New Crown Boiler AWR 105B shutting down after tripping transformer circuit breaker.

Vincent Valentino

Hi, I have a newly installed Crown AWR 105B (installed 3 years ago). Unit shutting off and tripping the circuit breaker at the transformer. Once the unit cools down and the circuit breaker is reset, the unit run normally until it heats up again. I have had the company that installed it a year ago, 2022, and they replaced the LWCO and it ran normally for the remainder of the year and until now. Could it be the same problem again? I have made a video describing the issue. https://youtu.be/DWGBtNOzdtI?feature=shared

HomerJSmith

Tripping a circuit breaker (fuse) on a transformer is indicative of a ground fault (short). Check the wires from the transformer looking for a pinch wire making sure the wires are intact. If intact, look for a problem with any device in the circuit.
It is temperature related, evidently. Jump every device in the safety circuit and see what happens. It may be the transformer circuit breaker, too. You can take Freeze, a coolant in a can, and spray each device in the circuit one at a time, looking for an affected device.
https://www.amazon.com/freeze-spray-electronics/s?k=freeze+spray+electronics

You can use a clamp meter on the transformer low voltage wire and look for a current increase that would trip the circuit breaker. Wrap the wire around the clamp several time to improve the reading. I assume the circuit breaker is on the low voltage winding of the transformer. If the circuit breaker is on the high voltage winding on the transformer, look for a failed transformer. You can also use a hair dryer on each component heating each device up before the 10 min and see if you can create the failure.

HVACNUT

It doesn't need to be a short. It could be exceeding the draw. I couldn't begin to offer what can exceed the draw, or short, after 10 minutes run time. Is there condensate protection or something where a relay or time delay would energize after 10 minutes?Well I'll answer my own question. With either of these controls, I believe there's condensate protection. Check to see if the breaker trips when C1 is energized. It could be a bad circulator relay coil if does.
Check all low volt connections. Check all grounds.
If you have the Beckett control, check the Thermistor Probe Sensor, and the Boiler Ground Stud. IDK what they are, but they sound important. 

HomerJSmith

I guess I was barking up the wrong tree, the coon's up the other tree. Nice post @HVACNUT.

EdTheHeaterMan

HomerJSmith said:

I guess I was barking up the wrong tree, the coon's up the other tree. Nice post @HVACNUT.

Homer, you don't need to call yourself an old dog!!! You can bark up whatever tree you want on this forum. Even HVACNUT gets it right sometimes.

Sounds like this short is going to be inside the control, because there are no external wires that get connected to either of those aquastats that can cause the transformer to trip for the protection circuit.

But if there is a zone valve involved... then there may be a situation where the boiler gets to temperature for DHW and once that is done (in about 10 minutes) the zone valve transformer does its thing and finds one of the zone valves are mis-wired or have some other form of short circuit. Then ALL zones are out of the picture.

So the next question is "Does @Vincent Valentino have more than one thermostat?"

HVACNUT

Apologies. I posted the incorrect wiring diagram for the OP's boiler.
The wording mostly relates.

The LWCO is constantly 24 volt powered and simply opens if needed. I don't see how it could cause excessive draw.

No codes on the operating control?

Vincent Valentino

First of all, thank you so much for all your expertise with this problem. Yes, I have 4 zones. Based on your suggestions, I went through the obvious exposed wiring (which is a bit like spaghetti) and wire nuts and reseated everything (should have included a pic). Still had the same issue. Then I checked the zone valves and found one that looked a bit askew. The head was loose on it. I disconnected and reconnected the wiring for it and then tightened the screws a bit and reseated it. That seemed to fix the problem although I don't know for sure. It's a Taco zone valve. The issue with the transformer circuit breaker blowing is fixed.



Should I replace the head on that zone to be sure the problem won't resurface?

You guys are the best.... I can't thank you enough. Happy Holidays.

HomerJSmith

If the problem reoccurs disconnect the wires to the ZV and see if that is a permanent cure. If yes replace the head.

HVACNUT

The head goes on in a type of twist lock motion. Are you saying the head wasn't locked onto the body, or the wires weren't secure?

Vincent Valentino

That particular zone valve has always been (since I bought the house 10 years ago) loose but, the system always worked. When I opened the valve manually it wasn't tight and was twisted a bit, not locked to the body. The pictures are after I secured it back to the body. I redid the wiring on just to make sure it was secure. Thanks again.

EBEBRATT-Ed

@Vincent Valentino

Those taco valve are pretty reliable but the heads can go bad. Just a few comments

When those zone valves get powered it takes a 1-1 1/2 min for them to open they have a wax motor that needs to heat up.

You can teel if a valve is open or closed by lifting the manual opening lever on the side of the valve. If the lever is resistant to moving the valve then the valve is closed. If the lever moves freely the valve is open.

