Wiring a 120 volt Stenner to a 240 volt Timer

Billrector

Well-known member
Nov 3, 2013
118
Fort Worth, TX
#1
I have a similar situation to this one with a 120V Stenner (already purchased) and a 240V pump. Rather than do what has been suggested there, why can't you install a 240V relay that is normally open. When the pool pump is running, it will close the connection which can be a 120V circuit running the Stenner and a timer for the Stenner. When the Stenner timer AND the pool pump are on, the Stenner would run. When EITHER the pool pump or timer is off, the Stenner will not run.

Anyone know of a relay that could be used to do this?
 

n240sxguy

Well-known member
May 17, 2014
1,802
Benton, KY
#2
If you have 120v run to the pad, that is the ideal way to do it. You can find an ice cube relay just about anywhere. RadioShack, Amazon, eBay, and local electrical supply houses all have them. They are usually just a DPDT relay that slips into a base. Shouldn't be more than $15-20 with the base depending on the brand and store you find it at.


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danpik

TFP Guide
Jun 4, 2012
1,682
western NY
#5
There was some potentially dangerous information implied in the link in the first post. If you do not have a separate neutral wire provided in that 240 volt circuit then you can not, by code, derive a 120 volt circuit from it. The ground wire present can not and should not be used for return/neutral current. This potentially energizes every piece of metal in the circuit that is connected to the ground wire. It has been against codes for several code cycles now to have a 3 wire circuit for Electric dryers and ranges for this very reason.
 

Billrector

Well-known member
Nov 3, 2013
118
Fort Worth, TX
#6
There was some potentially dangerous information implied in the link in the first post. If you do not have a separate neutral wire provided in that 240 volt circuit then you can not, by code, derive a 120 volt circuit from it. The ground wire present can not and should not be used for return/neutral current. This potentially energizes every piece of metal in the circuit that is connected to the ground wire. It has been against codes for several code cycles now to have a 3 wire circuit for Electric dryers and ranges for this very reason.
Thanks for your input. I'd like to clarify what you are talking about. Into my pool/spa subpanel, I do have two two hot wires, a neutral and a ground. Obviously, all the 240V breakers only have two hot connections. The neutral is used because I have two 120V breakers within the subpanel. So, I would potentially take one hot wire off the pump breaker and combine that with the neutral to get 120V. Is this okay or is this what you are saying to avoid?

My preferred approach at this point is what n240sxguy recommended and that is to use a 240V relay connected to the pump breaker and have that switch a separate 120V circuit (powered off one of the two 120V breakers) for the Stenner pump.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#7
The really dangerous thing to do is to use the ground wire as a neutral when there isn't any neutral wire. I believe that is what dank was talking about.

Using a true neutral wire with one side of the output of a 240 volt breaker is not nearly as dangerous, though it is still not a good idea. If the breaker is a CGFI breaker, which is required by recent versions of the electrical code, it simply won't work.
 

danpik

TFP Guide
Jun 4, 2012
1,682
western NY
#8
If it is a true sub panel then there should be no problems as long as, what Jason brought up, there is no GFCI feeding it. Generally, if it is a 240 volt circuit on a GFCI, there will not be a neutral from the panel back to the main. This is because, the neutral is not needed for a 240 volt GFCI to work. In this case the GFCI reads the voltage differential between the two hot legs of the circuit and the pigtailed neutral from the breaker to the neutral bar is only for the test portion of the 240 volt GFCI. If you indeed have a 4 wire service feeding the sub panel then using the neutral to derive a 120 volt circuit is fine. In fact that is why one (neutral) would be there.
 

racket

In The Industry
Mar 8, 2011
441
#9
The really dangerous thing to do is to use the ground wire as a neutral when there isn't any neutral wire. I believe that is what dank was talking about.

Using a true neutral wire with one side of the output of a 240 volt breaker is not nearly as dangerous, though it is still not a good idea. If the breaker is a CGFI breaker, which is required by recent versions of the electrical code, it simply won't work.
It may work as long as the neutral is hooked into the GFCI breaker.... For instance portable spas often have many different voltage items that don't draw across both hot legs but will draw through one hot and neutral.