power flickering from small 12vdc -> 120vac inverter attached to EV

[gthomas785]

It's gonna go between the xformer and the cable leading to the pump, no ? Doesn't it need to be double-pole and 10 amps or so contact rating ?

Yeah. You put the timer in series with the coil of a 30 amp contactor and power the pump with the contactor.

 

[RustyShackleford]

Yeah. You put the timer in series with the coil of a 30 amp contactor and power the pump with the contactor.

No such animal as a double-pole , 10+ amp, delay-on-make contactor, I suppose. Or insanely expensive.

 

[Pinesmoke]

Use a low amperage timing relay to trigger a motor starter (high amperage).

 

[gthomas785]

No such animal as a double-pole , 10+ amp, delay-on-make contactor, I suppose. Or insanely expensive.

I don't think I've seen one. No point making that when regular contactors are cheap and readily available. Also since these are usually used on HVAC compressors that are already controlled by a contactor.

 

[RustyShackleford]

I'm liking the idea of @Whitenuckler (I believe), but using a relay for the DPDT switch ...

It seems a little sketchy to install a piece of odd surplus-sourced gear into my house's electrical system. This option allows it to be:

1. Energized and used only when needed.
2. In a very accessible/visible location (next to the main load center in a utlity room).

The chief disadvantage is complexity. But that's mostly in the installation and I like doing that stuff (who knew). My main concern is ease of usage, and having the DPDT be a relay (instead of a switch) means toggling the 120vac breaker is the only step needed to enter or exit grid-outage mode.

Also I can test the thing without the switch (and the transformer always energized) and stick with that if it seems good. And I don't have to drag this 50lb hunk of metal into my crawlpspace.

 

[Whitenuckler]

I'm liking the idea of @Whitenuckler (I believe), but using a relay for the DPDT switch ...

View attachment 347051

It seems a little sketchy to install a piece of odd surplus-sourced gear into my house's electrical system. This option allows it to be:

1. Energized and used only when needed.
2. In a very accessible/visible location (next to the main load center in a utlity room).

The chief disadvantage is complexity. But that's mostly in the installation and I like doing that stuff (who knew). My main concern is ease of usage, and having the DPDT be a relay (instead of a switch) means toggling the 120vac breaker is the only step needed to enter or exit grid-outage mode.

Also I can test the thing without the switch (and the transformer always energized) and stick with that if it seems good. And I don't have to drag this 50lb hunk of metal into my crawlpspace.

I liked the switch better than a relay, as you would need N/C contacts or two relays and have all the coil circuits to worry about. You would also need to ensure the contact ratings are correct. If its all inside a "locked" metal box, I'd just use connectors rated for 240V. You don't need a neutral, just two hots and ground. You can shut off the normal feed, do your plug swaps, then turn the 120V breaker on with the box closed. It would be nice to have control over the pressure switch. Maybe a 2 pole switch (I use one for my heaters in my porch). Then you could turn that back on as the final step once the transformer is energized. The switch would be outside the box.

 

[RustyShackleford]

There are DPDT relays with 30amp contacts and a 120vac coil ...

https://www.automationdirect.com/adc/shopping/catalog/relays_-z-_timers/electro-mechanical_relays/ad-pr40-2c-120a

... so I don't see why I'd need to worry about the coil circuit, it's either energized or not (maybe I'm missing something). it's "break before make," so no need to turn off the 240vac breaker ever. Beefy 40amp contacts, and they only get toggled a couple times a year probably.

Unfortunately the pressure switch is 50ft away at the other end of the house in the crawlspace. I see that if the pressure switch is "on" when I switch to grid-out mode, I could have the problem of simultaneous inrush-current to the transformer and the pump, which could pop the breaker or the inverter, as discussed earlier. Could be a problem. But I did do another measurement of the pump current, and this time is was 4.3 amps and it ramped up to that over a period of 3-4 seconds, so I'm thinking that pump inrush current is a non-issue.

But the transformer will be here later today and I'll start testing it ! Is it too noisy ? Connect it to the little 1000watt inverter I'm using now and see if it can handle it, especially making sure the pressure switch is energized when I switch the inverter on. Then connect it to a 20amp/120vac circuit and do the same thing. Some fun.

