DIY water-heater timer

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
  • Hope everyone has a wonderful and warm Thanksgiving!
  • Super Cedar firestarters 30% discount Use code Hearth2024 Click here
Status
Not open for further replies.
RustyShackleford

RustyShackleford

Minister of Fire
Hearth Supporter
Jan 6, 2009
1,395
NC
Awhile back, in order to save electricity, particularly peak-hour electricity, I bought a water-heater timer, like this one:

http://www.amazon.com/dp/B00004W4XI/ref=pe_385040_30332200_pe_309540_26725410_item

It worked fine for awhile, but it has recently gotten quite noisy, so much so that it's annoying in the house even though it's in the crawlspace. Intermatic doesn't really stand behind the product that well - my argument, that it started getting noisy before the warranty expired a few months ago, fell on deaf ears - and they offered only to sell me a new motor for $20 or advice to spray in some WD40 or silicon grease (which doesn't seem to have helped much).

So I've decided to make a DIY one. The back-end will be a DPDT power relay like this one:

http://www.automationdirect.com/adc...en-Style,_40A_(AD-PR40_Series)/AD-PR40-2C-12D

Double-pole because I think it's best to de-energize both legs of the 240vac supply, and double-throw so that I can choose to have the thing "normally off" or "normally on". I'll put the relay in the crawlspace, where the timer now is. I chose the part with a 12vdc coil (many other options are available) so that I can have low-voltage wiring coming from the relay to a controller in the house. I'll probably wire the relay as normally-off, so if anything disturbs the 12vdc signal from the controller, the water heater will still function.

I'm now trying to figure out the controller design. Simplest case would be one of those cheap plug-in lamp timers, with a 12vdc wall-wart plugged into it. Having the thing accessible in the house will be nice, because I can: over-ride the "off" times if I need to use a lot of hot water during peak hours (house guests, etc); turn the water heater completely off for vacations; easily reset things after power outages (I live in one of the 3rd-world'ish parts of our country); etc - without having to crawl into the back of the crawlspace each time.

Thoughts on this, particularly how to do the controller ?
 
Why do them call 'em relay timers, I wonder (since they don't necessarily need to be driving a relay) ? I guess they have a relay built in to them ? It'd be cool to find one with 12vdc output - to drive the coil on the big 40A relay directly - but I guess having a wall-wart in between is no big thing, probably better than getting the one with 120vac coil and having to run Romex to it.
 
Last edited:
semipro said:
The relay (contactor) I used would trigger on the 120VAC from the wall timer.
Click to expand...
Oh yeah, I have a very similar timer to control my landscape lighting; but it's "astronomical", meaning it automtically adjusts the turn-on time according to when the sun sets.

I am torn over whether to get the version of that relay with a 120vac (or 240vac) coil or the 12vdc coil. The latter has the advantage that I don't need to run Romex down to the relay. If I had easy access to a place to put a switch box for a timer like yours, I'd buy the 120vac version in a New-York minute. Instead, I could use this:

http://www.amazon.com/Amico-Digital...d=1428081167&sr=8-2&keywords=12v+weekly+timer

... which has horrifyingly poor documentation, but apparently can be powered by the same 12vdc source that would be switched on its way to the relay. So I can mount it anywhere and run speaker wire (or whatever) down to the relay. The only rub is, I have to connect it to 12vdc from somewhere, probably a wall-wart.

I'm also wondering what's a good box to enclose the relay; it's got to be enclosed like any electrical connection.
 
RustyShackleford said:
Oh yeah, I have a very similar timer to control my landscape lighting; but it's "astronomical", meaning it automtically adjusts the turn-on time according to when the sun sets.

I am torn over whether to get the version of that relay with a 120vac (or 240vac) coil or the 12vdc coil. The latter has the advantage that I don't need to run Romex down to the relay. If I had easy access to a place to put a switch box for a timer like yours, I'd buy the 120vac version in a New-York minute. Instead, I could use this:

http://www.amazon.com/Amico-Digital-Power-Programmable-Switch/dp/B008999RYY/ref=sr_1_2?ie=UTF8&qid=1428081167&sr=8-2&keywords=12v weekly timer

... which has horrifyingly poor documentation, but apparently can be powered by the same 12vdc source that would be switched on its way to the relay. So I can mount it anywhere and run speaker wire (or whatever) down to the relay. The only rub is, I have to connect it to 12vdc from somewhere, probably a wall-wart.

I'm also wondering what's a good box to enclose the relay; it's got to be enclosed like any electrical connection.
Click to expand...
I guess you could convert the timer's 120vac output to 12vdc at the wall timer (wall wart?) and then use low voltage wiring, rather than romex, between that and your relay.
 
semipro said:
I guess you could convert the timer's 120vac output to 12vdc at the wall timer (wall wart?) and then use low voltage wiring, rather than romex, between that and your relay.
Click to expand...
That's probably the way to go. Unless I want to make it cleaner by putting in a box and running 120vac on Romex down to the relay - but what's the point really ?
 
