You are here:

Electrical Wiring in the Home/Residential, electric hot water heater with a countdown switch and DPC.


water heater wiring
water heater wiring  
Residential, electric hot water heater with a countdown switch and DPC.

I installed a Definite Purpose Connector (Square D = 8910DP32V02) to my electric hot water heater (residential) and control it with a countdown switch (Intermatic E1210W 120v 15amp). It ran for about 7 minutes and stopped. I canít figure out why.

The countdown switch has 4 wires; green, white and ground (ground running from the water heater box to the countdown switch) are wired together. Black on black-to the water heater box and red on white-to the water heater box.

The countdown switch, from the power supply Ė breaker side of the contactor Ė black wire to a 15 amp fuse (Fuse Holder, 15a, 250v and Fuse, 15A, MDA, 250VAC, PK 5) ĖĖ to the black wire coming from the countdown. The white wire from the countdown connected to the switch side of the connector. The opposite side of the connector white wire connected on the switch side of connector to the white side of the connector from the breaker.
I tied all the grounds together.

The water heater box, from the breaker white on left (upper right of the DPC in the picture) and black on right on the connector. Water heater same, but on opposite side of the contactor, white and black connected across from the breaker wires.

I have power going through the fuse so I ruled that out. I donít know how to test the switch because it gets its power from the controller and I donít know how to test the controller.

Like I said, it ran for about 7 minutes then stopped. The water in the heater is not up to temperature. When I went to the box I thought I could smell electricity, not burning but something. I thought it would be electricity running through new parts.

If I did the attachment correctly, it should be a picture of the box at the water heater. Top left is the breaker, bottom left the countdown switch, bottom right is the water heater, and on the bottom left in the back is the bussman fuse.

So where Iím at thinking wise, do I have a faulty countdown switch, faulty DPC, did I wire it incorrectly, did I wire it incorrectly and burn something out?

Thank you Will,

ANSWER: Randy,

Just following up,   have you been able to do more testing?   Find anything?  I worry when I am told about an electrical smell, so I wanted to know how you are doing,    if you want  we can go into this and with some more info,  maybe I can tell you how to test components,    but do not hesitate to drop me a note about anything     and I would like to know if you find the issue or need more help,     


If you had wired it wrong  I doubt it would have even come on,   

The drawing looks correct,   but you did not say what tripped or is everything still in place with no tripped breaker or tripped thermal anywhere?

Often times with these water heaters,  there is a voltage drop to the load,   wire size too small, the run too long,   cannot say if that is the issue,      but they can draw down power,   enough to start,  enough to run for a while and then some type of protective thermal or overload,  undervoltage or otherwise protection device or circuit trips out,  

Does your contactor have heaters/overloads?

Are they the correct size/setting?

The only thing that bothers me other than you have no hot water is this smell,   now I even think I smell sometimes when I am a bit over concerned but let's say you did smell something,

New should have nothing to do with smell,    if there is hot insulation, it will smell,   that is what people describe as electrical smell,  hot insulation, be it motor winding varnish, plastic insulation jackets so on,     

One cheap and dirty test,   power back up,   let it run and pay attention,  if it trips,   once it does,  kill the breaker,    make sure   then  feel or use a thermal gun   they are cheap at Radio Shack,    and see if you have a high resistance connection,      

It will show up as temperature comparing to the other connections,      

I don't read anything wrong with your connections or anything else,  fuse not blown,  breaker not tripped,      

Always possible something new from the box is faulty,    it happens all the times,  but if you have no idea how to test it,  then whomever sold it to you should,        

It is a fairly simple in line in series device,    

From my experience most who have problems with these types of hot water heaters is the voltage drop,    and if you have a volt meter  that will be easy to tell,  when you fire it up, before you see if trips again,      get a measurement at the heater, or as close as possible,   if the voltage is more than 10% lower than what the data plate calls for,  it is likely that is the issue,          

at the bottom here is my personal contact info,     try it again,   measure your voltage,  then look for some sort of high resistance [loose] connection,  

Recheck your feed size and length,   make sure you have enough wire size for the load,     and not too much of a run,         

From there  if voltage is good,   no hot connections,    then we have to look into testing individual components,    has a list of things to check based on the electrical problem  you might read through that site, as it is step by step    and I could write all that out, but it is already there and done very well,     

past all that,   if still no answers,  get back to me,   and this time send me a drawing of the connections, the photos are great,  good plan,  but I will need a diagram, even if it is scratched out on something,          

No smoke I take it,  so for now  we are cautious about the smell,    see anything,   concerned with anything shut it down,   

It is often borderline to get these type heaters in a home without having a dedicated circuit ahead of time,  and normally a huge one,        

But there will be an answer,     just take it step by step, do not try to wrap your head around the whole install at once,    piece by piece,    then let me know,    again my personal contact info is at the bottom    so feel free to contact me using here or whatever method suits you,        


---------- FOLLOW-UP ----------

If you look at my picture, on the DPC, on the top right you will see a white wire connected to the coil and power supply, giving me 120v. On the other side of the coil I have my switch connected and itís also connected to the power supply, another 120v.
After reading what you wrote and checking what I did, it looks like I connected 240v to the 120v coil and switch. I think the smell was the coil burning up. Your thoughts?

