12VAC Help Again

Thread Starter


Joined May 31, 2004
I posted a message yesterday about 12VAC breakdown and received a reply which sounded logical in theory and I agreed with. Unfortunately, it does not work in this application for who know's why? The company has replaced the pumps and again they do not work with over the amount of amperage needed for some reason. There transformer is rated at 12VAC, 60 hz, 8 watts, but it is an interior transformer.
I believe a lot of Electronic Techs look at these messages posted, and if someone could help me out here, it would be greatly appreciated. The original problem is listed under the first post 12VAC HELP, 12VAC Breakdown. Thank you for your time Bill


Joined Apr 20, 2004

Can't imagine why the motors would be unable to run on 12 volts from a higher capacity source. That makes no sense.

Your transformer is capable of 666 mills. Eight watts is 12 volts times .666.

If the "right" transformer is working, you can rig a weathertight box with a snap lid food storage container. Just poke holes for the wiring, and seal with some elastic glue, like RTV.

Good luck!


Joined Jan 22, 2004

let me try to clear up things before i give my two bits advice.

in your 1st post you said you have a 12vac 2.5A 300w transfo powering your lights and its doing fine, right?

now you want to add another device (fountain pump) rated at 12vac 300ma 2.5w

you also said, total wattage of the your lights is 240w but did not say at what current consumption.

in my usual practice i do not strictly use the stated rate of a device like a transfo. what i do is have an allowance like +/-15% due to various conditions like voltage fluctuations. so if you deduct 15% from your ampere rating of 2.5A it would be 2.125. likewise with you watttage rating of 300w it would be 255w

now armed with those figures like 2.125A and 255w, it would look like that your transfor can still accomodate your water pump rated at 300ma 8w. but the pump wont run and you even suspected that the pump motor must have a defect.

i can only draw one logical conclusion, the power rating of your transfo is not the exact figure, it could probably be lower than what is stated. massed produced transformers wont have the exact rating it claims, there will always be variances.

as an advice do not go beyond 75% of the rated figures. likewise for electrical devices add 25% to the rated figures.

hope this clears up your problem and good day.