DIY Powdercoat Oven - Val6 Diesel heater?

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martyy
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DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

I am just starting to look into powder coating and have decided that I will likely be building my own oven to try and keeps costs down. Probably going to be 4' wide X 6' tall or close to that size. I have seen various threads on using Mr. Heater propane heaters but I have a Val6 MPX diesel heater rated at 60k btu and was thinking it might be up to the task. The MPX is awesome and puts out a ton of heat. It does have a fan but works as infrared heat, so it does not blow crazy like those propane heaters. With it running you can have a conversation with someone right next to it. Seem like it would provide an even temp if I can get it to seal up around the edges of the heater. Any of you guys out there with more experience have thoughts on this being a worthwhile endeavor (as far as the MPX as the heat source)?

Link to heater
https://val6heating.com/models/mpx/

-Marty
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DieselFumes
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Re: DIY Oven - Val6 Diesel heater?

Post by DieselFumes »

I am not sure that would get it hot enough and unsure if any exhaust fumes would affect the finish. I would just go electric. Can pick up old oven burners super cheap or free and just wire them up.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by acourtjester »

This is what I use plus an oven element or two easy with no fuel to add.
https://www.ebay.com/itm/234591957598?h ... R_qvzLnLYQ
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martyy
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Re: DIY Oven - Val6 Diesel heater?

Post by martyy »

DieselFumes wrote: Thu Feb 16, 2023 9:34 am I am not sure that would get it hot enough and unsure if any exhaust fumes would affect the finish. I would just go electric. Can pick up old oven burners super cheap or free and just wire them up.
I think it will get plenty hot as I just ran some tests with the infrared thermometer. I set a piece of mild steel 2ft from the face of the heater and within 3 minutes it was almost 300 degrees with temps on the face of the heater over 900 degrees. The exhaust fumes are surprisingly low, well maybe it shouldn't be a surprise at the cost of these Val6 heaters. They are touted as extremely clean burning. Other than repurposing an existing item, one of the reasons that interests me is the speed in which a heater like this would get things up to temp. I am checking to see if there are any ovens on CL or FB. I have not even got a gun yet. Thanks for chiming in.
martyy
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

acourtjester wrote: Thu Feb 16, 2023 2:02 pm This is what I use plus an oven element or two easy with no fuel to add.
https://www.ebay.com/itm/234591957598?h ... R_qvzLnLYQ
That is dirt cheap.
34by151
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

You need a pid controller regardless of the heater type
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

34by151 wrote: Thu Feb 16, 2023 3:47 pm You need a pid controller regardless of the heater type
Yeah, i am looking at the one acourtjester posted. The Val6 already runs off of a simple manual thermostat which calls for heat. The Val6 heater is different than the propane torpedo style as it has a fan cool down period. I don't need the PID to control the load for the heater, rather just a dry contact to control the call for heat. Hope that makes sense.
34by151
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

I started with electric.
The issue with this is massive amount of power needed and the slow reaction times

I upgraded to a turbo type heater (50kw LPG) but replaced it with a Riello Diesel 2 stage heater (240Kw)

A turbo style is an open loop heater. This means it relays on air flowing though the heater
The only change is toy need a bigger exhaust port. If the port is too small the oven is effectively blocking the heater and it will either shutdown or burn up.

When I had the turbo hater my oven had 2 x 65mm exhaust ports at the bottom
After changing to the 2 stage heater the ports were reduced t 2 x 12mm
The 2 stage is a heat exchanger, heat is transferred to the second stage. This second stage draws in air from the oven heats it and pumps it back.
In other words its closed loop

You wont have any issues with the burner and surface finish in fact its better as your are forcing the fumes from the powedercoat out the exhaust port.