 

[Whitenuckler]

There are DPDT relays with 30amp contacts and a 120vac coil ...

https://www.automationdirect.com/adc/shopping/catalog/relays_-z-_timers/electro-mechanical_relays/ad-pr40-2c-120a

... so I don't see why I'd need to worry about the coil circuit, it's either energized or not (maybe I'm missing something). it's "break before make," so no need to turn off the 240vac breaker ever. Beefy 40amp contacts, and they only get toggled a couple times a year probably.

Unfortunately the pressure switch is 50ft away at the other end of the house in the crawlspace. I see that if the pressure switch is "on" when I switch to grid-out mode, I could have the problem of simultaneous inrush-current to the transformer and the pump, which could pop the breaker or the inverter, as discussed earlier. Could be a problem. But I did do another measurement of the pump current, and this time is was 4.3 amps and it ramped up to that over a period of 3-4 seconds, so I'm thinking that pump inrush current is a non-issue.

But the transformer will be here later today and I'll start testing it ! Is it too noisy ? Connect it to the little 1000watt inverter I'm using now and see if it can handle it, especially making sure the pressure switch is energized when I switch the inverter on. Then connect it to a 20amp/120vac circuit and do the same thing. Some fun.

I was thinking later (as always) that all you need is a double pole switch (20A) like mine and you can even mount it on the cover of your panel. It would just be a "load switch". That's the first thing I'd turn off, and last thing to turn on after you have done everything else.
The pressure switch and it would be in series with the pump. You would not need to worry about extra in rush as it would only be the transformer at the beginning. Then when you want to go back to normal, use the switch again. Yes the coil can be fed from a switch with one NO contact. The NC contacts would be for the 240V from the panel. The common point the 2 pole switch and the new transformer.

 

[RustyShackleford]

I was thinking later (as always) that all you need is a double pole switch (20A) like mine and you can even mount it on the cover of your panel. It would just be a "load switch". That's the first thing I'd turn off, and last thing to turn on after you have done everything else.
The pressure switch and it would be in series with the pump. You would not need to worry about extra in rush as it would only be the transformer at the beginning. Then when you want to go back to normal, use the switch again. Yes the coil can be fed from a switch with one NO contact. The NC contacts would be for the 240V from the panel. The common point the 2 pole switch and the new transformer.

I'm not quite following you, but I think you're just saying add a load switch to my design. Here's a revised drawing ...

 

[Whitenuckler]

I'm not quite following you, but I think you're just saying add a load switch to my design. Here's a revised drawing ...

View attachment 347061

AC Current Voltage Tester with 3-Digit LED Display Multifunction Voltmeter Ammeter Frequency Meter Multimeter Panel (White) : Amazon.ca: Tools & Home Improvement

AC Current Voltage Tester with 3-Digit LED Display Multifunction Voltmeter Ammeter Frequency Meter Multimeter Panel (White) : Amazon.ca: Tools & Home Improvement

www.amazon.ca

I'd also add some ,metering. Handy for knowing what the pump is drawing, the voltage ect. Also with the load switch off, you can verify it all looks good before switching the pump on. It would be wired before the switch. I'd for sure have a toggle switch for the relay coil circuit and some fusing. Fusing for the meter voltage input's too.

 

[gthomas785]

AC Current Voltage Tester with 3-Digit LED Display Multifunction Voltmeter Ammeter Frequency Meter Multimeter Panel (White) : Amazon.ca: Tools & Home Improvement

AC Current Voltage Tester with 3-Digit LED Display Multifunction Voltmeter Ammeter Frequency Meter Multimeter Panel (White) : Amazon.ca: Tools & Home Improvement

www.amazon.ca

I'd also add some ,metering. Handy for knowing what the pump is drawing, the voltage ect. Also with the load switch off, you can verify it all looks good before switching the pump on. It would be wired before the switch. I'd for sure have a toggle switch for the relay coil circuit and some fusing. Fusing for the meter voltage input's too.

Dude, this is getting complicated. Lol

 

[Whitenuckler]

Dude, this is getting complicated. Lol

I'm still waiting for the wiring diagram and schematic. This stuff is fun. Reminds me of work, although it was not always fun doing it for a living.

 

[RustyShackleford]

I'm still waiting for the wiring diagram and schematic. This stuff is fun. Reminds me of work, although it was not always fun doing it for a living.

Joking ? I put it in post #59. Yep, same here.

