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I have an incubator with an internal outlet that, according to the manual, "can provide a maximum of 1A". I'm trying to understand if this actually means that the maximum load is 120Vx1A=120W? In other words, is the limit set by the power or by the current? I ask because I would like to connect a shaker to the incubator's internal outlet, and the label on the back of the shaker says "19V, 4.74A", i.e. its load is 19Vx4.74A=90W. Will the internal outlet support the shaker?

Andrea
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  • Should be no issue. – winny Dec 21 '19 at 19:22
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    I think the 19V 4.7A listing is the output power of a power supply. Is the input power or current listed on that power supply? Since power supplies are not 100% efficient, the input power is always higher than the output power. So if the supply really puts out 90W, then the input power might be 110W or so. Probably OK. But not really enough information to 100% bless and guarantee everything will work. I would try it and keep an eye on it at first, and if it seems to work then all is well. – user57037 Dec 21 '19 at 19:22
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    If the outlet is 120 V and the shaker requires 19 V, DO NOT connect the shaker directly to the outlet! You will destroy the shaker. – Peter Bennett Dec 21 '19 at 19:24

4 Answers4

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Read more of the label on the power supply

The power brick for my laptop says how much input current it needs, yours should too. That is the number that will determine if that outlet is suitable.

The power supply brick for my laptop says "input 120-240V 1.3A" so this power brick would not be suitable (this is a 45W power supply: 20V, 2.25A), so based on that it's not looking good for your 90W power supply being compatible with that outlet.

You my need to ask the vendor to read the details on the power supply. this page seems to have their contact info

https://www.boekelsci.com/contact/general-info.html/

Jasen Слава Україні
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I have an incubator with an internal outlet that, according to the manual, "can provide a maximum of 1A". I'm trying to understand if this actually means that the maximum load is 120Vx1A=120W? In other words, is the limit set by the power or by the current?

You should check how it is wired inside the device, but... usually this means the outlet is controlled by a switch (in the case of an incubator, probably a thermostat) and the switch is rated for a 1 Amp current. Either that, or they used very thin wires for cost.

I would like to connect a shaker to the incubator's internal outlet, and the label on the back of the shaker says "19V, 4.74A",

So your shaker is powered by a 19V power supply which probably looks like a laptop brick. You have to use the power supply of course, you can't connect a 19V device to a 120V outlet, but you know that already.

Check the INPUT current rating on the power brick label. Something like "xxx mA 120V". This will probably be less than 1A, so it'll be OK. The output current rating like "19V 5A" does not concern the mains side of the adapter.

Since these supplies tend to draw a very large inrush current when plugged in, due to capacitor charging, I'd recommend checking if the incubator internal outlet goes through a switch or a thermostat. If it does go through a thermostat rated for a low current, like a few amps, I'd rather avoid having it switch the 19V power brick, as the thermostat contacts could be harmed by repeatedly switching a load with high inrush current.

If the internal outlet is only switched on/off by a manual switch on the incubator, then this won't be a problem as the manual switch won't be operated very often. Contacts only wear when they switch on/off.

bobflux
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The real key here is that IF the outlet provides 120 V power (you didn't say one way or the other), and the shaker requires 19 V. You will damage or destroy the shaker if you plug it into a 120 V outlet.

What kind of plug does the shaker have on it's power cord? I would be surprised if it's a standard 3-prong plug that's intended for 120 V use.

SteveSh
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  • The internal outlet provides 120 V AC, while the shaker specifications say "19.4 VDC, 4.74A via 100-240 AC adapter drum", so I guess that the shaker has an AC/DC adapter (I don't have the shaker yet, so I cannot check directly), so the voltage difference should not be an issue because of the adapter. The incubator manual is this one: https://us.vwr.com/assetsvc/asset/en_US/id/11989159/contents/at-user-operation-manual.pdf and the shaker (it's a tube rotator, actually) is this one: https://www.boekelsci.com/laboratory-tube-rotator-260650.html – Andrea Dec 21 '19 at 20:17
  • I guess the real question is where is this "100-240 AC adapter drum". If it's part of the shaker, you may be OK (need to verify currents). – SteveSh Dec 21 '19 at 20:21
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The circuit capacity is 1 amp x your line voltage, in VA

So if your line voltage is 120V, the socket supports 120 VA.

Watts is (roughly) the part of the sinewave the appliance uses, but it doesn't tell the whole picture about the thermal heating that occurs in the supply wires.

Look at the thing that has an AC power plug

Your shaker doesn't plug into a 120V outlet, so its nameplate is irrelevant. It plugs into a wall-wart or power brick; its nameplate is relevant.

If you don't agree with or believe the nameplate, you can get a tester like a Kill-a-Watt and actually measure the VA of the appliance at its most extreme operating mode, and go with that figure instead. That accounts for thngs like PCs with 850 watt power supplies that actually only have Intel on-board video instead of the dual 980s and six hard drives the power supply is sized for.

Harper - Reinstate Monica
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