Need Electrical Engineering help

[Shaun @ Tru6]

So I guess I celebrated a little too early having the silkscreen dryer hooked up. I hope someone here can help troubleshoot this enough to I know what to order/replace.

The dryer works with 3 unique heating elements suspended over the conveyor belt. After getting it working, I found:

1. one heater worked close to or at spec (13 ohms)
2. one heater worked half as well (26 ohms)
3. one heater did (no continuity)

I took the heater that did not work, opened up the sheetmetal, dug down through the clay wadding and found the 2 leads were rusted away. I welded new metal contacts to the coils (very difficult), took the heating element board, laid it on top of the another (sheetmetal box), hooked it up and it worked, and worked great! Put it back in its sheetmetal box and laid that box back in the frame, didn't bother to bolt it in.

I took the half-efficiency heater and pretty much did the same thing. Went back, wired it up, and...

NONE of them work.

here's where I am at.

All three have continuity at 13 ohms across the two contacts

All three have 120V going to each lead

All three are stone cold


What am I missing? How can they not heat up if each lead/contact has 120V going to it and each has good continuity?

There is a temp controller that could be bad, but I don't understand how e- can be going to the heaters but they don't heat up. Do the sheetmetal boxes need to be bolted to the frame essentially grounding them?

The wiring diagram is basic. 230 comes in and goes to a mercury contactor. Temp control (basic dial) goes to the mercury contactor. Leads go from the MC to the control strip which goes to the leads, which have current.

One thing has changed, one of the three heater lights is now lit. According to the manual, "When no voltage is goingthrough the heater panel, the heater circuit light is on, thus the teh heater circuits lights will be on when the dryer is off. The heater circuit indicator light goes off when voltage is going through the heater and heat is being supplied."



Wasted the entire day today working on this, and yesterday was a bust with the water pump going on the 4Runner, so any help will be much appreciated.

[peppy]

Shaun I am no electrical engineer, but did you disconnect the leads before you checked the resistance on the heating elements.

[Shaun @ Tru6]

good question. yes, tried that

[billybek]

You have line voltage at the contact and wire feeding the elements, what do you have on the neutral side? Take your meter and check for voltage line to neutral and then to ground. Check then the neutral to ground.
If you find that you have power on the neutral side of the element to ground, then your problem is downstream of the elements.
Just re read your post.
Take your meter and read across the elements when they are powered, you should see the full voltage 230 vac.
Check your power supply and make sure that you have 230 vac.
I would suspect that there is a safety open keeping the elements from heating. (over temp or high limit) May be a fusible link.
Is there a wiring diagram?

[SLO-BOB]

Definitely not an EE question. Any good electrician can figure this out.

The heating elements should be connected in parallel to a voltage source. Therefore, whatever you did to the last element would have no influence on the other two.....probably. There may be some interlocks, but I seriously doubt it.

You say that the heaters each have 120 v going to them but no heat. You also say that 230v is going to the contactor and then to the heaters. So it sounds like the heating elements require 230 volts to work, correct? I also assume that there are two leads going to two connections on the heating element correct? If so, you need to measure the voltage across those two leads and not to ground. You should have 230 volts if I'm understanding your scenario.

The boxes should have nothing to do with the return path.

PROVISOS - THIS INFORMATION IS MEANT FOR INFORMATIONAL PURPOSES ONLY. I STRONGLY RECOMMEND THAT A LICENSED ELECTRICIAN PERFORM THIS WORK. I CAN NOT GUARANTEE THAT THE INFORMATION I HAVE GIVEN YOU IS ACCURATE FOR YOUR SPECIFIC APPLICATION, NOR DO I ACCEPT RESPONSIBILITY FOR FAILURE, CATASTROPHIC OR OTHERWISE.

[Gogar]

This is a silly question, but are ALL THREE heaters supposed to have the same resistance? Or are they supposed to get colder the further down the line they are?

[Shaun @ Tru6]

I did some more testing this morning and it may come down to a bad relay. there's a high capacity switching relay on the temperature controller board that, I believe, used to click (something did) when turning the temp higher. makes a lot of sense. When I pulled the relay, the base was wet and I'm guessing the capacitor gave up the ghost.

