Our landlord has had a consumer unit fitted in place of a fusebox at the shop we rent.
One of the machines I use, when starting up, is causing a breaker to trip. The machine contains little more than a big motor.
What's the solution? Bypass the CU and put it on a fused switch?
What current is the appliance rated at, and what current is the relevant circuit breaker rated at?
It is likely that it is drawing too much current to start up the motor. A change to a 'C' type MCB may work (usually B type breakers are fitted, the C allows a bigger current to be drawn for a short time), or if the cabling allows, a bigger rated breaker.
Alan.
The machine has a plate on it stating 14 amp. I assume that is the start up current, I would be very surprised if it drew that while running.
I think the breaker is 16 amp but i'm not 100% (i'm at hone right now) that doesn't sound like much.
Electric motors suck up a lot of current to get started, so i wouldnt be surprised if that is causing the breaker to trip. A word with the sparky who installed it is my best advice, as he knows what the cables are etc, and could fit a C type MCB if he thinks it is suitable. Alan
What is the rating on the breaker (I take it you mean a MCB and not the RCD)?
What is the machine?
Induction motors in particular are renowned for drawing a high inrush current (5 to 9 times the normal rating). Ordinary B type breakers will typically enter the instant part of their trip curve on 5x current. Hence unless there is substantial headroom (e.g. 10A motor on 32A MCB) its quite possible to get a trip.
If the MCB is dedicated to the machine, then fit a Type C response curve breaker for it.
Possibly, or a HRC fuse carrier in place of the MCB.
Rating plates are normally their running consumption, though can be a bit loose in the defintion. What is the machine? 14A is only about
3kW, the inrush would be 3 or 4 times that. 16A would imply a spur rather than a ring. What sort of circuit is this?
The sparky merely scratched his head while the breaker kept tripping and told my landlord that we had too much equipment and that we were overloading the circuit. (All of the other equipment was idle)
I unplugged everything else and demonstrated that it was this one piece of equipment causing the problem. The sparky then said it was because the machine is old.
I argued that a new machine would work in exactly the same and would cost £16k so we needed to get it working. It ended up with a blistering row between my landlord and myself because the sparky has convinced him that I am somehow using his electrics inappropriately.
Another instance where I am sorry that a 'professional' was involved.
startup current on a big motor is up to 10 times the running current.
rewire with cooker cable and a 45A slow blow cutout..
Some motors have a resistor in series that gets shorted by a centrifugal switch to limit startup current. Others have 'slow start' using PWM power to the motor.
It's one of these,
Couldn't tell you. It's in a basement under a shop, I had assumed it was on the ring but it might be a spur.
Sparky is an idiot. Replace the breaker with a fuse, either cartridge or rewirable. I'm assuming it is a breaker tripping, and not an RCBO.
NT
I know it's an outside chance, but all the references to that machine on the first few pages of Google hits include prices in US Dollars and/or shipping from there. As this is a UK group, presumably you are in the UK, so are the motors UK or USA spec? 60Hz motors often don't like 50Hz and vice versa, even if the voltages match. It's even more fun if, for some reason, the motors are for 110 Volts. Has the machine worked satisfactorily in the UK previously?
I'm in the UK.
I know that the machine is made for the wrong frequency but it has been in use in the UK now on a consumer unit at our previous premises for approx 3 years and for 3 years since at our current place for 3.5 years.
As been said, have the breaker changed to a 'C' type one. Might have to be ordered - not every wholesaler keeps them in stock.
Worth noting, for general wibbling only, that there is also a type D breaker, which is even more tolerant. However, it also requires an extremely low phase-earth impedance to meet disconnection times and it's quite difficult to meet those requirements in a domestic setting.
I have seen a type D used in one situation only - computer room 32A circuits where a rack full of UPSes and machines starting at once took out the type C previously fitted. In that particular case, the substation transformer was just behind the building and the 600A distribution board where the breaker was about 15m from the load. And the earthing conductor to the substation was a bit of nearly inch thick green/yellow wire :)
Does not sound like a professional to me.
