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 shoulderlegs
Joined: 4/14/2005
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Hot water tanksPage 1 of 2    (1, 2)
To any electricians on here.....
Can I save some money on electricity by unplugging my hot water tank after taking a shower, then plugging it back in an hour before I take a shower? Yes.... it's an electric water heater!
 raxarsr
Joined: 7/10/2008
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Posted: 8/30/2011 10:15:39 PM
nope...you'll actually spend more
you'll save more money by turning off any lights your not useing at the moment.....and by keeping your fridge and freezer full....even if its just jugs of water
 Justmytypewriter
Joined: 2/8/2011
Msg: 3
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Posted: 8/30/2011 10:26:08 PM
Not an electrician but...

Can I save some money on electricity by unplugging my hot water tank after taking a shower, then plugging it back in an hour before I take a shower?

Probably not. Keeping the water hot (or warm) is probably requiring less energy than heating up an entire tank of cold water. It may depend, though, on how large the tank is, how many showers you're taking and on the temperature you're aiming for. You might also want to remember that your washer uses the hot water also.

If you are concerned about electricity consumption and electricity savings, think about these options instead:

* Get a thermo sleeve for your water tank. That won't cost more than $20, and it can shave $10 to $20 a month off of your electricity bill.

* Reduce the temperature of your hot water tank. Most water tanks are set to 140 degrees; but you don't really need for your water to be that hot. Turn it down to 120 degrees.

* Consider replacing your tank with a tank-less water heater. (Your electrical system might need adjustments, though, so have an electrician check your home first.) Replacing a conventional water tank with a tank-less water heater requires some upfront expense, but it will reduce your electricity bill down the road.
 OMG!WTF!
Joined: 12/3/2007
Msg: 4
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Posted: 8/30/2011 10:26:11 PM
You could probably save money by doing that as long as you drained the tank more or less completely with each shower. Otherwise water you've paid to heat would cool completely and thus be wasted. But you'll be so pissed off that one time you forget to plug it in again and all you want is a hot shower. So why not just buy a twenty dollar water tank insulation blanket at Home Depot. They work well. You could also insulate the outgoing copper line from the tank with those cheapy foam pipe covers.

http://www.homedepot.com/buy/plumbing/water-heaters/water-heater-insulation-blanket-75-in-x-48-in-x-3-in-42177.html
 Molly Maude
Joined: 9/11/2008
Msg: 5
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Posted: 8/30/2011 11:39:11 PM
when I called my electric company, gas company and the group that provides water, sewer and garbage to ask if they had energy efficient information for me ... suggestions how I could lower my bills ... save energy ... they were nicer than nice ...

the gas company immediately sent a woman out to my house who assessed the house, interviewed me and provided my house with energy-saving devices ... weather stripping on the doors, windows, etc. ... there was an open vent I didn't even know about that had been draining my house of warm air for years and they sealed it ...

the electric company had similar offers I'd never expected or heard of ... I was shocked at how nice they were, trying to save me from using too much energy ... they sent someone out to evaluate the house, too ... gave me freebies ... gave me a large discount for allowing them to put a governor on my air conditioning unit to turn off the unit no more than one hour a day, no more than one day a week ...

the water, sewer and garbage company just gave me a discount for being old!
 Hozo
Joined: 8/1/2006
Msg: 6
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Posted: 8/31/2011 4:56:23 AM

To any electricians on here.....
Can I save some money on electricity by unplugging my hot water tank after taking a shower, then plugging it back in an hour before I take a shower? Yes.... it's an electric water heater



I have been doing this off and on for over 2 years now, and my electric bill dropped by almost 1/3. Here are a few observations:

~I live alone, and take short 5 minute "military" showers, in which I run the water until hot, get wet, shut the tap, soap up & shampoo, then turn on the tap & rinse. I probably use less than 5 gallons of water per shower.

~If I shut off the breaker after fully heating the tank, my 40 gallon tank will keep the water hot enough for a shower for nearly 3 days. Every day the water gets a little cooler, so I must adjust the faucet's hot/cold ratio. By the 3rd day, I am tapping the hot side fully, & it is luke-warm. I do have a newer heater, less than 2 years old, so it is better insulated than older units.

