[Piedmont]

I want to take advantage of cheaper electric rates at night and have my 4500W 240v water tank (120 gallons) on a 30A breaker likewise only turn on at 1AM - 6AM.

Can anyone tell me what device will do this? I keep finding 240v timers but they're all "3-prong" my water tank has no prongs, the device has to be spliced in the line.

Thanks!

 

[wirenut1110]

You could get something like this or a reasonable facsimile thereof:
http://www.grainger.com/Grainger/items/1A573

 

[Piedmont]

That was a big help, I feel stupid I noticed from your link it's called water heater timer! Changing my search from 240v timer to "water heater timer" got me the right items.

I'm pretty sure I know the answer... if my water heater is on a 30A breaker even though it uses less than 20A (4500W at 240V) does that mean I must install a timer 30A or greater and can't install a 25A water heater timer such as the Intermatic WH21 like at
http://www.amazon.com/Intermatic-WH21-Electric-Water-Heater/dp/B00002N5FP ?

 

[Thurman]

I just have to say/ask this- -In my area the electricity supplier it Georgia Power Co. They also advise using high electrical useage devices such as clothes dryers, water heaters, heat/A/C units late in the evening or at night because of "lower electrical rates". My point is, GA. Power reads my meter once a month, my meter runs according to the amount of electricity that I use. I, for one, DO NOT believe that my meter runs any slower or faster at any given time of day or night nor does it know that there may be lower utility rates during any given hours within a twenty-four hour period. I cannot understand how they can suggest using any electrical appliance during any particular time of day to get better electrical rates. I can understand them wanting homeowners to use heavy electrical useage appliances later in the evening as this may be when GA. Power's electrical demands are lower. So says David

 

[Scuba_Dave]

Many companies can monitor your electric usage on an hourly basis. In many areas the cost is adjusted for off peak use

 

[Piedmont]

The main reason I want to do it is cause my hot water is heated by solar but has electric backup. I don't like to mention "solar" because I've learned it's cursed or something getting me 0 responses mentioning it :yes:

What I'm finding is sometimes after our showers (and a cloudy day or two) the tank may be around 90F. Then the electric element kicks on to reheat it and I don't want it to it's going to be sunny and our solar will more than adequately reheat it (usually to 140F+).

That's the main reason I want a timer... to maximize the efficiency of my solar and not have the electric element kicking on in the mornings of sunny days. It also minimizes electric use as maybe it was a bad day and the solar was only able to reheat the tank from 90F to 115F. When the electric element kicks on at 1AM it only has to heat the water 5F instead of 30F.

So... I hope the curse doesn't continue because I mentioned the word "solar" all I want to do is control when the backup electric element kicks on by making it only come on at 1AM - 6AM.

Can I use a 25A timer on a 4500W 240v circuit that's got a 30A breaker?

Thanks

 

[jbfan]

I just have to say/ask this- -In my area the electricity supplier it Georgia Power Co. They also advise using high electrical useage devices such as clothes dryers, water heaters, heat/A/C units late in the evening or at night because of "lower electrical rates". My point is, GA. Power reads my meter once a month, my meter runs according to the amount of electricity that I use. I, for one, DO NOT believe that my meter runs any slower or faster at any given time of day or night nor does it know that there may be lower utility rates during any given hours within a twenty-four hour period. I cannot understand how they can suggest using any electrical appliance during any particular time of day to get better electrical rates. I can understand them wanting homeowners to use heavy electrical useage appliances later in the evening as this may be when GA. Power's electrical demands are lower. So says David

The reason to run higher use devices later is to reduce peek demand, which the power company has to pay more for the power, thus pass the higher rates to you.

In theroy of course!:whistling2:

 

[220/221]

I, for one, DO NOT believe that my meter runs any slower or faster at any given time of day or night nor does it know that there may be lower utility rates during any given hours within a twenty-four hour period

They changed to digital meters in AZ here long ago. Old school meters strictly read KWH.....alledgedly.

Now you have made me think dammit!

How do they set the time after an outage? Are there peak and off peak readings?

I will go look at mine.......Ok. My digital meter has a two hole receptical in the meter face which I assume the meter reader guy sticks in his recording device.

Maybe they somehow send the time of day info thru the power wires somehow???

