DIY Auto transfer switch questions?

[Mike90250]

I hear exactly what you are saying, I did not know if your system was single or split phase. if everything works right, it would be fine, and I hope you are happy with it.

I was attempting to point out that relays used as a transfer switch, can fail in unexpected ways, such as shorting both poles ( A channel , In to Out) and not simply A to B.
As was observed, quality varys wildly.

[PNW_Steve]

I think that some are not understanding what I am asking.

Couple of points:

A 120v circuit does not need 2 lines and a neutral. Just one line and one neutral.

The DPDT relay is a break before make device.

If the relay contacts failed open, shorted or welded in one position I would not energize the incoming line. If shorted it would trip the over current protection.

,............ I keep typing and erasing. I am having a hard time finding a way to phrase further questions without starting an argument.

I'll try again later.

[ILFE]

I need to preface my reply to let you know I made an error in my previous post, above. I had been awake all night and was exhausted when composing the reply. I stated that:

EDIT: Whenever I had a relay fail, NO power was making it to the receptacles / power points, from either source.

That would be impossible. It should have read, "... from one source." I meant no power from the mains. When the relay is energized, it routes power from the mains to the receptacles / appliances. When mains fail, it routes power from the inverter.

The failures I had after building my ATS units, were the coils. It didn't take me long to sort out the relays I used were junk. When I began using the relays received from the US, that eliminated all of my failures. (The relays I ended up using were probably still Chinese made, but under a western eye?)

Unless you have a fail safe design relays can short out and not isolate a circuit especially if you have a "make before break" program.

Relays work and DIY can be built but you have to weigh the worst case scenario which could be someone getting electrocuted.

If the product is made by someone else and has a UL listing the user is pretty much kept out of the lawsuit. If it is a DIY equipment that fails then the user is at fault.

My ATS's are not make-before-break. They are on a farm, where our family and employees are too scared to even touch a 12vdc solar battery, much less anything that is 230vac. UL listings do not exist here. Many pieces of AC hardware are junk, made in Vietnam. Voltage regulators, 230vac plugs, sockets, etc., are junk. Thai made products tend to be of much better quality.

Relays can fail 3 ways.
Contacts all open
Contacts all shorted/welded
Some contacts open or shorted. I have seen all these modes, and if you are experiencing failures and need to change relays often, something is WRONG.

For high currents, contactors are used, like a well pump contactor, they are made to switch heavy loads. you would need 3 of them 2 lines and a Neutral

My inverter has a built in transfer relay, rated 60A 240V, and contact welding is a common failure mode in my inverter series And they are soldered in. But I'm off-grid and they are not exercised under load, so i expect to be fine.

But when you start building major electrical components from hobby store parts and they are not UL approved, you are assuming all liability for your actions

Living in SEA is a completely different experience than in the west. There is no UL here. Man, this place is closer to the wild west, than it is to modern civilization. Heck, OSHA would have a field day, here. Welding in the rain - using an open cased buzz box, no protection, no eye shield, no gloves, and wearing flip-flops. (No, I wish I were joking.)

The heaviest draw on an ATS here is a refrigerator / freezer. Frequently, when the mains does fail, the compressor isn't running. (Our other refrigerator has inverter technology. Smooth sailing with it, always.) I am sure, however, we have experienced mains drop outs when it was. I'm actually surprised that I haven't lost the compressor due to that action.

Regarding relay failures, all were coil related. I've never experienced any contact failures. And, the newer relays (from the states) have never failed. So far, I've been pretty fortunate with their service.

Incidentally, all mains power here is 230vac / 50hz. It will fluctuate fairly often, as well. Here in the city, it dropped to 178 volts, last evening.

[Mike90250]

Relays can fail 3 ways.
Contacts all open
Contacts all shorted/welded
Some contacts open or shorted. I have seen all these modes, and if you are experiencing failures and need to change relays often, something is WRONG.

For high currents, contactors are used, like a well pump contactor, they are made to switch heavy loads. you would need 3 of them 2 lines and a Neutral

My inverter has a built in transfer relay, rated 60A 240V, and contact welding is a common failure mode in my inverter series And they are soldered in. But I'm off-grid and they are not exercised under load, so i expect to be fine.

But when you start building major electrical components from hobby store parts and they are not UL approved, you are assuming all liability for your actions

[SunEagle]

Not sure I follow your comment, Mike? Steve is looking to buy or build a device, that will switch between mains and inverter, when power fails. If using a relay, it is, quite literally, impossible for both mains / shore power and the inverter to power the receptacles (power points), simultaneously. His original statement regarding this:



Or, am I missing something in your post? If so, my apologies.

EDIT: Whenever I had a relay fail, NO power was making it to the receptacles / power points, from either source.

Unless you have a fail safe design relays can short out and not isolate a circuit especially if you have a "make before break" program.

Relays work and DIY can be built but you have to weigh the worst case scenario which could be someone getting electrocuted.

