Piezo gas cooktop disrupting elec. oven
VPayne
| Posted in Energy, Heating & Insulation on
I tapped one side of the oven supply at the junction box right before the oven to provide power for a gas cooktop piezo ignition circuit. One time out of ten the operation of the ignition circuit will cause the Whirpool oven to register a power failure and restart after clearing the clock and settings. Is there anything I could do to keep this from happening other than running a dedicated circuit like a capacitor? When I plug the cooktop into a extension cord from a wall outlet the problem never occurs.
Replies
A piezo electric device does not need any external electrial power.
Those are what are on many gas grills where you push a button which mechanically generates the spark.
Yours probably has an electronics powered spark. Does it continously spark or spark several times then it is electrically powered.
It sounds like you have an electric oven and tapped off the 120/240 that feeds that.
If the wires and breakers are properly size then you can tap that circuit to feed both and oven and cooktop. I don't believe that it is specifically called out, but it is implied that it is for ELECTRIC ovens and ELECTRIC cooktops.
But the installation instructions rule. I suspect that they call out a 15 or 20 amp circuit and you can get that by tapping off the oven circuit.
You need to a separate 120v circuit.
William the Geezer, the sequel to Billy the Kid - Shoe
Thanks,
So I have just an electronic ignition that sparks only when lighting the eye for as long as you have it in the initial position before moving it to the other positions once the flame is lit.I came off one side of the 240 40A electric oven circuit to power the gas cooktop at 120.So would say a separate circuit is required back to the box? Any idea why i am getting the intermediate faults from the oven electronics? Is the oven just too sensitive?
There might be a "defect" in the oven and/or poor design.Most electronic equipment is not tested to see if anything else interferes with it. But will be test for "common" problems and/or found by field testing or call backs.But if you call them the first thing that they will say is that is not properly wired and not look for any other problems.The code does allow for a 120 receptacle to be installed on the kitchen small appliance circuits (countertop) for gas stoves. Again I have not looked at the details of the code for seperate cooktops, but I would assume that it would be the same.After all the current require is very, very little.No need for a dedicated circuit, but a 120v 15 or 20 amp circuit.
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William the Geezer, the sequel to Billy the Kid - Shoe
Find one of those clamp-on chokes that is used for computer cables and clamp it around the feed to the cooktop.
But note that likely you're violating the install instructions for the cooktop (and hence violating code) because it's not protected with the proper sized breaker.
Why would the cooktop not be protected correctly? Wouldn't one side of a 240v 40a circuit just be a 120v 20a circuit. Is it a problem back at the breaker box where the 40a fuse is just two 20a fuses connected so that if one side needed to blow the other might not go? But wouldn't the fuse need to be designed for this for a fault in one line but not the other.I even ran a ground wire as it is an old house to properly wire the unit and have grounded the metal junction box. The instructions asked for a 120v 15a or 20a circuit. I am willing to try the choke idea. Are they very expensive?If I run a separate circuit it might very well have to be off the dedicated dishwasher circuit. I don't want to have the same problems with the power electronics there. Are there capacitors that can fit into a junction box and be pigtailed into the line?Edited 12/17/2008 9:19 am ET by VPayne
Edited 12/17/2008 9:20 am ET by VPayne
"Wouldn't one side of a 240v 40a circuit just be a 120v 20a circuit."No. That is common mistake.It is 120v 40 amps.The panel has two 40 amp fuses (or a 2 pole 40 amp breaker). Each leg can have a maximum load of 40 amps."By the way, is there now something else like a power electronics breaker in line with the oven supply, like a GFCI maybe?"Are you talking about within the oven? There would not need to be anything like that within the house wiring. But someone could have installed a 2 pole GFCI breaker.These are the snap on ferrite chokes.http://www.radioshack.com/product/index.jsp?productId=2103222
http://www.radioshack.com/product/index.jsp?productId=3012599&tab=summary
http://www.radioshack.com/product/index.jsp?productId=2996360The problem with this is that without a few thousand dollars in test equipment you don't have any idea of what the characteristic of this "noise" is.There are many componets that can be added to filter noise both at the source and at the oven. But they are all designed for mounting within the equipment.It is hard to SAFELY just mount a capacitor in the electric box and even then it may not be effective.