Before finding that, here's what I did.

There are three heating elements, I labeled I, II and II. The 2 leads going to each one were already labeled 1 and 2, 3 and 4, 5 and 6, respectively to I, II and III.

With the leads NOT CONNECTED, POWER ON:
I have continuity between the two terminals in each heater
For heater I, 120V connecting 1 and 2
N or G and 1: 46V
N or G and 2: 120V

For heater II, 75V connecting 3 and 4
N or G and 3: 10V
N or G and 4: 120V

For heater III, 79V connecting 5 and 6
N or G and 5: 13V
N or G and 6: 120V


With the leads CONNECTED, POWER ON:
For heater I, 0V connecting 1 and 2
G and 1: 120V
G and 2: 120V

For heater II, 0V connecting 3 and 4
G and 3: 120V
G and 4: 120V

For heater III, 0V connecting 5 and 6
G and 5: 120V
G and 6: 120V



Here's how the single phase install goes. There are 3 terminals and a ground

T1 is hot, T2 is neutral, T3 is hot, ground is ground.

T1-T2 and T2-T3 is 115V between each. T1-T3 is 230V.

The basic e- flow is:
T1 to a Mercury Contactor (each of the 3 black elements on the left of the control box)
Temperature controller to Mercury Contactor
MC to terminal strip
Terminal strip to heating element
T3 to terminal strip and then to heating element

Only wiring diagram I have


macro view


Terminals


Controller face


Controller wiring. note 1, 2 and 3 are mercury contactors. Circuit board closest to the center is the temp controller board. note that the black rectangle is the receptor for the relay.


Board close-up. The 3 wires, red, green and black w/ spade connectors at the lower left go to the dial on the controller face. The braided wire goes to a probe that is inserted in heating element I.


Wide angle of controller

[Kroggers]

Shaun, have you tried to bypass heater control circuits to feed voltage direct to the heaters to make sure they are working?

[Shaun @ Tru6]

I would Pål, but something tells me sparks will fly! I wanted to take an extension cord, cut it up, splice to one of the heaters and then plug it in to a 110V outlet to see what it does.


What is so discouraging about this was that I made real progress in getting this thing to work, then it dies with no signs why...nothing burned up on a board, smoke, etc.

[SLO-BOB]

Maybe I'm missing this, but you need to have everything together, turn it on, and check one heater, in this case term inals 5 & 6 -



Put the VOM (but really a "wiggy" would be my choice) across the leads 5 and 6 only, not at all to ground. Any reading other than 230v (approx) means the circuit is not being completed. This is the 1st place to start. I can walk you through the rest after you do this and tell me how much, if any, voltage you have.

PROVISOS - THIS INFORMATION IS MEANT FOR INFORMATIONAL PURPOSES ONLY. I STRONGLY RECOMMEND THAT A LICENSED ELECTRICIAN PERFORM THIS WORK. I CAN NOT GUARANTEE THAT THE INFORMATION I HAVE GIVEN YOU IS ACCURATE FOR YOUR SPECIFIC APPLICATION, NOR DO I ACCEPT RESPONSIBILITY FOR FAILURE, CATASTROPHIC OR OTHERWISE.

[SLO-BOB]

Originally Posted by Shaun 84 Targa

I wanted to take an extension cord, cut it up, splice to one of the heaters and then plug it in to a 110V outlet to see what it does.

I am under the impression the elements operate at 230 v. Am I missing some information?

PROVISOS - THIS INFORMATION IS MEANT FOR INFORMATIONAL PURPOSES ONLY. I STRONGLY RECOMMEND THAT A LICENSED ELECTRICIAN PERFORM THIS WORK. I CAN NOT GUARANTEE THAT THE INFORMATION I HAVE GIVEN YOU IS ACCURATE FOR YOUR SPECIFIC APPLICATION, NOR DO I ACCEPT RESPONSIBILITY FOR FAILURE, CATASTROPHIC OR OTHERWISE.