Its important for the parts to get to temp as quickly as possible
Most powders begin to flow at 170c but need to get to 204c to start the bake cycle
The time to get from 170 to 204 is important to the quality, the faster the better
I'm refer here to the temp of the parts not the oven
The more parts you have and the ticker the metal the slower it will heat
The only option is more power. More heating in KW
How you heat it , electric, gas, diesel is not important just how fast it heats and how stable the temp is

My oven internals are 2.4m high x 1.5m wide x 1.2m deep
I can fill the oven with the 10mm thick parts and it will get from 170 to 240 in under 2 minutes
With a couple of 2mm signs that would be seconds

Why do I have diesel 2 stage
Its cheep to run, far cheaper than electric and about half LPG
Im limited to 64 amps per phase, 3 x 64amp @ 220V, roughly 35Kw

The small LPG heaters are in the 20-50Kw range
My Diesel heater is 240KW so in electric that would be 400amps 3 phase or 1200 amps single phase
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

The pid just monitors the oven. Its connected to a contactor or ssr that turns the power on/off for the heater.

The val6 will still not like a closed oven.
That's like blocking the heater, it will shutdown
The exhaust port needs to be a size that allows the heater to run without shutting down

All ovens need a vent anyway to rid if the powder fumes and allow for heat expansion

The specs say it needs a 110cfm air flow
Just pot in a big port with a flap that can be adjusted
When you test the oven have the port open. Keep testing till you find out how much you can close the port and not have the heater shutdown.
As you reduce the port the heating time will get quicker as well
martyy
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

34by151 wrote: Thu Feb 16, 2023 4:19 pm The pid just monitors the oven. Its connected to a contactor or ssr that turns the power on/off for the heater.

The val6 will still not like a closed oven.
That's like blocking the heater, it will shutdown
The exhaust port needs to be a size that allows the heater to run without shutting down

All ovens need a vent anyway to rid if the powder fumes and allow for heat expansion

The specs say it needs a 110cfm air flow
Just pot in a big port with a flap that can be adjusted
When you test the oven have the port open. Keep testing till you find out how much you can close the port and not have the heater shutdown.
As you reduce the port the heating time will get quicker as well
Tons of good info in your posts. Thank you.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

Starting to finally pick up the materials to get this oven done. Not sure I am going to use the Val6 heater as 34by151 turned me on to the Riello burners. Might look to find one of those units. Picked up metal studs, mineral wool insulation and rivets yesterday. Why not build an oven when temps are already 100 degrees outside? Might be winter before I get it done.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

If you have already got the Val6 use it, otherwise consider a bigger one

Just build your oven and worry about the rest latter as you will have to adjust anyway.

In you build a few things to consider
1. Insulation
I used a 25mm inner and outer steel frame with 25mm spacing. That gives a 75mm cavity and filled this with 100mm wool insulation bats. Inner skin lined with 2mm zinc Sheetmetal. Outer lined with a mix of 2mm and 1mm zinc sheets. Just used offcuts from the workshop for the outer sheets
2. Vent and Inlet
Make the oven taller than what you need allowing for the 300mm inlet. In other words bump the height by 300mm.
This leaves room to add a baffle for the inlet. I added a trangle baffle to direct the inlet air up the back wall. This caused the air to rotate around the oven and away from the vent (outlet)
Make the outlet bigger that you think you need you can always cap it smaller latter.
The val6 turbo type heater is not designed to be blocked off so the vent needs to be big enough to allow the heater to have enough airflow. A 2 stage heat can use a much smaller vent. I have 2 66mm pipes as vents in the lower right corner, diagonally opposite to the inlet.
3. Window. you want a window to observe the process without opening the door. I used 2 sheets of glass from an old wall oven. Bonded one to the inner wall an one to the outer wall then added a 2mm sheetmetal door
4. Lights. Make sure you use ceramic fittings otherwise it will melt. Make sure the wires are high temp insulation. I used the wires from the old wall oven.
5. Inspection port. Consider adding one. Its just a tube welded though the door with an flap on both sides. Link the flaps so when you open the outer the inner opens.
What you use this for is your laser thermometer to check the temp of the part. The usefulness is you can do a temp check without opening the door

