Relay channel loading.

Discussion in 'C-Bus Wired Hardware' started by pbelectrical, Aug 28, 2008.

  1. pbelectrical

    pbelectrical

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    L5512RVF - Documentation says that the individual channels are rated at 10 amps, now I am usually a believer in leaving a bit of headroom for longevity etc. but I am about to fit off an installation where I have installed radiant heating panels, DEVI Comfortline 3300 watt. Heaters are wired in pairs with the elements split over three channels to give hi, med, low. Assuming 230V this gives a load of 9.6 amps per channel. My question is does anyone have any experience with long term use of loads as close as this to the channel rating. Am I pushing it or is their plenty of margin built in to the contacts.

    Thanks,

    Peter.
     
    pbelectrical, Aug 28, 2008
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  2. pbelectrical

    znelbok

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    I have always wondered the same thing.

    If you take a 12 channel relay and put 10A through each channel, you will have potentially 120A at the output unit. That's a lot of current for a smallish looking relay.

    While I don't have experience with long term loads like this on a relay, I would have assumed that it was designed with a margin built in. It has been mentioned here that the duty cycle is 100%, so I think it would be safe to run 9.6A 24x7. At least if it fails you have a justified warranty claim.

    Mick
     
    znelbok, Aug 28, 2008
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  3. pbelectrical

    NickD Moderator

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    The relay current rating isn't like a dimmer where the limit is predominantly the power dissipation.. where you might be concerned about loading *all* channels up to their maximum capacity (although on C-Bus dimmers this is perfectly OK because that's how we specify the rating).

    For relays the rating is determined by the current carrying or more importantly the current switching capability of the relay contacts.

    A radiant panel heater should be a nice resistive load, which as far as a relay is concerned is about as friendly as it gets, so you should should be fine.

    I have a wireless plug adapter switching a 2kW radiant panel heater, which has been switched on and off on a schedule twice a day for the past 2 years with no problems... admittedly it's a different relay in that product but the rating is the same.

    Nick
     
    NickD, Aug 29, 2008
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  4. pbelectrical

    brodricj

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    I'm curious whether CIS is still advocating putting a capacitor across the output of a (change-over) relay for blind/motor control as a means for protecting the contacts from transient overload?
     
    brodricj, Aug 31, 2008
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  5. pbelectrical

    Newman

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    When using the change-over relay L5504RVFC then you should use a capacitor, in accordance with this application note.

    A much better way to go is to use the new L5501RBCP which is specifically designed for use with blind/curtain/shutter motors and has a configurable change over delay and different contacts.
     
    Newman, Sep 1, 2008
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  6. pbelectrical

    ICS-GS

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    My suggstion for what it is worth, is to use the wire the c-bus relay output to an external relay (1, 2 or 4 pole) on EVERY relay output. That way any contact damage is done to a relay that can simply be unclipped from its base, thrown out and easily replaced. For the sake of a few extra bucks the c-bus (internal) relays should almost never wear out...

    HTH

    Grant
     
    ICS-GS, Sep 1, 2008
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