3 phase single phase. help needed crossy

[carlyai]

House in isaan finished but I have been in Australia for 3 months so missed some electrical work.

Crossy and I talked about having 3 phase in the house but treating it as 3 separate phases and I designed the system around that with the help of this forum and expert crossy.

For some reason, that seemed good to me at the time,I put in 3 phase water heaters.

While I was away the Thai electrician (great electrician), got everything working but he didn't install the 3 10kva avrs or the input from the single phase desiel gen thru the changeover switch to power 1 phase with essential lights etc when the power failed.

He was worried about causing an electrical problem and I expect he may be correct.

Its a long time since I did my electrical theory but the nature of rotating phases, for 3 phase work may mean that the 3phase water heaters may have a problem if they are supplied from 3 phase mains but with 3 single phase avrs.

This is the only reason I can think of why the 3 single phase avrs may not work and I may have to buy a 30kva 3 phase avr.

What do you think?

Also, as I had cavity brick I installed earn wires with all active and nuetrals, so the electrician though that everything was protected against a fault and didn't install my RCD as he reckoned they would give false trips.

The problem is that we are protected against active earth fault but not against someone touching an active.

Should I install a 3 phase safety cut (if there is such a thing?)

[Crossy]

I would install your water heaters via 3-pole breakers direct from the incomer rather than via the AVRs, install a small 3-phase distribution box if you need to (do they need neutrals?).

Yes, 3-phase Safe-T-Cuts are available but I don't understand why your sparks thinks your RCDs will give a problem so long as there is no sharing of neutrals between the single phase boards. I'll bet he has done it Thai style and just picked up any old neutral which will play havoc with separate RCDs. Like you I missed my sparks doing the installation (I was in India) and I'm still sorting borrowed neutrals

The same issue could cause bits of your generator backed up 'essentials' supply to not work too, but shouldn't cause any damage

[IvanLaw]

Hells Teeth.

& I thought the Thai Language was hard to understand

[RichCor]

Maybe didn't know how to isolate the three-phase water heaters from the single-phase generator?

(Phase Loss, Under Voltage and Phase Sequence Monitor/Relay)

[LindaLovelace]

I have an issue somewhat related to this with which I have wrestled. Here, single phase is 220VAC (wires, line, neutral ground). In the US, sinlge phase is 110 VAC. 220VC is split phase with line 1, line 2, ground powering device.

Question: Can a device designed for 220VAC in the US (110VAC line 1 & 110VAC line 2) be operated in Thailand with 220VAC, single phase (220VAC line plus neutral)?

[Crossy]

Question: Can a device designed for 220VAC in the US (110VAC line 1 & 110VAC line 2) be operated in Thailand with 220VAC, single phase (220VAC line plus neutral)?

If the kit in question requires ONLY 220V then it should work, watch for overheating motors running on 50Hz.

However, much US 220V kit has the electronics powered from 110V so you would need to arrange for that.

To be honest, unless it's something exotic it would be less hassle to get a local one here.

[Naam]

any particular reason why 3-phase water heaters? we have them in Germany, they switch in steps, e.g. 7/14/21kW according to demand. but then the temperature of the water fed could be as low a +5ºC in cold winters.

[LindaLovelace]

Question: Can a device designed for 220VAC in the US (110VAC line 1 & 110VAC line 2) be operated in Thailand with 220VAC, single phase (220VAC line plus neutral)?

If the kit in question requires ONLY 220V then it should work, watch for overheating motors running on 50Hz.

However, much US 220V kit has the electronics powered from 110V so you would need to arrange for that.

To be honest, unless it's something exotic it would be less hassle to get a local one here.

Yeah, I forgot about the electronics that seem to pervade everything.

New Question: Is there any reason I cannot use a regular light switch, rated for 15 amps, as an on/off switch for a two horsepower pump motor (1,500 watts, running, 6.8 amps)? Are there inrush current concerns? I know contactors of often used for motors, but they are more expensive than a plain garden variety light switch.

[Crossy]

New Question: Is there any reason I cannot use a regular light switch, rated for 15 amps, as an on/off switch for a two horsepower pump motor (1,500 watts, running, 6.8 amps)? Are there inrush current concerns? I know contactors of often used for motors, but they are more expensive than a plain garden variety light switch.

Your 1,500 Watt pump (induction motor) will pull a start surge of around 3 x full load on startup = 20.5A, rather larger than 15A

In reality your 15A switch will be just fine, the surge is short and then reduces to well within the switch rating, it may suffer a reduced life due to contact pitting but they are cheap and easily replaced.

EDIT We've been switching a 2HP pump using a 15A 'light' switch for the last 2 years, it's showing no signs of distress (no I've not had it apart to look at the contacts).

[LindaLovelace]

New Question: Is there any reason I cannot use a regular light switch, rated for 15 amps, as an on/off switch for a two horsepower pump motor (1,500 watts, running, 6.8 amps)? Are there inrush current concerns? I know contactors of often used for motors, but they are more expensive than a plain garden variety light switch.