 

[Yoyizit]

I don't like to mention "solar" because I've learned it's cursed or something getting me 0 responses mentioning it

What I'm finding is sometimes after our showers (and a cloudy day or two) the tank may be around 90F. Then the electric element kicks on to reheat it and I don't want it to it's going to be sunny and our solar will more than adequately reheat it (usually to 140F+).
So you want to hold off the electric heat hoping for sunlight.

Solar is as much math as HVAC with more probabilities involved. Here is a good overview
http://www.discountbooksale.com/sto...&ProdID=113&utm_source=froogle&utm_medium=cpc

To actually save money without compromising comfort may take a pretty sophisticated strategy, if it is possible at all. People with heat pumps that have aux. elec. heat have the same problem, with sacrificing recovery time for elec. cost.

Can you post scenarios? I guess you already know the insolation for your area.
http://www.solarpanelsplus.com/solar-insolation-levels/
If your insolation is less than your average demand for hot water, you'll always need some elec. for this.

As to days of continuous cloud cover, these guys
http://www.ncdc.noaa.gov/oa/ncdc.html
supposedly can help with that.

One option would be a low level of elec. heat into the tank all the time. A better one would be a larger tank, to filter out the uncertainties of having to use sunlight.

A typical hot water shortage for you would be 25 gallons of water between 115°F and 125°F [one shower]? At 10¢/kwh this would take 20 cents.

 

[Piedmont]

I'm not sure I understand the question, I've had the solar installed a year ago.

My system is sized properly for my area, it has a 120 gallon tank (for just my wife and I) and our collector area is 50% larger than typical (96 sq ft). The issue happens when there's extended amounts of cloudy days, a sunny day can buffer us through 2-4 cloudy days and that may sound like a lot but on average our area has 2-3 days of cloudy/partly cloudy days for every 1 day of sunny. We do frequently hit a situation where the 4th day is going to be sunny but after our showers have run out of hot water and the electric element kicks on even though it's going to be a sunny day. But, that's just the best that can be done sometimes we've gone 38 days of full clouds... sometimes we get 21 straight days of sun. Especially in winter after our showers the tank can be 90F and the solar will heat it to 115F if the stupid stupid element didn't kick on until later... in winter especially solar is a lot more efficient heating 90F water vs. 120F I'd rather have the solar do it's thing and have the element kick on at night for the remaining boost for my wifes shower in the morning. We pay $0.23/kW, I am having to run down at night to turn the breaker on and then before my wife takes her shower turning the breaker to the tank off more than I'd like, I'd rather a timer.

Can this http://www.amazon.com/Intermatic-WH21-Electric-Water-Heater/dp/B00002N5FP be used on my tank (it's on a 30A breaker to a 4500W 240v water tank)?

 

[gp_wa]

I don't like to mention "solar" because I've learned it's cursed or something getting me 0 responses mentioning it :yes:

I've noticed that, too :laughing:

 

[Yoyizit]

I'm not sure I understand the question,
Neither am I!

it has a 120 gallon tank
So to heat this 1000# of water 30 F takes 8.7 kwH.

96 sq ft
At 60% efficiency this can supply 5200 w at the average power supplied by sunlight. What is your nearest city/town?

the electric element kicks on even though it's going to be a sunny day.
To what likelihood? Here's where the gamble of saving a few cents is pitted against the likelihood of a lukewarm shower.

But, that's just the best that can be done sometimes we've gone 38 days of full clouds... sometimes we get 21 straight days of sun.
So I'd say, at the extremes, you need the kwH supplied by full sun to equal 38 days of showers @ some gallon usage @ some minimum temp.


Especially in winter after our showers the tank can be 90F and the solar will heat it to 115F if the stupid stupid element didn't kick on until later... in winter especially solar is a lot more efficient heating 90F water vs. 120F I'd rather have the solar do it's thing and have the element kick on at night for the remaining boost for my wifes shower in the morning. We pay $0.23/kW, I am having to run down at night to turn the breaker on and then before my wife takes her shower turning the breaker to the tank off more than I'd like, I'd rather a timer.

Can this http://www.amazon.com/Intermatic-WH21-Electric-Water-Heater/dp/B00002N5FP be used on my tank (it's on a 30A breaker to a 4500W 240v water tank)?

4500w/240v = 19 A. For a 25A timer this should work. If both 4500w heaters turn on the life of the timer may shortened.