Shut OFF water heater during peak power times

SteveQ

Active Member
I have enrolled in a "peak power billing" program being offered by my electric company. The program offers a lower rate during non peak times and a much higher rate during peak hours. I am using my home automation system to shut off many things during the peak hours of 3 to 7PM. I would like to shut off my electric water heater during this period. My well water is very cold and causes the water heater to turn ON whenever the hot water tap is opened. I was planning to use an HVAC 30 amp contactor to disconnect the water heater but I discovered this would require the contactor to be ON all the time except when I want the water heater OFF. (Contactors are normally open[ N/O ] and do not have normally closed contacts). Although I could use this approach, it would be a significant waste of energy to keep the contactor and the 24V transformer ON 85% of the year!

So I am looking for a way to shut OFF the water heater with a 220V/30 amp switching device that offers a normally closed position.
Any ideas?

Steve Q
 
Contactors exist that use "Latch" and "Unlatch" coils, and require only a half second pulse to activate them. You could get one with a spare 'pole' and use that to provide a 12 volt monitor on the actual contact's position also.

I could try to get more info if you would like. I also don't think these will be cheap, and the pulse probably takes 24 volt (control industry standard) over 12 volts.
 
Contactors exist that use "Latch" and "Unlatch" coils, and require only a half second pulse to activate them. You could get one with a spare 'pole' and use that to provide a 12 volt monitor on the actual contact's position also.

I could try to get more info if you would like. I also don't think these will be cheap, and the pulse probably takes 24 volt (control industry standard) over 12 volts.

Thanks, I have tried to find a latching relay, but I can't seem to find anything that will handle 30A. I'm sure there is something out there, I just can't seem to find it. Google brings up lots of stuff but sorting through it is difficult.

I found a device made by ELK. http://www.smarthomeusa.com/ShopByManufact.../Item/ELK-9200/ But the info provided
does not say if it uses a latching relay or a NO or NC connection. Does anybody Know?

Steve Q
 
The "relay in a box" is a pretty cool device. I use several of them as part of a data logging solution to log when my water well pump runs, when my water softener regens, when my master irrigation valve is open, when my home standby genset runs, etc., with more on the way. I like them because they are completely self contained. I am also using some of their track-mount relays for other control devices I'm building where the complete device/system is enclosed in a box.

Ira
 
The "relay in a box" is a pretty cool device. I use several of them as part of a data logging solution to log when my water well pump runs, when my water softener regens, when my master irrigation valve is open, when my home standby genset runs, etc., with more on the way. I like them because they are completely self contained. I am also using some of their track-mount relays for other control devices I'm building where the complete device/system is enclosed in a box.

Ira

Ira,

Thanks, for the "relay in a box" info. These are indeed an elegant solution when a relay is needed. I wish I knew about these a year ago when I set up my electric baseboard heater control system!

It looks like the RIB24P30 will work perfectly!!! Thanks

BTW, which relay are you using to log your well pump, and how do you get the signal to your computer? I have the coil of a radioshack 275-217 relay in parallel with my pump motor, and the contact closure triggers a DS10A which sends a wireless signal to Homeseer.

Steve Q
 
The "relay in a box" is a pretty cool device. I use several of them as part of a data logging solution to log when my water well pump runs, when my water softener regens, when my master irrigation valve is open, when my home standby genset runs, etc., with more on the way. I like them because they are completely self contained. I am also using some of their track-mount relays for other control devices I'm building where the complete device/system is enclosed in a box.

Ira

Ira,

Thanks, for the "relay in a box" info. These are indeed an elegant solution when a relay is needed. I wish I knew about these a year ago when I set up my electric baseboard heater control system!

It looks like the RIB24P30 will work perfectly!!! Thanks

BTW, which relay are you using to log your well pump, and how do you get the signal to your computer? I have the coil of a radioshack 275-217 relay in parallel with my pump motor, and the contact closure triggers a DS10A which sends a wireless signal to Homeseer.