Your 1,500 Watt pump (induction motor) will pull a start surge of around 3 x full load on startup = 20.5A, rather larger than 15A

In reality your 15A switch will be just fine, the surge is short and then reduces to well within the switch rating, it may suffer a reduced life due to contact pitting but they are cheap and easily replaced.

EDIT We've been switching a 2HP pump using a 15A 'light' switch for the last 2 years, it's showing no signs of distress (no I've not had it apart to look at the contacts).

Thanks a million!

[carlyai]

I would install your water heaters via 3-pole breakers direct from the incomer rather than via the AVRs, install a small 3-phase distribution box if you need to (do they need neutrals?).

Yes, 3-phase Safe-T-Cuts are available but I don't understand why your sparks thinks your RCDs will give a problem so long as there is no sharing of neutrals between the single phase boards. I'll bet he has done it Thai style and just picked up any old neutral which will play havoc with separate RCDs. Like you I missed my sparks doing the installation (I was in India) and I'm still sorting borrowed neutrals

The same issue could cause bits of your generator backed up 'essentials' supply to not work too, but shouldn't cause any damage

[carlyai]

Thanks for the replys. Sorry not too sure with what I am writing with this new phone.

Instead of putting in 3 boxes for the 3 phases I was talked into putting in one box but the breakers are something like this: 1 red. 2 blue. 3 orange etc.

So I thought I would still get 18 breakers of red blue and orange but in the one box.

Hope I didn't miss anything there.

We did install 3 pole breakers for the two instant water heaters all in the same box.

I used the 3 phase heaters because the electrician recommended it and I think I read somewhere it would give me hotter water.

So what I've got do is route all the cables, except the water heater cables, to my single phase avrs then back to the distribution board.

Is this correct?

I did check when I was there that all the cabling had active and nuetrals and did stress not to borrow nuetrals.

Maybe I did stuff up somehow by putting all the phase breakers in the same box but at the moment not sure how.

Won't be at the house till next week and will check it out there.

Thanks again

[Crossy]

Better post a photo of your board with the lid off, it's not a Square-D or Schneider board perchance??

EDIT Sorry carlyai, I tend to get a bit unhappy when someone asks advice, goes against it, then asks to be rescued.

Anyway we can probably save it

Do your AVRs have enough grunt to supply the water heaters?

Why not ask the chap who told you to go with a 3-phase board to install the AVRs?

[carlyai]

Oh no. Did I fall for the oldest Thai sparky trick in the kingdom?

I have that feeling.

I think its one of the boards u mentioned.

Will be there next week and will take the photo,

Can't wait for the bad news.

[Crossy]

All is not lost, read my edit

[Crossy]

Actually, I make much of my money rescuing multi-million dollar projects that took the wrong advice

My invoice is usually of about the same magnitude as the amount they thought they were saving

[carlyai]

Sorry crossy.

After talking with you, long time ago, I drew up the plan for the 3 avrs and the 3 separate phase boxes. I bought the 10 k avrs and the sparky turned up with the combined single box. When I asked him he said the single box was the same.

[Crossy]

No worries.

Yet!

What size supply do you have? (15/45, 30/100)

How many Watts are your heaters??

[carlyai]

Here's a picture of the power board.

It is a Schindler.

When I was in Aus I asked the Mrs (who remained in Thailand keeping the money flowing), why the electrician did not install the avrs and the translation was something like this ' fire, sparks, boom!'.

I couldn't really understand this, because if the 3 single power boxes are the same as the one combined box, I couldn't see the reason, but then I don't know much do I?

From memory the 3 phase mains are 15/45 and previously powered the rice mill in the compound.

[carlyai]

I have attached some pics of the scale of the electrical installation, and at the end of the day, when the sparky changed the plans, I just couldn't argue or disagree any more with him.

I thought he knew fairly much what he was doing and I don't think I could have got anyone better in the area.

So hopefully I have not completely stuffed up the distribution box.

[RichCor]

[...]

Instead of putting in 3 boxes for the 3 phases I was talked into putting in one box but the breakers are something like this: 1 red. 2 blue. 3 orange etc.

So I thought I would still get 18 breakers of red blue and orange but in the one box.

Hope I didn't miss anything there.

We did install 3 pole breakers for the two instant water heaters all in the same box.

[...]

So what I've got do is route all the cables, except the water heater cables, to my single phase avrs then back to the distribution board.

Is this correct?

I did check when I was there that all the cabling had active and nuetrals and did stress not to borrow nuetrals.

Maybe I did stuff up somehow by putting all the phase breakers in the same box but at the moment not sure how.

What I read Crossy suggesting is that you:

Run a TAP on the 3 Phase MAINS (before it enters the board) and run it to it's own box/board and connect your 3-Phase Only equipment (Water Heaters) there.

Re-Route the original 3-Phase Mains into an external AVRS and send its OUTPUT into your current Board. I would think the current 3-Phase design board is fine. The breaker "buss" layout beneath the actual breakers is designed to make contact with an alternating Phase in a 1-2-3-1-2-3 pattern (as noted by the Black-Red-Blue repeating color strip next to the breakers, giving you 12 potential 3-Phase breakers or 36 1-Phase breakers (or a combination thereof).

the question would be... would load balancing between the phases in the original board/box still be suggested?

