Whole house distributed low-voltage power

[carry15+1]

When we moved here, I was flabbergasted to see that NM is commonly used on outside walls from the power lines to the meter and between the meter and the entrance panel. In our 1906 house in St. Paul Minnesota, all of the original wiring inside the house was at least 12 AWG and in threaded steel black conduit with walls as thick as standard gas and water pipe so knob and tube was not universal.



Thirty years ago, about 20 miles from where we now live, one of the country's worst supper club fires (165 deaths) made national headlines and Stan Chesley's name and fortune in establishing what became class action suits. It was caused by faulty aluminum wiring.

Six years later, ~ 1983, the folks that rewired this house used solid aluminum (not copper clad) for both of the AC compressors, both electric stoves, and the electric dryer. The same electricians cut slots from the bottom to the middle of the floor joist in the mid-point of the joist span in one of our first floor rooms in order to install wires. The joists were then 161 years old. Before I scabbed it up, the floor was like a trampolin. And there were enough bronze placques heralding the historical significance of the house plastered on the outside to _make_ the needed copper wire. And yes, it apparently passed local inspection -- sticker and all . ( I still shake my head ...)

Marc - these were NOT electricians!

When we moved in, the lights on one of the two side-by side electric stoves was intermittent. When found that I could 'fix' it by wedging a fork between the two stoves, it was time to rewire. The aluminum neutral on the one stoves had broken and the fork let one stove 'borrow' the neutral of the other through their chassis ( yes, these were 3-wire, not 4-wire also.) The heating elements still worked because they are 220vac and don't use the neutral

More recently, the 2nd floor AC compressor stopped working. Turns out the aluminum contacts in the circuit breaker in the entrance panel were melted and the plastic of the CB cooked .... That's the last of the inside aluminum except for the service entrance which really should have aluminum contact 'grease' added (no aluminum connection has/had it) and be retorqued.


For reasons I cannot now explain, I bought an inexpensive, natural-gas-powered _24vdc_ generator. It isn't installed yet. I should have bought an AC one because the DC one can't handle the refrigerator and freezer. If it were AC, I could simply connect the fridge, and the DC chargers, and one or two undedicated outlets to it and the DC system would have been backed up for even long outages with no switch-over needed for all the devices on the DC system owing to thge intrinsic battery backup. I may sell it and buy an AC one.


"What's a watt?" I thought you knew ... ;-)

If you substitute a 20 watt halogen MR-16 for a 90 watt can, you save energy regardless of whether the 20 watter is AC or DC ;-)

A watt is still a watt. If you sub your 50w lamp for a 90 watt flood you end up with less lumens (plus transformer losses) - no comparison ;-o

 

[politics123]

Any idea how much more efficient it is doing all the AC --> DC transformations using a large-scale system vs. individual transformers?

 

[hult]

When we moved here, I was flabbergasted to see that NM is commonly used on outside walls from the power lines to the meter and between the meter and the entrance panel. In our 1906 house in St. Paul Minnesota, all of the original wiring inside the house was at least 12 AWG and in threaded steel black conduit with walls as thick as standard gas and water pipe so knob and tube was not universal.

Thirty years ago, about 20 miles from where we now live, one of the country's worst supper club fires (165 deaths) made national headlines and Stan Chesley's name and fortune in establishing what became class action suits. It was caused by faulty aluminum wiring.

Six years later, ~ 1983, the folks that rewired this house used solid aluminum (not copper clad) for both of the AC compressors, both electric stoves, and the electric dryer. The same electricians cut slots from the bottom to the middle of the floor joist in the mid-point of the joist span in one of our first floor rooms in order to install wires. The joists were then 161 years old. Before I scabbed it up, the floor was like a trampolin. And there were enough bronze placques heralding the historical significance of the house plastered on the outside to _make_ the needed copper wire. And yes, it apparently passed local inspection -- sticker and all . ( I still shake my head ...)

Marc - these were NOT electricians!