 

[RustyShackleford]

Dude, this is getting complicated. Lol

Yeah, I intend to carefully measure the transformer's output voltage and current under stringent test conditions (garden hose running full blast), but if that all looks good, I don't feel the need for digital displays.

And I think the transformer is chock-a-block with fusing. Plus both inputs to the NEMA box will be a few feet removed from circuit breakers in my main panel. So I don't think I need any more fuses. But I'm open to different opinions.

I think having a DPST switch on the 240vac line leaving the NEMA box is a good idea.

But yeah, this stuff is fun. A sane person would just shell out a little more dough (more like a lot more) for a power station with 240vac split-phase output.

 

[RustyShackleford]

Excellent news, comrades ...

The transformer was supposed to arrive yesterday; but then UPS said the package was damaged and they're returning it to seller. So I asked the seller to tell UPS to deliver it anyhow and let me inspect it. Apparently they told seller they couldn't find it, so more or less simultaneously today the transformer and a full refund arrived. The transformer was indeed damaged. So I told the seller what's up. I dunno who ate the cost: the box was badly damaged, so maybe UPS. If it was the seller, I'll offer to pay half-price; otherwise I'll consider it a gift from UPS Anyhow ...

I hooked it up to a 120vac/20amp duplex outlet (measuring 122vac) and to the 240vac Romex going out to the pressure switch&tank and the pump (measuring 238vac with the pump off). When the pump came on, the two sides sagged to 119vac and 228vac, respectively. Everything seemed to be working fine, drawing about 9 amps from the 120vac side. I'm ok with the voltage sag, given the pump's spec is 200-240vac. When the pump was off, the transformer drew 1.6 amps; this 200 watts is unacceptable waste, so any scheme that leaves the transformer continuously energized is out. The 60Hz hum is very mild though, not an issue. I unplugged it while the pressure switch was "on" and plugged it back in; it did not pop the breaker, but there was a noticeable "thump", so not liking that scheme either. I then connected the 120vac side to a 1000watt 12vdc inverter which I can connect to our Nissan Leaf EV (which is my current inadequate backup scheme), and that worked fine too; so that gives me confidence a 120vac power station with at least 2000watts output (Ecoflow Delta 3 Max or the like) can handle it and a few other loads.

So I think I'm going to stick with the scheme I drew in post #59 above.

Also, how the heck to you ground this thing ? There appear to be no ground terminals on it. I'm going to put it inside a NEMA box (along with the DPDT relay and the load switch of @Whitenuckler ) and that will be grounded, so just the mechanical connection of mounting it to the box ?

 

[gthomas785]

When the pump was off, the transformer drew 1.6 amps; this 200 watts is unacceptable waste, so any scheme that leaves the transformer continuously energized is out.

Don't be fooled, the idle current of the transformer is at a very low power factor. If it were really putting out 200 watts you'd feel that

 

[RustyShackleford]

Don't be fooled, the idle current of the transformer is at a very low power factor. If it were really putting out 200 watts you'd feel that

Oh, good point. I did notice the 12vdc inverter didn't register anything, just my Fluke 87. I still like the scheme of post #59 though, even though the construction is a little more complex.

 

[Whitenuckler]

Excellent news, comrades ...

The transformer was supposed to arrive yesterday; but then UPS said the package was damaged and they're returning it to seller. So I asked the seller to tell UPS to deliver it anyhow and let me inspect it. Apparently they told seller they couldn't find it, so more or less simultaneously today the transformer and a full refund arrived. The transformer was indeed damaged. So I told the seller what's up. I dunno who ate the cost: the box was badly damaged, so maybe UPS. If it was the seller, I'll offer to pay half-price; otherwise I'll consider it a gift from UPS Anyhow ...

View attachment 347086

I hooked it up to a 120vac/20amp duplex outlet (measuring 122vac) and to the 240vac Romex going out to the pressure switch&tank and the pump (measuring 238vac with the pump off). When the pump came on, the two sides sagged to 119vac and 228vac, respectively. Everything seemed to be working fine, drawing about 9 amps from the 120vac side. I'm ok with the voltage sag, given the pump's spec is 200-240vac. When the pump was off, the transformer drew 1.6 amps; this 200 watts is unacceptable waste, so any scheme that leaves the transformer continuously energized is out. The 60Hz hum is very mild though, not an issue. I unplugged it while the pressure switch was "on" and plugged it back in; it did not pop the breaker, but there was a noticeable "thump", so not liking that scheme either. I then connected the 120vac side to a 1000watt 12vdc inverter which I can connect to our Nissan Leaf EV (which is my current inadequate backup scheme), and that worked fine too; so that gives me confidence a 120vac power station with at least 2000watts output (Ecoflow Delta 3 Max or the like) can handle it and a few other loads.

