Incubator - volts and watts!

Yep, your thinking is correct. A 10W lamp will produce more heat than a 7W lamp, when each is fed from its normal supply voltage.
It may not be a simple matter of changing the 110v bulb for a 240v one.
The cable and switch must also be rated for the higher voltage. As must any thermostat, if fitted. Earthing of any metal parts is also more important at the higher voltage. It is also important that the screw thread of the lamp fitting is not connected to the live wire but to the neutral, to minimise the chance of electric shock - the US power plug may not be polarised but the UK one has to be.
It may be better to allow an electrician to give it a look over - or your goose may get cooked.

------------------------- Sue,
Many thanks for your answer and the additional points that I need to address regarding the safety of the incubators.
I am still waiting for a reply from the manufacurer as to correct wattage bulb to use. I don't expect an early reply as the get hundreds of EMails every day.
Your answer has certainly made me sit-up and think before I do anything in a rash and cavalier manner . I'm not long retired and I think my wife would possibly like me to be around for a few more years to do all the jobs she has planned !!!
Thanks again for your advice.
Regards, Ron.

I'm wondering if you can get Kentucky Fried Chicken in the UK... it seems like for a 7 watt load a small 2:1 transformer would be an easy low cost solutrion.

Oh, extra crispy... I haven't had that for years and years! Do KFC still sell that in the US?
-- Sue

Sure do. Maybe they should sell egg and incubator kits for those with lots of patience who like fresh food.

Ron Murray presented the following explanation : 10watts is 10 watts of light and heat, irrespective of the voltage.
An 18watt bulb at 12v will output just the same as an 18watt 240v lamp.

Is there a bi-metalic thermostat or something? Just curious. My first guess would be they could not get 7 watt 240 volt bulbs and so used the closest approximation. Seems like there would have to be some sort of thermostat if the units are otherwise identical. On the other hand chicken eggs aren't terribly fussy. I've used a 25 watt bulb clamped above a cardboard box to sucessfully incubate chicken eggs.
Valid point about the switch rating. Most cables are rated for 250V even in the USA. It's just easier to have one kind of cable.
If the item was manufactured any time in the last 20 or so years it almost certainly has a polarized plug. If there are exposed metal parts it should have a 3-prong plug with a safety ground (earth) connected to the metal chassis parts. You'd likely want to replace the plugs anyway. In general the smaller of the 2 flat prongs on a the plug will be hot and the larger will be neutral. The 3rd, round, prong will be the safety ground (earth).
Bill Ranck Blacksburg, Va.

I purchased a couple of 240 volt 7 watt bulbs today and have put the incubator on test. It is running at a fairly steady 95-100 degrees F. I am using a 5 amp fuse? I will have to alter the reflectors (aluminium foil) to ensure that it runs no higher than 100 degrees F. Otherwise it will be Kentucky Fried Chicken for real!
Thanks once again for the advice.
Regards, Ron (UK)

at 230 volts and 7 watts the current is .03A
I would pick a 1/2 amp fuse for this.

The lowest plugtop fuse I have seen has been 1A. The lowest usually seen on the High Street is 3A. Either would be better than the 13A fuse that wireable plugtops tended* to come with as standard..
*I haven't had to buy one for a very long time. Everything comes with a fitted plug, these days..fitted with an appropriate fuse.
It always seemed crazy to me that plugtops were sold with the highest rating fuse by default, requiring the purchase of a fuse for lower demand items - rather than the other way around.

I had to look up "plugtop fuse" ... we call then Buss fuses here.
I guess i assumed that an item like this would use an AGC type (glass).

IIUC, you don't have a mains plug with a built-in replaceable fuse in the US, so they don't have an equivalent in the US. The plugtop fuses in the UK are invariably ceramic tube - the plug is in a socket supplied with 240v and fused at 30+ amps - potentially a lot of fusing energy for a glass tube to withstand.

There is a similar fuse in the USA, sold for microwave ovens. It is not supposed to be "user replaceable", (you have to remove the case). It is rated at 15A and is in a ceramic tube. It is not nearly as convenient as a plugtop fuse would be, but, as you state, US plugs don't accommodate fuses.
Kitchen circuits are 20A, but many people use microwave ovens on a regular branch circuit, which is 15A.

You used to be able to buy a bakelite plug made to take a pair of 3AG/AGC fuses in the US. They were not polarized, so you had a 50/50 chance of the fuse in the neutral side blowing, and someone being electrocuted so they stopped selling them.