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About how much electricity does an oil furnace use - Page 2

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Posted by Ron Rosenfeld on December 9, 2012, 2:10 pm
 


There's no real way to tell without either contacting the mfg (which frequently
does not work) or measuring the consumption for a few days.  Older units used a
lot more than modern units.  Labels on the machines will not tell you what you
need to know.  The labels generally indicate what size line should be connected
to the unit to meet code requirements, and this is often significantly in excess
of what the unit might require.  Furthermore, with regard to the refrigerator,
although there might be a sticker indicating the annual consumption in kWh, this
will not tell you what the maximum draw might be when it starts up.  You might
also need to consider a well pump, depending on their source of water.

However, the electric heaters ratings should be useful in determining their
draw, but from what you write, they are not planning to power those during an
outage.

The generator needs to be able to run all the critical appliances, and also
handle any startup surge, which can be significant with an older refrigerator,
and/or a well pump.  But you don't want to oversize it, as that would be
wasteful not only in initial cost, but also in operating costs (less efficient
at low outputs).

It is likely that a 5kW generator would be sufficient for oil furnace, fridge,
freezer and some lights, unless there is a large well pump with a high starting
surge, or if there are other items not mentioned which need to be considered.  
When you mention "a few appliances", this again adds uncertainty to the
recommendation.

Fuel is also a consideration.  Gasoline is hard to store for any length of time,
and may not be available during a widespread power outage.  Propane is a good
source, especially if it is used for other purposes.  Diesel is also OK, but may
be impractical for a small genset.

In one of our homes, which uses propane for heat, cooking, and dryer, and also
compact flourescents for lighting and also has a well-pump, I don't think we've
ever drawn as much as 5kW, and it is usually much less.  In another home, which
has an oil furnace, "normal" lighting, and electric cooktop and ovens, we can
run everything on a 15kW generator, except that we cannot have both ovens
running if we are using more than one cooktop burner.

Posted by amdx on December 9, 2012, 2:17 pm
 
On 12/9/2012 8:10 AM, Ron Rosenfeld wrote:

frequently does not work) or measuring the consumption for a few days.  Older
units used a lot more than modern units.  Labels on the machines will not tell
you what you need to know.  The labels generally indicate what size line should
be connected to the unit to meet code requirements, and this is often
significantly in excess of what the unit might require.  Furthermore, with
regard to the refrigerator, although there might be a sticker indicating the
annual consumption in kWh, this will not tell you what the maximum draw might be
when it starts up.  You might also need to consider a well pump, depending on
their source of water.


draw, but from what you write, they are not planning to power those during an
outage.


handle any startup surge, which can be significant with an older refrigerator,
and/or a well pump.  But you don't want to oversize it, as that would be
wasteful not only in initial cost, but also in operating costs (less efficient
at low outputs).


freezer and some lights, unless there is a large well pump with a high starting
surge, or if there are other items not mentioned which need to be considered.  
When you mention "a few appliances", this again adds uncertainty to the
recommendation.


It would be ideal to run the generator on the same fuel you burn to heat
the home.
                Mikek


Posted by Ron Rosenfeld on December 9, 2012, 3:39 pm
 

All other things being equal, I would agree.  But he's using oil and electricity
to heat his house, and the generator is being used to backup only essential
circuits.  A generator that can run on home heating oil may be overkill for what
he needs.  If they have prolonged outages, my recommendation would be a propane
fueled, water cooled, 1800 rpm generator with some kind of automatic weekly
exerciser, and, preferably, a good ATS.  But without knowing more of the
specifics, and the budget, I find it really hard to make an intelligent
recommendation.

Posted by Daniel who wants to know on December 10, 2012, 8:26 pm
 
If it is liquid cooled I would also do co-gen, I.E. use the coolant waste
heat to heat the building. You could even use a small DC pump on a battery
to circulate the coolant and use the building's heat to preheat the engine
block somewhat before starting it.


Posted by Jim Wilkins on December 9, 2012, 2:11 pm
 
For comparison a 3000W (3750 peak) generator is just barely able to
start the motor on my washing machine, which draws 800W or less in
use. The starting surge is over 25 Amps, even with the motor pushed in
to loosen the drive belt. I think they would have to borrow and try
gennys, and switch on all the loads sequentially at start-up. Do they
know what is on each circuit? What do the neighbors use?



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