Lincoln 1300 Impinger not getting hot enough.

[ectofix]

Appears the temp control is doing its part.  Logically speaking, the oven should continue heating then.

 

The schematic in the manual for that oven really sucks.

 

So…just because the HEAT light is on doesn’t mean the “relay” is remaining on.  Monitor amp draw of the elements with your amp clamp throughout operation.  That mercury contactor is silent, so you loose audible feedback of its function.  There could be an issue with it, although such an issue being consistent with a constant peak temp would be really odd.

 

Here’s an oddball question which I’ll ask only because I saw it happen once on a Blodgett oven.  Is the main fan turning the right direction?  That Lincoln oven also has a centrifugal blower wheel.  If it’s turning the wrong direction, that would be a big problem.

[jseigfreid]

I am finding odd ball things with these ovens.  This is because they are all used, and abused.  I am assuming if the blower is going in the wrong direction it would be due to being hooked up backward at the power supply in the oven control panel.  DC motors hooked up one way turn one direction, hooked the other way turn the other direction — like the conveyor motor, right?  So, do I need to take the blower motor panel off, turn the oven on, and watch the fan direction?  Not overly excited about this but guess I unhook the heating element first.  One can see the centrifugal blower wheel when the panel is off.  Is there a good picture somewhere where I could compare to see if it is on correctly?  I have two other panels off of other ovens, if all three have their blowers the same, can I assume the blower parts are on correctly — even though one is using a HVAC air handler motor.

Thanks for all your help.  I really am enjoying this.  A true learning experience.  My son keeps telling me, when I get these fixed, maybe we should start buying broken ovens and fixing them.  Of course, at 36, he has yet to learn how to use a screw driver, so, easy for him to say.  There is a small building a block or so from my office/warehouse/repair shop.  It is set up for two ovens and take out only pizza.  Think I may just lease it and make pizza.  My first job out of school was running a pizza place.

[fixbear]

I might be wrong, but this sounds like a air flow problem. Like the blower is sucking air from other than the oven chamber or the nozzles are not in correct.. The heaters will only give so much rise. If the incoming air is 200 and you have 100 degree rise, the oven will be 300. So either air flow is to high causing a low temp from bleed, Or air going into the heater is not coming from the oven correctly.

[fixbear]

That’s good. now you know it’s not the heater.

[ectofix]

jseigfreid wrote:

 

I am assuming if the blower is going in the wrong direction it would be due to being hooked up backward at the power supply in the oven control panel.  DC motors hooked up one way turn one direction, hooked the other way turn the other direction — like the conveyor motor, right?

The main fan motor is single-phase AC motor (since the oven is single-phase) and…NO, connecting it backwards would not make it run backwards.  That only applies to DC motors.

In a single-phase AC motor, direction of rotation is determined by the physical orientation of the stator poles.  You can’t change that.  Worth noting is that there ARE reversible AC motors designed for universal applications.  That oven’s OEM motor is not one of those.

 

I brought up checking fan rotation only because it’s a very remote possibility that it’s rotating backwards -for reasons unknown.  Could be a non-OEM reversible motor that’s wired incorrectly or a non-reversible motor that’s designed to run in the wrong direction from what the oven requires.  As an even less likely scenario, there could be something stupidly wrong in the OEM motor that’s starting it backwards.

 

Who knows.  I only brought it up as something you should check.

[fixbear]

You really should check the whole air flow system. Each of the fingers, columns, air ducts and end fascia. Seal on blower back. Often on a used oven some of these parts are missing. The seal has to be replaced each time the back is removed, so you only want to do it once. The air flow on a conveyor oven is very precise, and every piece is needed to be in place for it to work right. and get to temp.

 

Caution on oven thermometers, they are notorious for being off a lot, Like 50 degrees or more, but especially over a range. once one gets above 375F they really vary.

[jseigfreid]

Thanks to all for the great help.

The insulation seal on the oven (Lincoln PN 369470) is no good or gone on all of the ovens I have worked on.  Is there some place to acquire this in bulk and cut to fit the oven or is the specific piece the only one that will work.  At $25 each, this adds up, but, is worth it if it solves part of my problem.

 

Several of the ovens have Air Pump Panel Insulation that appears less than stellar.  Same question as above for this.  At $65 each, this adds up.

 

I realize spring type thermometers can be suspect.  However, in my good oven it reads 500F when I set the temp to 500F.  I will get a good thermometer as I continue.  Any suggestions will be appreciated.

 

The oven is clean – took me hours to get the burned on junk off of the fingers, covers, and inside oven cabinet.  The fingers are lined up just as the Lincoln videos show for cleaning the ovens.  I have disassembled as much of the oven as reasonable and cleaned inside and out. 

 

The amps appear to remain constant on the heating elements, I saw no drops as the oven heated and operated.

 

I think the only thing I have not completely checked is the Heating Element Relay.  The trouble shooting guide says “check for voltage to the relay coil”.  Then “Check for voltage across relay terminals”.  What is the appropriate value?

