I have a friend who just moved to the US from the UK. He went from a Victorian house with a gas (I think) tankless heating system to a modern apartment with an electric water heater tank; a new situation for him. He is responsible for the apartment utility bills.
He is frugal by nature and is used to having his domestic hot water system on a timer. I doubt it would be practical to put a timer on the apartment's water heater for the time he'll be there (and the apartment management might not like the modification), but he has asked me whether he should turn off the water heater when he leaves for work, and I wasn't sure of the answer.
My first thought was that he won't save much electricity -- it's not especially hot water (set to child-safe temps by management, I assume) and it's in an under-stair closet near the center of the building, so it's not leaking a lot of heat to cold outdoors -- I think it might be served well enough by wrapping the tank in an insulating blanket and wrapping the short exposed length of pipe.
But I also began to wonder whether a circuit-breaker switch is designed to hold up being switched on and off a couple of times a day, every day. Any trouble liable to result from him using the circuit breaker to turn off the water heater on a daily basis?
It may end up costing him more to overcome the temperature swings than to just leave it hot. It is also false economy to cool and heat some units and subject them to expansion and contraction over time, although the swings are minimal compared to a boiler.
Using the breaker as a switch is not a good idea either. It servers a purpose and it was designed to be a protection device, not a switch. Yes, I've seen it done often in industrial setting where breakers do control lighting.
The added insulation may help, especially if it is an older unit. The newer ones are more efficient.
We turned off lights with circuit breakers daily at the bookstore where I worked all the way through college. No problems.
I'd encourage your friend to try this for a month and then try leaving it on for a month and compare, though. I doubt he'll save much money turning it off, and it may even be more expensive.
There are switch rated breakers available from most manufactures. Required for switching loads since I think 1999 NEC. It would probably be cheaper and safer to go to Lowes and by their water heater time clock. Absolutely the least expensive I could find ~$35. This time clock needs an neutral to work and only switches one leg. I installed mine last February and no problems since. Remove it when he leaves
The amount of energy he will save is trivial and the circuit breaker will wear out unless (and this is unlikely) it is made to be used as a switch.
Bad idea.
I used to do it weekly on my cottage water heater, but then I put a real switch on it. Costs about $15 if there is enough slack in the wiring. (I ended up rewiring the whole circuit because I found out they used undersized wire!)
You are dead wrong about that. Basic physics dictates it will be cheaper to turn the heater off. But the difference will probably be trivial. No, I will not argue physics with you; if it is not obvious to you, you don't know enough to grasp it. (though I will give you a hint; heat loss is proportional to the difference in temperature)
That's another issue. I can think of several ways an electric water heater can fail. I suppose temperature cycling might be one. But operating time at full temperature might be another. (Hot water is more reactive than cold water.)
But in this case, the capital expense is the landlord's but the operating expense is the tenants.
That is nonsense. The water heater will always use less electricity if you let it cool down. Admittedly, the difference might be irrelevantly small. Think about it this way: If the unit is being kept hot, it needs to use energy to overcome the leakage of energy. This leakage is probably heating the house or basement around the water heater. But if you let it cool down, it will always leak less energy. Admittedly, if you let it cool down, you will eventually (when you heat it back up) have to use a lot of energy at once to bring it back up to temperature; but still less than if you had kept it at higher temperature.
Remember: In temperature swings, there is no friction. Getting the heater back up to temperature costs as much energy as the heater released when the temperature went down. Where did the heater release the energy to? Into the leakage - while the power was off. If we had kept the heater on, we would have had to pay for leakage. But there was less leakage (due to the lower temperature as the heater cooled down), so we have a small net gain.
There is an interesting counter-argument: It could be that the water heater is effectively heating the house. So if you let it cool down, then the house will get colder, which will then cause you to require more heating to keep the house comfortable. If the house heating were electrical, and you had a perfect thermostat on the house, this additional expense would exactly cancel the saving at the water heater. With other forms of heating, and in particular in warm weather, this can go either way.
True, but maybe irrelevant (there are other effects that counteract this effect - for example it doesn't corrode as fast as when it is cold, and the thermostat doesn't have to switch off and on as often while the heater is off). Can't tell whether this is a good or a bad effect.
Some breakers are rates as switches. Some are not. Some are rated to switch only resistive loads, while some are rated also for inductive loads (which may or may not include lighting loads, looking at fluorescents). Look at the Square D catalog (just as an example), and you will find a wide variety of breakers.
The garden-variety breakers installed in residences are TYPICALLY BUT NOT ALWAYS rated for switching duty. But two-pole (or 240V breakers) are TYPICALLY NOT rated for switching duty. Again, for example an look at the Square D catalog, and look for HOM120 breaker (a garden-variety 20A single-pole circuit breaker, the cheapest one you can get from Square D). The footnotes to it say:
a UL Listed as SWD (switching duty) rated. Suitable for switching 120 Vac fluorescent lighting loads. b UL Listed as HACR type for use with air conditioning, heating and refrigeration equipment having motor group combinations and marked for use with HACR type circuit breakers.
