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Joined: Mar 2005
Posts: 1,213
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I just built a 2000 square foot edition (1500 square feet of it heated, rest is the garage), and happen to have the BTU loss calcs handy. Dropping the thermostat by 3°F would reduce heating loss by about 700 BTU/hr (200W of heating). For a heat pump with a COP of 3-4x, that's about 60W at the meter. Saving, maybe, $1 a month to drop the temp overnight while you're sleeping wink My thermostats are the smart electronic kind so I have them programmed to drop the temp 2° at night anyhow.

Last edited by SteveFehr; 12/21/07 08:03 AM.
Joined: Mar 2007
Posts: 165
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Originally Posted by EV607797

Paul, please elaborate on the "contactor closing around midnight". Is that some kind of energy management program?

My house is about 3,000 SF, so my electrical requirement would be expected to be twice of yours, but we have a heat pump that does a pretty good job of keeping us warm. Resistance heating (backup) only kicks in when it gets below freezing here.

Talk about a hijack of an original thread. I have turned this thread into a completely different subject. Sorry!


Ego te absolvo. I'd like to know more also. cool

Last edited by Retired_Helper; 12/21/07 10:24 AM. Reason: Left out a bracket!
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I think Paul was referring to his Night-rate supply.
Heaters are switched on overnight via a contactor and are allowed to heat up (these are storage heaters with blocks of stone(?)in them to hold the heat) and are switched off again in the morning (usually about 7 or 8am), by the PoCo.
Power is cheaper on Night rate supply.

Joined: Aug 2001
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Quote
Paul, please elaborate on the "contactor closing around midnight". Is that some kind of energy management program?


As Mike has outlined, it's the "Economy 7" tariff, which is fairly common here for electrically heated homes.

We have a dual-rate meter (i.e. two sets of dials, selected by a small solenoid, or a modern electronic equivalent), and a timeclock switches the meter over to the cheaper rate for 7 hours each night (hence the "Economy 7" name). It runs midnight thru 7 a.m. winter, 1 a.m. thru 8 a.m. in summer.

At the moment, my rates are 10.31 pence per kW/h day rate and 4.65 pence night rate, so well under half price.

As well as switching the meter to night rate, the timeclock also energizes a contactor which supplies power to a completely separate distribution panel for the storage heaters. Again, as Mike said, these contain elements inside thermal bricks so that they are "charged" with heat overnight at the low rate. A thermostatic damper control then allows that stored heat to be radiated during the day.



Joined: Dec 2005
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Same systems are used in New Zealand with ripple or pilot control to switch on or off, fixed wired appliances like storage heaters and hotwater cylinders on a cheaper rate via a contactor in the meter box.

The kWh meter has two dials which are controlled via a timeclock or ripple control.

The difference between the tarifs used to be great, (half price for nite rate ). Unfortunately with the greed of POCO's it is hardly worth while anymore and the difference between day and night rate is less than a cent difference.

Most domestic supplies are rated at 63 or 80 Ampères, single phase at 230 Volts, for an average of 1200 to 1500 sq ft houses.


The product of rotation, excitation and flux produces electricty.
Joined: Oct 2006
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"sunlight resistant" is just that - resistant, not "proof"

I have seen UV burn through UF cable that was labeled sunlight resistant.

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