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William the Geezer, the sequel to Billy the Kid - Shoe
Thanks for clearing up several things regarding 40a versus 20a. I forgot about the wire being heavier for the oven circuit but I had just used the old oven wire so I didn't have to figure it.I think at this point I will just have to bring over another one of the kitchen circuits.
Edited 12/17/2008 11:01 am ET by VPayne
Since an electric range connects only to the 240V 40A circuit, but runs some 120V low amperage components like clock/timer, then would there be an on-board fuse or breaker at lower amperage to protect those smaller wires?
BruceT
Sometimes. Or sometimes the device is "internally protected". (Which is a back-handed way of saying that it will self-destruct gracefully.)
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
The only real reason for 120 in the past was for surface burner that had 2 elements and a 5 or 7 position switch that connected then in series or parallel and one or 2 across 240 or 120 to get the different heat ranges.Now days the oven light is the only thing that really needs 120.Now timers used to use 120. My guess is that they used the basic motors that where common in mechanical electric clocks. Otherwise it could have easy used 240 motors.But when was the last time you saw a new mechanical clock?The power supplies to operated the electronic controls could as well be made to work on 240 as to 120. Or even with the switching power supplies that are used 100 to 250 and the same components used in other countries.Now as to your question. Once past the connections it is all up the the UL or other standards listing. Same as you an plug in a lamp with a #18 zip cord into a 20 amp circuit.So I don't know what they do internally. It is possible that some do have a fuse. It is also possible that they have a fusable link.And it is also possible that they don't anything. The load is well know and won't be overload. The only other possibility is a fault and the design can be to limit any damage..
William the Geezer, the sequel to Billy the Kid - Shoe
Well, I guess that about covers the possibilities.Thanks,BruceT
without a few thousand dollars in test equipment
Aha, another good excuse to buy new tools!!
One can get a used Fluke123 scopemeter on ebay for about $400 these days, capable of deceiphering noise under 100 MHz.
> Wouldn't one side of a 240v 40a circuit just be a 120v 20a circuit.No, one side of a 240V 40A circuit is 120V 40A. Wiring the cooktop to the oven circuit leaves the cooktop improperly protected from overcurrent.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
The choke is a common computer item that any computer repair shop would likely have and might even give you for free. You want the type that comes in two halves and snaps around the wire.But of course the choke won't provide overcurrent protection.IMO it would be dangerous to attempt to use a capacitor to eliminate the interference. It would be hard to find one rated for use in this environment, and it would take me (an electrical engineer) probably an hour to figure out what size to use (counting the 45 minutes I'd need to brush up on my formulae). Someone without the backgound would risk picking the wrong size and creating a bigger hazard. (I've seen capacitors explode.)
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Edited 12/17/2008 3:19 pm by DanH
There may be a simple solution to your problem. You tapped off one of the leads of the 240V supply to the oven and now your sparker is interfering with oven electronics, right?
The electronic components of your oven are also running on 120 from one side of the 240V supply. If your sparker is interfering, I'd guess that it is tapped from the same side of the 240 as the oven controls. If that's the case, switching your tap to the other hot lead should effectively isolate your sparker from the oven electronics.
It's worth a try, anyway.
Please reply if the swap fixes it as the swap idea seems like a good idea
I thought about swapping the 120 tap to the other side to stay away from the control electronics and tried it earlier. After a test period of a few weeks I still had intermittent instances of the oven registering a power failure and resetting. I guess there is too much going on. By the way, is there now something else like a power electronics breaker in line with the oven supply, like a GFCI maybe? When I read the installation manual I got the hint that there was something there. Would this be tripped if the voltages are different between the two sides of the 240v circuit? I wouldn't think it should as there is the legal option to wire a electric cooktop (and presumably gas) to the oven circuit you just might want a 50a circuit.Edited 12/17/2008 9:30 am ET by VPayne
Edited 12/17/2008 9:31 am ET by VPayne