advice on mains relay

[nickdsjnk]

Hi all,

I have a 20a mains relay (<250v ac) with a 230v ac coil. The relay is the finder 22.24 as below:

http://www.findernet.com/comuni/pdf/S2221_22_23_24EN.pdf

The relay is normally closed and needs 230v across the coil to open the circuit.

The relay is going into a motorhome mains circuit and takes a low current live feed from a mains changeover unit to open the live and neutral on some circuits (split CU) when the inverter is used to prevent items such as battery chargers and air conditioners from being used from the inverter.

To get 230v across the coil shall I connect the live switching feed to A1 and attach the neutral to A2? or does the live go to both A1 and A2?

Thanks for your help,

Nick.

For anyone interested the changover unit used is this:

http://www.sterling-power.com/products-230vcs-auto.htm

It is a well built unit but I don't know how the DNO would feel about it's use.

 

[Paul_C]

To get 230v across the coil shall I connect the live switching feed to A1 and attach the neutral to A2? or does the live go to both A1 and A2?

The former. The relay will then operate when power is applied to the coil. If you connected A1 and A2 to the same point, it would never operate!

 

[bernardgreen]

I think you need to look carefully at the specification of the contacts for that relay and compare it with the loads it will be switching.

At first glance it appears to be UN-suitable for you application.

Also if it is being powered ( energised ) to disconnect excessive loads then when the change over switch switches to the invertor there will be a short duration delay before those loads will be dis-connected. This delay is the operating time of the relay. During this delay the possible over load on the invertor may mean the invertor shuts down. The relay will drop out ( de-energise ) and if the invertor then auto re-starts the cycle will repeat.

If you need to switch the CU over to the invertor then you need to disconnect all supplies to the CU first. Then disconnect the circuits in the CU that the invertor is not to supply and only then connect supply from the invertor to the CU. The change over unit might have the necessary sequencing controls for this function.

 

[nickdsjnk]

Thanks both for responding

I think you need to look carefully at the specification of the contacts for that relay and compare it with the loads it will be switching.

the maximum load if all circuits on the relay side of the consumer unit are active is about 17a, I assumed that the 20a rating of the relay meant that it was capable of disconnecting this load. Is this not the case? I am not familiar with specifying AC relays so I guess I missed something.

Can you suggest an alternative DPST-NC Relay or contactor? I guess a DPDT relay would also be ok because I could just leave the NO contacts unused.

With regard to the small delay between the inverter becoming active and the loads being disconnected, this is not an issue. The inverter being used is specified to provide more than 20a for a duration of 3.5seconds and can probably provide far more than this for the tiny period it takes for the relay to disconnect. However I suspect that the relay feed from the changeover is energised a split second before power changes over to inverter use anyway.

Thanks

Nick

 

[bernardgreen]

One option is

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7116247

 

[nickdsjnk]

One option is

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7116247[/QUOTE]

Hi Bernard,

Is it just to higher current rating which makes this contactor more suitable? Or are there other factors I should consider?

Also the coil voltage on that is 250 -500.

Would this one be better?

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7116234#header