Why dc? why not a doorbell transformer timer pluged into the wall timer. Would eliminate the need of a rectifier.
I'd also look at a contactor rather than a relay, it will be enclosed and have the option of an auxillary contact that could be normally open or normally closed. The aux then can be wired from the contacts on the waterheater back thru the aux and to the coil of the contactor, this would allo the contactor to stay in whatever state it need to be in when heating, allowing the heating cycle to finish and then not switching the relay/contactor under load. Not switching under load really isn't a problem but it will extend the contactor life.
Also, is the breaker box in a better location than the crawl space, you could place the assembly right along side the breaker box.

google search normally closed 40 amp contactor give's you a number of options.
 
  • Like
Reactions: ewdudley
johninwi said:
Why dc? why not a doorbell transformer timer pluged into the wall timer. Would eliminate the need of a rectifier.
Click to expand...
If I use a wall-wart, that's pretty simple, and provides DC. The coil only requires 1/2 amp, max. They do have a version with a 24vac coil though.
I'd also look at a contactor rather than a relay, it will be enclosed ...
Click to expand...
If I need some kind of enclosure for the relay anyhow, how does that help ? It looks like those still have exposed terminals, so the things needs to be enclosed, no ?
The aux then can be wired from the contacts on the waterheater back thru the aux and to the coil of the contactor, this would allow the contactor to stay in whatever state it need to be in when heating, allowing the heating cycle to finish and then not switching the relay/contactor under load.
Click to expand...
I see the point, but I'm not following how it'd be wired at all. Can you explain more ?
Not switching under load really isn't a problem but it will extend the contactor life.
Click to expand...
I thought about that. The spec (for the Automation Direct part) shows 50,000 operations. That comes out to almost 70 years, doing two operations per day (one on and one off) so I think I'm ok, if I understand correctly (that the spec is under full load).
Also, is the breaker box in a better location than the crawl space, you could place the assembly right along side the breaker box.
Click to expand...
There is actually a small subpanel in the crawlspace, driven by a 50 amp breaker in the main box, thinking I'd want to add a small water heater for the kitchen later (it's so far away that hot water takes forever). I don't think I want to switch the entire 50 amps. Instead, I thought maybe the relay would fit in the subpanel box (not in one of the breaker positions), if that's kosher, and it'd be cleaner 'cause I wouldn't need another enclosure.
 
Last edited:
Had to google the wall wart, assumed wallwart to be slang for a wallmart product. Learned someting new, it's a standard wall plug in power supply ;em

I spoke without thinking it thru, sorry about that, you were planing to turn off and on the wallwart and fire the relay, simple.

It can be done but will means more wiring, you'll need a small relay at the heater attached to the element. It would turn on with the heater. Add a second wallwart that is always on and it run to the relay at the heater and back to the control relay, this would keep the control relay energized till the heater t-stat turns off. It's really not worth the extra work, heater will be cool when it turns back on anyway.

RustyShackleford said:
If I need some kind of enclosure for the relay anyhow, how does that help ? It looks like those still have exposed terminals, so the things needs to be enclosed, no ?
Click to expand...
As far as the box goes, i'd agree, either should be in an encloser, the drawback to the open frame relay you had linked to is that it may need a greater clearance to the box cover since it's conductors are not sheilded in any way. I use that style relay at work, we had a few on the shelf that had a plastic cover, the cover caught my eye just because they were unusual, i'll look for a partnumber on it.

The relay you linked won't fail because of the contacts wearing out, it will most likely fail from the movable contact mounts becoming sloppy and where the moveable's meet with the stationary, the moveable's will spreadout and fail to connect, long before that happens it may need cleaning, a dollar bill or paper works well if not pitted, and if it gets pitted it can be cleaned up with emerycloth, and i doupt you'll ever see pitting.
 
johninwi said:
Had to google the wall wart...
Click to expand...
Sorry, I should've explained. Yeah, ubiquitous, I probably have at least one just lying around that would do the job. The only real issue is whether to have a 120vac timer with the wall-wart plugged into it, or the wall-wart plugged into an outlet and driving a 12vdc timer (like I linked is post #5). Probably doesn't really matter. Maybe I'll decide to hardwire the whole thing though, run Romex to the relay and get the version with a 120vac coil.
...keep the control relay energized till the heater t-stat turns off. It's really not worth the extra work, heater will be cool when it turns back on anyway.
Click to expand...
I thought the main point was to keep the relay from switching when the water-heater is drawing full current, thereby preserving the contacts ?
i'll look for a partnumber on it.
Click to expand...
No worries. Looks like that kind tends to be more expensive than the < $20 one I linked above, and I'll have an enclosure with plenty of clearance, probably metallic (since I doubt a plastic one would have mounting points for the relay and it's not ok to have metal screws exiting the box), and of course it'll be grounded.
The relay you linked won't fail because of the contacts wearing out, it will most likely fail from the movable contact mounts becoming sloppy ... i doupt you'll ever see pitting.
Click to expand...
Hopefully the 50,000 operation rating is at least close to valid.
 
