Do I need to shutdown/isolate solar inverter before using welder?

[aesmith]

Hi,

We've just had solar panels installed on the barn roof, running through a 6kW "Solaredge" inverter to a dedicated circuit from the garage DB.

My question is whether I should shutdown and isolate the system when I'm going to be using a welder. Both my stick welder and the MIG are inverter sets running from 13A socket.

As a cautionary tale from my youth, the outfit I worked for used to service and repair Solartron flow computers. We had one in from a distillery that had died, reportedly after an arc welder hd been run off the same circuit. We ended up replacing just about every IC as ech time we sent it out fixed, something else would fail a week or so later.

 

[hotponyshoes]

Any modern welder should protect the incoming mains against backfeed/interference/etc.

If your welders are modern branded sets I'd not worry about it.
If it's a cheap chinese machine or an old transformer type that's probably been 'modified' to stop tripping then maybe I would!

Probably be easy enough to fit some sort of changeover switch that isolates the solar at the same time as powering up the welder socket

 

[gaz1]

at the cost of your system id be asking back at the company that installed it

newer welding machines might be friendly towards solar systems but unless they are tested you always run the risk of blowing them

would i like to run a welder on solar power yes but i suspect its more based on mains power than solar

the issue also stands with which generator will power my welder as many wont even power them

its the pull rush of the welder when it starts up that can fry the install

 

[Gareth J]

Should be fine. I say should be as any modern inverter will be monitoring the quality of the mains which, if it gets outside of set parameters, will knock the inverter offline.

I regularly use a welder on lots of supplies with PV. The biggest welder on a high setting will distort the mains enough to trip out one of the inverters. That's likely a result of supply/cabling not being able to keep up with startup currents than an inverter issue.

Also, why not make use of the solar available!

 

[aesmith]

Probably be easy enough to fit some sort of changeover switch that isolates the solar at the same time as powering up the welder socket

I don't think that would be necessary, if the solar needs to be shut down it's not something I'm going to forget.

 

[hotponyshoes]

I don't think that would be necessary, if the solar needs to be shut down it's not something I'm going to forget.

What welder(s) are you running?

I've used plenty of welders etc on farms and plenty of those have solar. Never had any issues.
Although they normally have 'barn roof' size systems so possibly more robust than domestic..

 

[aesmith]

I've used plenty of welders etc on farms and plenty of those have solar. Never had any issues.
Although they normally have 'barn roof' size systems so possibly more robust than domestic..

As a matter of fact our solar is on the barn roof. We have around 150 sq.m of South facing roof on that building, but the electricity company won't allow us more than a 6kW inverter. So I guess it's domestic scale, maybe towards the higher end.

 

[gaz1]

As a matter of fact our solar is on the barn roof. We have around 150 sq.m of South facing roof on that building, but the electricity company won't allow us more than a 6kW inverter. So I guess it's domestic scale, maybe towards the higher end.

if your not using all of that space id be looking at other alternatives to store said power or heat than can be produced

that includes the sand battery but note that is much better used for heating whilst you could also top up your own battry system or few systems depending on what you build or add onto your own system

 

[Ed.]

At my new house I have a 13.3kw of solar running through a 10KW solar inverter. My welder is an old Miller Inverter 3 phase that can push out 600A, however nearly all of the time I only use about 190-250A. My previous home I had 5kW of solar panels connected to a 5kW inverter. Using the same welder up to 350A, it never tripped the circuit breakers. I had a meter installed in the shed (where the welder was located and it was the only place I had 3 phase power) to see how much power the 3 phase system was drawing and that Miller was remarkably efficient and used minimal power, after I put through about 2/3 rd of a 15kg roll of wire I checked the meter and there was stuff all usage, I actually thought the meter was faulty and had stopped working, that was until I switched on and used my big lathe. I think that had a 6.5HP motor on it and it used about 10 times more power than my welder.

Having said all that I never once had a problem with using the MIG, MMA and TIG welder with either solar systems, however in my last place (5kW system) the 3 phase 4 in1 TIG would occasionally trip a circuit breaker on first startup in the morning, but I suspect it was more to do with the TIG welder than the solar system. It was an Everlast, but after the first trip and reset it would work all day without any issues.

I think the main issue might be that your power lines are not adequate to carry enough power through them. My first place when I updated the 240V shed and house to the three phase we had 16mm cable from the street and the energy company added more 16mm lines, from the shed to the house I added 4C+E 16mm cable and from the sub-box to all the 3 phase sockets I used 10mm cable, So I didn't have any issues of "will my wires cope with large current drain. My new house now has 25mm 3 phase connected to shed and then to the house, and internally when I put a sub-board to the inside of the shed more 10mm cable will go the the 3 phase sockets. One of the my big dislikes is having to decide if I can buy some sort of machinery and will my wires have enough capacity to run something. Unless I get a big water jet and that will never happen. But as far as solar panels at the same time as an inverter MIG, never had a problem.

 

[aesmith]

I think the main issue might be that your power lines are not adequate to carry enough power through them.

We do have a limit from the DNO but that's on export, due to the size and length of the service cable from our transformer. DNO would only allow 6kW total system size to prevent excessive voltage rise at our end.

From the house there's 25sq.mm SWA to the workshop DB which is where the solar inverter connects, next door to the barn with the panels.

 

[Ed.]

Over here in Oz it seems that 6kW is also the max solar on single phase homes. Your welder shouldn't have an issue just because you have solar connected but I have been known to be wrong before. 25mm2 should be more than enough unless you are a really long way from the power lines in the street. At my house, everything I run gets it's power from the main PV solar inverter, should the drain exceed the available power then it uses the balance from the grid power. In other words if I switch on my aircon (8kW)in the afternoon and the solar is only producing 3kW then it uses the grid power to provide the 5Kw excess required. I can't see why your system would operate differently.