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Old 05-30-2012, 12:57 PM   #1
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Automatic Power Switch to Appliances


I've recently placed an under-sink water heater in my kitchen but the only place to power it is already being used by the dishwasher. This outlet is on a 15 amp breaker and when both appliances are on it goes over 15 amps and shuts everything off.

The water heater turns on automatically whenever it needs to heat up the water in the tank. I don't need to have power to the water heater all the time. It can run only when the dishwasher is off. What I'm looking for is an automatic switch that will deliver power to the water heater only when the dishwasher is drawing no power and keep the total power to under 15 amps.

Is there such a device available for purchase? Is there another option that I should consider?

Thanks for your time.

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Old 05-30-2012, 01:09 PM   #2
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Automatic Power Switch to Appliances


Install a new circuit for the WH.

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Old 05-30-2012, 02:06 PM   #3
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Automatic Power Switch to Appliances


Some of those point of use water heater require more than a 15A circuit on their own. You will need to look at the specs and see what is actually required and then install a new circuit and receptacle for the water heater (as rj stated above).
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Old 05-30-2012, 02:28 PM   #4
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Automatic Power Switch to Appliances


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Originally Posted by travisintrouble View Post
Is there such a device available for purchase? Is there another option that I should consider?

You can do what you are asking but it requires an expensive current sense relay and some knowledge of control systems to install. You would sense current to dishwasher and when you see current draw you would disable (open relay) to heater. I think it would be easier to run a new line from the panel.... But what you are asking is technically feasible.


http://www.patriot-supply.com/produc...item.cfm/31969
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Old 05-30-2012, 02:33 PM   #5
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Automatic Power Switch to Appliances


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Originally Posted by k_buz View Post
Some of those point of use water heater require more than a 15A circuit on their own. You will need to look at the specs and see what is actually required and then install a new circuit and receptacle for the water heater (as rj stated above).
It's not a big one. This model states that it takes 12 amps. It works fine when it's alone on this 15 amp breaker.
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Old 05-30-2012, 02:49 PM   #6
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Automatic Power Switch to Appliances


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Originally Posted by curiousB View Post
You can do what you are asking but it requires an expensive current sense relay and some knowledge of control systems to install. You would sense current to dishwasher and when you see current draw you would disable (open relay) to heater. I think it would be easier to run a new line from the panel.... But what you are asking is technically feasible.


http://www.patriot-supply.com/produc...item.cfm/31969
This is exactly what I'm looking for. Something simple and affordable.

THANK YOU curiousB! I don't think I would have found this on my own.

Last edited by travisintrouble; 05-30-2012 at 02:51 PM.
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Old 05-30-2012, 02:54 PM   #7
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Automatic Power Switch to Appliances


Doesn't your DW use the hot water from the tankless heater? Where does it get it's hot water from?

In the long run, you would be better off with adding a new ckt. Putting in the relay is a bandaid at best.
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Old 05-30-2012, 03:00 PM   #8
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Doesn't your DW use the hot water from the tankless heater? Where does it get it's hot water from?

In the long run, you would be better off with adding a new ckt. Putting in the relay is a bandaid at best.
The DW uses hot water from the main(gas) hot water heater on the other side of the house. It's a long way over there and so it took a very long time to get hot water to the kitchen sink. To fix this we installed this smaller heater directly under the sink for near instant hot water. Also, the under-sink heater has a small 1.5 gal tank on it so it can take hot water from there when it has no power.

I understand this is a bandaid. However, it's one I'm comfortable with.
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Old 05-30-2012, 03:43 PM   #9
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Automatic Power Switch to Appliances


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Originally Posted by travisintrouble View Post
The DW uses hot water from the main(gas) hot water heater on the other side of the house. It's a long way over there and so it took a very long time to get hot water to the kitchen sink. To fix this we installed this smaller heater directly under the sink for near instant hot water. Also, the under-sink heater has a small 1.5 gal tank on it so it can take hot water from there when it has no power.

I understand this is a bandaid. However, it's one I'm comfortable with.
Sounds like my house. I'm trying to decide if I use a tankless or go with a water circulating system.

Just out of curiosity....what size is your hot water pipe going to your kitchen?
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Old 05-30-2012, 03:57 PM   #10
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Sounds like my house. I'm trying to decide if I use a tankless or go with a water circulating system.

Just out of curiosity....what size is your hot water pipe going to your kitchen?
It's 3/4" and it's got to go something like 50-60' before it gets to the kitchen sink.
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Old 05-30-2012, 04:07 PM   #11
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It's 3/4" and it's got to go something like 50-60' before it gets to the kitchen sink.
I'm in the middle of a 2-story addition to my house right now...I'm getting ready to move the gas hot water heater which is next to my kitchen to the rear of the house where it will be about 30' (by pipe) closer to most of the demand....

Hence, my kitchen will end up being about 50' (of pipe) from the water heater...
The point where I will T off the hot water supply to go to the kitchen is going to be about 30' or so of pipe. Existing pipe is 3/4".

So I did some calculations...that 3/4" pipe holds about 1.45 gallons of water....so that means I have to turn on my tap and run out about one and a half gallons of water before I get hot water....

If I change that pipe to 1/2"...the volume drops to 0.645 gallons....or, more than half the volume with the 3/4"....

This translates to droping the time to less than half....

Since the only items using water are the sink and dishwasher...going to a 1/2" line is not going to have any real impact on flow....

I will most likely be replacing that section of pipe this weekend....
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Old 05-30-2012, 04:23 PM   #12
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Automatic Power Switch to Appliances


You can do it for a few bucks with a relay.
http://www.hosfelt.com/contents/en-us/d117.html

The relay coil needs to be 120 vac and powered off the DW just downstream of the DW controller
and the NC relay contacts control the WH and they are rated for the WH load, 1A or so.

Last edited by Yoyizit; 05-30-2012 at 04:29 PM.
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Old 05-30-2012, 05:17 PM   #13
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Automatic Power Switch to Appliances


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Originally Posted by Yoyizit View Post
You can do it for a few bucks with a relay.
http://www.hosfelt.com/contents/en-us/d117.html

The relay coil needs to be 120 vac and powered off the DW just downstream of the DW controller
and the NC relay contacts control the WH and they are rated for the WH load, 1A or so.
I considered this route before posting and I'll likely roll my own solution using something like this if the RIBX doesn't work out. The big problem is it's been about 15 years since my last EE class in college and so it would take a lot longer than it should. Thanks for the link and the advice.

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