The need for MCBs

[chris_j_hunter]

over on ukha at the moment, some of the C-bus enthusiasts seem using a lot of MCBs to protect C-Bus modules, particularly things like dimmers, which might suffer when bulbs blow ... should we be doing the same with Idratek, I wonder ?

[Gumby]

IMHO: No for relay modules, for dimmers it's too early to tell, I've only had one bulb blow on a dimmer controlled circuit and it was bulb down so didn't have the issue of the filament falling back onto the connection at the bottom, which I have seen alleged to cause the problem (eg with side lamps).

[jpdw]

Maybe not on the output, but Paul Gale's piccies of his CBus install made me think that an MCB on the input to the relay or relays (if commoned), fitted purely for it's switching properties, may be a good way have local switch-off.

One thought though... If you add MCBs to the circuit -- even if the circuit is already adequately protected nearer to the CU, then you are "affecting the circuit protective measures". Which I think would make it a notifiable job (even though the 'affect' you are having is to increase the protection).

Veering OT a bit, but can you get a simple, low cost, DIN rail double pole switch ? (like a DP face plate but in a 1M DIN ?).

[Gumby]

Yes - I believe you can get simple isolator switches, since I have them in my subsidiary junction boxes. These provide isolation without affecting circuit protection measures.

I'm not sure if you added subsidiary MCBs that you would be affecting the circuit protection measures, since you are adding new ones, not affecting the existing ones. But then if you used the same rating it could be argued that you have affected the discrimination. Refer to LABC again, I bet you get different answers ...

[JonS]

I got a c-bus installer to do the enclosures with my Idratek modules in and yes there are LOADS of MCBs. It does take a bit more room, but it does make isolation much easier. Most are TypeC 1A for lights etc so unless there is a short I cannot see them actually switching off. In fact when it was being commisioned a 1A MCB was termporarily on a 2A circuit and and it took several minutes to switch off. Having the isolation is definately useful when changing bulbs etc without having to isolate the entire enclosure
2p
Jon

[Gumby]

Can you get 1/2 width isolators or MCBs ?

That would be useful ...