The 2-pole 30A breaker (which is what one would typically use for a water heater) does NOT have footnote A.
This is EXCELLENT advice. We put a "heater blanket" (special pre-made encapsulated fiberglas insulation) around our heater (which was admittedly outdoors), and it saved about $10 per month.
We've gone through 2 sets of breakers in my church in 20 years by using them as switches ... thanks Mr. Architect. Now there are switch rated breakers installed ... time will tell. BTW, the breakers were replaced because they would run real hot and then trip. Each 20A breaker has an
I presume you want to start with two equal sized wooden buckets filled to the same level, one with hot water and the other with cold, set outside, no covers on 'em, on a day where the air temperature is below
32F. Right?
The wood provides some insulation between the cold air and the water, delaying heat loss through that path. The hot water will evaporate faster than the cold and leave the "hot" bucket with less water in it.
If things are tweaked right, you can find starting water temperatures and an air temperature which will result in the water remaining in the "hot" bucket freezing first.
Now, pray tell, where are you going with this? The fellow's water heater isn't open to the air, so evaporation won't be a factor.
OK, so I admit it, in nearly all cases cold water will freeze faster. Look at the limiting case: Take some water that is just about frozen (say it is at 0.001 degrees C, and yes I know that the freezing point of garden-variety water is not exactly 0 degrees). This water will freeze very quickly.
But there is a case where hot water will actually freeze first. This is one of the homework problems in "The Flying Circuis of Physics". I think it only works if you use an open cup of water with insulated sides, cool it with very cold air, and make sure there is strong air flow across the surface of the water (or something like this, look it up in the book, it was about 20 years ago that I read this). I think the trick to reproducing this at home is to use an otherwise empty frost-free freezer.
If I remember right (and this is a big if), I think it has to do with evaporation: The hot water will evaporate very quickly in this situation. So by the time you get to near freezing, there is a lot less water left, and at that point the somewhat empty cup (formerly full of hot water) will actually win over the full cup (which started out as cold water). I think this also doesn't work if you start with really hot and really cold water (then the really cold water will actually win the race); it works better with really hot and lukewarm water.
There are other tricks you can play. For example, put the water into an aluminum pan, and put both pans down on a non-frost-free freezer. In this case the hot one might freeze first. Why? Because it melted through the ice underneath, and the aluminum pan ended being in contact with the cold pipes in the shelf, whereas the cold water pan sat on top of ice (a pretty good insulator). This trick only works because non-frost-free freezers typically are covered in thick layers of ice.
There is even tricks you can play with density of water and layering, causing warmer water to hide somewhere (in a layer of water, I think it requires having part of the water below 4deg C, where the density inverts), thereby delaying the freezing because the cold can't get to it as fast.
I run all stop signs without causing problems. That proves stop signs can be ignored. You have violated a basic principle. Just because circuit breakers work as switched in one place does not mean it is acceptable everywhere. Do you know that those bookstore circuit breakers are specially designed to be switched? You should know such facts - the underlying theory - before posting.
If one cannot answer the question based both on the specifications (theoretical knowledge) and practical experience (experimental knowledge), then one does not have an answer. Experimentally I have proved that stop signs can be ignored. Given these two above requirements, can we say I have sufficient information to promote running stop signs? Obviously not.
Circuit breakers, like all switches, have life expectancy numbers and other parameters. The questi> We turned off lights with circuit breakers daily at the bookstore where
The breakers are pretty old Federal Pacific (I remember because my house had FP breakers once upon a time), and I'm guessing they're not rated as switches, so I'll dissuade him from that approach. I suspect the apartment management would disapprove of my tinkering with the wiring to the water heater (though we did ask about changing out an unattractive light fixture), and I don't recall it having much slack.
I think I'll wait until he gets some real winter weather before I mention that leaving the water heater on may be warming his apartment slightly -- he left near-freezing weather in the UK and arrived to record highs in the nineties, and is worried his air conditioning bill will be ruinous.
I'll just suggest an insulating blanket and will take him some leftover pipe insulation.
If the circuit breaker is rated "SWD" (switch duty), it is designed to be used as a switch as well as a breaker. If it is rated "FLD" (fluorescent duty?) it is further rated to be used as a switch for lighting circuits with an inductive load.
An SWD breaker would be just fine for switching a water heater. I just looked at my breaker panel and the 30A 2-pole breaker for the clothes dryer is SWD listed. The 60A 2-pole breaker is not SWD listed, it is HACR listed, which I haven't looked up to see what it means (probably has something to do with heating and air conditioning circuits)
Notice how I avoided the part about whether switching the water heater was a good idea.
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