We've just taken delivery of a control panel that has switches controlling power to two pumps, a 9kW tank heater and an over-temperature trip. The control voltage is all 230V. Our maintenance engineer says that the control voltage, according to EIC 60204, should be stepped down to 24V. Is this mandatory? The panel is fully enclosed with an interlock cutting power when it's opened. There are no complex plc's involved, all very simple controls.
Where is the wiring that he thinks should be reduced to 24V installed? - are there unusual risk factors, such as damp or unusually high risk of vandalism, fire or other damage?
Generally the answer is that correctly installed and labelled 230V controls are fine but there may be factors we cannot see, such as it all being in doorbell grade wire or underwater, or maybe open to casual touch during operation ;-)
60204 covers anything from ELV up to about a kilovolt, so we need more info as to the exact objection to comment intelligently.
Mike.
Mike
he control voltage is all 230V. Our maintenance engineer says that the control voltage, according to EIC 60204, should be stepped down to 24V. Is this mandatory?
No, Clause 9.1.2 of BS EN 60204-1 :2018 (the current Designated standard) and BS EN 60204-1:2018+A1:2025 (likely to take over as the Designated standard by 30 April 2028) states:
9.1.2 Control circuit voltages
The nominal value of the control voltage shall be consistent with the correct operation of the control circuit.
The nominal voltage of AC control circuits should preferably not exceed
– 230 V for circuits with 50 Hz nominal frequency,
– 277 V for circuits with 60 Hz nominal frequency.
The nominal voltage of DC control circuits should preferably not exceed 220 V.
I think that the confusion comes because where PELV is used (but it doesn't have to be, just if it is) there are different voltage limits to PELV in IEC 60204-1, i.e. 25 V AC or 60 V DC in BS EN 60204-1; 50 V AC or 120 V DC in BS 7671 ... unless, of course, there are lower limits in a relevant Section of Part 7).
There are specific wiring considerations in BS EN 60204-1 for panels that contain LV controls, and specific colour-coding where LV controls remain live when the panel isolator is in the "OFF" position to open the panel (e.g. so that electronic controllers can still relay status to other panels etc.).
Hi Mike, thanks for answering.
The wiring is properly installed inside an industrial enclosure rated to IK10 & IP66, with internal hinges and quarter turn locks. The wiring is all very professional looking (although hey, I'm just a chemical engineer so what do I know!), with the power supply coming from an independent isolator through a sealed gland into the enclosure. All terminals within the enclosure are labelled and the door is fitted with an isolator. It will be installed in a secure building inside a factory, with no exposure to rain or vandals!
The maintenance engineer is quoting Section 9.1.1 of the standard, that "where control circuits are supplied from an AC source, transformers having separate windings shall be used to separate the power supply from the control supply". But then Section 9.1.2 states that "The nominal voltage of AC control circuits should preferably not exceed 230V for circuits with 50Hz nominal frequency". These two statements seem to contradict each other, no?
The maintenance engineer is quoting Section 9.1.1 of the standard, that "where control circuits are supplied from an AC source, transformers having separate windings shall be used to separate the power supply from the control supply".
Clause 9.1.1 has the following statement:
Exception: Transformers or switch mode power supply units fitted with transformers are not mandatory for machines with a single motor starter and/or a maximum of two control devices (for example, interlock device, start/stop control station).
I would further ask what circuits are classified as "control circuits" for this panel?
Certainly the temperature trip is ... plus the inputs to the contactors (based on what, switched/controlled from where ???), but sounds like the pump and heater wiring are actually "power circuit" ?
Because of the Supply of Machinery (Safety) Regulations and Section 6 of H&S@W etc. Act, I would be inclined to discuss any queries about conformity with the supplier and manufacturer in the first instance.
Thanks gkenyon.
But the panel has 2 start/stop buttons for pump motors, an activation switch for a temperature controller, and an overtemperature interlock. Doesn't this preclude that exception?
But the panel has 2 start/stop buttons for pump motors, an activation switch for a temperature controller, and an overtemperature interlock. Doesn't this preclude that exception?
We don't know what the manufacturer classifies as control circuits.
Because of the Supply of Machinery (Safety) Regulations and Section 6 of H&S@W etc. Act, I would be inclined to discuss any queries about conformity with the supplier and manufacturer in the first instance.
But ... it is the right thing to do: check if things are not clear. In this case, it is very important for safety during maintenance.
Thanks.
Sadly the the supplier is less than happy we're questioning their work. But yes, safety is priority.
Sadly the the supplier is less than happy we're questioning their work.
Understandable, but since this is a safety-related question according to Section 6(1) of the H&S@W etc. Act, I'm sure they would be more than happy to cooperate.
Well, if their documentation as to how it is to be used and which standards apply to make it safe to do so, is so unclear you have to ask for clarification, perhaps you could suggest if they really can't get that data to you, maybe because they have not created it, then they should should not be putting stuff on the UK market at all and would they prefer to give a refund and take it back plus consequential damages for your loss of time/ business.
Or maybe reserve that for when they really rub you up the wrong way..
While thinking of paper trails and so on, I presume there is a UKCA or CE declaration about which standards they have applied and designed to meet in the documentation you received for starters, as that is required by law, though it may be pretty basic. - e.g.
"We declare his product is designed to meet all relevant clauses of the low voltage directive and the basic EMC directive" and an illegible signature from a technical director or similar.
Delving deeper expect to find
LVD met by following principles of EIC 60204 plus use of components tested to EN 61439 or other specific product standards.
EMC met by tests to IEC 61000 part something or even a slightly dodgy sum of parts reasoning that all the bought in bits are already CE marked.
A box of switches and relays and little else does not need very much more. .
If no such statement is available at all, then perhaps there should be a distant alarm ringing.
So parts that remain live with the door open need to be shrouded or otherwise inaccessible, and all the active bits inside need to themselves either have been tested by the assembler, or more likely bought from suppliers who already have declared compliance, and there needs to be a clear ADS (think fuses and circuit breakers) approach and clarity about if those protective measures are in the box or must be provided by the user.
Mike.
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