Oh... and don't forget the RCD units for the main board and in front of each Water Heater

Then again, Crossy may have some other brilliant plan.

Edited March 28, 2015 by RichCor

[Crossy]

That's pretty much what I was thinking:-

3-phase Safe-T-Cut on the incoming supply

Feeding

Small 3-phase board with the water heater breakers in it.

AND

3 x single-phase AVRs

TO

The existing 3-phase board

VIA

A 3-phase generator transfer unit (only 1 phase wired to the genset)

I'll do a diagram later when I get a mo, been a bit busy today.

You'll need to take the lid off your AVRs to determine which terminal is fed direct input to output, that will be the neutral (no matter what it says on the box)

We can cross that bridge later.

[carlyai]

Thanks again.

I did buy a three phase, single phase change over switch, but as I have not been there I am not sure how the sparky wired it in.

I got rid of the builder in the very early stages, like brick laying stage, and since then I became a bit overwhelmed with looking after, and getting rid of many contractors to end up with hopefully what we wanted.

You know the story: one contractor was good laying the bricks and bond beams, so we gave him the rendering job and his team couldn't do it how we wanted; the gyproc team was great, so we gave them the painting job, but again they couldn't do it how we wanted etc.

Thanks for the offer of the drawing and all the other help and replys.

[Crossy]

Can you post a piccie of:-

Your transfer switch with the lid off.

One of your AVRs with the lid off.

Knowing exactly what you have will help us determine how to help get it working and safe.

Task 'A' is that front end Safe-T-Cut.

[carlyai]

Will do next week when I get to the house. In Pattaya at the moment fixing up about a broken toe.

[Crossy]

Don't do medical here, 'lectrics only

Do it something like this:-

Before we go hooking anything up it is essential that we know how the AVRs are wired internally, specifically the connection which is straight through input-output, as noted earlier this should be the neutral.

Note that is is vital that your transfer switch opens all three phases and the neutral even if only one phase has generator supply. Leaving two dead phases connected whilst running on generator will cause interesting (potentially explosive) effects when the power returns.

[RichCor]

[...]

Thai electrician (great electrician), got everything working but he didn't install the 3 10kva avrs or the input from the single phase desiel gen thru the changeover switch to power 1 phase with essential lights etc when the power failed.

[...]

I just noticed that Crossy isn't suggesting you put an RCD on the 1-phase Diesel Generator output.

While this is probably fine for "Essential Lighting", I would suggest you mark the inside of the Panel Lid and indicate which phase line you are designating/restricting to "Essential Connections Only", and list what those "Safe and Essential" connection types might be (written in both Thai and English).

While "I" might be willing add an isolated power socket or two on that restricted phase, I would hope you'd add an additional RCD on the line from the Generaror before giving-in and adding an "Essential" kitchen appliance (or any circuit where human contact to current might be a real potential).

I don't know how long your power outages typically are. So, besides lights, what other "Essentials" might you have?

Overhead Lights

Water Pump

Power Socket for recharging phone batteries

Power Socket for a Fan or two

Deep Freezer

Wine Cooler Cabinet

Kitchen Refrigerator

Kitchen Hotplate *

Microwave or Turbo Oven *

(*Most Thais easily convert to Charcoal Fire for heating and cooking needs)

[Crossy]

Good point RC, that was a drop off (brain was tuned to having RCDs in the distribution board).

Add an RCD to the genset supply

We run our entire home (minus water heaters and aircon) on our little 5kVA KwaiThong gasoline genset.

[RichCor]

[...]

We run our entire home (minus water heaters and aircon) on our little 5kVA KwaiThong gasoline genset.

Hmm. So if the OP wanted to do the same (run the whole house from a generator) then he'd have to either,

A) Swap out the single-Phase Generator and for a 3-Phase Generator into the Transfer Switch, or

Use an "Add-a-Phase" Converter on the existing single-Phase Generator to produce 3-Phase into the Transfer Switch, or

C) Convert 3-Phase mains to DC, then Convert to single-Phase AC into the Transfer Switch, --AND--

Replace the 3-Phase board with a single-phase whole house Board

...to power up the whole house (minus 3-Phase Water Heaters)?

Any other way of doing this?

I know the 3-Phase was recommended to provide the necessary current the OP might draw. Is it still necessary to load balance between the three Phases with his current setup? Then having to drop 2 of the Phases during a power outage... previously balanced but non-essential? What gets connected to Phase 2 and 3 that you can go without, not knowing how often or how long a power outage might last.

Note: You can IGNORE this speculation, especially if it creates issues with completing your current electrical dilemma.

[Crossy]

Since our OP has no 3-phase appliances other than the water heaters (which are not connected to the genset) he can simply link all three phases at the genset input to the transfer switch.

Obviously he now has to mitigate his load to stop sending the genset into orbit.

I would put the aircon and any other power hungry kit on the non-genset phases and the rest of the house on the phase provided by the genset.

Although we are single-phase that's effectively what I did. We have two distribution boards, one with aircon, water heaters, irrigation pump directly from the mains, the other with lights, telly, kitchen etc. powered by the genset when the mains is off. Works very nicely for us.