Really didn't know where else to ask but this group and being an electronics geek myself, I'm sure a fellow tinkerer out there may have some experience with this issue.
I've been thinking about a tankless water heater for my medium size, 2 bathroom home and actually after thinking about it, something I've never tried is putting a timer on my water heater. (It's electric).
Has anyone ever done this?
I can live with just having hot water available in the early morning and (maybe) evenings also and was wondering if I'd save enough to get close to what tankless effieciency would offer?
Maybe time both the AC going in and the thermostat as well, so it doesn't "try" to kick on?
I suppose I could get fancy and rig up a microcontroller and a he-man relay but you can buy the old style analog timer for about 30 bucks. (Intermatic I think?).
Two things. One, it takes a while to bring a tank of water up to temperature, so you might find that you have to turn it 'on' a few hours before you think you will need it. Also, remember you have dish washing, clothes washing, etc. during the day that you might need that hot water for.
Second, an electric hot water heater takes a good bit of current. It will take a heavy duty timer rated for permanent connect to turn it on and off.
I replaced an electric tank water heater with a tankless (EEmax... I'd have to look up the part number.) I had problems with the first one. They had a 'digital' circuit borad replacement, that had issues of it's own. But the current offering seems to be working fine. (~six months of operation so far.) (I need one with a thermostat on the output becasue my water is pre-heated in an outdoor furnace.)
The electric tank heater had a timer, so that it could be turned off, but I never used it. It's not clear it would save that much money. When are you going to turn it off, and how long does it take a tank full of luke warm water to heat up?
more I look into it, it may be a waste of time -- it looks like many of the newer tank heaters are very efficient and cycle on for very short periods of time, so the "start up" vs always on -- MAY be 6 to 1 etc.
starting to look at a smaller tankless -- I'm single so I don't know why a smaller tankless couldn't be used as a "whole house" unit.
I have a friend who did this some years ago. He did report a savings, he turned it off about 9 PM, and back on at about 4 AM... Also used a water heater jacket to help retain heat overnight. Whether it was cost effective, he never said--just said it was noticeable on the bill.
I've considered doing this myself, I do have a nice (mechanical) 240 timer setup with the ratings that will work (240 volts, 40 amp contacts), but I've never wired it in. It is on my 'someday' project list.
Are tankless heaters all that more efficient, or is it just the way they're usually plumbed? In our house the hot water took forever to make it to the kitchen (it's a long ranch style house), so we put a little 3-4 gallon heater under the kitchen sink. We get hot water instantly, instead of after filling the pipe with a tone of water (seemed like a gallon, but was probably more like 1/2 or so).
If I shave without taking a shower, I just go to the kitchen and fetch a pitcher of hot water.
I'm not sure that a well-insulated hot water heater, without circulation, is going to lose all that much heat during the day if you just refrain from turning on the taps.
You can test this -- some day when you're going to be away from home, turn off your hot water heater at the breaker box in the morning as you go out. Then when you get home, check the water to see how hot it is. If it's essentially the same temperature after 12 or 24 hours, then you're already spending money heating the water you actually use, and just putting a different heater in the same spot as the one you have isn't going to do much for you.
If you're bound and determined to do this, then call an electrical supply house -- if someone doesn't make a 220V timer, then you can get a contactor that's actuated by 110 and handles 220, and you can run it from a timer.
You'll need to do some homework, because if you don't have your terminology dead nuts on then the electrical supply house won't sell to you (they'll be envisioning burning buildings, and lawsuits). If you happen to be from out of the area you can use that -- when I lived in Massachusetts I'd go places and say "well, back in Oregon we called it an XYZ, but I'm not sure what you call it here". Often they'd then accept me as an expert and say "oh, here we call it a QRZ", and I'd remember that, yup, that's what they called it back in Oregon, long ago when I installed the only other one I'd ever touched.
You should also check your local building codes, both to make sure that you can do this at all, and to make sure that you are allowed to make the changes. Most jurisdictions in the US will at least want you to get it inspected, even if you're doing the work. I'm not going to stop you from making the changes if they aren't allowed -- but if you do make them against code it'll be a barrier to selling the house, and your insurance company could use it as an excuse to deny a claim in case of a fire. Having a building permit with all the right sign-offs pretty makes it much harder for the insurance company to duck their responsibility.
But I think that if you do anything, you should just change your water use habits. At worst, put a blanket on your hot water heater.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
Years ago, I installed a water heater timer like the one at Home Depot
formatting link
. I used it for several years without any noticable difference in my electric bill until I installed an insulation jacket around the heater. That made a much more noticable difference than the timer did. I figured the insulation paid for itself in less than a year, whereas I don't know if the timer ever paid for itself. Since both I and the wife worked all day, I had it set to trip off at 7AM and back on at 4PM, and back off at 10PM and back on at 5AM. As has been mentioned, if the water has cooled during the off time, then it has to be reheated when the timer switches on, so you're not really saving much, energy... just changing the times that it's being consumed. For my money, the insulation jackey is the real saver.