~Here is the sweet part: After exhausting ALL hot water, I can flip the breaker back on for 5 MINUTES just before my shower, shut it off again, & that 5 minutes will heat the top 5-10 gallons of water hot enough for a comfortable 5 minute shower.

~So basically, I run my tank less than 5 minutes per day when I am here. I am not home alot...probably averaging out to 5 days per week here, & 2 days gone. When I leave for a weekend, etc, I dont power the tank.

I have a gas stove & furnace, so my major electric appliances are the hot water tank, fridge, & compact chest freezer. My electric bill for July was $37. It is rarely over $100, & that is the dead of winter . My yearly average around $60.

I suggest experimenting with it at least. You wont hurt anything trying.
 U make it entertaining
Joined: 7/17/2009
Msg: 7
Hot water tanks
Posted: 8/31/2011 6:50:06 AM
Many you should invest in one of those automatic heaters, where they heat on demand.
 matchlight
Joined: 1/31/2009
Msg: 8
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Posted: 8/31/2011 10:59:40 AM

This does require a rather large electrical circuit


No kidding! Most of the tankless heaters on the market use gas. I'd think an electric tankless unit would be powerful enough for a wash basin, or a bar sink, or maybe a puny shower, but not much more.
 Hozo
Joined: 8/1/2006
Msg: 9
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Posted: 8/31/2011 12:15:47 PM
In most homes, the electric hot water tank is the appliance that uses the most electricity....by far. Only an electric furnace, or perhaps using multiple elements on your electric range uses more, but the hot water tank cycles automatically on/off 24/7, unlike most appliances.

The EnergyGuide sticker on my newer tank shows it costs $503/year to operate. That is $40-$50/month just for that 1 appliance, and it is a smaller 40 gallon unit. In comparison, the EnergyGuide sticker on my small chest freezer shows that it costs $39/year to operate.

Most homes have 55 gallon or larger tanks, which would consume much more electricity. Most tanks draw 30-50 amperes when on. That's alot of juice. That is probably more consumption by itself than all your lights, TVs, small appliances, etc. combined. That is how is is in my home, even with my smaller tank.
 shoulderlegs
Joined: 4/14/2005
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Posted: 8/31/2011 8:09:32 PM
Actually, I already have the two thermostats on the tank down to 120. And I ALWAYS keep jugs of water frozen in the freezer.
 a_lonewolf
Joined: 5/21/2010
Msg: 11
Hot water tanks
Posted: 8/31/2011 9:03:49 PM
Your best way to save money would be to down size the water heater. Water heaters are sized by the amount of bedrooms in the house and size of bath tubs. The standard tank is a 55 gal with usually 4.5 kw consumption. If you aren't filling up a bath tub and use hot water for the washing machine, you can downsize the tank to a 6gal with 3kw heater. The time it takes to heat and maintain 6 gallons of water is far less than doing the same for 55 gallons.
I have done this at my cabin and have noticably cut my power bill. Haven't even had a complaint about running out of hot water either.
 matchlight
Joined: 1/31/2009
Msg: 12
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Posted: 9/1/2011 12:58:36 AM
Does anyone have any experience combining a tankless heater with a 20-30 gal. electric water heater tank, with the heating element removed and the hole plugged? Seems like a fairly cheap way to get both the continuous flow of tankless with a reserve capacity for bathtubs, laundry, etc. If you took hot water from the tank, instead of from the tankless heater, it might not cycle off and on so often.