RustyShackleford said:
I thought the main point was to keep the relay from switching when the water-heater is drawing full current, thereby preserving the contacts ?
Click to expand...
There are benifits, but every relay and contactor has a wiping or sliding action as the contacts make and break, it helps keep them clean. This wipe will also cause it's own wear, in time you'll see a dust collecting that's the color of the contact's.

The 50,000 cycle's should be easy to reach, like you said, it'll cycle twice a day. It will outlast you and i and by the time it fails you'll have long forgotten what you had built.

I wouldn't worry about the opening under load or wearing out the relay, i have lots of these at work and they are all opened under load, some the loads are high enough that the arcing has turned the movable contact blue in a short time and the relay will function for years. In the unlikely case of the contact having sustained arcing you'd need the same relay with a magnetic blowout, it's just a magnet stood up between the contacts. The arcing creates an ion field and the magnet blows it out, ac rarely requires it, it's really only used on large dc coils.
 
johninwi said:
I wouldn't worry about the opening under load or wearing out the relay ... In the unlikely case of the contact having sustained arcing you'd need the same relay with a magnetic blowout...
Click to expand...
I shan't worry about contact degradation, but that magnetic blowout is interesting. What about a capacitor on the contacts, like in an old-fashioned car ignition system ? I guess that only works for DC.

Now just trying to figure out if I should use a normally-closed or normally-open relay. The latter seems more natural (water-heater is on when relay coil energized) and it's only 4 watts; but the water-heater should be off for only 4-5 hour periods (my peak-billing hours, though I might leave it off for additional night-time hours), so it seems more straightforward to program those, implying I want normally-closed. Question: those weekly timers that fit in a switch box, what happens if you select "on" or "off" manually and then it hits one of its programmed on/off times - does it just stay in the on or off state you manually commanded ? I'd like to be able to turn the thing off and have it stay off, like when leaving for vacation; if I used normally-open, I could just cut off the power the coil completely, instead.

P.S. Thanks for sticking with me on this, John, and good luck Monday night !
 
The shunts i've used have been on the coil side, think of a generator, every time a coil is deenergized it becomes a generator and kick a spike back into the circuit. Computer boards hate it, causes all sorts of electric noise in the lowvoltage dc the computer likes.
As for a capacitor on the contacts, wouldn't worry untill i'd seen an arc when the relay changes state. It would need to be a very sustained arc to shorten the relay life also and ac won't systain the arc.
As for setting it up NC or NO, i could run myself in circles trying to decide which is best. Initially, i'd do NC, that way if it fails i still get a hot shower. When it's all proven then you'll need a multiday timer to swap in place of the daily timer for vacation.

If your looking for a group of engineers try here, they'll certainly have a number of options we've not considered.
http://www.electronicspoint.com/
 
Yeah, I'm definitely going in circles on the NC vs. NO question. Making me want to not integrate the timer into a switch box - which would be cleaner - and instead something that plugs in (a plugin timer driving a wall-wart, or a wall-wart driving a 12v timer) - so I can easily override to always-on (for lots of house guests) or always-off (for vacation), by simply unplugging everything , or leaving the timer out of the loop.

Thanks for the link on that EE forum. The only other one I've tried, eng-tips, is the most unbelievably tight-assed internet forum I've ever seen.
 
What got me hooked on the EE forum was a guy had a treadmill that the board had fried, he posted pics and the forum guys disected the functions of the board and had the OP test it. After some weeks and many pages they got it running again.

Rusty and SP, you've both done this control of your electric hot water heater. Does it really make a noticable difference in the bill? Thinking i need to get my butt out of the chair and do some wiring.
 
johninwi said:
Rusty and SP, you've both done this control of your electric hot water heater. Does it really make a noticable difference in the bill? Thinking i need to get my butt out of the chair and do some wiring.
Click to expand...
I have to admit I don't know. Not too long after I installed the timer I replaced the electrical resistance water heater with Geospring heat pump WH and disabled the timer. It didn't make sense to use it with Geospring.
 
johninwi said:
Rusty and SP, you've both done this control of your electric hot water heater. Does it really make a noticable difference in the bill?
Click to expand...
Hard to say if it makes a difference in the overall number of kilowatt-hours I use each month. But, the reason I installed my mechanical water-heater timer (and am thinking of upgrading, per this thread) is that I am on a peak-billing (aka. time of day) rate plan.