109A_5

Hello @Vincent Valentino,
Looking at the on line manual for the Crown AWR 105B that does not look like the original (Honeywell AT140B1297) 120 VAC to 24 VAC transformer. It looks like a more universal type replacement transformer like this https://www.supplyhouse.com/Resideo-AT175F1023-Plate-or-Panel-Mounted-120-208-240-Vac-Transformer-with-9-in-Lead-Wires-and-Metal-End-Bells That has a built in circuit breaker. So I'm guessing the original problem burned up the original transformer, so it was replaced and the original intermittent (heat or time related) problem still exists.

Since the transformer has a built in 'Lil Popper' the 'Lil Popper' fanboys can explain their troubleshooting techniques.

If you don't have a paper copy of the Crown AWR 105B manual.
https://www.velocityboilerworks.com/documents/9807815-Rev-C-6-22-Aruba-5.1-IOM.pdf

My guess is the first device they encountered on the wiring diagram is what they changed, not actually finding the actual problem.

delta T

@Vincent Valentino I work for Crown in tech support. Are those zone valves being powered by the on board transformer? That is not the original one, that looks like a 75 VA transformer, originally it would be a 40 VA without a breaker. The on board transformer is supposed to power the gas valve, the LWCO, the damper and the control, it is not designed to power anything else. Those Taco heat motor zone valves draw a lot of current. It is likely when the boiler was installed, they fried the transformer trying to pull too much load, then replaced it with the 75 VA one you see installed now. I would recommend isolating the transformer using a zone relay to power the valves, and using dry switch contacts to close the thermostat wires on the boiler.

If you have any questions you can call me at 215-535-8900 X 1214

109A_5

Hello @Vincent Valentino,
As @delta T suggests with 4 zones (4 zone valves) the zone valves should not be powered by the transformer inside the boiler, that probably would overload it. The zone valves are specified at 0.9 Amps each so a 86.4 VA transformer just for the zone valves, not including the boiler's electrical equipment. In reality a slightly smaller transformer (than 86.4 VA) can be used (zone valves only power) since the Wax motor inside the zone valve's head ends up duty cycling its self so it does not overheat.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/571-2-brochure.pdf

Vincent Valentino

First of all, thank you all for your expertise and time in this matter. I've gotten a lot of time saving help and saved a lot of money with this forum and in as much appreciated.

Responding to Delta T and 109A_5. In the fall of 2022, I went ahead and had the tech come out and he in fact replaced the transformer because he said it had most likely gone bad. But that did not fix the problem and he was out the next day troubleshooting again. I had told him when he arrived that I thought the problem had to come from LWCO because I tested everything else with a multimeter myself and found all the voltages to be in line with the schematics. At the end of the day a different technician came out and stated it was indeed the LWCO and that they had had multiple issues with that failing. He replaced it and the problem went away for a year. So to bring you up to date, 2023, both the LWCO has been replaced and the transformer as you noted.

Should I replace the transformer with the original 40 VA or is it okay with this general 75 VA unit? Or should I install the zone relay you recommended?

Happy Holiday's

109A_5

Hello @Vincent Valentino,
Are the 4 zone valves actually power by another transformer or a zone valve controller? The 'Big Picture' of the entire boiler electrical system would help.
I would think if the LWCO was bad and overloading the transformer the system would not run as long as it does.
A 75VA just has more capacity it should work fine to replace a 40VA transformer. The circuit breaker is a nice feature to protect the transformer and the boiler wiring.
I'm still thinking the LWCO is fine and the transformer is being overloaded by the added loads of the zone valves.
As a guess with the limited information, I would leave the 75Va transformer where it is and power the zone valves from another like transformer maybe an 80 VA or 100 VA transformer to power all 4 zone valves independently from the boiler.

Or two transformers like this configuration, maybe only two zone valves per transformer.

Jamie Hall

You can leave the transformer, I suppose. However, you cannot leave the excess load on the control board. I'm not sure which component on there finally objected to handling the excess current -- could be a relay coil, a resistor, a capacitor, even a SCR or transistor -- but something did and eventually degraded enough to burn out. Remove all the loads from the board other than the ones it was intended to serve -- a relay will do that for you -- and power the rest of the stuff with its own power supply.

Vincent Valentino

Vincent Valentino

Not great picture but at least you can get an idea. Thanks again.

109A_5

Hello @Vincent Valentino,
Looks like you have two transformers mounted on the wood on the block wall. They look like they power the 4 zone valves, 2 Honeywell and 2 Taco.
So the transformer in the boiler should be just powering equipment inside the boiler jacket. However a chafed wire all the way out the the zone valve end switches could be problematic. Careful troubleshooting with some test equipment would be needed to prove it is the LWCO again or something else.

Since the low or common side of the transformer is usually grounded (Green Annotation) anything along the Red annotation path could be the issue.

Vincent Valentino

Thanks again. I'm going to be traveling for the next couple of weeks so I'll check it when I return. Best,
Vincent

HVACNUT

This is why they make zone panels.