Steve Q

Hopefully you won't mind if I go off topic for just a moment (If you would prefer, I could start another topic). I think you are using Homeseer too, correct? Are you using Homeseer to control your heat? What are you using to gather temp data? If you are using HS do you have any redundant/fail safe built in? I am (hopefully) purchasing a LARGE property that has electric in floor radiant heat and I'd like to have much finer control of it.

Thanks,
Nick

P.s. Ira, thanks for the link!
 
BSR and Ira,

The "relay in a box" is really a great looking product. I have a question: the "relay in a box" appears to be designed to be mounted to an existing electrical box. I would like to mount it to my main electrical panel. But the 24V coil wires would be inside the main box. It is my understanding that it is a code violation to have low voltage wiring inside the main panel??

Steve Q
 
I have enrolled in a "peak power billing" program being offered by my electric company. The program offers a lower rate during non peak times and a much higher rate during peak hours. I am using my home automation system to shut off many things during the peak hours of 3 to 7PM. I would like to shut off my electric water heater during this period. My well water is very cold and causes the water heater to turn ON whenever the hot water tap is opened. I was planning to use an HVAC 30 amp contactor to disconnect the water heater but I discovered this would require the contactor to be ON all the time except when I want the water heater OFF. (Contactors are normally open[ N/O ] and do not have normally closed contacts). Although I could use this approach, it would be a significant waste of energy to keep the contactor and the 24V transformer ON 85% of the year!

So I am looking for a way to shut OFF the water heater with a 220V/30 amp switching device that offers a normally closed position.
Any ideas?

Steve Q

I'm not overly familiar with electric tank heaters, but might it be possible to adjust the temperature swing threshold so that the tank does not come on if you are just using a couple of gallons for hand washing (as Im sure you are restricting activities like showering and washing clothes and dishes to off peak. If it would work it would obviously be much cheaper (although not nearly as foolproof) than installing a relay.

Just a thought,
Nick
 
Nick, My baseboard heater control is pretty simple. My objective is to better manage the amount of electricity I use. I consider it to be fail safe because I have not modified any of the original design. All of the baseboard heaters contain thermostats and these thermostats control the temperature. The system is adjusted to maintain the desided room temperature when the system is ON. I use Homeseer to control contactors which turn the heaters ON/OFF just like a setback thermostat. Typically they come ON at 6AM, OFF during the day, ON again in the evening, then OFF at midnight. This approach has worked very well for me for the past 2 winters. My only concern would be a failure of a contactor or Homeseer which would prevent the heat from coming ON when I am away from home. I have 1-wire temperature sensors throughout the house which would alert me via email if the temperature drops too low. You can find additional info on the Homeseer board. I did multiple posts about my setup.

Steve Q
 
BTW, which relay are you using to log your well pump, and how do you get the signal to your computer? I have the coil of a radioshack 275-217 relay in parallel with my pump motor, and the contact closure triggers a DS10A which sends a wireless signal to Homeseer.

Steve Q

I use a RIBU1S relay in a box to "monitor" the pump. I tapped into one of the hot wires coming off of the pump side of the pump controller. That wire plus a neutral and ground go to a wall outlet mounted next to the pump controller. I have a wall wart plugged into the wall outlet that controls the coil in the RIBU1S. Note that the RIBU1S coil allows 120Vac so I could have gone directly from the controller to the RIBU1S, but I like working with low voltage.

On the contact side of the RIBU1S, I have a state/event logger from onsetcomp.com (the U11-01). The U11 logs state changes (dry contact opens/closes) as long as the new state lasts at least a second. Since my well will stay on for close to a minute whenever it comes on, the one second requirement is not a problem. Also, the U11 can track up to three separate state change devices/relays, so this particular U11 tracks well pump on/off, irrigation master valve on/off, and water softener regen. I have another U11 that logs things dealing with my electrical system.

