Surprised...

[ssbtech]

I had a neighbour tell me something today. I live in an apartment building and we have three phase power coming into the building. She had a problem with a heater in her suite and her electrician replaced the thermostat.

In the process of testing the thing, he told her that both hots to ground were 120v, but between the hots he only got a reading ov 204v where he was expecting 240v...

I explained that since we are three phase the expected voltage is 208v and not 240v, etc...

I was a little surprised that the electrician didn't think that we'd be three phase power. We have 30 apartments with 100A panels in each suite and an elevator.

Anyway, I'm assuming his reading of 204v was accurate. If so, is that a sign of trouble (down from the expected 208v)?

Cheers.

 

[nehog]

...

Anyway, I'm assuming his reading of 204v was accurate. If so, is that a sign of trouble (down from the expected 208v)?

Cheers.

That reading is fine. That's a possible four volt difference, but it is just as likely his reading, writing down, memory, meter, or eyesight are off. It won't make a hill of beans.

What's the down side: the electric stove will be very slow (where we stay in Boston it's three phase, 208 to the stove, and it takes forever for the over to warm up.) Electric heaters won't put out as much heat either.

 

[ssbtech]

Yeh, I explained to my neighbour when she asked about it that the three-phase is the reason our ovens take too long to heat up, etc... (drives me nuts, I have a beautiful new slide-in range and I end up using the toaster oven more...)

I think I was just more shocked that the electrician thought there should be 240v there...

 

[the gypsy]

This is an interesting post, and I will verify the voltage across the the two wires for the oven in one of my wifes apartment building (20 units). I will post what I find.
So if fed by a single phase, it should equal 240V. if fed buy 3 phase, it should read 208V. is this correct.

 

[Stuart in MN]

I don't know about Canada, but at least in my neck of the woods you can find 240vac three phase as well as 208vac three phase. It's much less common and is mainly found at older buildings, but it's still around. You'd really have to go look at the main service to the building to see how it's labeled to be sure.

 

[the gypsy]

So then it is best not to assume, it is better to go to the mechanical room and check.

 

[Milton Shaw]

Yes all heating elements run very slow. Oven, stove top burners, water heater, electric dryer all with take 25% longer to heat up. Some of the large Professional style home ovens even have an extra element in the oven to wire in with the others if you are on 208 instead of 240. Some wall unit air conditioners had a 208/240 volt switch that basically changed the fan to a faster low speed. . Takes longer to heat up but will cook all right if you give it a good 30-40 minutes to heat.

 

[Aceman]

She needs to hire a better electrician if he didn't understand why he had 204 volts.

 

[wyliesdiesels]

Sounds like he only knows single phase wiring.

Amazes me but shouldnt, how some electricians dont know the systems theyre working on.

I was working in a com tower shed a few weeks ago up in New Castle, and a set of 120v 5-20r outlets had 208v hot to neutral. Went and checked main service panel(service is 240/120v Delta)and someone had the breaker for the culprit outlets on the c-phase, DESPITE THERE BEING A BIG RED LABEL ON THE PANEL WHICH SAID THE STINGER IS THE C-PHASE! Now yes the stinger usually is the b-phase....but still, he shouldve checked his work!

I had a neighbour tell me something today. I live in an apartment building and we have three phase power coming into the building. She had a problem with a heater in her suite and her electrician replaced the thermostat.

In the process of testing the thing, he told her that both hots to ground were 120v, but between the hots he only got a reading ov 204v where he was expecting 240v...

I explained that since we are three phase the expected voltage is 208v and not 240v, etc...

I was a little surprised that the electrician didn't think that we'd be three phase power. We have 30 apartments with 100A panels in each suite and an elevator.

Anyway, I'm assuming his reading of 204v was accurate. If so, is that a sign of trouble (down from the expected 208v)?

Cheers.

PoCos usually have a guarantee to deliver power within 5%+/- of nominal voltage so 204v is fine. If u put a monitoring meter u will fid that it will vary depending on the loading on the transformer and incoming primary lines.

