which is what makes the connection between B and R on the high limit switch. I also tried jumping B to B1. Both resulted in the relay buzzing and sparking. I checked solder and don’t see any bridges. Without that jump the relay powers the circ pump just fine. I thought I was making headway! Ugh. 

109A_5

Overcurrent, so you can't go back to the factory supplied jumper on the mating connector if the Damper fails. However the Pico fuse can be replaced.

matt9090

B to B1 jumped still caused the buzzing. 

109A_5

Assuming your solder connections are fine disconnect the S8600 at B1 and try it again, see if there is no buzzing.

matt9090

I am about to throw in the towel. I have a new aquastat coming today but was hoping to save the $300. I think I’d like to not connect the damper and leave the jumper and fuse in tact. I’ve seen mixed reviews on whether that’s safe but it seems it more for efficiency than safety. 

matt9090

No buzz with B1 disconnected

109A_5

With B1 disconnected does the Damper work correctly ?

matt9090

The damper does nothing with B1 disconnected 

109A_5

Interesting, may be the Damper control need to see that load to operate.
OK what I now suspect is two things

1. There is an overload toward the S8600 and the poor solder connection acted like a self resetting fuse, did you ever find those safety limit controls ? Chafed or crushed wire going toward the S8600 from B1 or the S8600 its self.
2. Something is loose toward the transformer causing the 24 VAC to drop with a normal load.

Since you get a big spark I am thinking number 1.

109A_5

What is going on now may have had hand in the cause of the failure of the first transformer. In the present case the solder joint got beat up. I would put an independent 24 VAC load that draws about 1 Amp between B1 and B2 and see how it acts. Not sure if you have any thing like that.

matt9090

Yes. I removed one of the wires and then tested continuity between the two prongs assuming that is the right way to test it. Both had continuity. 

matt9090

Can I just connect the 24VAC transformer directly to B1 and B2 or does that still need to be active in aquastat for this test? I assume you want to see if we get a spark?

109A_5

I would measure using an Ohmmeter (boiler power off) the wire you disconnected from B1 to Ground and also the disconnected wire from B1 to B2. Both readings should be about the same since I believe B2 is grounded through the S8600 and the green wire to the gas valve. I would expect this measurement to be 24 Ohms or higher.

At this point I believe you repaired the Aquastat and you are now seeing the real original defect.

109A_5

No, actually I am wondering if the damper and the Aquastat is now OK and a normal-ish load on B1 to B2 would prove that, no spark.
Well if you want to do a spark test take the wire you removed from B1 and touch it to Z. If it sparks the S8600 or the wires going to the safety limits (if actually connected from B1 to the S8600 per the boilers wiring diagram) or one of the safety limits themselves is shorted to ground.

matt9090

Sorry I’m not following. I tried the disconnected B1 wire to B2 which is still on the board. I got .1 which is what I get when I touch the probes together. What ground should I use? I tried a few things on the board and a pipe and got weird readings. Nothing gave me 24 ohms

matt9090

B1 connected to Z just makes a mild hum and nothing else happens. When I put everything back where it goes and turned it on the damper kept spinning round and round again. Back to square one!

109A_5

Any ground would do, boiler jacket, gas valve, junction box, etc.

109A_5

It appears something highlighted in Red is shorted to ground (ultimately back to B2).

matt9090

Ok yeah I just tested that and it’s .1 ohm. It actually fluctuates between .0 and .1

109A_5

Connecting the wire that is disconnected from B1 and touching it to Z should fire the boiler with no other control involved. I suspect the Hum is the transformer being overloaded. Are the safety limit switches wired between B1 and the S8600 as referenced on the boilers wiring diagram ? In other words B1 to safety limits then on to the S8600 ?

109A_5

While monitoring the 0.1 Ohm resistance (wire disconnected from B1 to B2) disconnect the 24 VAC wire to the S8600 does the 0.1 Ohm go away ?

matt9090

No. B1 goes to S8600 24GRND and B2 goes through both safety limits and then to 24V

109A_5

OK, ultimately probably don't matter much but good to know. B1 is just referenced to ground.

Disconnect 24 VAC wire at the S8600, with the Ohmmeter
Measure from 24GND to 24 VAC on the S8600.
Measure from 24GND to the wire removed from 24 VAC on the S8600.

Which has the 0.1 ohm resistance ?

Peter_26

When you replaced the aquastat last year, was the transformer bad right out of the box? Why was the aquastat replaced? Was the aquastat replaced with an OEM? The manual has a replacement parts list and item 10 CONTROL L8148E1257 (AQUASTAT) 1010002 is what the boiler came with originally?

When you say it worked all last year, is the damper the original damper that came with the boiler or was it changed at some point?

109A_5

I now believe the 0.1 Ohms is the
S8600 or a safety limit device or the wiring to the safety limit devices shorted to ground. Disconnecting these things to isolate them you can determine what is shorted to ground. Also visual inspection of the wires for defects. I'll be back in a few hours, Good luck.

matt9090

24GRND to 24VAC directly on the s8600 terminals (no wires used) is 8.5 ohms. 

