On Feb 13, 10:14 am, Paul M. Eldridge
wrote:
Hi Mike,

My apologies for asking this, but is this something relatively new or
has it always been this way? I don't have a lot of experience with
electric ovens because I've always used gas, but this time around I
had to settle for a combination unit because an all gas version wasn't
available.

I did experiment with mine just now and here's what I found. There
are basically three heating options I can choose: "bake", "broil" and
"convection" and as far as I can tell all three work independently of
each other. When I turn on "broil" I can safely leave my hand on the
lower bake element and it remains cool to the touch; likewise, the
broiler never comes on when I select "bake" and neither of these two
elements are used when I pick "convection" (that appears to be a third
element hidden somewhere inside the oven's back wall).

In any event, this second element arrangement I had imagined would be
used in bake (or convection) mode and would be very low wattage --
just the minimum required to maintain a steady operating temperature
and effectively "lock out" the primary element that is used during the
initial warm-up. It may be that we only need 500 or 1,000-watts
during this extended cooking phase to keep things moving along.

There doesn't appear to be any real benefit in terms of utility-wide
peak shaving (sorry to say it took a couple blows to the head to drive
that point home), but there may be some benefit in terms of reducing
the strain on the local distribution system. If, for example, my
neighbour and I share the same pole transformer and our ovens both
cycle on at roughly the same time (and we can safely assume there will
be at least some overlap during their operation), the combined load of
these two appliances might be 6 or 8 kW. However, if we don't turn
our ovens on within ten minutes of each other (i.e., during that
initial warm-up phase),

And how are you going to coordinate not turning on ovens with your
neighbor at the same time? Use a flag hanging out the window?
This is simple physics. If you expect to limit the power, then the
oven isn't going to heat up as fast. And that could be solved just as
simply by just putting in an oven element that was say 25% smaller to
begin with. You really only need the max when you're trying to take
the oven from cold to operating temp. After, that, it cycles anyway
and could easily get by with probably 1/2 the existing element
capacity. Of course the downside is that instead of waiting 15 mins
for the oven to heat up, now you're gonna wait a half hour and few
people will put up with that to solve a problem that doesn't exist to
begin with.



with this dual wattage arrangement, our
combined load may never exceed 4 or 5 kW and our steady-state
operation may drop to just 1 or 2 kW.

You still don't get it. The amount of energy that it takes to
operate an oven is independent of whether you have 1 element or 40.
You could have a 4000 watt element on for 15 mins or a 2000 watt
element for 30 and it uses exaclty the same amount of energy. You
can't just decrease the steady state amount of power and have the oven
be just as hot.





It would seem that as we move closer to the point of use (i.e., from
sub-station/feeder to local line, to individual pole transformer) the
potential benefits to the utility become increasingly more attractive.
And in the case of a large condo or apartment complex, I imagine the
potential load reduction could result in some capital savings (i.e.,
smaller service requirements) and perhaps reduced monthly demand
charges.

You're focusing on one small nit here and ignoring everything else.
Condos typically have all kinds of loads, AC, heat pumps, furnace
blowers, electric water heaters, etc. Reducing some oven power
isn;t going to be a big factor that now means smaller gauge wire or a
smaller transformers can be used. And to reduce the oven loads,
what you fail to realize is that you are either asking people to:

a - Wait longer for their ovens to warm up, because the power into
them is being reduced to limit peak during start up.

b - Hang flags out the window so unit A can't start cooking dinnner at
the same time as unit B

Who is going to put up with that?






Ideally, if dual wattage elements added an extra $50.00 to
the cost of each appliance, this extra cost would be fully offset by
these other capital savings and any additional savings in terms of
reduced monthly demand charges would simply add extra gravy in the
pot.

Cheers,
Paul



What reduced monthly charges? You still need the same amount of
energy going into the oven to make it hot. In fact, your idea could
take MORE energy. By reducing the max power, its' going to take
longer for the oven to get to 400 deg. While it's talking the extra
10 or 15 mins, heat is being lost out of the oven throught the walls,
or even worse, people opening the door to see what's going on.







On Tue, 13 Feb 2007 06:43:18 -0600, Mike Hartigan



wrote:
Many (most?) electric ovens already do this. The pre-heat stage
energizes both the bottom and broiler elements. The idea, though, is
to pre-heat the oven faster, not to help the power company balance
its load.- Hide quoted text -

- Show quoted text -