This is an interesting post, and I will verify the voltage across the the two wires for the oven in one of my wifes apartment building (20 units). I will post what I find.
So if fed by a single phase, it should equal 240V. if fed buy 3 phase, it should read 208V. is this correct.

Youre in canada so u may have different system voltages than us south of the border. In the US, we have several- 120v/240v split/single phase(3-wire), 240/120v 4-wire 3-phase Delta with a 208v phase to neutral stinger/high leg, 208Y/120v 3-phase 4-wire Wye, 480v Delta 3-phase 3-wire, and 480Y/277v 3-phase 4-wire Wye. In Canada, in addition to what we have Ive heard u guys have 600Y/347v...So yes if you want to know then you will have to check. Never assume when it comes to electricity

Yes all heating elements run very slow. Oven, stove top burners, water heater, electric dryer all with take 25% longer to heat up. Some of the large Professional style home ovens even have an extra element in the oven to wire in with the others if you are on 208 instead of 240. Some wall unit air conditioners had a 208/240 volt switch that basically changed the fan to a faster low speed. . Takes longer to heat up but will cook all right if you give it a good 30-40 minutes to heat.

Tell me about it. We live in a town house with 208Y/120v 3-phase service(only single phase in the units) and my oven takes foorreveerrr to warm up. However, our dryer drys clothes in 45mins. Go figure...

 

[Norcal]

It would not be very useful to supply 120/240V 3Ø to a multi family dwelling, as only 2 legs would be usable for supplying the units because of one leg being 208V, but 208Y/120V can be balanced at the meter stacks AB, next one BC, then CA, & repeat, most electric appliances do have a 120/240V, & 120/208V rating, & air conditioners have a 200-230V rating, on a packaged unit one just has to change the primary tap on the control transformer from the factory default of 230V to 208V,a split system is different. Many years ago A/C equipment had to be ordered for 208V.

 

[wyliesdiesels]

It would not be very useful to supply 120/240V 3Ø to a multi family dwelling, as only 2 legs would be usable for supplying the units because of one leg being 208V, but 208Y/120V can be balanced at the meter stacks AB, next one BC, then CA, & repeat, most electric appliances do have a 120/240V, & 120/208V rating, & air conditioners have a 200-230V rating, on a packaged unit one just has to change the primary tap on the control transformer from the factory default of 230V to 208V,a split system is different. Many years ago A/C equipment had to be ordered for 208V.

No it wouldnt. The whole system would be unbalanced. I just wish our range was better made to run on 208v!

 

[canbug]

In Canada, 120/240 single phase
120/208 3 phase
347/600 3 phase
and the very rare 277/480 3 phase. Used in some older blgs and most pump jacks out west.

Tim

 

[damienga15de]

Electricity is so complicated in the us/Canada,

Here in Ireland we have 2 basic supply types, single 230v and 3 phase 400v each phase has 230v between live and earth and 400v between phases. No delta/y/high legs

 

[ishiboo]

Electricity is so complicated in the us/Canada,

Here in Ireland we have 2 basic supply types, single 230v and 3 phase 400v each phase has 230v between live and earth and 400v between phases. No delta/y/high legs

Ireland is 32,000 square miles. US is 3,806,000. So there is more opportunity for variances.

The electrical system is really not that complicated. When you work with electrical stuff you work in many voltages, AC and DC, etc. You just have to be smart enough to know what system you're working on which should not be hard

 

[Norcal]

Electricity is so complicated in the us/Canada,

Here in Ireland we have 2 basic supply types, single 230v and 3 phase 400v each phase has 230v between live and earth and 400v between phases. No delta/y/high legs

Before Ireland ever got electricity, the US already had legacy power systems based on Edison's DC system.

 

[Dagny]

all those slow heating elements will also last longer on 208.

 

[theoldwizard1]

Surprisingly many appliance are now 208-240V rated !

 

[slow]

use a buck boost transformer on your range if you want better performance.

http://www.schneider-electric.us/si...lang=en&id=FA91925&locale=en_US&redirect=true

 

[Norcal]

use a buck boost transformer on your range if you want better performance.

http://www.schneider-electric.us/si...lang=en&id=FA91925&locale=en_US&redirect=true

Not going to work as there is a neutral present.