Ease my nervous mind :-) (mes 20070910)

[fivetricks]

I've owned my Gen1 for about 3 years. On Sunday it suddenly wouldn't heat past 80 or so degrees. There were no concerning smells being put off by the unit. So that's good anyways.

Ok, so I took it apart in search of a reason why. Upon inspection of the PCB, thermostat, snap-disc, wire, and connections the only problem I could see was a bit of scorching (not really burning) on the two connections to the heating element.

There was also evidence of long term overheating in the general area of the element service panel. So I stripped the protections off of the push connectors which were both junk anyways due to the over heating. I also pulled the thermostat and heating element and wirebrushed all of these parts and connections.

Before this "repair" was made, the unit typically would heat up to 250-255 ish when the controller read 275. Now with clean connections, it heats up to 320 (trusted thermometer placed less than 1" from the unit thermostat) with the controller reading 275.

The device seems to be cycling normally. The readings on the element posts topped out at 195 and 165 from left to right



My questions are fourfold:

1. You can see evidence of the overheating that took place overtime on the insulation. Seems to me that drilling a few holes in the element service panel would relieve most, if not all of this from happening in the future.

2. Does anyone know what temps the insulation is rated for? I never (or so I thought anyways) had an issue before, but now with the uniter heating to north of 300 degrees, I wonder if I'll be exceeding the specs of the foam.

3. What should I use to replace the now missing insulation from the push connections? I don't think that exposing the rubber housing in the element service panel to 200 plus degree temps would be advisable. I have red RTV, but that seems like it would be a big hassle to get off for when I have to service in the future.

4. Should I trust this thing to run unsupervised overnight (at some point)? I did an extensive inspection and saw no other issues. The wires and all connections were honestly in great shape. No scorching of the PCB leads, no loose parts on the snap disc, etc.

Thanks for your time :-)

Attached also is a larger picture in case there is some greater concern with the damage to the insulation than I thought.

 

[tallbm]

Hi there and welcome!

I have replaced some removed insulation from an MES40 with the following Oven and Appliance insulation rated at 1000F. I would only remove as little as you can get away with since the foam insulation is what gives the body it's sturdiness so if you remove it there is nothing to give the sheet metal support. I think that spray foam insulations is probably rated to a minium 300F continuous or maybe a little higher and probably up to 350F or a little higher for temporary swings in temp so non-heavily compromised insulation should be good at 275F continuous.
https://www.ebay.com/itm/Johns-Manv...riorityFlatRateEnvelope!75287!US!-1:rk:2:pf:0

For covering the connectors you can use heat shrink insulation tubing. The following as a max continuous operating temp of 275F and 10ft amounts in various widths are available for less than $7:

I use tubing like this on my MES connector jobs. Also you did well in fixing the connectors and such but I would highly recommend you use hi temp stainless steel connectors on the heating element and on the safety rollout limit switch (if you replaced those) to avoid them corroding and going to hell like the cheap ones did. These would work for you:

or these if you have the correct kind of crimper or you want to solder them:

Best of luck with the work!

 

[fivetricks]

Thanks a bunch. Was hoping to hear from you :-)

Thanks as well for the product reccomendations.

I didn't actually replace anything parts wise, or even wires wise. Just did some cleaning up. Never really considered replacing any of the foam. Do you think that the areas of compromised foam have any consequences besides heat loss in the affected area?

 

[tallbm]

If your foam is just discolored and not compromised then I wouldn't worry about replacing any of it. So far in the 3-4 units I have opened up and worked on there has been various amounts of discoloring in the foam. I think a little bit of smoke seeps into the areas where the heating element and the rollout limit switch are so that is normal and depending on age and use the discoloring may be very dark or light.

If your foam is burnt up then that would be of concern that your foam's integrity is compromised and the foam may ignite causing a fire. This is something you will have to determine for yourself in person because pictures and coloring can be deceiving.

I'm no professional in this area but I would just check it out and use good judgement unless you want to have someone who is well qualified to inspect it for you. Your call :)

 

[fivetricks]

Well thank you thank you. I'll prob toss some new insulation in there :-)