Electrician installed transformer in wall

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SumBodi

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#312275 2-Apr-2024 23:44

Hi there

I hired an electrician to wire in my Eufy Video Doorbell. They installed an enclosed Halcyon brand 12V transformer inside the wall cavity (weatherboard - and there is insulation but I don't know how much there is where the transformer is sitting). They issued a safety certificate for the installation.

I've been researching transformers since the install, because I think the doorbell needs more voltage. In the process I've found that it is recommended that transformers do not sit inside wall cavities due to fire risk, and may be a code violation in some countries.

Does anyone have any knowledge of this?

Cheers

Dynamic

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#3213440 3-Apr-2024 04:48

I don't have a direct answer to your question.

In 2018 I was throwing a cable through a client's suspended ceiling and happened to touch the transformer of one of their halogen downlights. It was too hot to touch, for me at least, and was sitting on the compressed cardboard ceiling tiles. I recommended they get their Sparky to check it. They had an electrician visit, and I understand he said it was fine. My research after that suggested that paper and cardboard won't spontaneously ignite until over 220 degrees Celsius. That fact did not make me more comfortable.

The instruction manual of a number of household appliances like fridges and microwaves typically tell you they need x amount of space around the edges for airflow. Do transformer safety sheets have this sort of information?

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snnet

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#3213446 3-Apr-2024 06:57

Transformers in walls are not a code violation in nz. It's fine.

johno1234

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#3213451 3-Apr-2024 07:23

Airflow around fridges is critical for efficiency of heat transfer but not really a safety issue.

Bung

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#3213455 3-Apr-2024 07:46

Dynamic: In 2018 I was throwing a cable through a client's suspended ceiling and happened to touch the transformer of one of their halogen downlights. It was too hot to touch, for me at least, and was sitting on the compressed cardboard ceiling tiles. I recommended they get their Sparky to check it. They had an electrician visit, and I understand he said it was fine. My research after that suggested that paper and cardboard won't spontaneously ignite until over 220 degrees Celsius. That fact did not make me more comfortable.

Too hot to touch for most people is 45-50⁰C

SumBodi

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#3213464 3-Apr-2024 08:46

Thanks for the information, appreciated

In answer to the question above - the documentation just says that it needs to be installed above insulation.

Cheers

MadEngineer

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#3213479 3-Apr-2024 09:32

Is it accessible? Terminations of any kind must be made so.

You're not on Atlantis anymore, Duncan Idaho.

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MadEngineer

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#3213481 3-Apr-2024 09:37

Bung:
Dynamic: In 2018 I was throwing a cable through a client's suspended ceiling and happened to touch the transformer of one of their halogen downlights. It was too hot to touch, for me at least, and was sitting on the compressed cardboard ceiling tiles. I recommended they get their Sparky to check it. They had an electrician visit, and I understand he said it was fine. My research after that suggested that paper and cardboard won't spontaneously ignite until over 220 degrees Celsius. That fact did not make me more comfortable.

Too hot to touch for most people is 45-50⁰C

My experience and what I was taught in engineering school back in the day was that you can withstand touching a surface at 70 deg c for 3 seconds. This was in reference to the surface of an IC. The type of material can have an impact on this but consider your tap hot water temp which should be say 55 deg c, with a suggestion that water at 60 deg c will burn after 5 seconds.

You're not on Atlantis anymore, Duncan Idaho.

SumBodi

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#3213486 3-Apr-2024 09:45

MadEngineer: Is it accessible? Terminations of any kind must be made so.

It is accessible if a light switch panel is removed, as it's sitting just behind and below it.

johno1234

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#3213493 3-Apr-2024 10:01

MadEngineer: My experience and what I was taught in engineering school back in the day was that you can withstand touching a surface at 70 deg c for 3 seconds. This was in reference to the surface of an IC. The type of material can have an impact on this but consider your tap hot water temp which should be say 55 deg c, with a suggestion that water at 60 deg c will burn after 5 seconds.

55 degrees is plenty hot enough to cook a sous vide steak to medium rare... although it does take a while!

networkn

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#3213513 3-Apr-2024 10:59

johno1234:

55 degrees is plenty hot enough to cook a sous vide steak to medium rare... although it does take a while!

Well, it would be 'cooked' in about 40 minutes, but I wouldn't touch it until it was in for at least 90 minutes, ideally two hours, as then it would be tender.

MadEngineer

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#3213923 3-Apr-2024 21:53

OK, now I'm hungry.

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Bung

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#3214093 4-Apr-2024 10:43

MadEngineer: My experience and what I was taught in engineering school back in the day was that you can withstand touching a surface at 70 deg c for 3 seconds. This was in reference to the surface of an IC. The type of material can have an impact on this but consider your tap hot water temp which should be say 55 deg c, with a suggestion that water at 60 deg c will burn after 5 seconds.

Using a jam maker's thermometer in a metal pot of hot water I've tried holding my finger on the outside of the pot. 3 seconds @ 70⁰C and ~5 seconds @ 60⁰C are sensible times to let go. At 50⁰C i could press my finger on the side of the pot for 60 -70 seconds before the "this is stupid" signal.