You are overloading the MCB, however any sparks should be able to work out of you can safely use a C type breaker on that circuit, or indeed a 20A MCB or a 20A C type MCB to stop the tripping.
I am afraid that you cannot just swap the MCB to a C type without doing some measurements which of course the sparky should be able to do - assuming that he is a sparky and not a drinking pal of the landlords.
If you have access to the installation certificate that was issued with the CU swap then we can tell you what breaker you can use:-)
I saw a 20A D type on a lighting circuit at a recently rewired dance studio. It had been used as there were far too many fluorecents on the circuit. I had quoted for that rewire but would not come down by £300 so they used a different guy. I was called in to sort his mess out and it cost them more than £300 for me to do so.
Type C, type D and fuse are all good options, though I couldnt guarantee a C would be slow enough to work. I'd pick the fuse simply because its a lot more tolerant of startup current than a C type breaker.
Replacement is simple enough. However, if you do decide you dont want to do this for some reason, another option is to start the machine with a series current limiter, then switch the limiter out. Better to avoid automated starts if you do this, as it makes motor stall possible.
Bear in mind your 14A rating will no longer apply at 50Hz, the motor will draw more when running, somewhere upto 16.8A. This wont be a probem for a 15/16A fuse/breaker in that that wont trip it. It may all be clearer if you look up some trip curves for type B&C breakers and wire fuses.
In theory you could probably fix the CU problem and take it out of the rent. But running a 17A load on what could be argued as being a 15A circuit could leave you on less certain ground in negotiating terms, even if its a nonissue in real terms.
NT
That is a potential fire risk. A US AC motor designed to run on 60Hz mains when run on 50Hz UK mains will spin slower and draw higher currents. If that additional current puts any magnetic cores into saturation then the current can climb rapidly and the whole thing overheats. That this hasn't happened already suggests that the motor is somewhat over engineered and can tolerate this abuse. However it does mean it will be drawing ~20% more current than its nominal rating.
The trip is probably because from a standing start the motor will draw a very high transient current determined by its DC coil resistance and then when running 20% more than nominal 14A rating exceeds your 16 amp breakers limit. Once it is spinning properly the current drawn should fall to normal operating levels.
It is also possible that this US kit is designed for 220V and is getting nearer 240V in the UK so current draw could be another 10% higher still. Best to measure it properly and find a sparks that actually knows what they are doing. 20A breaker might stand a chance.
Cheap US made Remington mains electric razors were designed to use mechanical 60Hz resonance which meant that sold in the UK they were next to useless (usually as Christmas presents - slogan "so good I bought the company"). Caveat emptor - I bet they are still selling them.
I have known US made colour computer monitors catch fire on UK 50Hz video refresh rates in the bad old days before Multisync monitors.
So, as I suspected then the landlord has employed some f****it at the cheapest price he can find to upgrade the electrics.
Then when the electrician is scratching his head because the mcb is tripping every time I switch a machine on and muttering about us overloading the circuit the landlord thinks the way forward is to enter into a slanging match with me.
That's the thanks you get for being a model tenant for over 3 years. Time to buy summat methinks, this rental game is for mugs.
FWIW if extra work was needed because of the gear I use i'd be more than happy to stump up for it myself which I told him when we'd all finished screaming at each other and I could get a word in edgeways.
I seem to make extremely poor decisions about who I will have dealings with. Either that or the majority of people are knobheads. Maybe i'm the k*****ad, I can't rule it out.
A pal bought a BFO low voltage chandelier. Had it fitted by an electrician. Took out the MCB - it had a massive transformer in the base.
The instructions actually said you may need a type C breaker. And therefore it should be fitted by an electrician. The electrician of course either didn't read or understand the instructions and told them the fitting was faulty. When I explained what they meant he refused to fix things without his full call out charge, etc.
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