# National Screen Printing Equipment Dryer Questions



## mrwalshiii (Jan 29, 2015)

Hey guys,

I've got a couple questions about my National Screen Printing Equipment dryer (N3611). I was hoping I could get some help since this company has long since gone out of business.

First, what type of thermocouple does this dryer take (Type K, Type J?) I've linked some images below to help. Also how does this thing attach is it just hardwired at the controller or something? 

My dryer temp tends to "float" and I was told that the thermocoupler should be the best place to start. 

Second question is about the DC motor on the bottom of the dryer. It doesn't work. Where would be the best place to start testing it? I'm assuming it's some type of forced air and I'd like to get it working if at all possible. 

Last I want to replace the insulation in the top of the dryer. The old stuff is in pieces, and I figured since I'm going to be in there it'd be best to replace it. Would this work?

Thank you for any responses. I would really just want to get the thermocoupler figured out first, the forced air would be a bonus. 

Thank you for your time.

Photo 1

Photo 2

Photo 3


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## maikman (Apr 19, 2011)

https://www.amazon.com/gp/product/B017LB3BQA/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1


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## sben763 (May 17, 2009)

maikman said:


> https://www.amazon.com/gp/product/B017LB3BQA/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1


Matt does that have the original controller? If so the enire unit should be replaced. I did this on my old Lawson. Here is a example of the unit. Not sure if this works on your unit as you need to know amp draw number of heat panels etc and if you not familiar with electronics you will need to have it installed. A appliance tech or good electrician should be able to do with no problem. https://www.amazon.com/Inkbird-Temp...rd_wg=11jRm&psc=1&refRID=Y1HP8VZGRT3DA2Z6K5D0

Most of those old controllers have a mercury relay/contacts which tend to stick while cycling on and off as the panels do this continuously to regulate temp. If replacing the PID buy a kit or make sure to get a solid state relay.


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## maikman (Apr 19, 2011)

Not my dryer but it looks like it has a PID controller on the panel. The thermocoupler in the kit you linked is a little nub that doesn't accurately read temperatures in my experience, that's why I ended up getting the 8" wand.


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## mrwalshiii (Jan 29, 2015)

Hey guys, thanks for the responses. Been busy printing so I hadn't had a chance to read them until today. I went ahead and bought that one from Amazon. Should be here in a day or so. 

I really want to replace the whole thing. It does in fact have those mercury relays, but I'm a little afraid to mess everything up. These are the relays that are in there now One has a surface crack on it too. 

The controller that is in there now is the Love Series 8500. The manual can be found here. 

I'm not an electrician, I can do basic stuff but I don't know what to buy to replace everything. 

Thanks again for the help guys! I'll update everything when I swap the thermocoupler in the next day or so.


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## maikman (Apr 19, 2011)

You should be able to replace the mercury relay with an SSR (solid state relay). It looks like pin 14 and 15 would hook in to the trigger side of it and this in turn switches the high load on the other side on and off. The thermocoupler let's the controller know when to switch the SSR on and off to regulate the heat, make sense?


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## sben763 (May 17, 2009)

maikman said:


> Not my dryer but it looks like it has a PID controller on the panel. The thermocoupler in the kit you linked is a little nub that doesn't accurately read temperatures in my experience, that's why I ended up getting the 8" wand.


The nub as you call it is the K thermocouple. They are commonly screwed into a heat tube which is exactly what the 8" wand is. the actual K thermocouple are identical. 

Without heat tube they are actually more accurate for pinpoint temp. The heat tube allows for a average and since there is more metal surface area they are more prone to cooling and therefore will read lower the actual temp. 

All that is moot though since with a conveyor dryer you will never read precise with the ends open and if there is a vent. They are a reference point. My PID with the SSR and coupler recommended by the manufacture runs at 384F with shirts in the 8' of heat for 1 min to get the ink deposit 325F completely though as when testing strips are placed under the ink deposit inside the shirt


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## mrwalshiii (Jan 29, 2015)

Thanks for all the help guys. 

I got the new thermocoupler in the mail and replaced it yesterday. Pretty simple to swap out. At first I had the wires crossed and it started reading in the negatives haha. 

It didn't seem to fix my problem though, but I think I found a solution. So my problem was that the controller would float around too much. It would be fine until it got close to the set point, but then would jump up a few degrees and then drop down about 30. The shirts themselves seem to be coming out fine though. 

So after looking at the manual I found this digital filter option. I it's there to help stop flutter in the temp. So I THINK instead of sampling the temp every second you can change it to kinda get an average? Not sure, but I cranked it up a good bit. It goes from 0-99..I went to about 45. I don't think that means 45 seconds, because it still floats around 10 degrees from the set point, but it seems more constant now.

I don't think that this is a correct fix though. 

Does the floating temp have to do with sticking relays? Like its getting up to temp then shutting off then kicking back in, but a bit late? The rise and drop I was experiencing only last a few seconds though.

As for replacing the relay with a solid state, I'm just not sure what I need. Since the old relay is 3 pole 35 amps 110/120 vac, does that mean I need a relay to match that? Also following number 14 and 15 from the controller it goes to this thing? What does it do? 

I'd like to fix everything myself so I know my equipment inside and out so I'm not at the whim of a repair guy if anything goes down, but I will get someone if needed. 

Thanks again for all the help guys! I really appreciate it!

On a side note I found out the issue with the fan on the bottom of my dryer. It was FULL of lint! Seems to work fine now.

EDIT: Also I meant to mention this in the body of my text, but I saw someone mention that they have to run their dryer at like 380 to get it to hit curing temps. On this dryer I only set it to about 200 210 to get it to hit 340 or so. Does this sound bad? I know dryers run differently and the temp reading is based on the type of coupler. The shop that I was production manager at bought a brand new M&R Economax and it ran at 900 but I believe that is because the coupler was in the actual element. Seems odd to run it lower. Before this National dryer I had a really long used Hix dryer that I bought used and I only ran it at about 300 to get 340 or so.


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## stemoc (Aug 2, 2018)

Hi Guys. I am looking for a wiring diagram for the following National Equip Dryer.

Model - N2411
Amps - 50
Volts - 220

Any help would be great.


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## finkink (Feb 17, 2011)

Hi Just see if there was any other info you could add about the national dryer you were fixing or you found a manual. i just replaced all the elements in mine and the thermocouple that was told to use and im not getting my temps to rise. we have had this dryer for 15years and we never had any problems at setting it a 330 and 40sec belt and getting are stuff cured. im adjusting the thermocouple alittle higher to try and get a hotter reading thanks


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## finkink (Feb 17, 2011)

Hi im fighting with my dry right now did you ever get yours to work right? I bough the thermocouple you were told to get and it wouldnt turn the light on past 250. i have the old style barrel thermostat. i had just a wire as a thermocouple is that what yours looked like before replacing it? this all started with replacing the elements this week. im thinking it may be the MDI paks because i just cant get it to stay at a steady temp when im sending the doughnut therm. threw thanks


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## RedDotStudios (Dec 30, 2020)

What new elements did you use? Where did you get them from?


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