Thought you would be interested….
Recently installed a 9K electric boiler on dual fuel. Service WAS through a 10K transformer next to my driveway that I always thought hummed a little louder than it should…load or no load…but never had it checked out. When the co-op guy came to install the dual fuel meter and load control device, he commented that the 10K transformer was probably adequete because they are rated for 20K peak loads.
This boiler modulates depending on flow and outlet temperature set point. Standing right next to the boiler when it is modulating, you can hear a slight buzz that varies in an almost rythmic pattern.
Anyway, I noticed a new, pretty loud buzz from the transformer the other day that seemed to be in synch with the boiler modulation. Called the co-op, they said they would send service crew out.
The service crew guy called yesterday and said they had REPLACED the transformer…said it must have some sort of internal fault, because they noticed it was buzzing abnormally even without a load. Put in a 15K for good measure, even though he repeated that a 10K could handle 100% overload , or 20K. Now little or no noise at all even almost no hum compare to other unit.
I guess the moral is, don’t hestitate to call your local PO-CO with any anomally that you notice.