Apparently one of the drawbacks of tankless units is that if they're not under a steady load--which most of the time they're not--they're not as efficient as the 80-85 per cent lab ratings suggest. So you save whatever energy hot water loses by being stored in a tank, but you lose part of that savings by having a tankless heater that doesn't run at its highest efficiency most of the time.
 robin-hood
Joined: 12/2/2008
Msg: 13
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Posted: 9/1/2011 1:00:54 AM
Electric water heaters are almost perfect conversion from electric to heat, so it takes 0.244 KW to heat 1-gallon of water 100°F. There is no way around this energy use to heat water using electric resistance. If your inlet water is 60°F and you heat it to 120°F then the temperature rise is 60°F, or 0.244 x 60 / 100 = 0.1464 KW per gallon.
-----------------------------
For those who want to play with the numbers
1 KW = 3412 BTU
1 US gallon = 8.34 lbs at 60°F and density approx the same at 140°F
Specific heat of water =1, its the standard other materials are referenced to.
KW = Gal x 8.34 x 1 x (T2-T1) / 3412
Example: Gal=50, T2=120, T1=60 or KW=50 x 8.34 x 1 x 60 / 3412 = 7.333 KW
------------------------------------
Your standby losses are through the insulation and hot water pipes. Standby losses depend on where your water heater is located. I will assume its the occupied space such as a utility room or interior closet. These standby losses depend on your jacket insulation, but lets use an example of 20" dia x 57" high with insulation R-value = 12. This about standard off the shelf 50 gallon water heater sold today. The WH's about 12+ years back used R-values of about 6 to 8 using fiberglass insulation.

Q= 20 x 57 x 3.14 x (120-65) / (144 x 12) + 2 x 20 x 20 x 3.14 x (120-65) /(144 x 12 x 4) =
135 + 23.6 = 158. 6 BTH/HR or 0.0465 KW/hr. For 24 hours it 1.12 KW/day

One thing not accounted for is the standby loss for the pipe attachments (hot & cold). Use a thermal break at the connections. This is just a short section of CPVC (plastic pipe) to keep copper from conducting. Then insulate the 1st couple feet of hot & cold pipe.
---------------------------------------

Location of WH with regards to fixtures and frequency can increase your energy use. Example of kitchen sink where you might draw hot water 10 maybe 20 or just a couple times a day. The pipe if its copper sucks heat from initial flow, and then whats left in the pipe after you turn water off. Lets use 1/2" type-L copper for 20-ft. The inside volume is 1/4 gallon. If you draw hot water ten times a day thats 2.5 gallon of heat lost or 1.46 KW if water temp is set at 120°F, and thats not accounting for the pipe warm up on each draw.
 robin-hood
Joined: 12/2/2008
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Posted: 9/1/2011 2:23:07 AM
Regards my post #22 above. I made an error on KW for 20-ft of 1/2" pipe the KW should be 0.366 KW instead of 1.46

-----------------------------------
Matchlight
Yes you can combine instantaneous gas with storage tank, but you need a pump and aqua-stat for tank. The stat turns pump on and circulates flow through heater. This piping will all need insulation. Then you have some standby losses and electric consumption. Pump can be small Grundfos or Taco. One problem with the small instantaneous gas water heaters is inside tube fouling, from hard water deposits. This usually happens at lower flows. They even have flush kits with mild acid or vinegar to clean tubes. Whats the BTU rating on instantaneous heater?

Many people don't realize that they make condensing gas water heaters that are 95 to 97% efficient. The minimum burner size is usually 100,000 btu/hr and smallest tanks are usually 80 to 100 gallon. These are not cheap and cost about $3000 to $4500 to purchase plus installation. The numbers work well for people in colder climates that can also heat their homes off same water heater.
 Earthpuppy
Joined: 2/9/2008
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Posted: 9/1/2011 5:46:18 AM
I've been using a Bosch Aquastar tankless LP heater for 8 years without any problems..knock on wood. Paid $550 including venting and gas lines. It has a hydrostatic ignition, thus no pilot light to be concerned with.

Keeping a 55 gallon tank hot for occasional use is extremely wasteful, the the tankless option will pay for itself in short order. The Bosch units are made to last for a minimum of 20 years. While the Bosch gas units have gone up in price since then, the electric versions can be had for $350-500. There are other brands that sell for even less. Home Despot has a 240v PowerStar unit for $229. Since markups for appliances can approach 100% or so, shopping around or buying online cans snag you a decent deal.

