Immersion water heater in a metal cup

Thread Starter

thomas01

Joined Jul 9, 2017
8
I am creating a non-profit product for charity and I have a simple electrical question.

In this product a single cup immersion water heater will go inside a stainless steel cup. So the heater will be touching the metal cup. But I am going to have a plastic safety cover that goes over the metal cup, so someone can not touch the water or metal.

Does this sound safe enough to sell to the public? Or is there anything else that might be a problem?

Thanks so much for any advice.

ps: I live in Thailand, so it might take me a while to answer any questions, cause of the time difference.
 

Reloadron

Joined Jan 15, 2015
7,548
Normally cup immersion heaters are low voltage, such as 12 VDC. They are also isolated so the heating element is not touching the sheath materiel. Here are a few examples of what I am getting at. I also assume Intrinsic Safe:
Intrinsic safety is a design technique applied to electrical equipment and wiring for hazardous locations. The technique is based on limiting energy, electrical and thermal, to a level below that required to ignite a specific hazardous atmospheric mixture.
Ron
 

Thread Starter

thomas01

Joined Jul 9, 2017
8
I know these heaters are the safest things, but people use them all over the world, everyday. And companies like Wal-Mart sell them, so I feel it's probably safe enough, I hope. When I think about products that are not safe, the 4th of July and fireworks come to mind ;-)
 

dl324

Joined Mar 30, 2015
17,022
And companies like Wal-Mart sell them, so I feel it's probably safe enough, I hope.
It doesn't sound like you're convinced yourself that it will be safe for your customers.

The one you referenced stated that it should not be used with metal or plastic containers. That would include the cup and lid you were considering.

Read the safety information for any that you consider and carry a lot of liability insurance to cover injury claims.
 

Thread Starter

thomas01

Joined Jul 9, 2017
8
I think what it says in the product info is written by the people that are selling the heater. Is there a reason why a heater of this type shouldn't be used with a metal cup, other than the possibility of shock from a ungrounded wall socket?
 

dl324

Joined Mar 30, 2015
17,022
There is a plastic cover to protect from heat transfer. But this cover does not touch the heater.
How are you preventing the cover from touching the heater?

How are you preventing the heater from touching the metal cup?

How are you justifying not following the safety instructions provided by the eBay Seller?
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crutschow

Joined Mar 14, 2008
34,719
I think the reason for not using it with a metal cup is safety.
If a short were to occur between the cladding and the wire, the customer would still be reasonably safe using a non-conducting cup unless he put his finger in the water while it was plugged in.

One way to increase safety if you want to use a metal cup, is to use a GFCI plug as they often do with hand-held hair dryers.
But that would likely considerably increase the cost.
 

Thread Starter

thomas01

Joined Jul 9, 2017
8
I think the reason for not using it with a metal cup is safety.
If a short were to occur between the cladding and the wire, the customer would still be reasonably safe using a non-conducting cup unless he put his finger in the water while it was plugged in.

One way to increase safety if you want to use a metal cup, is to use a GFCI plug as they often do with hand-held hair dryers.
But that would likely considerably increase the cost.
Thanks for your reply. So I guess water and metal are about the same thing when it comes to electricity?
The heater will go inside the cup and a 2mm plastic cover will completely shield anyone from touching the metal cup or water. I included the safety cover in case of a short, bad grounding, heat transfer, etc.
 

dl324

Joined Mar 30, 2015
17,022
The plastic cover is fastened to the heater cord in a way that they can't really use one without the other.
How are you going to prevent complete immersion of the heater?

I saw one of these things 40 years ago that had a bend in the heating element that was placed on the rim of the cup to prevent complete immersion. Metal cups weren't common then; aside from in jails or prisons where those appliances wouldn't have been allowed.
 

Thread Starter

thomas01

Joined Jul 9, 2017
8
How are you going to prevent complete immersion of the heater?

I saw one of these things 40 years ago that had a bend in the heating element that was placed on the rim of the cup to prevent complete immersion. Metal cups weren't common then; aside from in jails or prisons where those appliances wouldn't have been allowed.
The heater connects to the plastic cover and the heater is taller than the water, so complete immersion of the heater is not possible.

It's now past midnight where I am. Gotta sign off until tomorrow. Thanks for the comments.
 
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