House electrical problem - question

[srewbigbrother]

I hope I'm posting in the right place.

Here's the problem I'm having. When our electric furnance (its really
an oil/electric hybrid) kicks in, our lights dim and the UPS devices
that are connected to my computers all jump into battery mode and
don't come out until the furnace goes off. This usually means the
computer shuts down first. Now, this doesn't happen every time, but
enough to be a real annoyance.

The house was built in 1968, and has a 200 amp service from that era.
Its also a Medallon home, for those familiar with houses in British
Columbia from that time.

Now, any idea what is going on, or if there is an easy solution to
this problem?

 

[srewbigbrother]

Actually, I already went through this process. I called BC Hydro and
they sent a crew (two guys) out a few hours after I called. They
disconnected the power outside, replaces something (I don't know what)
and left. They never provided a report to me. But the problem
continues. I'm suspecting it must be something inside the house.
I'll likely call an electrician, since I don't know how to do the
things already recommended here. Thanks all.

 

[Mark or Sue]

Actually, I already went through this process. I called BC Hydro and
they sent a crew (two guys) out a few hours after I called. They
disconnected the power outside, replaces something (I don't know what)
and left. They never provided a report to me. But the problem
continues. I'm suspecting it must be something inside the house.
I'll likely call an electrician, since I don't know how to do the
things already recommended here. Thanks all.

Another thing to check is the capacity of your service. I'd hope the BC hydro guys did this, but you
may want to follow up with a call to them. How big is the transformer that feeds your house (may
have a big number stamped on it like "12", "20", "50", etc)? How many houses is it serving? Have
houses been built since your house was built that use this transformer, or have you or neighbors on
this transformer increased their electrical load from when it was first installed (like changing
from pure oil to oil/electric)?

My house was built in 1966 with a 200A panel. However, the transformer (which serves only me) was
just a 10KVA unit because the house at the time only had about 80A worth of installed load.
Additions by future owners increased my power demand calculation to nearly 200 amps, and I'm
planning to go to well over 300A. Needless to say, the voltage dropped horribly when I turned on
enough stuff to suck 100 amps. You should have a transformer rated for at least half the calculated
amp value of your service (e.g. 200A service x 240V = 48KVA so you'd want a 24 KVA transformer
assuming you really need all 200 amps of your service). I now have a 50 KVA transformer and larger
wires from the transformer to my house.

 

[art]

As far as I know utilities install often under-rate transformers, and during
the peak hours use them at say 125% of their FLA. It is conscious decision,
for economical reasons. Obviously if the old transformer would be very much
under rated (~50%) then voltage would be a problem. Marks or Sue's
suggestion seems to be very reasonable, because the area where the voltage
drop happens must dissipate a bit of heat. It is likely to be transformer or
the entire length of the conductors, not a spot.
Art.

 

[Ross Mac]

Actually, I already went through this process. I called BC Hydro and
they sent a crew (two guys) out a few hours after I called. They
disconnected the power outside, replaces something (I don't know what)
and left. They never provided a report to me. But the problem
continues. I'm suspecting it must be something inside the house.
I'll likely call an electrician, since I don't know how to do the
things already recommended here. Thanks all.

I had a similar problem some years ago and detected it by measuring the
voltage at the outlets when high current devices, such as electric heaters,
were turned on. My normally 114 volts would drop to under 100. The
connections were good. The next winter, during a rainstorm, the transformer
on the pole blew and was replaced. That's when the problem disappeared.
Obviously, if my connections were good, the transformer was either bad or
undersized. A good amp clamp and a good digital volmeter should tell the
story!
Good Luck, Ross

 

[B J Conner]

If this is a recent developement it could be the furnace motor. If it is a
capacator start motor a bad switch on the capacator will cause the motor to
draw excessive current as it will not switch into the "induction run" mode..
The motor will run but sound different. The switch in such motor is usually
a cheap POS and they fail after so many years ( besides the shaft it's the
only moving thing in the motor).
Also check the motor, fan and belt to see if there turning easily. You
could have and obstruction that is loading the system ( bent fan, dead cat,
etc.) and that will produce symptoms similar to what you have.

 

[srewbigbrother]

Another thing to check is the capacity of your service. I'd hope the BC hydro guys did this, but you
may want to follow up with a call to them. How big is the transformer that feeds your house (may
have a big number stamped on it like "12", "20", "50", etc)? How many houses is it serving? Have
houses been built since your house was built that use this transformer, or have you or neighbors on
this transformer increased their electrical load from when it was first installed (like changing
from pure oil to oil/electric)?

