Need a high amp relay!

[$lacker]

Hi guys, I would appreciate whatever help you can offer

I've got a new detached garage built, and to make a long story short, the 100 amp panel won't provide enough power to run the welder and the electric in-floor heating at the same time (each needing a 50 amp breaker).

My plan is to have a 240V 50 amp breaker that feeds a DPDT relay. On the NC side it would provide power to the heater. On the NO side it would provide power to the welder.

A manual transfer switch would do the trick (basically a sub-panel with a cage on 2 breakers so they can't be energized at the same time), but I would prefer something that can be hooked to a timer, so that I can switch it to the welder and then it will revert to the heater after a predetermined amount of time (in case I forget to switch it back)

This would be the ideal sort of timer - http://www.ebay.com/itm/190714665916?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

As regards to the relay, I feel like one of these might do the trick, but I am unsure - http://www.ebay.com/itm/NEW-50A-220...165?pt=LH_DefaultDomain_0&hash=item3f3a0245fd
They can be found with a 120v coil, but I don't know if it would handle the load of the welder (which is what, resistive?)

One of the variations of this looks like it would work too, but I don't know
http://www.gordonelectricsupply.com...h~product~part~5589317~ds~dept~process~search


What do the experts/DIYers say?
Thanks!

 

[rockwithjason]

welders are inductive loads. you need to read the data sheet for the relay and see if they will break an inductive load of that size. of the two the square d would be a better choice.

 

[Norcal]

You need two, 2-pole contactors with a mechanical interlock between them so that cannot be energized at the same time or use auxiliary contacts to electrically interlock them or both, the SQ D definite purpose contactor in the link is a UL recognized component, not UL listed so is not kosher to use it, the UR logo means it's a UL recognized component for use in UL listed equipment which is not the case in the OP's situation.

 

[nine4gmc]

welders are inductive loads. you need to read the data sheet for the relay and see if they will break an inductive load of that size. of the two the square d would be a better choice.

The welder does not pull that much amperage if it's not being used, I would not recommend trying to flip the circuit switch while welding. In-floor heating I know nothing about.

 

[A_Pmech]

More than likely, you'll never draw anywhere close to 50A when using the welder. If it's a homeowner / light commercial machine the duty cycle is limited to 30% or so at max rated power anyway.

 

[$lacker]

Thanks
Anyone have a link/listing for a component that would do the job?

 

[theoldwizard1]

As regards to the relay, I feel like one of these might do the trick, but I am unsure - http://www.ebay.com/itm/NEW-50A-220...165?pt=LH_DefaultDomain_0&hash=item3f3a0245fd
They can be found with a 120v coil, but I don't know if it would handle the load of the welder (which is what, resistive?)

What do the experts/DIYers say?
Thanks!

As a fellow DIYer, I like your idea especially with timer ! High current DPDT "safety switches" are crazy expensive, unless you get lucky on CL.

This relay is rated 80A and has a 110v coil. If it fails, it was only $15.

What kind of current does the in-floor system draw ?

 

[_Dock_]

Are you sure you need all of this? I don't think either breaker would trip when running both at the max. If you need to do this for a feel good have at it but I doubt it would ever be a problem.

Look at a 200 amp panel in a moderate size home. Probably has 300 amps + of breakers but the actual fla of the circuits would never reach 200 amps at the same time.

 

[theoldwizard1]

Are you sure you need all of this? I don't think either breaker would trip when running both at the max. If you need to do this for a feel good have at it but I doubt it would ever be a problem.

Worth a try ! The duty cycle of the welder is in his favor.

I wonder what size the breaker feeding the sub is ?

 

[$lacker]

As a fellow DIYer, I like your idea especially with timer ! High current DPDT "safety switches" are crazy expensive, unless you get lucky on CL.

This relay is rated 80A and has a 110v coil. If it fails, it was only $15.

What kind of current does the in-floor system draw ?

Ordered one of these
Thanks!
Should be interesting to see the build quality

 

[theoldwizard1]

Show us some pictures of your implementation !

For longest life, try to toggle the relay when there is no load on it, either the heated floor or the welder.

 

[zmaxmotorsports]

Have you tried running what you have to see if its actually a problem?

 

[Rock knocker]

The duty cycle of the welder is in his favor.

The duty cycle has no bearing on the amperage draw of the welding machine, it is only a measure of how long the welding machine can be used at a particular output.

If the 100A sub is being fed by a 100A breaker at the main, I think it's unlikely that he'll ever break one of the 100A feeds

 

[Rock knocker]

Are you sure you need all of this? I don't think either breaker would trip when running both at the max. If you need to do this for a feel good have at it but I doubt it would ever be a problem.

Look at a 200 amp panel in a moderate size home. Probably has 300 amps + of breakers but the actual fla of the circuits would never reach 200 amps at the same time.

I agree

 

[s10xtremist]

Just because each device is on a 50 amp breaker doesn't mean each device is pulling 50 amps. Actually, the devices would only be pulling a portion of that and the rest is headroom. Also, the only time your welder might pull it's rated 50 amps is when you're welding something with it cranked to the max. I'd say you're over-thinking and over-complicating this. But, if it helps you sleep at night...

 

[knobby]

Like this?
http://www.ebay.com/itm/The-Power-T...u-dryer-outlet-for-lights-dryer-/231063795848

 

[CGT80]

I agree with trying to run both at the same time, if you haven't already, OP. You didn't state how much amperage your welder takes, or what percent of output you usually use. My little mig welder is 120v and takes 20 amps or so max. I often run it at max voltage, but sometimes don't. My TIG, on the other hand, takes 104 amps at 240v for full output (460 amps). I can only use the 0-250 amp range on it, due to a 50 amp circuit. I do run it at 250 amps but also have used it quite a bit at lower amperage.

Breakers and wiring will handle extra amperage for a short period of time. Welding is often done in short bursts. Once the breakers warm up, then they will trip easily. It is best to not push a circuit to the max rated amperage, but it can be done. It would be better to just shut off the heat when you think you will max your welder, even if it turns out to be a problem.

Another idea..............just put a timer on the heat. I have not worked with in floor heat, but I have worked on AC/heat pump units. If it has a thermostat and works similar to an AC unit (low voltage thermostat wiring) you could set a timer that would break the circuit to the thermostat while the timer is set. You may need a relay for this, but it would be low voltage, low current. The office spaces I used to work on, had a 12 hour timer that would break the circuit to the thermostat when the time ran out. It was supposed to keep the AC from running all night, but the timers often failed or just got bypassed.

With the above idea, you would set your timer to something like 30-60 minutes and go weld what you needed. After that amount of time, the heat would run as normal again.

 

[wyliesdiesels]

OP is WAY over complicating things. Continous loads are sized at 125% so the heating is not gonna be pulling 50a. And the welder may pull 50a AT MAX setting. I would try running both and see what happens. The worst that could happen is the breaker trips. Big deal!!

 

[theoldwizard1]

OP is WAY over complicating things. Continous loads are sized at 125% so the heating is not gonna be pulling 50a. And the welder may pull 50a AT MAX setting. I would try running both and see what happens. The worst that could happen is the breaker trips. Big deal!!

And if it does, turn the thermostat down when you are welding.

 

[Rock knocker]

I've been running my TA 181i multiprocess machine for almost a year on a 230x20A breaker instead of a 30 or 50A breaker while i fix several things in my shop. Running 1/8 7018 and solid .035 mig wire with no problems.