 

Could it be the heating element?  Is the element on it’s leg and just can’t get up to heat?

Thanks,

Jay

[olivero]

Well, if your elements drawing amps, the relay’s working. All a relay is, is like the switch you flip when turning the oven on, except its automatic is controlled by something else.

 

In this case, it probably goes through a T-stat and the voltage goes to the coil of the relay which energizes and throws a magnetic field out which pulls the contact in and lets power flow through it and completes the circuit for your heaters.

 

If your heaters don’t come on, it could be the relay but sounds like they do come on and heat. Either that or you got a partial ground and your drawing amps through that but I really, really, doubt that.

 

If you got mutiple elements and they are all drawing the same amount of power, that’s good, means its in order. You can measure phases of power if you want to see if the legs are fed correctly but once again, if they weren’t you would have seen it by now, loosing a leg will make it operate oddly and is mainly when heaters are fused, otherwise it could be a severed wire which would have shorted to ground by now I am sure.

[fixbear]

The insulation seal on the oven (Lincoln PN 369470) is no good or gone on all of the ovens I have worked on.  Is there some place to acquire this in bulk and cut to fit the oven or is the specific piece the only one that will work.  At $25 each, this adds up, but, is worth it if it solves part of my problem.

 

They are specialized material and die cut just for the oven model. And they have to be replaced every time the back is removed.

Several of the ovens have Air Pump Panel Insulation that appears less than stellar.  Same question as above for this.  At $65 each, this adds up.

Explains some of the heat loss. Be aware that the blower wheel and fan wheel have to be properly placed on the shaft for circulation and to prevent rubbing.

I realize spring type thermometers can be suspect.  However, in my good oven it reads 500F when I set the temp to 500F.  I will get a good thermometer as I continue.  Any suggestions will be appreciated.

I like Fluke 51 or 52. But that is just me. There are several brands out there, just make sure they use the standard plug for the K thermocouple.

The oven is clean – took me hours to get the burned on junk off of the fingers, covers, and inside oven cabinet.  The fingers are lined up just as the Lincoln videos show for cleaning the ovens.  I have disassembled as much of the oven as reasonable and cleaned inside and out.

Commercial foaming oven cleaners work well for that, but you have to use protective gear and rinse well. Make sure that the duct fillers are tight and in place. The two fascia’s on the ends of the oven have to be present and down to under 2 inch opening to reach full heat. If one or both are missing there is a lot of heat loss.

The amps appear to remain constant on the heating elements, I saw no drops as the oven heated and operated.

 

I think the only thing I have not completely checked is the Heating Element Relay.  The trouble shooting guide says “check for voltage to the relay coil”.  Then “Check for voltage across relay terminals”.  What is the appropriate value?

 

Could it be the heating element?  Is the element on it’s leg and just can’t get up to heat?

Thanks,

It’s not your heater as you have 24 amps draw. That means it is heating . Electric Heaters are no more than a high resistance wire, usually inconel. they can be bare like in a domestic oven broiler, or jacketed like your heaters. The wattage is voltage times current. Lincoln used 5600 watt, 5800 watt and 6000 watt heaters in these units. your amprage is in that range, but I do not know your line voltage on site.My public service commission allows all the way down to194 volts before the electrical company has to do something.

   As for the contractor, they are mercury switches. they work by a plunger that a electromagnet displaces the mercury so that it covers the contacts and close the circuit. As you look at the contractor, their are two screw terminals on the top and two on the bottom. They are line and heaters.terminals for the number 10 gauge wires. (high current) In the center is a coil with 2 terminals to control voltage. The power for these comes from the ETC to the high limit (which is open in your picture) then to the air pressure switch (belongs behind the control panel high limit) and to the contractor and light. The schematic shows 5 connections from the air pressure switch to the  contractor back to L1. Only 2 for the light. The top terminals go the heater, so make sure they have line voltage when running as sometimes with mercury switches they get arc corrosion internally and create resistance causing a voltage drop.

   You say it doesn’t have a air switch. This is in the system as a protection devise so that their has to be air flow before the heater comes on as fire protection  ther methods that are costly for the customer are the use of centrifugal proofing switches in the motor. Motor cost triples with this method. But it is less troublesome and more reliable. If someone removed it because they needed to “make it work”, They assumed a enormous responsibility. You will not be able to sell this oven safely without it.

 

Hope this incite helps you on your endeavor. Been there and done that..

[jseigfreid]

Thanks so much for your input.  One thing for sure, if we buy more of these ovens, I know what to look for before closing the deal. 

One more thing, just to make sure, which schematic are you using?  There are quite a few in the service manual and I want to make sure I am on the same page, literally.

I have two salvaged ovens and am thinking I have a couple choices based upon the air switch.  Either move the parts to one of the salvaged units as both have air switches or buy a switch and install it in the working oven.  My only issue with this is one of the ovens has been converted to 240V, the other is 208V. 

I bought a thermometer, thanks for the info on that item.

I should finish this project next week, I hope, and will leave an update.