[Shaun @ Tru6]

Originally Posted by SLO-BOB

Maybe I'm missing this, but you need to have everything together, turn it on, and check one heater, in this case term inals 5 & 6 -



Put the VOM (but really a "wiggy" would be my choice) across the leads 5 and 6 only, not at all to ground. Any reading other than 230v (approx) means the circuit is not being completed. This is the 1st place to start. I can walk you through the rest after you do this and tell me how much, if any, voltage you have.

OK, I get .01V on I, .003V on II and .000V on III (5 and 6)

Yet I get continuity between those two terminals with the leads disconnected.

Historically, III worked the best and I haven't touched it. I didn't work at all and welded the terminal back to the coils inside. II worked weakly and I did the same. After I fixed I, I connected it up (the raw element), laid it on II and I and III worked beautifully.

After working on II, nothing works.

[Shaun @ Tru6]

Quick update. I get those same values when the relay is unplugged, so at a minimum, I have a bad relay on the temperature board. I think that's the culprit but I would love to SAFELY short the circuit without the temp board just to see if the heaters work at all.

[SLO-BOB]

provisos - this information is meant for informational purposes only. I strongly recommend that a licensed electrician perform this work. I can not guarantee that the information i have given you is accurate for your specific application, nor do i accept responsibility for failure, catastrophic or otherwise.

[Shaun @ Tru6]

Originally Posted by SLO-BOB

1. You should have 230v across the terminals T1 and T3 all the time. Do you?
Yes


2. If you do have voltage, manually override (M on my pic) the contactor to get voltage to the element terminal strip. Can you override the contactor ("M")? If so, do you have 230v across the terminals at the heating element terminal strip (on my pic).

So far I'm not confident that you are actually checking voltage across the terminals - are you? Describe your proceedure. BTW, you should be wearing leather gloves and safety glasses.

OK, on the M, each has 4 contacts.
T1 goes to the top
Just below that, there's a blue wire that connects in series to the temp controller
Just below that is a white wire that connects in series to the temp controller
Bottom is black and goes to strip.

I would like to take a wire and bypass the top and bottom of the M's.

here is some additional testing.

Top wire on M (T1) to:
T1: 0V
T2: 120
T3: 210 all of these are what you would expect

Blue wire to:
T1: 120V
T2: 0
T3: 120

White wire to:
T1: 120V
T2: 0
T3: 120

Bottom Black wire to:
T1: 210V
T2: 120
T3: 0

I'm testing simply by poking the spear leads of volt meter to each lead. When test 5 and 6, I can either poke the screws on the strip or the leads at the heating element.


Here's an interesting test. voltmeter leads at top and bottom of M's reads 210V.

no gloves or safety glasses. I'm hoping to fry completely actually and just be done with all of this.

[Shaun @ Tru6]

UPDATE

With a crude bridge between T1 and the strip contact for M for heater III, I donned the welding mask, rubber chem gloves and flipped the breaker.

III heated right up with 210 across 5 and 6.

So, do I have bad M's or I think more likely, bad temp controller, probably that relay was was wet at the base.

Thoughts?

Edit: I and II also work. can't tell you how happy I am about that! welding those coils together was something else.

[turbo6bar]

Sounds like your temp controller is not sending the signal to close the contactors. If you feel compelled to test the heater elements, just disconnect the leads, tie to pigtail of a power cord and plug them into a 110 outlet. That should make the element hot.

I have no idea what voltage the contactors use. Could be 24VAC as it looks like there's a transformer on the temperature controller.

[turbo6bar]

OK, your elements are fine. I would not blame the contactor (M), yet. You need to figure out how to get power to the contactors.

Shaun, without that relay in the temp controller, I doubt you'll get power to the contactors (blue and white wires).

When you're testing the contactors, put probes on the blue and white wires. If you get voltage there, you will know your temp controller is trying to close the relays.

[turbo6bar]

I also think it's the temp controller or relay on temp controller, because it would be odd for all three contactors/M to go bad simultaneously.

[Shaun @ Tru6]

nothing in between the blue and white, either across the Ms or at the temp controller board.