I think I may try this 13kw tankless Rheem at Home depot and use it as whole house -- only 234.00
It's just me in the house and the longest pipe run would only be 15 feet. (So, you wait through an initial 15 feet of cold water).
Can mount the heater in the basement which is typical basement temperature -- I bet it works out fine as long as I don't have the washing machine or anything else running while in the shower -- and I never do.
They are widely available - we had one in the house we've just sold - and make a lot of sense inplaces where the hot water is only going to be turned on briefly.
formatting link
I actually measured the time constant of my - tolerably well-insulated
- hot water tank in Cambridge. The time constant was about 36 hours, which is to say it would take 36 hours for its temperature to decay to
37% (e^-1) of the initial difference between the tank temperature and ambient.
Putting a timer on that tank would have saved us about $8 a year.
A timer is a waste of money on any tolerably well-insulated hot water tank.
I think that heaters at the point of use make sense: you're not paying to heat all the water in the pipes. But that means that tankless only makes sense it it's little, and at the point of use.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
In Phx where you have to cool the house 9 months a year it makes perfect sense to reduce the heat/energy input to the house which you then have to pump back out.
In a colder climate where you have to heat the house for 6 months, or more, per year it makes less economic sense.
The same argument applies to the payback of CF vs incandescent bulbs. All the promotional BS I've seen seems to completely ignore this. The greenies are just as guilty as the sellers/manufacturers. Art
Take the money you were thinking of spending on this and put it into pipe insulation, and possibly extra tank insulation (decent newer ones actually have enough from the factory, to the point that may not help much at all.) There's no point in turning off an electric tank type heater unless you are taking a week-long vacation.
Replacing an electric tanked with an electric tankless will save almost exactly nothing if you actually use the water any.
Barring a great alteration in the price of fuels, the other BIG savings easily available is shifting to gas or oil from electric. That does require some investment in getting the venting done when changing the water-heater, but it's less invasive (it used to be that you had to build a chimney) with new high-efficiency burners and direct-vent systems. If you have a lot of capital to put into it, geothermal heat pump electric can beat both of those (and heat your house as well) but it's godawfully expensive to get into.
The new electric hot water heaters that use a heat-pump (air-air type, inside the house) are a win all summer as they pump out cool air and use less electricity to heat water, and shift the load to your heating system (no win at all if electric, somewhat better with a typical "costs less than electric heat" fuel heating system) in winter, as they are still pumping out cool air.
If you have any sun exposure, solar hot water heating is a far better bang for the buck than solar electric panels are - as such, a much better place to start if you have any intentions along that line, or simply want to save money on hot water, even if you don't see yourself as "one of them solar nuts."
In PHX, if your air conditioning system is not already heating your hot water 9 months a year, you should get a better air conditioning contractor. The magic word is desuperheater. And in any climate, if your pipes are not insulated, you're wasting money.
Tankless systems are often used for whole of house installs here in Australia (where they are called intantaneous systems). Drop your water temp down to 45C / 110F, that will save $$ and still be practical.
So is everyone is agreement here? Water heater insulation jacket is much better than timer?? For an "average" household use - which I equate to mean: 2 or 3 morning showers, and the occasional dishwasher use at night.
If I had a clamp-on meter that would time-stamp, I could do the math. Believe it or not, ours is on a standard 240-volt wall switch (not a timer.) I've been thinking about a timer (just out of pure laziness, and the occasional forget-to-flip the switch -- but then, I'm too lazy to put the damn thing in, too.!!) However, an zippered or taped insulation jacket would be a breeze. Ten minutes top. (Even I could muster that much enthusiasm.) Our electric water heater only has it's internal insulation, which I suspect isnt' all that much. (?)
Tankless heaters with decadent American flow rates pretty well have to be gas-fired, because it takes too much energy to raise gpm of 20C water to 50-60C in real time.
OTOH, I've got a buddy who uses a 2.5gal point-of-use like one of these:
formatting link
He fires it up a bit before showering, turns it off, and showers comfortably. No waste, no thermal loss to speak of. If you're willing to settle for 'waiting a few minutes' rather than 'instantaneous,' everything gets easier.
I agree with Bill that a timer's a waste on a big heater. And a small heater heats up so quickly that you hardly need a timer, just a few minutes' warning.
Under a tenth of the price and a lot more effective. It increases the time between the heater coming on by keeping the bulk water warm.
They are cheap now and also very effective at finding a 10% saving on your electricity bill. All those wall warts for prehistoric modems that are still plugged in somewhere can add up. And you also find which handful devices consume a *lot* more on standby than you might reasonably expect - digital TVs are pretty bad in that respect.
Or an offcut of loft insulation will do the job if you have some to hand. DIY stores will sell you more expensive tailored versions for a hot water tank but the important thing is depth of insulation and a foil radiation barrier on the outside. If you are very tight on space the aluminised bubble wrap is only 1cm thick and surprisingly effective. Stick on LCD thermometers will let you see how much better.
It is an easy saving to make and you get hotter water for longer too.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.