EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: mp on June 22, 2023, 01:03:27 pm
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I have a new low voltage 12V AC SELV bathroom extractor fan that somehow needs to be wired to an old 14V AC transformer (measured with a voltmeter). The transformer was designed to be 12V AC but is delivering 14V. The 14V cable end sits in a 100mm wall duct ready to wired to a fan. I have no access to the transformer hidden in the ceiling above the bathroom to be able to replace it.
What's the best way to drop the 14V AC to 12V AC, just prior to the fan wiring terminals please?
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Just connect it. It is normal for a "12 V" transformer to measure a slightly higher voltage when not under load. The voltage will drop when the fan is running, and the fan will not care if the voltage is up or down by a volt or two above the nominal value.
If you actually measured 12 V on a 12 V transformer you would have to assume the transformer was faulty.
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Connect the fan? The transformer will drop because it's loaded.
Transformers usually have higher open circuit voltage, doesn't need to be that exact. Does it?
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Great, thanks both for your help. I just didn't want to risk damaging or reducing the life expectancy of the fan components. So 14V ac no-load voltage is fine, great 😃
If you have any hint or tips to add? Maybe something I should had asked but didn't.
Thanks.
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Transformers willl show way higher voltage than nominal when unloaded, measure again but connecting a 100ohm resisto.
If mesuring 14V unloaded, the working voltage will be maybe 9-10V, no more!
Just connect it, even if it was really 2V more, it wouldn't make any difference.
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Hi,
just connect the fan directly.
It won't be an issue.