Unless the inspection sticker was forged, they were what passed for licensed electricians in this part of US at that time ;-)

When we moved in, the lights on one of the two side-by side electric stoves was intermittent. When found that I could 'fix' it by wedging a fork between the two stoves, it was time to rewire. The aluminum neutral on the one stoves had broken and the fork let one stove 'borrow' the neutral of the other through their chassis ( yes, these were 3-wire, not 4-wire also.) The heating elements still worked because they are 220vac and don't use the neutral

More recently, the 2nd floor AC compressor stopped working. Turns out the aluminum contacts in the circuit breaker in the entrance panel were melted and the plastic of the CB cooked .... That's the last of the inside aluminum except for the service entrance which really should have aluminum contact 'grease' added (no aluminum connection has/had it) and be retorqued.

For reasons I cannot now explain, I bought an inexpensive, natural-gas-powered _24vdc_ generator. It isn't installed yet. I should have bought an AC one because the DC one can't handle the refrigerator and freezer. If it were AC, I could simply connect the fridge, and the DC chargers, and one or two undedicated outlets to it and the DC system would have been backed up for even long outages with no switch-over needed for all the devices on the DC system owing to thge intrinsic battery backup. I may sell it and buy an AC one.

"What's a watt?" I thought you knew ... ;-)

If you substitute a 20 watt halogen MR-16 for a 90 watt can, you save energy regardless of whether the 20 watter is AC or DC ;-)

A watt is still a watt. If you sub your 50w lamp for a 90 watt flood you end up with less lumens (plus transformer losses) - no comparison ;-o

Yes. There is no disputing/arguing/avoiding that part of the physics of the matter.

That said, there are other physical principles that can be brought to bear that pertain to the actual intensity and perceived quality.

What matters if you are trying to read a newspaper is not the output of the lamp in lumens per se, but lumens/unit area ('illuminance" ) on/at the newspaper.

That is part of the nature of the 'task' and 'mood' lighting that I referred to previously. So depending on the application, circumstances (especially distances and geometry) and preferences, one can get 'better', and more intense lighting with less wattage.

Specifically, a 20-watt, narrow-spot, low-voltage lamp can provide greater _illuminance_ than a 90-watt flood lamp that obviously has greater total output in lumens. Track lighting makes aiming and 'tasking' more practical. This is of course true regardless of whether the lamps are low-voltage or 110vac. But my experience is that there is greater flexibility and variety with low voltage lamps at the low range of outputs and output angles than with 110VAC. And one needs that flexibility to avail one self of the physics. If the only option is what kind of lamp to put in a ceiling can, the options are few.

Anyway, in our case, the use of low-voltage halogen MR16's is most likely an intermediate solution that will make way for MR16 LEDs and perhaps other more efficient technologies just as the Edison-base halogen floods in the cans have migrated to Edison-base CFL floodlamps.

... Marc

 

[Digger]

Any idea how much more efficient it is doing all the AC --> DC transformations using a large-scale system vs. individual transformers?

Many of the "wall warts" are very ineffecient and can waste over 1 watt just sitting there plugged in without a device attached (such as a cell phone etc). Then when in use many are less than 70% percent effecient.

The California Energy Commision enacted regulations to limit the amount of power wasted in the "no load" state to less than .5 watts and a minimum loaded effeceincy of 75% (increasing to 85% I think next year) for all external power supplies. The impact on manufacturers is significant since a linear type of wall wart will cost significantly more to manufacturer due to the increased cost of a better core material (and larger size, more weight etc).

If you have a central high effeceincy switch mode power supply (which could be about 90% effeceint) that can be distributed as a power limited circuit over multiple branches it might be more cost effective over time. The real benifets would be to incorporate battery backup up and solar. Solar cells are not that effecient and then you add into the mix an inverter and you are even more ineffecient. Eliminate the inverter and the cost is down and the effeceincy is greater so in this application they could be benificial. Besides look at the emergency backup power and enviromental benifets.