Getting back to the heater
The key is not that it will get to temp (204 degC) but how fast it will get to temp.
Remember you need to get the part (metal) to temp for your cooking time (around 12min)
The powder will flow around 175 degC but he part will still be below 175
The critical bit is how fast you can getting the part from 175 to 204
In other words channel your inner "Tim the tool man" you cant have too much power or in this case heat
Ideally your aiming to get the parts from 175 to 204 in under well under 5 mins

A bigger heater get the parts to temp faster
This sorts out a lot of power issues like cracking, orange peal and poor adhesion.
This issues can be caused by other things but you dont want you oven do be causing it
It uses a lot less energy overall because a slow heater will have a lot more heat soak into the oven walls which is wasted energy
Once you get to temp your heater will mostly be off unless its too small and is need to maintain the heat
My heat rarely turns on more than once in the 12min cooking cycle and if it does it will do it once for about 3-5 seconds
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by semperfi1919 »

I have not tried a diesel heater but from what I found in my research before building my oven was that if you get some bad fuel or run out of fuel you may have some smoke issues, I went with a propane heater, run off of a 100lb bottle, hooked to a PID controller, make sure you have auto ignition. My heater will heat my 4x4x6 oven to 450 in less than 5 mins.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

I am making good progress on the oven this week. I am not good at taking pictures during the process, especially when I am just winging it. Thankfully there are lots of threads and videos to help. Had a little bit of a mental slip and thought I would save some money on the oven glass, so I bought a nice replacement one for a stove on Ebay that I planned to cut in half and used for a window. Tempered glass does NOT cut well, but does shatter outstanding... Waiting on the new ceramic glass to arrive and some latches for the door.

One thing that I just started thinking about which I have not seen addressed in forum threads was the heat on the concrete floor causing issues with radiant PEX tubing? I dont expect to run the oven for hours upon hours but just wonder if there is a concern here? I want to be able to roll a cart into the oven, so right now I am just planning on put down a 14ga sheet for the floor. Thoughts on heat issues with the radiant PEX? Slab is 6" thick. PEX lays on pink board at bottom of concrete.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

I guess time with tell if I have any issues with the PEX infloor tubing. I just cant see it being an issue. I took advice from 34by151 and just built the darn thing and will adjust as I need to.

Anyway here are some progress pics. Waiting on more rivets as I have emptied my bag of 1000 already. I made it so it can be moved easily as well as added onto much easier. Just used 20ga CR for most with some 14ga in places for rigidity. I may paint it if I can find a light colored high temp roll on paint. Used rockwool insulation and ceramic glass ultimately after I shattered some oven tempered glass.

(Sorry about the rotated pictures, looks like phpBB doesn't like the EXIF data)

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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by Dirtmotor »

Looking great , you will get quite a bit of heat transfer through the metal studs . I am trying to figure a way to build mine with staggered 1 5/8 studs to help with that . Who knew a drywall jack could be so handy !
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

Dirtmotor wrote: Mon Sep 11, 2023 9:37 am Looking great , you will get quite a bit of heat transfer through the metal studs . I am trying to figure a way to build mine with staggered 1 5/8 studs to help with that . Who knew a drywall jack could be so handy !
Interesting idea on the staggered studs, similar to noise transfer in home building with 2x6 bottom plates and staggered 2x4 for walls. I thought about put some red chaulk on each stud before sheeting it, but didnt really think it would do much. The jack is my 2nd HF drywall jack. It isnt very nice or smooth but comes in handy.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

I just welded the inner sheets on and sealed the seams with hi temp rtv sealant. Inner sheets are 2mm zinc sheet metal
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

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martyy
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

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martyy
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

So I have a bit of information to report with some basic testing I did today. Tests were done with the inlet port (near bottom of door) mostly blocked off to hold heat better. Bottom of door has 1/8 to 1/4" gap which allowed intake. I did not have all the interior seams RTV'd at this time. But did not notice any significant hot air exiting any of the seams. Did ultimately get some thermal transfer.