I think I should have had a separate supply 120v to power the switch/coil. At the switch, upstairs, I can pigtail 120v from the neighboring light switch. Your thoughts?
Or from one side (120v) of the 240v DPC power, follow me if you can, go to the fuse, out of the fuse connect the black wire from the switch and one side of the 120v coil, then the white wire from the switch to other side of the coil. Your thoughts?

I have another DPC and countdown switch ordered and it should be in this Friday. Hopefully Iíll have time this weekend.
Thank you Will.

110 for control voltage,  I read it as you did that by using one side of the 220  but yes the components need rate control voltage,    such as a 12 volt control voltage,     if you ran 220 to rated controls at 115  too much voltage,         but you are thinking right,   if just to test a separate control voltage supply is fine,      but it appeared from the one photo and your description you had the control on one side of line          let me know when the new components arrive   we might want to talk this over on the phone, no charge  it might help move things along    

I forgot your beginning comment,  sorry,  YES if you put 220 on a 115 rated coil you would get smell too much current and because many are potted no smoke,  it burns inside,   but not sure how you did that,   

any chance I can get a sketched drawing?  
About Electrical Wiring in the Home
This site answers questions related to home electrical wiring, home wiring, general electrical help,and other electrical questions related to aleternating current (AC). You can find help on the National Electical Code, home electrical issues, wiring electrical outlets, installing lighting, electrical grounding, and general electrical help for do-it-yourself projects not require an electrician. If you do not see your home electrical wiring question answered in this area then please ask your electrical wiring question here

Electrical Wiring in the Home

All Answers

Answers by Expert:

Ask Experts


Will Babbitt


Electrical issues of all types, wiring, control, appliances, components, specialty in Electric MOTOR or APPARATUS trouble shooting, electric motors, electrical problems, single phase, three phase, DC, capacitors, elevator MG-Sets, modifications, reverse engineering, VFD Drives, single to three phase convertors. Repair of most any electrical/mechanical/electronic apparatus, OEM, AC, DC, Industrial Applications, Three phase, single phase failure mode, determining the root cause of the equipment failure BEFORE failure repeats, Antique appliances, electric motors, fans, ceiling fans, base mount fans, poor equipment performance, Modifications, habitual failures, vibration, redesign, obsolete issues, collectible items restored, rewinding. Owner of EMR Repair Inc More information on electric motors, under Engineering/Motors Ask about any electrical or mechanical problems in the home, office, or even at your work. B2B or business to business CONSULTING I can do but it would be a much more complex issue, that would require a significant amount of time. from there we can discuss and begin work on about anything. Industrial electric motors, controls, troubleshooting, vibration, alignment, any type of industrial or commercial electric/electrcical equipment For the home owner, renter, apartment if you have odd things going on, describe to me, photos are normally very helpful, appliances, heating and air conditioning issues, light switches, installation, DIY PROJECTS FOR THOSE NOT EDUCATED IN ELECTRICAL, we can do some things, but for safety and sanity reasons, I may refer you to a local electrician, and help you find one, help you with pricing and even speak directly with anyone you hire if you have issues,


Over thirty years with a major repair and sales company, VP of Operations, and former owner of my own specialty repair shops, MEAR Services local to Kansas City Missouri EMR Repair Inc., located in Kansas City Missouri, 2014 sold both businesses to JCI Industries, Lee's Summit Missouri Evaluation and repair of electrical/mechanical apparatus. Electrical and mechanical repairs, trouble shooting including, vibration and balance issues. provides this service, and the huge costs to provide help on about any subject. They provide the servers, the people to vet the experts, costs that would be the same as operating a good sized business, They should be appreciated for what they do, the huge costs and the great help they provide for free, Electric motor questions, can be answered here but there is a dedicated category that has other experts to help and add to a solution. Other common questions, are noises in the walls, breakers tripping, devices not starting or shutting down for no apparent reason, smoke alarms buzzing, thermostat change outs, or sizing wire or needing information for a new project, but anything can be resolved, anything, with enough effort and patience, DIY, with electrical is possible, but in most cases the use of a simple ohm meter or volt meter is needed, they can be purchased at any hardware store for a few bucks. If you have smoke, or smell smoke, don't be writing me, call 911 the Fire Department has no problem looking for smoke smells, better then spraying water on a blazing fire. DO NOT GET CAUGHT INVESTIGATING AND TRAPPED IN A BASEMENT LOOKING FOR A BLOWER FAILING< As to the tip jar, it is up to you, it is appreciated, every expert spends out of pocket that I know, we spend on IP time, computer wear, printing documents, books, and of course our time, but if we prevent a $400 service call, we did well,

Former IBEW, EASA, IEEE, UL, ..............


10 plus years, various Technical Schools, followed by Industrial College Credit and non Credit Courses, electronics courses, experience in most any electrical apparatus, electric motors and generators, AC OR DC, fractional to above 5000HP, other electrical apparatus, slip rings, sleeve [plain] bearings, lubrication, identification-no data plate, control components, service and sales. I have continued night schools for decades, the list is extensive. I have been in the business of repairing most anything with wires or mechanical parts for decades, I have some helpful hints and directions you won't have to dig up. Or hopefully not have to pay a huge service call invoice to find.

Awards and Honors

Past/Present Clients
Federal Government, National Weather Service, NOAA, Commercial Power Plants, Major Vehicle Manufacturers, Printers, Other industrial and Commercial Businesses

©2017 All rights reserved.