enclosures 1

[Jakelian]

Dear users, I am a member of a team developing a new electrical product. I have a couple of questions about the enclosures and circuits; I appreciate your attention:

Q1. It has a metal box (enclosure) containing contactors, relays a circuit etc. Does this box also have to be UL listed/recognized?

Q2. In EU law, the components dont require CE if they are not critical in the functioning of the equipment. We build the circuit that controls the equipment and it has no approvals. But we put some other components inside the box, (contactors, thermal fuses, thermal links, etc) with all the agency approvals (UL&CSA) and those components control the operation of our new circuit. In case our circuit makes a mistake, the whole equipment is being safely stopped by those recognized components.
This way, we tried to make it 'not critical'. Do you think we can go through the UL with this approach?

best regards,

 

[DRWeig]

Q1: Yes. Or else it has to meet the same standards as a listed box, and it will be investigated to those standards, so in the end it'll be a listed box. It will save you time and money to start with a listed box if possible. However, if you need a special shape, size, window, or other feature not readily available, you'll have to go through the investigation anyway.

Q2: Depends on the component and its place in the circuit. Best thing to do is get a copy of the UL standard you're trying to meet, and study it. You might find that your non-listed (or non-listable) controller may have to be protected by designing a limited-energy power supply for it, plus protecting all inputs and outputs in a certain way, and isolating it physically from everything else, and by labeling it in certain ways. Or you may find it can't be done. Depends on the standard and type of product. It's a bad idea to send something to UL without having studied their standard first! They're a little pricey, but so is the fee to re-inspect.s

Good luck with your project, it's always a bit of an adventure...

Good on ya,

Goober Dave

 

[Jakelian]

Dear DRWeig,

Thank you very much for your answer. I am the designer of the product but not an engineer, but I still have to choose the box among alternatives, to find an appropriate place for it while designing, this is why I was searching. Also, I have the EN and CSA standards, but I will get the UL thanks for your attentionand detailed answers!

I would like to mention another issue and ask another question if you have some more time:

Absolutely NONE of the products in our sector has UL approval, as a whole product. Instead, they have approvals from Intertek, TUV, etc. And they still sell in the U.S.

TUV Rheinland or CSA will test our product and they said that if they test it according to UL standard also, they can give us UL/TUV, or UL/CSA, some certification stating that the product complies with the UL standards. I would like to learn your opinion on this if possible?

I appreciate your attention,

best regards,

Note: Where are you by the way, in the U.S.?

 

[DRWeig]

I'm in Tennessee, Sunchallenger. Memphis, the home of Elvis, actually...

We see some stuff tested to UL standards by CSA, but not much -- local authorities are pretty bad about only accepting UL in the states, especially in the really big cities.

There are others who will certify to UL standards, like ETL, METLabs, etc... And they charge lots less too. If you decide to get your UL cert outside of UL, it's worth shopping around. Just be prepared to get rejected in some locations, or at least be prepared to argue a case. It's getting more loose lately.

Good on ya!

Goober Dave

 

[Jakelian]

Dear DRWeig,

Since I dont have your email, I am thanking you here by posting, I hope it is OK to write personal messages here! Thanks a lot for all your attention for me, I really appreciate it because that so valuable for me, since I am not the expert in the area and I am not in the States.!

P.S. When I was little, I loved Elvis. He has a voice like no other.

I hope to communicate soon.

 

[DRWeig]

Thanks for the kind words, we hope all goes well for you!

Dave

 

[Jakelian]

Dear DRWeig,

How are you?

If you have some time for me, I really appriciate your guidance:

I see in some web pages of American sauna/hottub builders that little models require 120V but bigger ones require 240V. In Europe, when we need more power, we make a model that uses 3 phase system (3x230) . How does it work in the US? Is 240 the way to upgrade the outlets? Or do you have something like 3x120?

thanks in advance,

Sunchallenger

 

[DRWeig]

Hi Sunchallenger,

If residential, you need to do 240V single phase for larger loads. Only commercial buildings here in the US will have three phase power available. Anything above 120V/20A, consider using 240V. Utilities will provide residential customers with very large services at this voltage, I've see up to 800A panels, and a home can have more than one panel as long as the main disconnects do not exceed six in number.

Even small commercial businesses may be stuck with single phase services sometimes if they are located away from the main commercial business districts.

Keep us posted with your progress!

Good on ya,

Goober Dave

 

[Jakelian]

Dear DrWeig,

Thanks a lot!!!!

In that case, how high can I go in Amperes without exceeding safety limit, when I produce 240 single phase? (of course it will be a dedicated line)

best regards,

sunchallenger

 

[DRWeig]

You may have stumped me! I don't know the actual limit. I can tell you that it's easy to purchase a plug-on 200A 2-pole circuit breaker for a residential panelboard, and also a 200A 2-pole disconnect switch, so I think you could easily install a 240 VAC, 200A appliance in a residential application -- but I'm not sure how UL and the NEC may treat your particular product. If you have multiple motors or heaters, you will have to subdivide your elements into smaller circuits with individual protection for each within your control panel.

I can't imagine a 200A hot tub though, that would be a big puppy! Note that anything over about 50A won't be considered a do-it-yourself installation for the electrical portion.

Good on ya,

Goober Dave