Jump to content
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
Dr Bob

Confused over relays

Featured Posts

Ok, need assistance from the experts - @Tony Brooks @nicknorman @MoominPapa   @WotEver etc

My nice shiny new bote comes complete with a fancy electric cupboard but a post on one of the Aqualine farcebook sites has got me thinking about saving 35Ahrs of power a day.

Most of the 12V circuits are wired first to a relay (https://uk.rs-online.com/web/p/latching-relays/9143995/) and then to a circuit breaker before connecting to the +ve bus bar. The nice switch panel on the outside of the electric cupboard has around 15 rocker switches which I understand activate their dedicated non latching relay when each switch is turned on. The idea suggested is to by-pass the relay and just use the circuit breaker switch to turn the circuit on or off. I have posted a link to the relay which quotes a coil power of 3W so that suggests a power draw of say 0.25A. Bypassing say 6 of the relays and using the switches in the cupboard instead therefore would save me 35Ahrs per 24 hours.

I am confused though because as I turn each rocker switch off in turn, I do not see a reduction in Amps on the battery monitor (with that circuit not drawing power – ie light switches turned off). If the relay is taking 0.25A, wouldnt I see that on the battery monitor or is the coil in the relay live all the time? I was confused as the relays are DPST – so not sure why they are Double pole – but there are 6 wires to each relay. On the relay diagram, the bottom two connections look to the be the power wires to and from the circuit and the other 4 must be to the rocker switch – but why 4?

The bank of 14 relays is hot to the touch so they are taking some power. I can see where over 1A is going or 2A ....or 3A!!

The other problem is that access to the relays is not easy and it will take me some time to dismantle stuff to get to the wires so don't want to start until I fully understand what I have got.

Share this post


Link to post
Share on other sites

Thanks but I am no expert in what looks like over complicated modern systems but some comments.

 

I would expect each circuit to have its own fuse/circuit breaker for protection and you didn't mention any so might those rocker switches be circuit breakers?

 

If they are they might be only AC rated (but I can't see that if they look like rocker switches) so the relays may be to minimise DC current through AC breakers - only a thought.

 

The relays contacts seem to be rated AC only (no mention of DC) and only 3VA. So as we are talking DC that is about 0.75 amps. I don't see how that is enough for most 12v circuits. Even if they have paralleled the two sets of contacts that is only 1.5 Amps.

 

The spec says "AC and DC Coils". That is plural' rather than coil rated for AC & DC so taking the spec literally its a bit worrying, I suspect low quality tech. specification  writing.

 

The diagram on the front of the relay looks pretty standard to me for DPST relay but apart from what looks like a silly low contact rating I cant see why they would parallel the contacts. It can only be to handle higher currents.

 

I think I would be thinking the same way as you are even if it means buying a new switch/mcb panel and doing some rewiring. At least that way you can attempt to ensure its all specified for the loads they need to carry.

 

I agree you need to consider warrantee but if that contact rating is as it seems then one must ask is it of merchantable quality and fit for purpose. I think you need to go back to the vendors for a lot more information and if its not forthcoming suggest doing what you want under warrantee so everything is properly rated.

 

 

   
   

Share this post


Link to post
Share on other sites
9 minutes ago, Tony Brooks said:

Thanks but I am no expert in what looks like over complicated modern systems but some comments.

 

I would expect each circuit to have its own fuse/circuit breaker for protection and you didn't mention any so might those rocker switches be circuit breakers?

 

If they are they might be only AC rated (but I can't see that if they look like rocker switches) so the relays may be to minimise DC current through AC breakers - only a thought.

 

The relays contacts seem to be rated AC only (no mention of DC) and only 3VA. So as we are talking DC that is about 0.75 amps. I don't see how that is enough for most 12v circuits. Even if they have paralleled the two sets of contacts that is only 1.5 Amps.

 

The spec says "AC and DC Coils". That is plural' rather than coil rated for AC & DC so taking the spec literally its a bit worrying, I suspect low quality tech. specification  writing.

 

The diagram on the front of the relay looks pretty standard to me for DPST relay but apart from what looks like a silly low contact rating I cant see why they would parallel the contacts. It can only be to handle higher currents.