The U11 data logger is a USB device. I haven't set up the communications side of things yet, but I have prototyped it and it works. The U11 works with a device called a USB server by Keyspan (part of Tripp-Lite). The USB server is used to communicate with the data logger via a LAN. So the USB server plugs into the LAN on one side, and has four USB ports. Once the data logger is on the LAN, I can use the onsetcomp.com software to get the data from the logger to my PC via a "readout", which is basically just dumping the data from the data logger to the PC. The software has various options for graphing the data, automatic readouts, etc. It also has alarm/event notification capabilities but that part doesn't support the U11, e.g., you can't trigger an alarm if the data logger sees a state change. For me, that's the biggest downside of the software. To get around it, I will probably do frequent readouts to a CSV file, then interrogate the file with CQC. The alarm/event notification stuff works with most of their other sensors, e.g., temp, humidity, voltage, current, etc. I have spoken with the manufacturer about enhancing the software in a couple of relatively easy ways that would make their loggers/software great for HA stuff, but they haven't committed to any of the enhancements. I don't think they see HA as a big market because they haven't heard such requirements from HA folks. I just got a sensor from them yesterday that will be used to monitor the voltage of the battery used by a standby genset. In this case, I will be able to get an email notification when the battery drops too low. I will use CQC to process the email and trigger an alarm.

I still like the loggers. They are small (half the size of a deck of cards), easy to use, seem to be very reliable, relatively cheap (around $40 per sensor if you buy a multichannel logger), and I like the idea of a self-contained device doing that kind of stuff.

The long term goal is to feed everything into CQC and display it visually like an industrial process control monitor with animated graphics to show the pump running, water flowing, etc. I've got a couple of flow switches to monitor water flow on/off thru a couple of main pipes (one to the house, one to the irrigation system). I've built a box that contains a pump protector that will shut off power to the pump if rapid cycling or current problems are detected. The box also contains a pump relay that will shut off the pump if a future ELK M1 detects a water leak. I have additional "monitor relays in the box that detect when the pump protector or leak relay shuts off power, or if the circuit breaker trips. I hope to have a few pressure sensors somewhere in the system, but I haven't found a reasonable solution for that yet. If I can get a graphics artist to do the animated PNG files on the cheap, it should really look good. I should be able to detect things like the pump running but no water being used (not good, unless it's just topping off the pressure tank), power shut off from the circuit breaker, pump protector, or leak detector, water softener regens, etc.

Ira
 
BSR and Ira,

The "relay in a box" is really a great looking product. I have a question: the "relay in a box" appears to be designed to be mounted to an existing electrical box. I would like to mount it to my main electrical panel. But the 24V coil wires would be inside the main box. It is my understanding that it is a code violation to have low voltage wiring inside the main panel??

Steve Q

The enclosed RIB's are made to be mounted pretty much anywhere that you have the room (and that code allows). Mine are simply screwed to a piece of plywood that is nailed on the wall.

Ira
 
I used to have an electric tank. Tried various things to improve the power use. Just make sure that your "off" period is long enough to make it worth while, as a setback is generally better then an "OFF".

That's why when the wife and I upgraded (before we moved :-( ), we went NG tankless. WELL WORTH it. I WISH we didn't install it in the last house and took it with us, then replaced the NG tank in this house. Power bill went down by $80+ / mo. Just make sure it's a large enough unit to handle the load in your house.

--Dan
 
BSR and Ira,

The "relay in a box" is really a great looking product. I have a question: the "relay in a box" appears to be designed to be mounted to an existing electrical box. I would like to mount it to my main electrical panel. But the 24V coil wires would be inside the main box. It is my understanding that it is a code violation to have low voltage wiring inside the main panel??

Steve Q
Steve;

I believe that as long as the wires to the low voltage are rated the same as any high voltage they could become exposed to you will be ok. FYI, I'm not an expert in code. :)
 
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