My house was built in 1966 with a 200A panel. However, the transformer (which serves only me) was
just a 10KVA unit because the house at the time only had about 80A worth of installed load.
Additions by future owners increased my power demand calculation to nearly 200 amps, and I'm
planning to go to well over 300A. Needless to say, the voltage dropped horribly when I turned on
enough stuff to suck 100 amps. You should have a transformer rated for at least half the calculated
amp value of your service (e.g. 200A service x 240V = 48KVA so you'd want a 24 KVA transformer
assuming you really need all 200 amps of your service). I now have a 50 KVA transformer and larger
wires from the transformer to my house.

Well, I had an electrician come in this morning. He says its 100 amp
service (even though his boss said it was 200 amp a couple years ago).
He tightened everything up, we then switiched on the furnace, dryer,
oven to see if we could "dim" the lights and trigger the UPS. No
problems...no diming, and the UPS run without tripping. Max. draw was
60amps.

But he had a theory much like yours. He said to see if its worse from
around 5pm to 9pm. He believes its the neigbours coming home and
drawing more from the transformers. Sure enough, the UPS tripped in
around 5pm briefly, and right out at 6pm when the furnance kicked in.
I'll call BC Hydro again tomorrow.

 

[srewbigbrother]

On Sun, 28 Dec 2003 21:41:35 GMT, "B J Conner"

Nope. Replace the furance motor last year.

 

[srewbigbrother]

On Sun, 28 Dec 2003 19:04:16 GMT, "Ross Mac"


Now, I'm also wondering if my neigbours would also notice the same
things that I am...that their lights are dimming, etc. Or, if they
have 200 amp service, they wouldn't notice?

 

[Ross Mac]

On Sun, 28 Dec 2003 19:04:16 GMT, "Ross Mac"


Now, I'm also wondering if my neigbours would also notice the same
things that I am...that their lights are dimming, etc. Or, if they
have 200 amp service, they wouldn't notice?

A 200 amp service won't help you if the current isn't available from the
xformer....Ross

 

[SQLit]

Well, I had an electrician come in this morning. He says its 100 amp
service (even though his boss said it was 200 amp a couple years ago).
He tightened everything up, we then switiched on the furnace, dryer,
oven to see if we could "dim" the lights and trigger the UPS. No
problems...no diming, and the UPS run without tripping. Max. draw was
60amps.

But he had a theory much like yours. He said to see if its worse from
around 5pm to 9pm. He believes its the neigbours coming home and
drawing more from the transformers. Sure enough, the UPS tripped in
around 5pm briefly, and right out at 6pm when the furnance kicked in.
I'll call BC Hydro again tomorrow.

Utilities do not have to follow the same rules as we in the private/public
sector. I share a 20 kw transformer with my neighbor, both homes have 150
amp services. I doubt that I can produce a 60 amp draw on it even with my
air conditioner (fla is 45 but it rarely pulls above 40).
Voltage is another issue. Try to get them to raise the taps on the
transformer, usually there are taps at 2.5% up and down. Or kindly ask them
to record the voltage in your home for at least 48 hours.
The IEEE states that they must hold the nominal voltage at plus 5% to minus
10% except for short periods of time. I think Canada follows the same specs,
if not never mind.
The utilities I have dealt with in the US, Canada and Mexico want happy
customers if it is within the realm of possibility.

 

[Ross Mac]

worth
of installed load. at
least half the calculated want
a 24 KVA transformer

Utilities do not have to follow the same rules as we in the private/public
sector. I share a 20 kw transformer with my neighbor, both homes have 150
amp services. I doubt that I can produce a 60 amp draw on it even with my
air conditioner (fla is 45 but it rarely pulls above 40).
Voltage is another issue. Try to get them to raise the taps on the
transformer, usually there are taps at 2.5% up and down. Or kindly ask them
to record the voltage in your home for at least 48 hours.
The IEEE states that they must hold the nominal voltage at plus 5% to minus
10% except for short periods of time. I think Canada follows the same specs,
if not never mind.
The utilities I have dealt with in the US, Canada and Mexico want happy
customers if it is within the realm of possibility.

You appear to know a lot more about the utilities than I so I have a
question for you. If the voltage is normal during low use periods wouldn't
raising the taps cause it to be too high?..... Thanks, Ross