Ran a Honeywell Vista panel on a 30 year old transformer and fried it

I took a shortcut last week on a job in Austin. Old house had a 30 year old 16V transformer still running from the 90s. I hooked up a new Vista 20P without swapping it out and the panel died after 2 hours. Learned the hard way that old transformers can spike voltage when they get loaded fresh. Anyone else have a panel die from an overlooked power supply?

2 comments

2 Comments

noran212d ago

Man that's rough. I once swapped a transformer on a Saturday and the new one smoked before I even got the panel screwed in. Old parts don't always play nice.

walker.andrew2d ago

Honestly, "old transformers can spike voltage when they get loaded fresh" is close but it's not really a spike issue with old transformers. It's more that those old units can't regulate voltage anymore and just sag or let bad AC through when you put a modern panel's draw on them. Tbh, the real killer is often a worn-out rectifier inside the transformer that sends AC ripple straight into the board.