Can I install double pole MCBs instead of double pole switches for a water heater?

[Luderic]

Hi,

I'm currently working on the wiring of a small guesthouse and I'd like to replace the usual double pole switches with double pole MCB's - directly in the distribution board. The reason is that I don't want the guests to switch off - or on - the water heaters and I want to keep total control of them (the distribution board will be installed outside the bedrooms).
In other words, is that a legal requirement to install a double pole switch between the distribution board and the water heater even if you have a double pole MCB in the distribution board?

Thank you.

 

[Jono Pashley]

Depends what the manufacturers instructions say, but there is nothing to stop you using lockable isolators or hiding them behind a access panel.

 

[Murdoch]

This is yet another failing of the regs..... I like to see double pole isolation for all fixed equipment, relatively close and accessible .......

Is this your own property?

 

[Luderic]

Yes it is, but it's a hotel, so I don't want to guests to mess up with the water heaters. Is it really a requirement, or is it because "you like to see them close and accessible?" 

Thank you.

Sorry: "I don't want THE guests" not "TO guests" obviously!

 

[Phoenix]

I think I'd be tempted to use 20A double pole secret key switches. I seem to remember there being a bit of confusion about whether they are suitable for isolation because the BS they are made to does not require the 3mm contact gap needed for isolation, however I beleieve MKs product litriture states that their version is suitable for isolation (you'd have to check i've not mis-remembered this though)

 

[Murdoch]

Is this a small guest house or a hmo?

Seems a bit odd to have water heaters in each room

 

[Evans Electric]

An electrician is obliged to fit a "local isolator"  to any  device  or equipment.     There is no choice .   As Phoenix says  , a secret key switch  , DP  or an actual key switch  , ( bit more pricey)   .

MCBs are not made to be switched on & off all the time  as far as I am aware ,   I'd go with the key switches , I'm sure the MK or Crabtree   20A  X DP  would be fine . 

 

[Luderic]

An electrician is obliged to fit a "local isolator"  to any  device  or equipment.     There is no choice .   As Phoenix says  , a secret key switch  , DP  or an actual key switch  , ( bit more pricey)   .

MCBs are not made to be switched on & off all the time  as far as I am aware ,   I'd go with the key switches , I'm sure the MK or Crabtree   20A  X DP  would be fine . 

Thank you for your reply.

Actually they would not be switched on and off all the time, but constantly on (except on very rare occasions when an intervention is needed for example) as they will be on a timer switch. So really a double pole switch is totally useless in my case - if not to comply with regulations.

 

[Evans Electric]

It won't be useless ,   its a requirement of the Regs  to have local isolation .  It can be a standard DP switch  or a key switch  if you need to prevent  guests from switching the heater off.  

 

[Luderic]

It won't be useless ,   its a requirement of the Regs  to have local isolation .  It can be a standard DP switch  or a key switch  if you need to prevent  guests from switching the heater off.  

OK fair enough. What I don't understand though, is that in my opinion, it makes more sense to be able to easily switch off a water heater from the DB rather than from a key switch (especially in case of emergency: you first need to run to the reception, find the appropriate key, go up again, and then switch off the water heater).
Besides, if this key switch HAS TO (I don't know) be located near the water heater, it means that you have to enter the room and disturb the guests to switch it off. Not very customer friendly... Nor security friendly.

 

[Luderic]

Is this a small guest house or a hmo?

Seems a bit odd to have water heaters in each room

It's a small guest house (6 bedrooms), but I want to make sure each room has its own water heater to 1) save water, 2) avoid that all all rooms have no more hot water in case the centralised  water heater fails.

 

[Andy™]

the local switch is there for the person doing maintenance so they can safely isolate it

 

[Luderic]

the local switch is there for the person doing maintenance so they can safely isolate it

So if this person switches off a double pole MCB in the distribution board instead, it's exactly the same isn't it? 

 

[Andy™]

more hassle since they would then have to lock it since its out if sight and anyone could turn it back on. they would also have to find it and go back and forth checking its the right MCB turned off etc. if its next to the appliance, turn off the switch and youre done. its also sometimes necessary for fault finding to need to turn it on and off a few times. that means a lot of walking about to the DB. so no, its not 'exactly the same'

 

[Rob_the_rich]

What timers are you using? And where will they be fitted?

 

[Luderic]

What timers are you using? And where will they be fitted?

I used the word Timer to make it more simple, but in fact it's going to be a zwave switch (I don't know if you're familiar with this protocol) connected to a home automation box. It will allow me to switch off the water heaters - and towel heaters -  remotely if the room is not used for some time. 
And these switches will be fitted in the distribution board.

 

[Luderic]

more hassle since they would then have to lock it since its out if sight and anyone could turn it back on. they would also have to find it and go back and forth checking its the right MCB turned off etc. if its next to the appliance, turn off the switch and youre done. its also sometimes necessary for fault finding to need to turn it on and off a few times. that means a lot of walking about to the DB. so no, its not 'exactly the same'

OK fair enough, but frankly every time I've seen electricians working on a water heater they would also trip the breaker to make sure  no electricity was running anywhere!

 

[Doc Hudson]

Table 53.4 BS7671 wiring regulation  titled "guidance on the selection of protective , isolation, and switching devices", give a list of various means of disconnecting power from a circuit or device. It has five columns Labeled "Device Standard Isolation Emergency Switching and Functional switching.  The list includes circuits breakers to BS-EN 60898, and states that they are acceptable as a means of all types of isolation. Section 537 has further regulations regarding isolation and switching. I cannot see any regulation prohibiting the method you are suggestions for this application. The MCBs will need a means of locking off during maintenance work. I am of course open to others to point to any regulations I have missed.

Doc H.

 

[Rob_the_rich]

I am of course open to others to point to any regulations I have missed

554.3.3 although depends on the type of water heater.

I can't see why control needs to be done at the reception. Surely at the end of each 'tenancy' the rooms would be cleaned and any switches which were intentionally switched off could be switched back on ready for the next occupants.

The water heaters might be a bit noisy, and the tenants might be within their rights to switch them off if interfering with a good nights sleep

 

[Luderic]

554.3.2 although depends on the type of water heater.

I can't see why control needs to be done at the reception. Surely at the end of each 'tenancy' the rooms would be cleaned and any switches which were intentionally switched off could be switched back on ready for the next occupants.

The water heaters might be a bit noisy, and the tenants might be within their rights to switch them off if interfering with a good nights sleep

No I don't want the guests to be able to switch them off (and the models I intend to install don't make noise). I already have the problem now in short term rental apartments, people switch them off either because they think it's a nice thing to do it when they leave or because they don't know "why this switch is on" (even if it's written "Water Heater do not switch off" on it!). Then they don't have hot water any more and... they complain!
I'm much better off controlling when I want them off or not.