Forums

how to reduce the mains voltage

Started by default July 13, 2020
I have an older window air conditioner that I'd like to hang on to for
a few more years.  The name plate says it is 220 VAC and since the
power company went through and upgraded the distribution network and
replaced HT and transformers my service which had been running 210-220
volts is now a steady 250 volts and my bill is up ~15%.

The increased consumption is tied to how much I run the AC and since
the upgrade I've already had to replace both the compressor and fan
motor run caps.  The compressor one died a quiet death, and the fan
cap melted and smoked. The compressor cap went out the week they
changed the transformer and the fan cap about a month later. I put in
higher voltage ones and the AC is back on line.

I was wondering if putting in 240 VAC to 24VAC center tapped, 10 amp
power transformer, wired to buck the voltage makes any sense?  
On Monday, July 13, 2020 at 11:31:34 AM UTC-4, default wrote:
> I have an older window air conditioner that I'd like to hang on to for > a few more years. The name plate says it is 220 VAC and since the > power company went through and upgraded the distribution network and > replaced HT and transformers my service which had been running 210-220 > volts is now a steady 250 volts and my bill is up ~15%. > > The increased consumption is tied to how much I run the AC and since > the upgrade I've already had to replace both the compressor and fan > motor run caps. The compressor one died a quiet death, and the fan > cap melted and smoked. The compressor cap went out the week they > changed the transformer and the fan cap about a month later. I put in > higher voltage ones and the AC is back on line. > > I was wondering if putting in 240 VAC to 24VAC center tapped, 10 amp > power transformer, wired to buck the voltage makes any sense?
How about a variac to lower the voltage. (kinda spendy... might be better to invest in new AC unit.) George H.
On Mon, 13 Jul 2020 08:47:27 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

>On Monday, July 13, 2020 at 11:31:34 AM UTC-4, default wrote: >> I have an older window air conditioner that I'd like to hang on to for >> a few more years. The name plate says it is 220 VAC and since the >> power company went through and upgraded the distribution network and >> replaced HT and transformers my service which had been running 210-220 >> volts is now a steady 250 volts and my bill is up ~15%. >> >> The increased consumption is tied to how much I run the AC and since >> the upgrade I've already had to replace both the compressor and fan >> motor run caps. The compressor one died a quiet death, and the fan >> cap melted and smoked. The compressor cap went out the week they >> changed the transformer and the fan cap about a month later. I put in >> higher voltage ones and the AC is back on line. >> >> I was wondering if putting in 240 VAC to 24VAC center tapped, 10 amp >> power transformer, wired to buck the voltage makes any sense? > > How about a variac to lower the voltage. (kinda spendy... >might be better to invest in new AC unit.) > >George H.
That would be ideal, but at a cost of ~$140 versus a transformer costing ~$35.
On 7/13/2020 11:25 PM, default wrote:
> On Mon, 13 Jul 2020 08:47:27 -0700 (PDT), George Herold > <gherold@teachspin.com> wrote: > >> On Monday, July 13, 2020 at 11:31:34 AM UTC-4, default wrote: >>> I have an older window air conditioner that I'd like to hang on to for >>> a few more years. The name plate says it is 220 VAC and since the >>> power company went through and upgraded the distribution network and >>> replaced HT and transformers my service which had been running 210-220 >>> volts is now a steady 250 volts and my bill is up ~15%. >>> >>> The increased consumption is tied to how much I run the AC and since >>> the upgrade I've already had to replace both the compressor and fan >>> motor run caps. The compressor one died a quiet death, and the fan >>> cap melted and smoked. The compressor cap went out the week they >>> changed the transformer and the fan cap about a month later. I put in >>> higher voltage ones and the AC is back on line. >>> >>> I was wondering if putting in 240 VAC to 24VAC center tapped, 10 amp >>> power transformer, wired to buck the voltage makes any sense? >> >> How about a variac to lower the voltage. (kinda spendy... >> might be better to invest in new AC unit.) >> >> George H. > > That would be ideal, but at a cost of ~$140 versus a transformer > costing ~$35. >
I agree about the cost advantage of the variac/transformer. I was about suggest a variac too but refreshed my newsreader before hitting the Send button and saw that George had beaten me to it. This reminds me of the time some 35 years ago when the power supply in a friend's TV kept breaking down. It turned out that the mains voltage in their house was persistently high. I improvised a step-down autotransformer with a 12-0-12V 1A transformer and fitted that inside the TV. It never broke down again.
On Mon, 13 Jul 2020 11:31:30 -0400, default <default@defaulter.net>
wrote:

>I have an older window air conditioner that I'd like to hang on to for >a few more years. The name plate says it is 220 VAC and since the >power company went through and upgraded the distribution network and >replaced HT and transformers my service which had been running 210-220 >volts is now a steady 250 volts and my bill is up ~15%. > >The increased consumption is tied to how much I run the AC and since >the upgrade I've already had to replace both the compressor and fan >motor run caps. The compressor one died a quiet death, and the fan >cap melted and smoked. The compressor cap went out the week they >changed the transformer and the fan cap about a month later. I put in >higher voltage ones and the AC is back on line. > >I was wondering if putting in 240 VAC to 24VAC center tapped, 10 amp >power transformer, wired to buck the voltage makes any sense?
Where I live we get 250 volts pretty steadily. In my shop are several CNC machines, one of which cannot easily tolerate the 250 volts. So I use two buck/boost xmfrs wired in a particular buck configuration to lower the 3 phase voltage going to that one machine. Since doing so the machine has not once alarmede out due to over voltage. I also wired up a little 120 to 12 volt xmfr in buck configuration to lower the 125 volts from the outlet to the 110 volts needed for a tube amp. There are directions online on how to select the proper sized xmfr for the load it will be seeing and how to wire the thing in buck configuration. Eric
Your bill went up because of light bulbs and shit with heating elements, maybe the microwave if you use it alot, and of course if you have an electric stove. 

