3-Phase or Not?

[Darkness]

A fortnight ago, I got new motors fitted outside and every 10 minutes or so the motors kickin for a second or two.

When they kickin, the whole lights in the house go dim for a second as if someone was trying out the electric chair. My gf has blamed this as the cause of my 4-month old LCD tv to fail.

Anyhow, I was told to get 3-phase which will fix this problem.

Is this the answer and if so, what's required for 3-phase, any alterations needed etc?

Cheers.

 

[plugwash]

what are theese motors for?

how many of them are there?

who told you to get 3 phase?

 

[securespark]

What are these motors for, and why do they switch on every 10mins?

Can't see the extra demand damaging equipment.

3 phase sounds extreme. You need to ensure no adjacent accessories are fed from different phases, else they need to be labelled with

"DANGER 400 VOLTS"

 

[JohnD]

Do I smell air split-unit conditioners?

 

[Darkness]

These units are part of a cooling system which kickin to keep pressure built up.

It was a guy up the road from me that mentioned 3-phase. No very little about it to question if he was talking bull or not.

 

[plugwash]

some dimming of lights on startup of heavy loads is fairly normal.

upgrading the supply will improve it, the next step up for most domestic properties would be a small 3 phase supply but this won't come cheap (at least everything up to and including the CU will have to be replaced and possiblly some other stuff too)

if the dimming bothers you a cheaper option might be to put the lights on a UPS, what is the total power rating of the lights in your house?

 

[Pensdown]

I don't know why AC companies are still selling DOL AC units to domestic customers when they should only be selling inverter units. They've been around for quite some time now and get over the problem of high starting currents.

I'm not sure if you can retro fit inverters to DOL compressors but that would probably be the most cost effective solution if it's that much of a problem.

 

[Darkness]

Well it looks like 3-phase is out of the question if the CU has to be changed cause I only got the outside CU changed from an old type cartridge cu as alot of wiring was needed for the new system let alone the cooling system. The two individual coolers kickin together which causes the power drain and each cooler has their own seperate 40A supply from the CU. I think its 40A.

 

[Maxxy]

3 phase would fix the problem, but would prob cost over 5k to upgrade your house to it. You will also have to replace the aircon units to take 3 phase motors.

Two 40 amp units sounds like a hell of a lot though for a house. I dont know a thing about air con units, but for a company to install two of these on a house that probably only has a 60 or 80 amp main fuse is taking the pi**

Putting the lighting on a UPS is probably not an ideal solution, because you would still get the power loss to sockets, which as you've stated has already damaged equipment in your house.

I'd get back in touch with the people who sold you the aircon unit, or the electrician who installed it.

 

[Darkness]

I'd better clear a few things up.

I have two seperate 100A service fuses with one for the house and the other to the outside electrics.

The cooler units outside all run of its own 100A supply fuse.

But from the transformer, I have the two overhead cables that run to the 2x100a supply fuses.

Maybe this is a reason for the problems in my house caused by the cooling units?

 

[Spark123]

I take it as the lights are dimming that both the fuses are from the same phase? Theoretically you could escalate the problem by having the motors put on a separate phase as when they kick in they they momentarily pull the phase voltage down and neutral voltage up. If something else was to be fed on the same neutral and a different phase the result could be a voltage spike instead of a voltage dip. The effect of this will depend on the size of the neutral conductor v phase conductor and the size of the voltage dip though.

 

[Steve]

The units shouldn't be cycling every 10 minutes anyway. Every half an hour maybe. Anyway, even 3 phase motors have huge startup currents. We have a bank of 3 phase fridge compressors at work, and when they kick in, all the lights flicker momentarily. There's also 2 coldrooms with single phase 13A compressors mounted on them. They have a huuuge starting current. Thankfully you only notice in the office, all the other lights are on the other 2 phases, or divided between the phases on the shopfloor. The supply there was built for it though - the cutout fuses are in a big metal cabinet, sealed, and the meter is of the current transformer variety. Nice.

What are the compressors for? ie. where does the refrigerant go indoors? What is the rating of the compressors? A picture of the supply would be nice - in some cases, a 3 phase upgrade is easy.

 

[JohnD]

I think I smell a pole-mounted transformer, probably in a rural location.

Are the coolers for air-conditioning, or milk tanks?

How about some pics?

 

[Darkness]

It's a pole mounted transformer and for a milk tank.

I'll do my best to get some pics when I steal my camera back tomorrow.

I've noticed last night and tonight, the power drain isn't happening as often as it should. It seems like every half hour or more now.

I wonder if the major drop in temperature outside has anything to do with it.

There are 4 fans which are 140w each which isn't bad but all I get on the compressors is the wording 'RUN CAP 55mf'.

Haven't a clue what the mf stands for.

 

[Adam_151]

There are 4 fans which are 140w each which isn't bad but all I get on the compressors is the wording 'RUN CAP 55mf'.

Haven't a clue what the mf stands for.

Milli-farad probably, it'll be refering to the capacitor that gives one winding a phase shift