So I think I'm going to stick with the scheme I drew in post #59 above.

Also, how the heck to you ground this thing ? There appear to be no ground terminals on it. I'm going to put it inside a NEMA box (along with the DPDT relay and the load switch of @Whitenuckler ) and that will be grounded, so just the mechanical connection of mounting it to the box ?

Yes you want to ground your metal panel and then mount the transformer in it. You should clear the finish off a spot and get a good ground wire that can be seen, plus any ground from mounting it. There should be taps that you can get more voltage out of it.

 

[RustyShackleford]

There should be taps that you can get more voltage out of it.

Here's the label:

I connected 240vac output between H1/H3 and H2/H4.

 

[Whitenuckler]

Here's the label:

View attachment 347094

I connected 240vac output between H1/H3 and H2/H4.

I checked it out and I was wrong. You can't adjust the voltage. You have what you have. I you have 120V in you should get 240 out

 

[RustyShackleford]

Well, with no load I'm seeing 122vac in and 238vac out. I imagine the discrepancy is because of the reverse feed. and some 2nd-order effects related to that.

This excerpt from the catalog hints at it ...

ACME dry-type distribution transformers can be reverse connected without a loss of kVA rating, but there are certain limitations. Transformers rated 1 kVA and larger single phase, 3 kVA and larger three phase can be reverse connected without any adverse effects or loss in kVA capacity. The reason for this limitation in kVA size is, the turns ratio is the same as the voltage ratio. Example:A transformer with a 480 volt input, 240 volt output can have the output connected to a 240 volt source and thereby become theprimary or input to the transformer, then the original 480 volt primary winding will become the output or 480 volt secondary. On transformers rated below 1 kVA single phase, there is a turns ratio compensation on the low voltage winding. This means the low voltage winding has a greater voltage than the nameplate voltage indicates at no load. For example, a small single phase transformer having a nameplate voltage of 480 volts primary and 240 volts secondary, would actually have a no load voltage of approximately 250volts, and a full load voltage of 240 volts. If the 240 volt winding were connected to a 240 volt source, then the output voltage would be approximately 460 volts at no load and approximately 442 volts at full load. As the kVA becomes smaller, the compensationis greater— resulting in lower output voltages. When one attempts to use these transformers in reverse, the transformer will not be harmed;however, the output voltage will be lower than is indicated by the nameplate.

However, according to this, my 2kVA transformer should be giving 1:2 and it's not quite, and it's a little worse when it's loaded and the input drops to 119 and the output is 228. But it's hard to fathom it means something is wrong with it, and I'm not concerned given the pump is rated as low as 200vac.

In fact, I kinda wish I had the 1500VA sister of this one, because I believe it'd be fine, and this one is a beast. I'm a little worried that when I bolt it to the back wall of the NEMA box I bought ...

https://www.amazon.com/dp/B0924DJGJ9?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

... that it'll bow the thing. Laying it flat would be awkward but maybe doable.

But hey, this transformer was apparently free. And the issue that something might not be quite right with it supports the decision to power it up only during grid outages.

 

[RustyShackleford]

If I'm going to have a switch on the output, I might as well make it a DPDT one with center-off (ON-OFF-ON) and forget the DPDT relay.

 

[EbS-P]

All this work, I just have to ask how many hours you have been without power in the last 24 months? I think I’m at like a total of 6-8 hours.

 

[RustyShackleford]

All this work, I just have to ask how many hours you have been without power in the last 24 months? I think I’m at like a total of 6-8 hours.

Yeah, something like that. Keeps me off the streets. Actually hasn't been that much work, just a lot of jaw-flapping in this forum

 

[RustyShackleford]

I just realized there's no need to bring 240vac AND 120vac into the transformer box. Just bring a 3-wire romex cable with two hots and a neutral. So the transformer box looks kind of like a subpanel. Pull off one of the hots for the 120vac feed to the transformer.