I ran the heater for exactly 60 minutes.

PID only got up to 360F. But at the end of the time, I opened the window and took many readings. Almost all readings were over 400 with some around 460-480. The 14ga hanging cart was a fairly consistent temp around 400F except where close to the burner. Defiantly will need to work on some deflectors, but seemed like the fan on the heater moved the air plenty. Little confused why the PID read so low. It is what came with the REX C100 PID. After the burner was off for just over a minute with fan still running, temps on most all walls were stable at 360F.

Observations
1. smoke coming from of the seams. ( just realized I never put in an exhaust vent, need to do that. would like to put in door somewhere)
2. After turning off PID power which removed the call for heat on the Val6, the fan on the heater does a cool down. After a couple of minutes it seemed to flicker in and out, which made me think the heat from the oven was backing up into the housing and getting too hot. I don't want to ruin this heater as it is my alternate shop heater.

Conclusion
I just don't think the heater is going to cut it. According to a calculator I used, the fastest it should have been up to temp would have been around 29 minutes. I just think I am going to need more BTU. Probably going to look at Carlin or Riello. I have no preference diesel vs propane but gonna have to find a good deal as I am over my already tight budget. Will have to decide if I use existing 15" wide burner hole or cover it and put the burner in down lower.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

Have you calibrated your pid?
Put the probe in boiling water and adjust the temp

You will get some heat back though the heater when its off
Some is caused by how high you have it and how close you have it
I used some ducting to move the heater away that helps a lot
Used an elbow at the oven which also saves some space
You can also add an s bend effect with the duct and baffles to minimise loss

Id work on your calibrating the pid first
Then seal your seams
Finally test your exhaust

The oven effectively blocks the heater
If the oven was fully sealed it would trip the heater (over heat) as it's airflow is blocked
The vent prevents this
So you need need to reduce the vent size till you trip the heater then open it up a bit
You need the seams sealed first though

Once you do this you will know your heat up time and it will also give you an indication of how long after that it will take to get the parts up to temp (204c)

Your heater will work but might not be ideal its going to be about half your heat up time to get the parts from 175c to 204c
That will work but not produce an ideal finish
This why I went from a LPG burner up to to the Diesel burner
My times we around 30mins for for the LPG and 3mins for the diesel
The Difference was 40KW vs 240Kw output
Added benefit the bigger heater cost a lot les to run but may be due to diesel/lpg cost haven't worked that out
martyy
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

I have now calibrated the thermocouple with the PID a couple times. First time I adjusted 6 degrees. Then I ran the tests below.

I have also sealed all seams with exception of under the door. Waiting on some silicone P Seal.
I also purchased a gas oven thermometer that I hung near the sensor to compare with what I am reading on my IR temp gun.

Run some more tests today.
15 minutes
PID showed 251 F
Oven gauge showed 300 F
IR gun showed 305 F

30 minutes
PID showed 338 F
Oven gauge show 375
IR gun showed 382 near the oven gauge and 357 about 18" away.

After the above testing, I decided to change the mount of the K thermocouple and isolate it (with high temp caulk) from the metal walls to avoid it reading the metal surface temp. Doing so has reduced the lag in the temp rising on the PID, but it still seems like the temps are 30-40 degrees off. Not sure if if the issue is with the PID or the thermocouple or the fact that I spliced the wire as it was short. Or my IR gun might not be accurate. Gonna have to do more testing tomorrow.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by martyy »

added the vent adjustment piece and added a small exhaust pipe with adjustment.
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Re: DIY Powdercoat Oven - Val6 Diesel heater?

Post by 34by151 »

Did you use thermocouple wire and thermocouple connectors for the splice?

If not 100% the reading will be off
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