Troubleshooting a Friday Afternoon Boiler Service Call Without a Diagram

RayWohlfarth · May 1

In this week's video, I talk about how to electrically troubleshoot a friday afternoon no heat boiler call without an electrical diagram.

https://www.youtube.com/watch?v=N27uW7dAeIU

109A_5 · May 2

Is this really what you meant to show at 2:30 ? Wouldn't you want to measure the voltage across the thermostat and its wiring (terminals 1 to 2) ? If the thermostat (or its wiring) was open there would be 24 VAC as you show.

RayWohlfarth · May 2

@109A_5 Thanks for watching and the question. I was showing that if there is power on terminal 2, it means the thermostat was closed and calling for heat.

JUGHNE · May 3

For me, finding an open switch/limit is easier to check for voltage across its terminals with the power on. No wires to disconnect. If you have power across the switch then it is open.

I have read many posts on HH about someone trying to TS by checking terminals to ground, showing power and then being confused. Feedback thru devices can show you power to ground on both sides of a switch/limit.

One item often overlooked is the low gas pressure switch that requires a manual reset. The gas was shut off last spring so the switch opens. This phone repair has saved me several times from making a road trip.

Jamie Hall · May 3

Couple of thoughts, @RayWohlfarth . The first is sort of obvious… and sort of not. Be a little careful when measuring voltage at the various limits — not all safety circuits are on the 24 VAC side. Some are on the line side at 120 or so. Of course, if the power is off that shouldn't be a problem! But still…

The second is that tracing circuits can be a bit tricky. Not all boilers are wired neatly…

109A_5 · May 3

https://forum.heatinghelp.com/discussion/comment/1895556#Comment_1895556

OK… I would not rely on bonding between the 120, 230, 240, 277, 480 VAC (primary) side typically L1, L2 and the 24 VAC control voltage (secondary) side. To me Measuring between terminal 2 and terminal L2 may be meaningless.

I also find 'power on' troubleshooting works best, you just have to be more careful.

And yes, I agree with @Jamie Hall there is no guarantee the control voltage is 24 VAC. Find the control transformer and know what to expect.

retiredguy · May 4

That was a good explanation for how to check a no heat call on a power burner. If you are speaking to a newby you may have to explain it in more detail. By the way, are there still Gordon Piatt burners out there. They were one of my least favorite burners and that Bryan boiler was a mess. I saw a lot of them in that same condition. Thanks Ray.

RayWohlfarth · May 8

Welcome @retiredguy I hated them as well and we used to repp them eons ago.

You all make some great points Sorry it took me a while to respond. I just got a new Mac mini and the learning curve for me was steep

jbjb · May 14

I'm in the UK and work on protection & control systems for HV power transmission. I get to trace a lot of panel electrical faults! My chosen tool for this would not be a multimeter, but something like a Fluke T130 electrical tester. Why?

1) It will automatically indicate voltage on DC or AC circuits automatically, and tell you what you're seeing. Most multimeters won't - if you're set to DC volts, they won't measure AC and vice-versa. That can lead to false confidence that something is dead when it isn't.

2) The indication (LEDs by voltage and and LCD display) are where you're looking - at your fingertips. You don't have to look away and risk the connection slipping off and you getting hurt.

3) It has a torch built in 😀

4) It is self-testing to some degree. But, whenever you use a device like this you must prove its operation on a known live voltage source (or with a proving device) immediately before and after use.

I still carry numerous multimeters but for proving stuff dead prior to work or tracing faults, the electrical tester wins hands-down every time. Something for your next birthday or Christmas wish-list?

JB