Help me stop frying speed controllers

[Whatever]

I've been using Johnson Controls A419 15A SPDT thermostats for a few years now. I want to wire one up so I can toggle a fan full speed above the setpoint and controlled speed below the setpoint. Last time I tried I fried the controller. Obviously I don't know what I'm doing.

Here's the controller wired to two outlets...one always being active:

Here's the wiring diagram...if you can call it that:

Here's the internal wiring for a standard setup, it's blurry but I tried:

Now here's what I tried and fried the controller:

What I attempted to do was just switch the hot cause I figured ground and neutral are actually common. The grounds and neutrals on both outlets are jumpered, thus common, so figured I only needed to switch the hot to the fan so split the power cord.

Here's a pic of the power cord. On the other end is an old water pump I sacrificed.

I'm wondering if I can make this work with an SPDT thermostat? I tried to find a DPDT unit but could not as that would probably solve my problems. I also tried to find an off-the-shelf product that does what I want but could not find one so trying to create my own.

Any help or input is appreciated...thanx!

WHY CAN'T I UPLOAD PICS? I get an error message saying the post contains one or more URL's that need to be removed but why since they were in my gallery here???

 

[DIGITALHIPPY]

looks like a nice controller. are you sure that black cable is supposed to go from the white to the black??? i can c ur pics just have to look in the gallary

 

[Whatever]

Thanx DH for making the effort to look through my gallery...which for some reason I can't post...WTF is with this place? Anyway, couldn't get a quality pic but the left terminal block (3 terminals) is labeled 'AC INPUT' and left to right is 240V, COM, 120V. I think this is what you're asking about. For the 'COM' terminal I have the neutral (white) coming in from the main power cord and then another white going out to the neutral on the 2 outlets which are jumpered and common basically. Black, hot, goes into the right hand terminal and is jumpered to the right terminal block which then becomes switched (NO and NC). The right hand terminal block labeled 'OUTPUT' reads NC, C and NO. From here I run one wire each to one of the outlets and they are not jumpered/common. The C terminal is the input from the black jumper from the left terminal block. The black wires you see on the left and right sides of the right terminal block are the NO and NC...switched.

Normally I'd have two separate devices, whether 2 fans or a fan/AC combo or fan/heater combo switched run off this configuration.

Since a SPDT I'm basically switching the hot between the sockets. I have neutral jumpered/common between the sockets.

Anyway...hope you can follow this cause I really can't...lol.

 

[PharmaCan]

What you want to do is bypass the control whenever you want.

Take a jumper from your power (hot) BEFORE it goes to anything else, put in a switch then another jumper to the fan receptacle. Hook the controls up according to the mfgr's specifications. When you want the fan on full bore, turn on the switch. When you want the control to control the fan, turn off the switch.

PC

 

[Pharma Geddon]

It's easy enough to do what you want using a cheap relay.

Relay contacts A,B and C. AB making contact and C having no contact is how it comes out of the box. When the coil is energised then BC make contact and A has no contact.

Variac to A. Fan to B. Live/hot to C.

Solenoid coil, one side to neutral/common, the other side of the coil to the T/stat.

So the T/Stat flips the relay according to temperature.

 

[Whatever]

I'm posting the pics up as seems it now works just fine. For those that posted please see if anything else to add now. I'll look closer through the replies. I figured a relay would be the missing piece but not familiar with but I guess time to learn.

Here's the controller wired to two outlets...one always being active:


Here's the wiring diagram for a standard setup:


Here's the internal wiring for a standard setup, it's blurry but I tried:


Now here's what I tried and fried the controller:


Here's my professional...lol...powercord assembly with the old water pump out of view:

 

[DB2004]

Are you using a variable speed control for the fan. It's easy to wire up, full speed when setpoint is reached and variable when under setpoint. I've built several controllers like that. Let me know if you're using a speed controller.

Best Regards

DB

 

[Whatever]

Go ahead DB2004...tease me with that gizmo porn...lol. That's exactly what I'm trying to do. I still need to back through this thread and digest the input as I've been crazy busy the last few days. I'm in no hurry so no biggie.

Yes...the speed controller is variable.

Thanx y'all cause when it comes to wiring custom stuff like this I'm at a loss.

 

[DB2004]

You probably have the wiring down, it's the heatsink attached to the SCR on the speed controls circuit board. What happens is there is leak voltage through the metal tab on the SCR, and the SCR is attached to the heatsink. When you mount the speed controller, the heatsink is grounded to the metal gang box. The back of the SCR should be insulated from the metal heatsink. I have a few controllers burn out before I discovered the problem. Use a plastic, weatherproof gang box to mount the fan speed control to. If you'd like, I can build you a unit. If you are a DIYer, than the plastic gang box will solve the problem.

Best Regards

DB

 

[Whatever]

Hey DB...I worked in the electronics industry '80 to '85 so have a little background but still a wiring dork...lol. I was mainly quality control. Here's a pic of the inside of the solid state controller I most recently fried. It's in a plastic case already. I'm assuming the device you're talking about shows up clearly in the pic. It's attached to a metal plate where the actual knob is attached which doubles as a heatsink but the heat sink is not grounded. The ground on the input and output for the controller is common and goes no where else that I can see. It basically loops through the controller from the wall outlet to the controlled device. The heatsink is floating so don't know where any leakage would come from.

This time I blew a resistor. I tried something a bit different once and blew the surge suppressor. Anyway...I think the way to go for me is with a relay but just have to dive in and figure that out.

Thanx for the input y'all...time to play with some relays based on Pharma Geddon's input

Pharmacan...I want this to be automatically controlled by the thermostat and not manually. I'm guessing DPDT thermostat would be the most convenient solution but figuring out the relay thing is probably the ticket. The switch thing would work but not what I'm after.