How common are full-power 208 volt ranges and dryers in the US?

[Beachcomber]

If you live in certain apartment or condo complexes in the US, you
might be stuck with 208/120 volt service instead of the traditional
split-phase 240/120 volt service common to single family houses. (The
208 V. transformer secondary voltage is the result of a more
economical 3-phase wye connection scheme available in urban areas that
balances the load to a three-phase primary.) The upside of the
208/120 service is that 3-phase power is available for elevators,
pumps, etc.

Just how readily available are electric dryers, for example, that
operate on full-power at 208V instead of 240 V?

I am aware that you can operate a 240V dryer on 208V, but the heating
element will operate at 20% less capacity than at the higher voltage.
The dryer is likely to run longer to get the clothes to dry.

Googling around, I found that there are some dryers that can be
ordered full power (lower resistance) at 208 V. (One source says that
this is illegal or at least highly discouraged in Canada).

I can understand that if you move your 208 V. dryer to a new home and
put it on a 240 V. circuit, you may have a serious overheating
problem.

In general, I didn't find a lot of specific information on the
Internet that addresses this concern about the difference in voltage.

When these multi-unit buildings are constructed, do the developers
actually specify and insist on 208 V. appliances or do they just
install the more common 240 units and hope that no one notices or
complains?

Finally, is it the same deal for electric ranges that are connected to
208/120 instead of 240/120 voltage? Are there full power 208 models
that are readily available?

Beachcomber

 

[[email protected]]

| If you live in certain apartment or condo complexes in the US, you
| might be stuck with 208/120 volt service instead of the traditional
| split-phase 240/120 volt service common to single family houses. (The
| 208 V. transformer secondary voltage is the result of a more
| economical 3-phase wye connection scheme available in urban areas that
| balances the load to a three-phase primary.) The upside of the
| 208/120 service is that 3-phase power is available for elevators,
| pumps, etc.

I'd rather see them run the "big stuff" on 480/277 or even 600/347.
If it needs some "umph" to go, it could use some 480 or 600.

Then put in 3 transformers to drop 480 or 600 down to 120/240 and
divide the place up into 3 roughly equal sections. All the out of
reach HID security lighting could be run directly on 277, 347, 480,
or 600.

The utility might not like the extra transformers involved, though.
OTOH, some very large buildings do have transformers at various
levels. I know the college dorm I lived in for a couple years had
a transformer closet every 3 floors (and the lock on the door was
NOT a part of the building master key system). I have no idea what
the supply voltage was (whether it was 600 volt class or higher).
But I do know the elevators were supplied by 480/277.


| Just how readily available are electric dryers, for example, that
| operate on full-power at 208V instead of 240 V?
|
| I am aware that you can operate a 240V dryer on 208V, but the heating
| element will operate at 20% less capacity than at the higher voltage.
| The dryer is likely to run longer to get the clothes to dry.

Not accounting for resistance change due to temperature, at 208 volts
there would be only 75% of the power used. So that would mean a 25%
reduction. But at the lower temperature, the element would draw a bit
more current since it would have slightly less resistance. But is
that effect enough to put this in the 20% range? I don't have the
formulas to figure that out. Is that where you get "20%"?


| Googling around, I found that there are some dryers that can be
| ordered full power (lower resistance) at 208 V. (One source says that
| this is illegal or at least highly discouraged in Canada).

You can get replacement heating elements designed for 208 volts for many
models of dryers, stoves, water heaters, and I presume also for central
heating systems. I don't know how well that addresses the increased
current that would be drawn.

But see below.


| I can understand that if you move your 208 V. dryer to a new home and
| put it on a 240 V. circuit, you may have a serious overheating
| problem.

Maybe. If the heating is thermostatically controlled, especially with
solid state switching at a fast rate, it should be possible to have an
element that handles a wide voltage range.

My current kitchen stove has cooktop and oven elements that even at
the highest settings are not on more than about 2/3 of the time. It
seems to me they could handle 208 volts by being on for a longer time.

Keep in mind that although an element designed for 208 volts would draw
more current than one designed for 240 volts, when used at the design
voltage, to produce the same heat, one that is thermostatically
controlled would not matter so much. While it would have a higher
current at the higher voltage and a lower current at the lower voltage
to achieve the same heating, the heating effect on the wiring that
supplies it, and on the thermal element in the breaker that protects
that wiring, would follow the same pattern on average. It just needs
to switch on and off fast enough to avoid heat surges. For a range
of voltage from 208 to 240, on and off every 10 seconds or so could
be enough.


| In general, I didn't find a lot of specific information on the
| Internet that addresses this concern about the difference in voltage.
|
| When these multi-unit buildings are constructed, do the developers
| actually specify and insist on 208 V. appliances or do they just
| install the more common 240 units and hope that no one notices or
| complains?