 

I think I would be thinking the same way as you are even if it means buying a new switch/mcb panel and doing some rewiring. At least that way you can attempt to ensure its all specified for the loads they need to carry.

 

I agree you need to consider warrantee but if that contact rating is as it seems then one must ask is it of merchantable quality and fit for purpose. I think you need to go back to the vendors for a lot more information and if its not forthcoming suggest doing what you want under warrantee so everything is properly rated.

 

 

   
   

Ok, this is not as straightforward as I thought

 Aren't the relays rated at 25A at 240V?

I will post some pics in a couple of hours.

Share this post


Link to post
Share on other sites

I probably misunderstood what they meant by switching power, i think they probably mean maximum coil current and that's a lot more reasonable. Yes, second look (actually about the sixth) agrees with  you, 25 amps.

 

Share this post


Link to post
Share on other sites

Those relays are AC coils at 230v so current consumed will be .013amps, are you sure the coils are being used on 12vDC?

 

Share this post


Link to post
Share on other sites
8 minutes ago, Loddon said:

Those relays are AC coils at 230v so current consumed will be .013amps, are you sure the coils are being used on 12vDC?

 

Yes, all on 12 v.

 

Some pics.

 

The first pic is the bank of circuit breakers.

The second pic is the black rocker switches on the outside of the electric cupboard door

And the 3rd pic is the relays.

Therefore the +ve 12V cable from the horn circuit will go into one of the bottom 2 contacts on the relay K3 and then out of the other bottom contact , up to the circuit breaker Q5 then out to the 12v +ve bus bar. The black rocker switch on the top left row I assume is then wired into the K3 relay to activate it and make the horn circuit live. The horn then sounds when the horn button is pressed. If the relay is taking 0.25A all the time then it would be better just to take the relay out of circuit and use the circuit breaker Q5 switch as the isolation switch for that circuit?

 

1927248729_Circuitbreakers.jpeg.89591892070936519f96bbfb455af3dd.jpeg270276884_rockerswitches.jpeg.5b290578cdb1dc3f65bf6a5d04a0c881.jpegrelays.jpeg.4edb293ce1edc69ddaf2fab2490f844a.jpeg

Share this post


Link to post
Share on other sites
1 minute ago, Dr Bob said:

Yes, all on 12 v.

Not the same relay as in the RS link, the RS ones are 230v coil, the ones in your pic are 12v coil.

 

  • Greenie 1

Share this post


Link to post
Share on other sites

I'm not confused. Relays are only really there to protect lightweight naff switches. It's cheaper to fit them rather than fit decent hefty switches and extra heavier cabling. Cars began doing this with relays in the late 1960's, made ancilliaries less reliable because of the extra complications.

  • Greenie 1

Share this post


Link to post
Share on other sites

The front panel switches look pretty weedy, perhaps that’s why there are relays? Seems overkill though. What I don’t understand is why the 2-pole relays have both poles connected though.

Share this post


Link to post
Share on other sites
1 minute ago, Tony Brooks said:

At least we now know where the circuit breakers are.

I've been looking for a spec written in English for them to check if they are rated for DC as most MCBs are not!

To get rid of the relays will mean a complete new front panel with suitably sized switches, unless of course the switches are high enough rated at 12v DC to carry the loads.

 

Share this post


Link to post
Share on other sites

The LED's built in to the weedy panel switches will also be consuming 5 to 10mA each all the time. It all adds up. I can see nine illuminated, so that is another 2Ahr a day at 10mA each.

Jen

Share this post


Link to post
Share on other sites

Very poor practice to duplicate relay contacts to double current carrying capacity,  It is not a sensible idea as there is always a contact that makes or breaks fractionally before the other.

When I worked on Admiralty and Army equipment it was a total no-no.

 

Those rocker switches are weedy, I've had loads fail, hence the power wasting relays.  Who in his right mind designed all this gear?

 

I would dump all the rocker switches and the relays and use the Hagar MCBs as switches, I not sure though that the Hagar product is intended for DC use. I do know that Merlin Gerin, now Schneider, are approved, we used them in telephone centres.

Edited by Tracy D'arth

Share this post


Link to post
Share on other sites
Just now, Jen-in-Wellies said:

The LED's built in to the weedy panel switches will also be consuming 5 to 10mA each all the time. It all adds up. I can see nine illuminated, so that is another 2Ahr a day at 10mA each.