24GRND at s8600 terminal to the wire (that goes through the limits) is 1.5 ohms. 

Peter_26

There should be high impedance in the mega ohms between 24GRND and 24VAC connections. If you are reading 8.5 ohms without any wires connected then it's possible that the diode VR1 in the S8600 is shorted.

matt9090

I didn’t disconnect all the wires - just the two from the terminals I tested. I’ll go remove everything else and test again. 

As for your other questions my memory sucks and can’t remember the specifics. The house is older so everything was already here when I moved in. The molex for the damper was loose years ago and I resoldered that. When I replaced the whole aquastat I didn’t troubleshoot it like I am now so it’s possible a solder connection was bad and/or the transformer went. So I got a new one. The original transformer was good for a while - at least a full season. Then I figured out it went bad at some point and replaced it. I have been thinking I’ve had way too many issues with these aquastats. 

109A_5

Hello@ Peter_26,

Peter_26 said:

There should be high impedance in the mega ohms between 24GRND and 24VAC connections. If you are reading 8.5 ohms without any wires connected then it's possible that the diode VR1 in the S8600 is shorted.

Do you have a schematic for the S8600 ? I'd like to see that.

109A_5

I agree both those readings seem very low. Unless the meter auto-ranged and you did not see that. Noting where things were, I would disconnect the S8600 from the wires 24 VAC wire and the 24GND wire then Ohmmeter the S8600 terminals.

Also I would then disconnect the wire at B2 that goes to the limits and Ohmmeter that wire to the ground, maybe at different clean ground places.

matt9090

No schematic that I could find but seems straight forward. The you can see the wires coming down which are the B1 and B2 wires. B1 goes straight to the terminal and then You can see B2 connects to that other wire which goes through the limiters and then comes back to the other terminal. 

I’ll give those other tests a shot

109A_5

The schematic comment was for @Peter_26 he mentioned VR1 which is a schematic component designation. Just wondering if he had a schematic for the S8600. Maybe he ripped one apart.

Peter_26

@109A_5 I do not have a schematic for the module, but I do have a module as a backup. I traced the conmections from 24VGRND and 24VAC and they are connected to a diode,VR1, and it looks like it’s a protection diode. 

From you previous post @matt9090 you stated:
24GRND to 24VAC directly on the s8600 terminals (no wires used) is 8.5 ohms.   

If you still had wires connected then what I mentioned about VR1 possibly being shorted might not apply to your issue then. 

I tested my backup module, which is laying on my bench, with nothing connected and that’s how I arrived at my measurements . I upgraded my boiler from a standing pilot with no S8600 module to an intermittent pilot ignition with the use of the S8600U a couple of years ago and added a vent damper about a month ago. My backup module is not an S8600U, it’s an S8600M like yours, it’s basically the same just that the S8600U has the connection for the 6 pin molex from the harness from the vent damper built in. The S8600U also has all the extra electronic circuitry to control the damper. 

matt9090

I removed all wires from S8600 and measured between 24V and 24GRND. It started going up to about 18-19ohms then cut off. It happened again after I came back 20 min later. Tried it a third time and got 8 ohms. 

B2 removed from aquastat and clean ground gave me nothing back. 

109A_5

Well it is kind of sounding like the S8600 is bad. If it was intermittently drawing too much power that would explain the old transformer failure and the sparks after you repaired the Aquastat Relay solder joints and when you connected the S8600 directly to 24 VAC the Burner did not fire and the Hum from apparently the transformer got louder. I just wanted to be sure the 24 VAC wire between B2 and the S8600 was not compromised to ground somewhere (wire insulation or a limit switch). The confusing thing is the boiler's wiring diagram does not match the actual wiring in a few places.

The Green wire between the S8600 and the Gas valve most likely bonds the secondary of the transformer to ground, actually via B1 and not B2. There is probably a connection internal to the S8600 between 24GND and GND (Burner).

What I had in mind before was if you had a independent 24 VAC load (like a resistor or a lamp) that would draw an Amp or so it could be connected across B1 and B2 to prove the Aquastat and Damper operation is now normal. A 24 Volt lamp would work or two 12 Volt lamps in series.

matt9090

Yeah I don’t have anything to put it under load. Things definitely seem to be pointing to that and it’s worth just replacing at this point.

I have the 8600M but it seems that’s a deprecated part so now I need to find the newer model. It might just be the 8610M. 

109A_5

Well since you have a Multi-meter and a soldering iron (more than most folks) I don't know what else you may have. With a quick look the 8610M should work as a replacement and it has some more diagnostic features. looks like the date code on the sticker is 9832, so the 32nd week of 1998, it has been around for a while.

109A_5

One thing that still bothers me is where did the 0.1 Ohm resistance go ????

109A_5

If your Damper needs to see a load between B1 and B2 to activate and you have an old 100 Watt, 120 VAC incandescent light bulb and a way to connect it to B1 and B2 it may be enough load for a test. At 24 VAC a 100 Watt lamp will draw 0.3 to 0.4 Amps and glow dimly. Just an idea to prove the Aquastat and the Damper operation.
If the S8600 draws too much current when the Damper's end switch closes it may cause the Damper's odd behavior.