Eletrical question

[Sticks]

Will running two relays in parallel reduce the amount of amps being drawn to power a component... one relay has 30 amps running through it when activated, will two have15ish each?



What I thought was a solenoid problem with my exhaust brake turned out to be a relay that had arc'd enough times that it finally welded it self closed and would not release - thus locking my e-brake closed. I have replaced both relays (one to close it, another to hold it closed).



What I am thinking is that if I have two relays on each of the actions, there should be less amps running through each one and less likely to arc themselves to death.

 

[rfcom]

Two relays in parallel will share current to some degree although it may not be exactly 50% each. However, unless they switch at exactly the same time, the one that switches first will still see the full load until the other one comes on. It would be much better to get a bigger relay rated for the current draw you need.



Jim

 

[jkern]

current takes the path of least resistance. i am sure that you will never find two identical relays, electrically that is. one larger rated relay is really the way to go. or use a starter solonoid. you know the little metal can looking thing that has four threaded posts on them. you can get them in a continous duty rated coil and contacts... little more expensive than the black plastic ones but may be worth it later.

 

[Sticks]

The solenoid that is on my exhaust brake is a heavy duty. I suspect more than your standard starter solenoid. The manual calls for 15 amps (at least on the breaker), the specs on the solenoid (Syncro Start solenoids - 2370ES) states 58 amps. The first relay that got cooked was a 30 amp. Are 60 amp relays available? The largest that I have ever seen is a 30 amp.

 

[Joe G.]

You can get a 70 amp relay from LarryB or at a local electronic store. Larry sells them for fuel solenoid relay replacements for engines with P7100 pumps. I don't think Radio Shack has them. I bought one at a electronics store (they don't sell toys or computers or cell phones) near here.

 

[DavidC]

You could check with Radio Shack and see if they have a DC surge arrestor. We use the AC style at work on relays that control mag starters for motors. They essentially absorb the arc the relay contacts make when closing and opening. It will have 2 leads and wires across the solenoid + and -. We get ours from an Allen Bradley electrical distributor and I know they stock both styles. I believe the DC model has a resistor and capacitor in series in a encapsulted device. We have relays that have been in use for at least 5 years and the contacts still look and work like new. You may have to use a DC ammeter in series with the solenoid to measure what the activated current draw is so that you can size the arrestor appropriately.



Dave

 

[LarryB]

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THIS will work for you!!

You will need to get some larger spade connectors because the load/line lugs on this 70 amp relay are larger.

 

[Sticks]

Thanks Larry. I am going to keep an eye on the situation and do some tests to verify the amperage. The last set that I bought, were in the same packaging, same amperage, but one is definitely a heavier duty construction than the other (already popped the cover off to check the contacts).



Will your relay plug into most standard relay sockets on automotive PDCs? I am going to be junk yard diving this weekend looking for a mid size PDC (pre wired fuse and relay block) as part of a coming project that involves doing a complete re-wire of all my after market BS that I have installed. It's going to be nice having a clean wire harness going into the truck, I just don't know how I am going to get the connector through the hole into the cab.

 

[LarryB]

This one has the large 70 amp lugs so will not fit in the standard 30 amp socket. You would need to wire this up seperately like Dodge did (70 amp relay on the firewall for the fuel solenoid).

 

[jrandol]

Originally posted by sticks

Thanks Larry. I am going to keep an eye on the situation and do some tests to verify the amperage. The last set that I bought, were in the same packaging, same amperage, but one is definitely a heavier duty construction than the other (already popped the cover off to check the contacts).



Will your relay plug into most standard relay sockets on automotive PDCs? I am going to be junk yard diving this weekend looking for a mid size PDC (pre wired fuse and relay block) as part of a coming project that involves doing a complete re-wire of all my after market BS that I have installed. It's going to be nice having a clean wire harness going into the truck, I just don't know how I am going to get the connector through the hole into the cab.

Ooooohh!! Sticks I think I know what you have planned. sticks bomb tool!! Swcheeeett!!



Oo.

 

[Huff N Puff]

You can get a 140amp relay at

Most local part stores sell a 140amp constant duty relays,used in aux. charging systems in campers golf carts ect. It looks identical to a Ford starter relay but the coil windings have increased resistance to handle the increased on time. Merv

 

[JohnE]

Read those ratings carefully.

A 35 amp AC rated contactor (relay) will usually be much less for a DC rating. You hit the failure point, too. It isn't the current load, but the resulting arc from opening that is tough on things.

 

[David Oxland]

Electrical engineers will tell you that oversizing relays is not always a solution. Relay contacts are meant to arc and in doing so resurface and refinish themselves. Running an insufficient current can inhibit the arcing ability and thus the ability to keep their contact surfaces operable.