Doorbell transformer wattage

Hi all
I am replacing an old doorbell transformer (Edwards #894 16V). I cannot find the wattage of the old transformer. Home Depot sells 16V 10W and 16V 15W transformer. Which one should I get? Doorbell is coonected to two switches neither of which are lighted. No info on the doorbell either. Sorry. Thanks in advance.
N2
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This is Turtle.
the higher the wattage makes no difference in hurting it if you have lower wattage use. now having a Higher wattage use and have a lower wattage transformer. it will burn. so get the 16 volt and the higher wattage at 15 watts. if you don't use all the watts , it does not matter.
TURTLE
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Nick Nicholas wrote:

Doesn't matter. Transformers are rated for continuous use. Unless you have Halloween tricksters, a one-second button push won't even be noticed by the transformer, let alone get the transformer hot enough to fail. A one-watt transformer would probably work as well.
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HeyBub writes:

The solenoid types that hammer a chime require quite a bit of current, and a too-small transformer would ring weakly or not at all.
I suggest the OP get the smaller, and return it for the larger if it doesn't work satisfactorily.
Better yet, install batteries. Much cheaper than running a multiwatt transformer 24/7/365 for a 1 second/day duty cycle.
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Richard J Kinch wrote:

Hi, Too small one won't even actuate the hammer. I have such a chime. Needed bigger Wattage tranny. I don't what the price difference is, I'd go for 15W one. Tony
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The smallest size doorbell transformers, 10 VA (watts) are for the old fashioned buzzers and bells with the clappers. (You don't see these much in residential installations these days...)
The higher capacity 10 and 15 VA transformers are used for the regular solenoid (ding-dong) and the musical (Westminster Chimes type) doorbells that need more power.
I disagree about the batteries. The cost of batteries each year will easily surpass the cost of the no-load power consumed of a small transformer on the line that will probably last 50 years with no maintenance required. 15 watt rated means 15 watts delivered when the transformer is connected to load and lets say the ballpark efficiency is at worst is 90%. That thing will barely get warm even when continuously loaded.
Beachcomber
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Batteries won't work. The ding dong is designed to work off AC power. Batteries supply DC.
Get the bigger transformer. One extra trip to the store will burn more money in gas & wear and tear on the car than you would save buying the smaller transformer.
stretch
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in part:

I am much more pessimistic about the efficiency of smaller transformers such as doorbell transformers. I would expect power consumption of about 2 watts unloaded. This amounts to about 17.5 KWH per year. Now, it appears to me that USA's average residential electricity cost is about 10 cents per KWH, so that would be $1.75 per year. But I would surely prefer to pay this than to use batteries for my doorbell.
A doorbell transformer consuming only half a watt on standby can be made by making the laminations thinner and by having enough turns on the primary for the core to not be pushing saturation. Such a transformer would be a little larger for the same VA rating and cost a little more. This is also true of "wall warts", which are normally made as inexpensively as possible. But some "wall warts" are used 24 hours a day, such as ones for answering machines and cordless phones. Making these small transformers more energy efficient will actually save people money. But I wonder if this will ever see the light of day without a government mandate?
- Don Klipstein ( snipped-for-privacy@misty.com)
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Switch in the primary and load in the secondary equals Zero no load power.....
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Beachcomber writes:

A small transformer uses perhaps $10 in electric power each year, more for larger.
Alkaline batteries will last for 5 years and cost $10.
DC batteries run my AC doorbell just fine; solenoids don't care.
Actual experience beats your speculation.
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I had the 10 w transformer and wanted to run a second bell (on patio) in parallel. The 10 watt transformer wouldn't even get both bells to grunt. I replaced the transformer with the 15 watter and they both worked like a charm. I think the 15 watt one is also required for larger/fancier chimes. RM ~
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Thank you all for your replies. I was leaning towards the lower wattage to save on _stand-by_ power consumption. My understanding from the various posts is that a doorbell transformer does not consume power at stand-by. I will choose the higher wattage. Thanks again.
N2
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the secondary load is switched so a doorbell xformer does consume power during standby (you can feel it getting warm) but it is very small, not enough to worry about. In the winter it contributes (slightly) to keeping your house warm so it's not really wasted.
Take a walk or bike ride to the store instead of a drive once a year and you will save 100's of times more energy.
Mark
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