This means I pay about half the normal cents-per-kwh rate most of the time, but during peak hours, I pay about thee times the normal rate (or 6 times the off-peak rate); this is basically weekday mornings in the winter and weekday afternoons in the summer. It works well with my somewhat abnormal diurnal cycle (sleeping roughly 2-3am 'til 11-12am); in winter I am asleep during peak hours, and in summer, I like to sleep cold, so the house is chilly enough when I wake up to stay comfortable 'til peak ends at 6pm.

Anyhow, I haven't measured it directly, but having the water-heater turned off during those thrice-as-expensive peak hours is undoubtably saving me money. Of course, I also labor under the perhaps self-righteous illusion that I am doing a good thing, socially, by limiting my peak usage.
 
30 amp 2 pole single throw relay rated for 30 amps at up to 300 volts ac
http://controlscentral.com/eCatalog...Default.aspx?gclid=CLT39pGN6MQCFccdgQodix0AuQ

Control it with a normal plug in timer
http://www.amazon.com/GE-24-Hour-Mechanical-Grounded-Outlet/dp/B0035GF8NA/ref=sr_1_7?ie=UTF8&qid=1428544076&sr=8-7&keywords=light timer

Mount it on the side of a 4" square box with cover, run a lamp cord to your timer and done. Simple easy.

If you still want to use your wall wart to power the relay they make them with a 12 or 24volt coil
 
So I decided to go with this relay:

http://www.automationdirect.com/adc...en-Style,_40A_(AD-PR40_Series)/AD-PR40-2C-12D

... 40 amp contacts, DPDT so I can wire it up as NC (so the controller will specify when I want the water-heater off), and 12v coil.

And control it with this widget:

http://www.amazon.com/gp/product/B008999RYY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

...which is a nifty little unit, $6+, easy to program, versatile.

Now my only question is if it's ok to put the relay in the little subpanel in the crawlspace - it has room, but wonder if that's kosher. Only reason is to save cost of separate enclosure, as there's no standard box that's big enough (the relay is 2" high and needs a little clearance, of course).
 
Got this thing working - it's great. I ended up putting the relay in a small metal box next to the water-heater, then ran the 12v control wire up to the timer thingy (which is driven by a 12vdc wall "wart"), in a convenient location in the laundry room:

1. No need to crawl into crawlspace and reset time after power outages.
2. No need to crawl into crawlspace and change time for DST begin/end.
3. No need to crawl into crawlspace and change "off" times when peak-rate period changes.
4. Not necessary to turn water-heater off on weekend days (to avoid peak-rate hours, at least).
5. Able to add additional "off" periods (in addition to peak-rate hours), mainly in the middle of the night.
6. Easy to disable water-heater during trips.
7. Easy to over-ride off times when necessary.
7. No creaking noise from motor in old timer.

Total cost was roughly the same a I paid for the crappy old mechanical one: relay w/ shipping $25, box via Amazon prime $15, control gadget via Amazon Prime $7.
 
Nice thread. I'm considering a WH timer for a different reason, which is to provide power only during daylight hours -- because I have solar PV and this way I will maximize use of the power I otherwise would dump into the grid, thereby reducing use of electricity generated by coal, the primary fuel source for our utility. There will be no effect on our electric bill. I'm doing the same thing for our basement dehumidifier, using a mechanical timer switch I had in my "useful" junk box.

A way to actually substantially reduce your electric use for hot water is a super insulated hot water heater. I did this and the result was a 50% reduction in use of electricity for hot water for my wife and me. [URL="https://www.hearth.com/talk/threads/hot-water-thinking-of-going-electric.20296/#post-294798"]hot water[/URL]
 
  • Like
Reactions: semipro
Status
Not open for further replies.

Similar threads

P
Indirect Water Heater - Quick Install question
Replies
1
Views
1K
The Boiler Room - Wood Boilers and Furnaces
maple1
maple1
ToltingColtAcres
Alternative to Thermguard
Replies
1
Views
2K
DIY and General non-hearth advice
peakbagger
P
P
  • Locked
Hooking up the hot water heater after 15 years
Replies
3
Views
1K
The Green Room
DBoon
DBoon
Mr A
  • Locked
Water Heater Timer?
Replies
28
Views
6K
The Green Room
BoilerMan
BoilerMan
webbie
  • Locked
Installed kickspace heater off of gas hot water heater
Replies
3
Views
3K
The Hearth Room - Wood Stoves and Fireplaces
elkimmeg
E
Top Bottom