I had iron water in my last abode with a 50 gallon tank heater. The maintenance was a royal pain, replacing heating elements once or twice a year, even after using whole house filters. I like the ease and dependability of my tankless unit. Thankful for tankless.
 matchlight
Joined: 1/31/2009
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Posted: 9/1/2011 5:29:42 PM
I can see you'd need a pump when there was no demand. The water in the tank would gradually cool off, and when it had dropped 5 degrees or whatever, the pump would send it through the heater until the tank had come back up to the set temperature.

When there was a demand, you wouldn't need the pump. The cold water could go to a into the heater and from there into the tank. The output to the demand would come from the tank as usual. I'm not sure--maybe someone knows if the modulating tankless heaters are set up to maintain a certain outlet temperature, by varying the burner output according to the volume and temperature of the inlet water.
 Earthpuppy
Joined: 2/9/2008
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Posted: 9/1/2011 6:09:37 PM
Tankless heaters are set up for flow. I run mine on a simple RV 12 volt pump. Flow rate hits the hydrostatic ignitor and it turns itself on. Add too much cold water and it can cycle off . It's really not that different than human relationships. Just learn what turns it on, and off, and adjust accordingly. If it seems like rocket science at that point, it's time to re-examine all things in life in general.
 Hozo
Joined: 8/1/2006
Msg: 18
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Posted: 9/1/2011 6:57:25 PM
I am guessing that all the OP wants to do is find out if he can save $20-$30/month by switching off his existing tank for periods of time. Since he can, I am sure he is not going to spend $500 installing a tankless unit complete with new heavy gauge wiring, pump, holding tank and corresponding additional breaker, for the same reason that I don't need to. We both can attain fairly generous savings being creative with our existing appliance by merely flipping a $10 breaker when needed.




About the only thing not specifically pointed out is the fact that all of these standard HWH have two 4.5KW elements as well as thermostat for each one. The beauty of the first T-stat at the top element is that it functions as the master T-stat. 4500 watts divided by 220 V = 20.454545 amps.
That's why almost every person out there with this type of standard HWH will find it connected to a 2 Pole 30 amp breaker in their panel box. The lower element is still waiting for it's turn and once the master T-stat becomes satisfied, a switch then engages the other half of the 220 and sends it to the slave T-stat Down Under.



When I switch the breaker on my COLD tank, BOTH elements are powered up & heating until temp is reached. You can plainly hear both top and bottom elements churning, roiling, hissing when on. I assume I am using 20 amperes per leg. Is that probably because all the water in the tank is cold?

When you turn on the hot tap, hot water flows out of the tank from the top, but at the same time cold water is taking its place, flowing into the tank at the bottom. It all works on upflow from the bottom. While in use, there can be several "layers" of water in your tank at varying tempertures.

Hot water rises, & cold water sinks, so while you are drawing hot from the top, the cold at the bottom is accumulating, which causes the bottom element to kick on.

I can turn on my COLD tank for only 5 minutes, and have a small amount(5 gallons or so) of fairly hot water to shower with. The top element heats a small amount of water at the top quickly, which is fairly close to the hot water outlet of the tank. This hot water exits the top of the tank and into your piping directly. The bottom element will take much longer to heat the remaining 30-40 gallons of cold water to temp, thus me running out of hot water after using 5 or so gallons with my 5 minute setup.

The bottom element on my old tank burned out, and I used it like that for over a year. The only drawback was you couldnt take a 20-30 minute shower. I ran out of hot water after 10 minutes. The only reason I installed a new tank was because the old one started leaking from the bottom. That is what gave me the idea of switching my new tank on only when needed.

If I felt ambitious, I could unwire the bottom element, mimicking my old tank, with the same results probably.
 shoulderlegs
Joined: 4/14/2005
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Posted: 9/1/2011 7:15:57 PM
"We're starting to stray a bit from the OP, but I am enjoying this. OP, do you have any other questions yet?"

Sawdust.... more to the point, do YOU have any questions for ME!?? Please ask them!