Those types of motors usually run more efficiently on slightly higher voltage. Voltage up, current is the same or lower. Well power actually, it might be the same current but the phase changes the power factor. You pay by the watt, not the amp. 
On Monday, July 13, 2020 at 8:31:34 AM UTC-7, default wrote:
> I have an older window air conditioner that I'd like to hang on to for > a few more years. The name plate says it is 220 VAC and since the > power company went through and upgraded the distribution network and > replaced HT and transformers my service which had been running 210-220 > volts is now a steady 250 volts and my bill is up ~15%.
...
> I was wondering if putting in 240 VAC to 24VAC center tapped, 10 amp > power transformer, wired to buck the voltage makes any sense?
It doesn't make much sense to me; ask, instead, the power company to adjust the line voltage to an acceptable value. The taps in their transmission line drops are the solution to many such problems, if they know that you have found an excessive voltage. I'm not sure 250V average is excessive, but if there are peaks and dips...
On Mon, 13 Jul 2020 16:49:33 -0700 (PDT), jurb6006@gmail.com wrote:

>Your bill went up because of light bulbs and shit with heating elements, maybe the microwave if you use it alot, and of course if you have an electric stove. > >Those types of motors usually run more efficiently on slightly higher voltage. Voltage up, current is the same or lower. Well power actually, it might be the same current but the phase changes the power factor. You pay by the watt, not the amp.
I think you are mistaken. Some years ago I put a voltage stabilizer on a large fan. (adjustable AC voltage regulator intended to be used for large motors) As I adjusted the voltage lower the current dropped linearly until it reached about 95 VAC then started rising exponentially as I dropped it lower. Torque of the motor may be dependent on voltage, but the torque required for a refrigeration compressor varies with time. Starting up with the system equilibrated, there's little back-pressure on the compressor so it is lightly loaded, as back pressure builds the torque necessary to maintain synchronous speed increases. The only other change in my habits, I shower more with hot weather - but use less hot water showering... I still use 4 compact fluorescent bulbs in closets where they stay off, every thing else is LED. I use the electric range less - in summer. I get a monthly report card from my power company with a graph of the last 13 months. I normally track well below the average and below their idea of what an energy efficient home should use. Last month I was up to "average." I believe it too. Years ago I mistakenly opened my neighbors power bill (without looking at the addressee) and found he was paying $120 when I was paying $30.
On 2020-07-14 07:04, default wrote:
> On Mon, 13 Jul 2020 16:49:33 -0700 (PDT), jurb6006@gmail.com wrote: > >> Your bill went up because of light bulbs and shit with heating elements, maybe the microwave if you use it alot, and of course if you have an electric stove. >> >> Those types of motors usually run more efficiently on slightly higher voltage. Voltage up, current is the same or lower. Well power actually, it might be the same current but the phase changes the power factor. You pay by the watt, not the amp. > > > I think you are mistaken. > > Some years ago I put a voltage stabilizer on a large fan. (adjustable > AC voltage regulator intended to be used for large motors) As I > adjusted the voltage lower the current dropped linearly until it > reached about 95 VAC then started rising exponentially as I dropped it > lower. > > Torque of the motor may be dependent on voltage, but the torque > required for a refrigeration compressor varies with time. Starting up > with the system equilibrated, there's little back-pressure on the > compressor so it is lightly loaded, as back pressure builds the torque > necessary to maintain synchronous speed increases.
<snip> But if you have a momentary power dropout, it has to restart into the full back-pressure of the evaporator. If the A/C isn't a tiny one, I sure wouldn't be mickey-mousing anything that would increase the mains impedance. Electrical codes contain a lot of non-obvious and very expensive wisdom. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
On 7/14/2020 8:07 AM, Phil Hobbs wrote:
> On 2020-07-14 07:04, default wrote: >> On Mon, 13 Jul 2020 16:49:33 -0700 (PDT), jurb6006@gmail.com wrote: >> >>> Your bill went up because of light bulbs and shit with heating >>> elements, maybe the microwave if you use it alot, and of course if >>> you have an electric stove. >>> >>> Those types of motors usually run more efficiently on slightly higher >>> voltage. Voltage up, current is the same or lower. Well power >>> actually, it might be the same current but the phase changes the >>> power factor. You pay by the watt, not the amp. >> >> >> I think you are mistaken. >> >> Some years ago I put a voltage stabilizer on a large fan.&nbsp; (adjustable >> AC voltage regulator intended to be used for large motors) As I >> adjusted the voltage lower the current dropped linearly until it >> reached about 95 VAC then started rising exponentially as I dropped it >> lower. >> >> Torque of the motor may be dependent on voltage, but the torque >> required for a refrigeration compressor varies with time.&nbsp; Starting up >> with the system equilibrated, there's little back-pressure on the >> compressor so it is lightly loaded, as back pressure builds the torque >> necessary to maintain synchronous speed increases. > <snip> > > But if you have a momentary power dropout, it has to restart into the > full back-pressure of the evaporator.&nbsp; If the A/C isn't a tiny one, I > sure wouldn't be mickey-mousing anything that would increase the mains > impedance. > > Electrical codes contain a lot of non-obvious and very expensive wisdom. > > Cheers > > Phil Hobbs > > > >
My central AC won't restart immediately after a dropout. It has a delay time to allow the pressure to drop. Bill