If the product is made by someone else and has a UL listing the user is pretty much kept out of the lawsuit. If it is a DIY equipment that fails then the user is at fault.

[ILFE]

This is the fun, fail safe part of a UL certified transfer switch, if it fails and cooks a lineman, you don't have to go to jail for manslaughter..

Not sure I follow your comment, Mike? Steve is looking to buy or build a device, that will switch between mains and inverter, when power fails. If using a relay, it is, quite literally, impossible for both mains / shore power and the inverter to power the receptacles (power points), simultaneously. His original statement regarding this:

Just to be clear, I want certain receptacles to be fed shore power and when shore power disappears I want them to switch over to inverter power.

Or, am I missing something in your post? If so, my apologies.

EDIT: Whenever I had a relay fail, NO power was making it to the receptacles / power points, from either source.

[Mike90250]

This is the fun, fail safe part of a UL certified transfer switch, if it fails and cooks a lineman, you don't have to go to jail for manslaughter..

[ILFE]

It sounds like you have had to replace relays periodically. Is that correct? What sort of failure are you seeing?

At first, fairly often, due to being stupid and trying cheap Chinese made garbage. Afterward, due to buying several from a US company, none.

[PNW_Steve]

Like I said, no worries. Just mount the relay base for your circuit and you can plug / unplug the relay whenever needing to replace it. easy peasy. Just leave all power cords plugged in, otherwise. Not sure if he is a member here. But, the guy who made the project I copied, goes by 2manytoyz, on at least one other solar related forum of which I am a member. Give 'er a try. Worst case, you are out a few bucks. Best case, you will be making more of them.

In fact, Robert (2manytoyz) may be the person who uses a similar circuit to switch between two appliances, a refrigerator and a freezer, in order to be able to run both from a single, smaller inverter. I believe, when the freezer is powered, the relay breaks the connection for the power feeding the refrigerator. When its compressor drops out, the refrigerator can then be powered. Pretty nifty idea, whomever came up with it. I will be using one of these for the same purpose, at our farm. We now have two refrigerator / freezer units out there and only want one running at a time. It's easier (READ: cheaper) to do that, than to worry about trying to get another PSW inverter from the states.

I saw a similar setup for running two roof a/c's on an RV years ago.

It sounds like you have had to replace relays periodically. Is that correct? What sort of failure are you seeing?

[PNW_Steve]

They have ATS in them. And an inverter. And quick switch-over time, no glitching the computer. Even if you have your DIY transfer switch, how do you turn the inverter on, or are you leaving it on all the time ? If you leave it on all the time, just get a semi-smart battery charger to keep the batteries charged, and run off the inverter 24/7

I'm trying ideas to help you out. maybe jar a random stray thought loose

Thank for the suggestions.

This is for an RV with 4x L16 batteries and a Prosign 1800/24 inverter. I have everything lined out except the shore/inverter transfer switch.

[ILFE]

Thank you for sharing that link. That is exactly what I was considering. It looked like it should work but I was concerned that I may be overlooking something that could bite me in the backside.

Like I said, no worries. Just mount the relay base for your circuit and you can plug / unplug the relay whenever needing to replace it. easy peasy. Just leave all power cords plugged in, otherwise. Not sure if he is a member here. But, the guy who made the project I copied, goes by 2manytoyz, on at least one other solar related forum of which I am a member. Give 'er a try. Worst case, you are out a few bucks. Best case, you will be making more of them.

In fact, Robert (2manytoyz) may be the person who uses a similar circuit to switch between two appliances, a refrigerator and a freezer, in order to be able to run both from a single, smaller inverter. I believe, when the freezer is powered, the relay breaks the connection for the power feeding the refrigerator. When its compressor drops out, the refrigerator can then be powered. Pretty nifty idea, whomever came up with it. I will be using one of these for the same purpose, at our farm. We now have two refrigerator / freezer units out there and only want one running at a time. It's easier (READ: cheaper) to do that, than to worry about trying to get another PSW inverter from the states.

[PNW_Steve]

Build your own, perhaps? I've built a couple, like this Auotmatic Transfer Switch on Robert's site. They work great, and have for some time. If the relay fails, just unplug and replace it with another one.

Thank you for sharing that link. That is exactly what I was considering. It looked like it should work but I was concerned that I may be overlooking something that could bite me in the backside.

[ILFE]

Build your own, perhaps? I've built a couple, like this Auotmatic Transfer Switch on Robert's site. They work great, and have for some time. If the relay fails, just unplug and replace it with another one.

[Mike90250]

They have ATS in them. And an inverter. And quick switch-over time, no glitching the computer. Even if you have your DIY transfer switch, how do you turn the inverter on, or are you leaving it on all the time ? If you leave it on all the time, just get a semi-smart battery charger to keep the batteries charged, and run off the inverter 24/7

I'm trying ideas to help you out. maybe jar a random stray thought loose

[PNW_Steve]

Maybe you need a large computer style UPS ?

Not sure how a UPS fits in to the discussion?