Jen

Yes. It's easy to turn the led off by disconnecting the negative lead behind the panel on each switch but happy to loose 2Ahr.

Share this post


Link to post
Share on other sites
3 minutes ago, Tracy D'arth said:

 

I would dump all the rocker switches and the relays and use the Hagar MCBs as switches, I not sure though that the Hagar product is intended for DC use. I do know that Merlin Gerin, now Schneider, are approved, we used them in telephone centres.

Well that is the whole point of this thread!

Why waste power heating up the relays when the circuit breaker can act as the switch.

My question in the OP was about how much power is each relay taking as I cant see any difference when I turn off the black rocker switches. By connecting together the bottom two wires on each relay, it takes that relay out of circuit so easy to do without - but able to put back in circuit if we sell the bote.

Concerned now though that the MCBs are not designed for 12V. However, its not that we use these switches (the black rocker ones). The only one we have used (with current flowing) is the water pump switch - to turn off the pump when the water runs out in the tank! The ones that need to be on are usually on all the time.

Share this post


Link to post
Share on other sites
2 minutes ago, Dr Bob said:

Concerned now though that the MCBs are not designed for 12V. However, its not that we use these switches (the black rocker ones). The only one we have used (with current flowing) is the water pump switch - to turn off the pump when the water runs out in the tank! The ones that need to be on are usually on all the time.

Its not the 12v that's the problem its the DC, the breakers may not have a contact designed to deal with the arcing caused by DC, AC self extinguishes the arc. Its an easy job to change the MCB to ones that are DC rated ;)

 

Share this post


Link to post
Share on other sites

I think it was Paula Ratcliffe who dropped the relay batton thingy but she still won the race for her team without it.

Share this post


Link to post
Share on other sites

The Fraud Motor Co did a similar trick. Remember those nice chromeum framed front quarterlight windows on hinges that could be turned inside out to get a nice cool draught through, well Fraud did away with em on the Mk 1 Cortina. It was cheaper to put a diverting flap in the heater box with trunking up to the eyeball outlet vents at both sides of the dashboard, but they still retained a fixed solid quarter light window in black paint. Similar thing happened about the anti smoking thing. Car makers quickly did away with ashtrays and fag lighters and saved bombs of money doing so. But soon along came electronic gadgetry heralding the fag lighter sockets return, which it did, but no ashtray :(  We're being hoodwinked and ripped off all the time. 

Share this post


Link to post
Share on other sites
1 hour ago, Jen-in-Wellies said:

The LED's built in to the weedy panel switches will also be consuming 5 to 10mA each all the time. It all adds up. I can see nine illuminated, so that is another 2Ahr a day at 10mA each.

Jen

40mA is about an amp-hour a day. I had an old fuse panel with illuminated rocker switches which I suspect were pre-LED, and they drew about 40mA per switch. I built a new panel using big toggle switches with built in LEDs from 12v planet, and from memory they drew about 15mA each, so I made up a pack of 2.2k resistors which brings them down to a couple of mA each, and plenty bright enough (if you like illuminated switches, that is...). 

Share this post


Link to post
Share on other sites
1 hour ago, Dr Bob said:

Well that is the whole point of this thread!

Why waste power heating up the relays when the circuit breaker can act as the switch.

My question in the OP was about how much power is each relay taking as I cant see any difference when I turn off the black rocker switches. By connecting together the bottom two wires on each relay, it takes that relay out of circuit so easy to do without - but able to put back in circuit if we sell the bote.

Concerned now though that the MCBs are not designed for 12V. However, its not that we use these switches (the black rocker ones). The only one we have used (with current flowing) is the water pump switch - to turn off the pump when the water runs out in the tank! The ones that need to be on are usually on all the time.

If you aren't breaking the MCB's under load, then there won't be a current flowing to form a long lasting arc that will erode the contacts over time. If they spend most of their time switched on, then all should be fine. AC currents and DC currents will be similar. It is only breaking a DC current that would be a problem. If it was my boat I'd bypass the relays and switch from the MCB's, with the possible exception of the water pump for the reason you say. If need be, just carry a spare MCB to replace any that give up the ghost.

Jen

  • Greenie 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.