Hozo... you are quite correct; I just want to save some money on my monthly electric bill, and a tankless water doohickey is DEFINITELY not an option!
 shoulderlegs
Joined: 4/14/2005
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Posted: 9/1/2011 10:18:00 PM
Sorry about that!
Yeah... the HWT has a plug just above it that you can - obviously- unplug from the wall... it's a flat, grey wire about 3/4 inch wide.
 Hozo
Joined: 8/1/2006
Msg: 21
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Posted: 9/2/2011 6:17:48 AM

When I switch the breaker on my COLD tank, BOTH elements are powered up & heating until temp is reached. You can plainly hear both top and bottom elements churning, roiling, hissing when on. I assume I am using 20 amperes per leg?

Your assumption is incorrect. if both elements were on at the same time, and each element was rated at 4.5 KW, each leg would now be carrying close to 41 amps each. (Assuming a 220 volt source of course.) I have real doubts about you being able to hear both elements being on at the same time. In the mean time, if you're interested, there are ways to actually test and confirm your results.



Blimey, you are right, according to what you said, & what I also found online. Here is a cut & paste:


Both elements are never 'on' at same time unless tank is wired for other purpose (see owners manual). This is called 'non-simultaneous operation' since both elements are not 'on' at same time.

Either upper element is 'on' or lower element is 'on,' or both are off.


BUT...I switched my tank on again for about 30 seconds, and put an ear directly on BOTH covers of both upper & lower elements, and they both are making the obvious same very specific localised noise, top and bottom. You can actually hear them both without putting your ear up to them....just standing a few feet away they both are audible in my quiet basement. I am now curious, and unless I remove the covers and test with a voltmetre, I may never know!


Upper thermostat is main controller: it turns on upper element until top of tank reaches temperature, and then sends power to lower thermostat. Lower thermostat heats bottom of tank, and turns on and off to maintain tank temperature during standby hours when no hot water is being used.


This explains why my old tank with a burnt-out bottom element worked fine for a 10 minute shower. It may just be simpler to unwire the bottom element for people like me, or the OP, thus using about half the electricity as compared to the full dual element standby mode. If you only turn your tank on periodically & shut it off after a short time, it's the top element doing all the heating....the bottom element is never powered up using this practise.
 matchlight
Joined: 1/31/2009
Msg: 22
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Posted: 9/2/2011 10:22:32 AM
Thought someone might be interested in these wall-mounted boilers and combination units. The technology is amazing, but bring your wallet--they wouldn't make sense unless you were building a house or completely remodeling one.


http://www.triangletube.com/TriangleTubeProduct.aspx?CatID=1&PID=19
 robin-hood
Joined: 12/2/2008
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Posted: 9/2/2011 9:12:43 PM
Matchlight,

Saw this brand specified on a job the other day. They have a small tank inside on some models. About 95+% efficient with PVC intake and flue. All stainless steel heat exchangers, which basically eliminates corrosion, but weld spots can suffer fatigue cracks if not done properly. This little tank prevents the shot of cold associated with instantaneous.

http://www.navienamerica.com/product/ts_heater_02.aspx?skin=ts_heater

Located in Irvine,Ca. Price ?, but will guess the 200,000 model is $2000.
 matchlight
Joined: 1/31/2009
Msg: 24
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Posted: 9/3/2011 4:50:50 PM
^^^^^Looks like good stuff. I noticed the 10 to 1 turndown ratio on the burner--a lot higher than most of them. If you use them for radiant heating, that matters, because even at 20 Mbu, the burner will be switching off and on when the house just needs a little heating. More efficient to have a small flame on all the time. I guess they can only design the burner to run just so low for fear the flame will go out, but there may be something else that sets the lower limit.
 TooShadows
Joined: 9/26/2008
Msg: 25
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Posted: 9/4/2011 2:50:47 PM
This is an easy one. Just have a geo-thermal heating and cooling system installed. These can be set up to heat water as well and your hot water tank becomes simply a storage unit,as the water is continuously circulated back and forth while being heated for pennies a day. The geo-thermal system should only cost about $15-20,000,but think of all that free hot water.
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