My inflatable hot tub says "don't use with an extension cord"... but can I?

Question

Sadly they don't explain WHY not to use it with an extension cord. I wonder if it's to do with the risk of having such connections outside in the elements?

The cord it comes with is 7m long, and where we want to site it is 6m from our outhouse. I've drilled a 1ft long hole through the stone wall of the outhouse to thread the spa's cord through... But once in the OH the plug still ends up 3m away from the socket. Would it be considered ok to run a standard 13A indoors extension cord to bridge the gap?

The OH socket is grounded (I'm in the UK) and on an RCD-protected circuit, and the spa has an RCD in its cord (and another in the pump/heating unit, I think).

Maybe their concern is voltage drop in the thinner conductors of a typical extension cord. Maybe I can buy a "heavy duty" one which would be largely equivalent to wiring a new socket in?

Or do I need to just admit defeat and wire a new socket in?

Thanks

Answer 1

I think you have likely answered your own question. The use of an extension cord could cause a voltage drop, especially since the factory cord is long already and the spa probably has an electric motor that would be damaged by voltage drop. Also, cord/plug connections are not weatherproof.

This is a CYA (cover-your-arse) by the manufacturer. Your plan of using a short heavy duty cord (same wire gauge as the factory cord) with the connections indoor should be fine.

Answer 2

The basic reason is that if they said, "Feel free to use an extension cord", someone would connect up a 50m, 3A, two-core cable with no Earth and a loose socket. They would then sue the company when it didn't work (too much voltage drop across long thin extension cables) or it caught fire (current drawn exceeds capability of thin extension cables) or they got electrocuted (no Earth).

In reality, if you use a short (2-3m), heavy-duty, 3-core (with Earth), outdoor extension with a good stiff socket and shield it from spillage, you should be OK. However, remember that, as Abraham Lincoln once said, "don't believe everything you read on the Internet".

Answer 3

I have always heard that the reason for the "no extension chords" is because they are not supposed to be used for permanent installations, only temporary, i.e., Christmas lights. Extension chords are pretty cheaply made and the ones I have had fail on me always fail at either the male or female end. If you're going to keep your tub inflated year-round, think about adding a new socket. Enjoy it,

Answer 4

As with all Q&A on this site, answers are in the context of the question.

The issue is electrical drownings

One thing people really don't understand about electricity and water: a shock that would be trivial anywhere else is fatal when water is around.

You're hit with a triple whammy. First, ordinary water and wet skin conduct electricity well, meaning a shock you barely felt before, now has much worse effect.

"Water doesn't conduct electricity" only true for artificially demineralized water; water does not like to be demineralized. Demin is corrosive and will attack anything it can leach minerals out of. The city's water source is not demin, and they don't entirely demin it; it would eat the pipes if they did.

Second, when water is around, a stun is as good as a kill. People in electrical drownings weren't electrocuted to death. They just lost control of their muscles and fell down into the water. They did not raise their nose out of the water because they were unable; either their muscles would not do what their brain commanded, or they were laid unconscious by the fall (or the shock). See how this becomes a domino effect: your legs malfunction, your head cracks the ground, which knocks you unconscious, and then, you drown.

And third, the same thing happens to the people who try to rescue you. In one famous drowning in a fountain, one girl fell, another girl went in to rescue her, the other two went in to help them, and all four died.

That's how it goes; the third or fourth cohort of rescuers recognizes they're looking at a victim and a rescuer who has become a victim, and does not repeat the mistake.

Of course it's made worse by the first factor; people who have been bit in the past and live to tell the tale, start thinking they're immune to electricity, and don't realize they've just been lucky so far due to being in the dry.

There is no way to insulate an extension cord connection. If it gets wet, it will leak current.

"Oh, but my house is protected by the bog-standard Euro 30ma RCD! I'm fine!"

Nope. Personnel protection is not the purpose of Euro style 30ma RCDs. 30ma will stun pretty much everybody, and will directly kill a more vulnerable person. That is why North America requires 6ma GFCIs where the objective is personnel protection (e.g. kitchens/bathrooms/pool areas).

Now, your hot tub's electrical cord may have a lumpy 6ma GFCI/RCD on its electrical plug. Obviously, the extension cord connection will be before that, so, not protected.

Answer 5

The manufacturer will be guarding against both voltage drop on the supply (which could affect the operation) and creating too high a fault loop impedance (which could affect the disconnect time of the circuit breaker in case of a fault).

At a guess, a minimum length, heavy duty extension lead will likely be fine.

However, for peace of mind, if you can readily add an extra socket in the right place, I’d suggest that is the correct thing to do.

Answer 6

I have seen the same rules on devices for a bathroom. In my opinion its all about exposing bare wires. If the two (the extension and the power cord) are not a waterproof connection and resting on a floor (very common), then there is risk of shock. That is far more likely in a bathroom (or near a hottub) where water is common.

I believe a better way is to replace the current power cable with a longer, properly rated, power cable. That cable would connect to the hot tub (You will likely have to open up a cover where the current power cable is screwed into the electrical of the hottub) and plug directly into the outlet without any breaks.

Obvious disclaimer: Its better to pay an electrician than trust a random guy on stackexchange.

Answer 7

To Avoid Fire

As noted in other answers and comments, there are issues related to wire size and length that can cause overheating if not appropriately dealt with, and the issue of waterproofing the connection, both that can lead to shorts and fires.

So You and Your Family and Your Friends Don't Die

A person, just out of the hot tub, is covered with water, walking around dripping it on the ground, it's pooling in to puddles, their barefoot (who wears shoes in a hot tub?), they're in the UK where power is 240v and likes to really mess things up if shocked, AND then let's effectively put an outlet and plug on the ground nearby in the form of a cord to extension cord connection. It's as if someone just got out of the shower and then throws water at the wall socket and then puts both hands all over the wall. Sooner or later, it simply a matter of time, someone is going to get a major shock, or worse, electrocuted.

Related, recall how smart and vigil we are, and think how much is the same for the average person, then recall that half the people in the world are below average, and that the instructions are written for everyone, not just us.

They make those statements as a CYA yes, but also a COA (Our in place of Your) because we really do need protecting from ourselves, at least some of us do. It's very likely a government mandated item that the instructions note not to use the extension cord.

Answer 8

Depends on the current requirement of the tub

Your tub will likely have a label that specifies the rated current draw and/or rated power. If only power is stated, divide Watts by RMS voltage (220V) to get amps required. You mention using a 13A cord - comparing to the rated draw of the tub is necessary to determine if this cord is up for it.

The adequacy of the 13A cord will probably turn on whether your tub is electrically heated. Some tubs have gas or propane heating, and others heat electrically. An electrically heated tub would undoubtedly require much more amperage.

This is in addition to the other very valid considerations already mentioned.

Answer 9

Earthing protection is an important consideration. You cannot have a situation where you may not be earthed...even temporarily.

Answer 10

In the EU-style consumer power grids (220-240v, separate ground) these marks "don't use extension cords" are put on all appliances that draw 1kW or more. AFAICRecall, every space heater has it.

I don't know the reason, but it has to do something with the risk of overloading a single outlet (~3.5kW) by plugging few heavy loads into it. The most probable outcome of overloading is usually a tripped breaker, but sometimes the breaker allows for some tolerance and contacts or cables overheat.

IMHO, if you use a good extension cord and promise not to plug a total of more than 3.5kW, you are OK. Avoid using a cord longer than you need, avoid covering the cable w/ carpets or likes.

And for sure, avoid water near the plugs.