Apparently the latter happens a lot. But do not assume malice where
mere incompetence can explain it. The developers might well not even
know the issue at all.

If I were developing a large building for residential purposes like
that, though, I would be fighting to get normal genuine 120/240 in
each unit.


| Finally, is it the same deal for electric ranges that are connected to
| 208/120 instead of 240/120 voltage? Are there full power 208 models
| that are readily available?

Absolutely yes, at least for older stuff (see above).

My grandfather managed to get three phase power for his wood shop. But
he made the mistake of getting it all on a single drop (the wood shop
was a detached building, though not as easily reached by an overhead
service drop). Apparently it was 208/120 wye/star, instead of 120/240
center tapped delta. It was well known that the stove and electric water
heater were always "slow". The A/C worked, but was especially sensitive
to brownouts. The house was built around 1956.

 

[Beachcomber]

| If you live in certain apartment or condo complexes in the US, you
| might be stuck with 208/120 volt service instead of the traditional
| split-phase 240/120 volt service common to single family houses. (The
| 208 V. transformer secondary voltage is the result of a more
| economical 3-phase wye connection scheme available in urban areas that
| balances the load to a three-phase primary.) The upside of the
| 208/120 service is that 3-phase power is available for elevators,
| pumps, etc.

I'd rather see them run the "big stuff" on 480/277 or even 600/347.
If it needs some "umph" to go, it could use some 480 or 600.

I don't know Phil... The higher voltages are, in theory, more
efficient. But it seems to me that there are distinct advantages to
the North American system where no conductor entering a residential
dwelling is at a potential of greater than the (nominal) 120 volts to
ground.

I still think the safety advantages of the lower voltage are of
greater value than efficiences and savings and conductor size at the
higher voltage (and the need to use one or more whole-house RCDs on a
Euro wiring scheme).

On the European 240 volt systems I've seen in the UK, for example, the
conductors may be thinner, but then there is the awkwardness of the
increased spacing requirements for the plugs and sockets, bigger and
uglier receptacles, sockets that need to have switches on them for
safety, the ban on anything but reduced voltage shaver outlets in the
lavatories, and, if I'm not mistaken, isn't there also some overly
restrictive rule about the placement of wall mounted bathroom light
switches?

Beachcomber

 

[[email protected]]

| On 26 Jan 2008 16:43:45 GMT, [email protected] wrote:
|
|>
|>| If you live in certain apartment or condo complexes in the US, you
|>| might be stuck with 208/120 volt service instead of the traditional
|>| split-phase 240/120 volt service common to single family houses. (The
|>| 208 V. transformer secondary voltage is the result of a more
|>| economical 3-phase wye connection scheme available in urban areas that
|>| balances the load to a three-phase primary.) The upside of the
|>| 208/120 service is that 3-phase power is available for elevators,
|>| pumps, etc.
|>
|>I'd rather see them run the "big stuff" on 480/277 or even 600/347.
|>If it needs some "umph" to go, it could use some 480 or 600.
|>
|
| I don't know Phil... The higher voltages are, in theory, more
| efficient. But it seems to me that there are distinct advantages to
| the North American system where no conductor entering a residential
| dwelling is at a potential of greater than the (nominal) 120 volts to
| ground.

These days, I would not be worried about 277 volts (L-G) entering my home.
But _transitioning_ to something like 240 volts (L-G) would be a serious
problem because people here are not accustomed to how to deal with it.
But comparison, they know more about it, and respect it more, in UK and
other places that have had it for decades. Of course ther are lots of
other issues that would block such a change.

OTOH, we could transition a lot of stuff over to the style of 240 volts
we already have in the USA.


| I still think the safety advantages of the lower voltage are of
| greater value than efficiences and savings and conductor size at the
| higher voltage (and the need to use one or more whole-house RCDs on a
| Euro wiring scheme).

With a 240 volt system having ground tapped in the middle, we the
advantages of both. And we already get much of that by having the
split pole system, when loads are reasonably near balance, as that
means for the same kVA or kW load, we have the same current as UK
would, at least on the service drop into the home. But I would like
to extend that to other circuits in the home.


| On the European 240 volt systems I've seen in the UK, for example, the
| conductors may be thinner, but then there is the awkwardness of the
| increased spacing requirements for the plugs and sockets, bigger and
| uglier receptacles, sockets that need to have switches on them for
| safety, the ban on anything but reduced voltage shaver outlets in the
| lavatories, and, if I'm not mistaken, isn't there also some overly
| restrictive rule about the placement of wall mounted bathroom light
| switches?

