Rational cpc 201 heating element problem

[ectofix]

vtech wrote:

 

Hi, I’m in hands with a Rational cpc201. The heating elements won’t kick in as they should. Fans and display starts as normal after turning the unit on. I see that the on / off switch is missing a connection, does anyone know where this is supposed to be connected? Part number for plug/cable would have also been very helpful. Thank you.

 

 

 

CPCs?  I maintain five of them.

 

The pictures were helpful. A SERIAL NUMBER would’ve been nice too.

 

The CPC ovens went through MANY changes from 1997 until 2004.  From looking at your pictures, your oven was made prior to 10/99 (No IQT controls).  So..probably an original version “A” oven (there were four versions).

 

You said HEATING ELEMENTS, so it’s electric heat.

 

I’m at home, so don’t have access to one presently.  Perusing the internet, it appears that the connector you referenced with an ARROW comes like that installed on a new control board.  Probably just a jumper plug with no wires to it.  If you don’t see some correlating wire harness laying in there without a plug on them, then don’t worry about it.

 

The nature of your problem is way too broad to give you an answer to what your problem is.  Could be any number of things causing it.  You offered no results of any tests you might have performed to troubleshoot the problem.  Could be anything from an erroneous temp setting, a bad temp probe, a loose control connection at a contactor/solid-state relay, a critical electrical cable burned off behind the side panel…or a list of other things.  Ya never know until you see it.

 

If troubleshooting electrical problems is not within your capabilities, then call a service company.  Those ovens are very complex in their operation.  Although the actual cause to the oven’s problem may be simple, knowledge of the oven’s overall system operation…along with skilled use of test equipment and experience in troubleshooting electricity – are key skills that are required for effectively resolving your problem.

 

Doing a proper repair is kinda important too.

[bush]

As I see it, your on/off pushbutton switches have been replaced with a rotary aftermarket control. Nevertheless, if it powers on your combi, that’s great.  For the elements to be energized, the controller needs to send a D.C. voltage to the solid state relays, to complete the circuit to the elements.  These relays are prone to failure, you will notice a change in design when you order the OEM replacement. (part# 40.00.453P).  Make sure the mounting surface is clean, and remember to tighten these relays securely to the heatsink. 

[vtech]

Thanks for all the information! Much appreciated! . The serial number is: E21CA98071414.
 I have been an electrician for about 4 years now and I see this project is a bit outside my expertise, but i like it!. I have checked continuity on the heating elements and they seem fine. Checked all wires for damage, found some bad ones but that didn’t fix the problem. Checked all connectors and fuses. When going into diagnostic mode I am supposed to press key “5” and select the time 11:11 in time display at the same time, release key “5” and then pressing it again for function test.  It will not let me select time when pressing “5”. If I hold down the time button on the other hand, everything shuts off and the display changes between the real time and “001” if that means something. When the dry heating and time is set, the timer does not count down and I can’t hear any contactor switching on. No voltage through A1/B2 on relay which goes to the heating element as you foresaw. But there is no voltage differential on the controller that goes to relays when switching on/off heating, could the problem be here? Or would it be possible that all the relays have failed?  

 

[ectofix]

AH…good eye, bush.  I didn’t see that rotary switch up there.

 

I guess that was cheaper than replacing the whole board just to replace the OEM DPST push button switch that’s part of the board.

[fixbear]

One should also have heat sink compound on hand for them.

[bush]

I agree, I’ve used it also when the heatsink has some pitting or other irregularities.  These CPC combis will usually tear thru these relays because of failing elements in the steam generator.  I’ve considered placing metal oxide varistors across the terminals in an effort to protect them, but ended up having better results from adding a 3 pole varistor block that Rational offered as an upgrade.  When the last CPC unit in my territory finally is replaced I will celebrate!  The SCC versions are much more service friendly than the CPC or CM-P versions.

[bush]

The diagnostic and function modes on these old units are frustrating to say the least.  But a word about these  solid state relays, think of them as a SPDT relay. You need power to enter at the common and from there it can be switched momentarily to the steam elements or momentarily to the hot air elements.  When proper temperatures have been reached there is no voltage output at all from the relay.  You may even experience low ampdraw from these relays when they are beginning to fail.  They are not cheap, and yes there have been times I had to replace all of them at once.    Good luck, you’ll fix it !

[bush]

Sometimes a picture is worth a thousand words!

[ectofix]

I see the other guys posted while I was typing.  I’ll put this here anyway:

 

Great enthusiasm for stepping up to the challenge.  I like that.

 

When you say key “5”, are you referring to how it’s numbered on a Service Reference chart?  That’s the button labelled PROG/START?

 

Do you have an operators manual?

 

Do you happen to have your hands on a training manual too?

 

A schematic?

 

Just wondering.

 

DISCLAIMER:  Although I do have five CPCs, I’ve never encountered your particular problem.  Heck, I have a fleet of older C-line ovens and even more of the newer SCCs, too.  Their control boards are all different.  Doing a function test on the CPCs isn’t exactly straightforward, so I might’ve only tried it ONCE several years ago when I absolutely had to.  Otherwise, I can function test the newer ovens with my eyes closed (not really)

 

As for an initial search for a problem, I would’ve initially done all of what you did (wires, fuses, connectors/connections).  I’ve found faulty board connections more than once that was the root to resolving a problem once I correct it. 

 

FWIW, The board on the control panel is primary just the user interface.

Of those stacked boards BEHIND the control panel

The top one is the CPU.  It does all the sensing. The bigger one behind it is the I/O board.  It receives the various input voltages and direct that to wherever it’s designated to go throughout all three boards.  Of course, it energizes everything, depending on operational mode (steam, combi or air).

 

So…what heat is NOT working? Air?  Steam?  BOTH?

 

What ACTUAL cabinet temperature is the oven seeing (sensing)?  By default, the oven displays set temperature.  Push and hold in the temperature button (I think) and it will display will show you ACTUAL temperature.  If there’s a probe issue, it may not be calling for heat if the probe circuit is satisfied by a faulty probe.

 

FYI.  If you find that the probe may be questionable, those probes are type K thermocouple and are easy to test.  Do so by immersing the probe tip in an ice bath.  Set you digital meter to temperature.  While observing proper polarity and with the probe leads isolated from the board, connect your test leads to the probe leads.

[john]

Was the CPC one of the Rationals you completely disassembled and remanufactured in that YouTube video? I was looking for it but couldn’t find the link. Quite a job there, ectofix