I brought an old electrical heater into our house whilst we’re getting our central heating renovated. Every time I switch it on, or off, there’s an electrical spark at the plug socket - behind the socket is where it seems to be.
I was wondering what is causing this? Is it hazardous, and what can be done about it?
Electric heaters draw a lot of current when you first turn them on, more modern ones have thermostat controls on them and these deal with the turning on and off.
If you pull the plug from the socket whilst the heater is drawing current, there is every chance you will draw a small arc, and repeating this action many times might cause some pitting of the plug and socket contacts, in the long run this isn’t something you would want.
I assume that you are switching at the socket, and the arc is produced when you operate it, if there is a switch on the appliance, then use it. The switch on the socket is intended mainly for isolation, to turn off the supply to an appliance that has already been turned off.
Over time this socket switch may develop pitting and eventually burns and perhaps even the contacts might weld together.
If the heater does not have an on/off switch, you would be advised to put one inline on the power lead, but it will need to be rated to handle the load, so a little table lamp switch will not be good enough.
Yes.
It’s most likely a “series” arc, and is occurring due to a poor connection somewhere in the circuit. Basically, when a connection has too much resistance, and the spacing is very close, you’ll get an arc when the voltage between the contacts rises above a certain threshold value. More info here. The culprit may be the spring terminals in the receptacle, or it may be a poor connection where one of the wires connects to the receptacle (e.g. loose connection between copper wire and screw). Though less likely, it might be the heater plug.
I would start by replacing the receptacle. Kill the power before doing this, obviously. After removing the old receptacle, examine the wires and make sure they’re in good shape (i.e. no burnt or charred insulation). If they’re long enough, I would cut one or two inches off each wire and strip the ends, thereby giving you “fresh” copper to work with. If they’re not long enough for you to do that, scrape the copper wires with some fine sandpaper to remove any oxidation.
If it’s a 15-amp circuit (14 AWG wire + 15 amp breaker), install a 15-amp receptacle. If it’s a 20-amp circuit (12 AWG wire + 20 amp breaker), install a 20-amp receptacle. In either case, buy a high-quality receptacle. Given a choice between a $0.50 receptacle made in Mexico and a $3 receptacle made in the U.S.A, I would choose the latter.
And finally, make sure the circuit can safely power the heater. What is the wattage of the heater?
Most likely a crappy outlet (the terminals inside the outlet are worn). You would be wise to replace the outlet as soon as possible.
Does the heater spark like this in other outlets or just this one?
Thanks for the replies - I think the outlets are OK, I’ve plugged the heater in to a few different ones and it always sparks, so I’d favour it being a problem caused by the heater. I’ve never noticed a problem with other appliances. The heater has no switch, but it does have a dial, so I’ll control it with that rather than the wall socket as per CasDave’s suggestion.
So the heater doesn’t have a power switch? Well if it has a thermostat dial, I would try turning the setpoint temperature to max cold before plugging into (and disconnecting from) the receptacle. If it still sparks, see next paragraph.
Sparking at the receptacle is never a good thing. If it sparks when you connect/disconnect from any receptacle, the arcs are occurring between the prongs on the plug and the contacts in the receptacle. These contacts are not designed to withstand arcing. I would install an inline, AC switch that is rated for the voltage and current. Or buy a new heater.
Well, we’ve not ruled out the possiblity that **all **of your receptacles are worn out or have bad connections.
Any sparking within the heater itself is going to be a problem in the heater. Sparking at the receptacle will be either a problem with the receptacle, its wired connections, or possibly, the heater’s plug is bad.
When the heater is on, does the plug and power cord get hot?
Your observation made me think of “back stab” receptacles, wherein the line is stripped and pushed into a spring loaded contact instead of the usual loop bound with a screw. A hazard waiting to happen, and ( I believe) since oulawed.
Releasing the line and using the screw connection is a minor hassle, once you’ve killed the circuit.
Is this just for outlets? I have a light switch (single pole single throw) for my bathroom light that uses that connection technology. It also had screw contacts, which I used given that’s my preference.
The amperage of the load being switched determines the hazard. Typical bathroom lighting loads would be less likely to produce the heat/cool cycle leading to spring fatigue than a wall outlet that could see up to the breaker, or fuse’s, rating, but poor connection hazard still exists.
Hold on just a minute. The OP said he was turning the heater on and off by plugging it into the wall socket. Anytime you plug a high current draw appliance into a wall socket it will spark. It looks to me like everything is normal with the OP’s situation - it’s just that you should never plug a heater that’s “on” into a wall socket. I also don’t believe there is no on/off switch on this heater! That dial almost certainly has an “off” position.
From the OP’s description, the sparking is happening behind the receptacle - ie: inside the box, rather than at the slots. “…behind the socket is where it seems to be,” in their words.
If it’s sparking at the slots when the heater is plugged in, then yes, I’d expect that.
Backstabbing is a NEC approved method. Some localities may have more stringent requirements, but national code allows the practice.
While I know of no electricians that would do so for a single family home I know a number that would do so when it comes to large developments like condo’s and such where the jobs are bids and the time savings for backstabbing is significant when doing a thousand devices.
A majority of the time a back stabbed device will cause no problems. In instances where you are using a heavy load such as a heater it can cause problems as described in this thread. Simple solution is to replace the outlet and not use the backstabbing method.
How about having an electrician come and and look at your whole system? Do you have fuses and not circuit breakers? Are the various outlets grounded? Do your wires have shorts? Are the wires insulated. All of these things need looking at. Your system should not do this and a modern one that was up to code would not.
No one has thought of this, does the OP have Al wire?
Most everyone is trying too hard in this thread. As flex727 suggests, the sparking in question is almost certainly arcing between the plug and the outlet, which is expected if not desired whenever plugging in an unswitched high draw device. The solution has already been described - setting the thermostat right down, or if that isn’t adequate, adding an in-line switch. While it’s not inconceivable that there’s some further wiring issue in the OP’s house, none of the information presented points to anything beyond the simple, obvious explanation.
One attempts response based on OP’s points; “behind the socket is where it seems to be” seemed worthy of address.
Really easy test: plug heavy-duty extension cord into wall socket, turn heater on and plug it into the extension cord while watching both socket and extension cord. Spark at wall socket means problem there. Spark at extension cord would be normal.