I think the spacing is legacy. Compare the UK plug/socket (I forget the
designation) to the US NEMA 6-15 or 6-20. The spacing of the NEMA ones
are just as close for 240 volts as for 120 volts. There is enough space
for the voltage. I want have a power cord with a NEMA 6-15P on one end
to use on my computers (I do know where to get them ... it's the outlets
I need to have).

What we could do better on are things like protecting pin contact by
the time the pins have contacted the socket contacts. Insulating
part of the pins would do this. The round pins of Europlug/Schuko and
the thicker pins of the UK plug could do that easier than the US plug.

I don't feel a need to have shutters that are opened by the ground pin.

 

[Beachcomber]

What we could do better on are things like protecting pin contact by
the time the pins have contacted the socket contacts. Insulating
part of the pins would do this. The round pins of Europlug/Schuko and
the thicker pins of the UK plug could do that easier than the US plug.

I don't feel a need to have shutters that are opened by the ground pin.

Yes, we could add shutters to the plug pins and blades. I believe
that there are already code compliant receptacles for children's rooms
that do that sort of thing.

But do you really think that having "baby-protected outlets"
everywhere is necessary?

There is a trade off and an added value in simplicity.

Beachcomber

 

[bud--]

Yes, we could add shutters to the plug pins and blades. I believe
that there are already code compliant receptacles for children's rooms
that do that sort of thing.

But do you really think that having "baby-protected outlets"
everywhere is necessary?

The [US] NEC does. Required in the 2008 code for most 15/20A 120V
receptacles in dwellings (406.11).

 

[Dean Hoffman]

Yes, we could add shutters to the plug pins and blades. I believe
that there are already code compliant receptacles for children's rooms
that do that sort of thing.

But do you really think that having "baby-protected outlets"
everywhere is necessary?

The [US] NEC does. Required in the 2008 code for most 15/20A 120V
receptacles in dwellings (406.11).

I think GFCI is required (2008 code) on all outlets not protected
by arc fault protection. Shuttered outlets seem redundant. Is this a
case of the left hand not knowing what the right hand is doing?

Dean

 

[[email protected]]

|
|>What we could do better on are things like protecting pin contact by
|>the time the pins have contacted the socket contacts. Insulating
|>part of the pins would do this. The round pins of Europlug/Schuko and
|>the thicker pins of the UK plug could do that easier than the US plug.
|>
|>I don't feel a need to have shutters that are opened by the ground pin.
|>
|
| Yes, we could add shutters to the plug pins and blades. I believe
| that there are already code compliant receptacles for children's rooms
| that do that sort of thing.

But those are mechanical opening shutters. The ground pin does not have
sufficient extra length to reliably open other shutters upon insertion.
I presume the UK plug does (I've never obtained the exact dimensions or
an instance of one of these).


| But do you really think that having "baby-protected outlets"
| everywhere is necessary?

I would in areas where the "baby" might be left alone for a while. But
these do not need to be the kind that block non-ground usage. They just
need to be the kind that block non-parent usage. The kind that require
sliding the shutter sideways manually while inserting the plug would do
the job.

 

[[email protected]]

| bud-- wrote:
|> Beachcomber wrote:
|>>> What we could do better on are things like protecting pin contact by
|>>> the time the pins have contacted the socket contacts. Insulating
|>>> part of the pins would do this. The round pins of Europlug/Schuko and
|>>> the thicker pins of the UK plug could do that easier than the US plug.
|>>>
|>>> I don't feel a need to have shutters that are opened by the ground pin.
|>>>
|>>
|>> Yes, we could add shutters to the plug pins and blades. I believe
|>> that there are already code compliant receptacles for children's rooms
|>> that do that sort of thing.
|>>
|>> But do you really think that having "baby-protected outlets"
|>> everywhere is necessary?
|>
|> The [US] NEC does. Required in the 2008 code for most 15/20A 120V
|> receptacles in dwellings (406.11).
|>
|
| I think GFCI is required (2008 code) on all outlets not protected
| by arc fault protection. Shuttered outlets seem redundant. Is this a
| case of the left hand not knowing what the right hand is doing?

While I don't agree with a universal requirement for shuttered outlets,
I do not see this as a case of left hand vs. right hand. There are things
the shuttered outlet protects against that GFCI does not. I just don't
think we need them in every dwelling outlet. It's simple enough to add
them where needed. It's simple enough to replace them after the inspector
is gone (and then donate the loose items to someone with actual babies).