Oven Heating Problem

[petshe25]

Ok, I've been reading alot of posts and have learned alot. The problem I have is that I have built a 4' X 4' X 6' oven and it is taking about an hour to get to 350 degrees. I have (4) 2500 watt elements running in parallel on the bottom of the oven. It is in the horizontal position with 2" insulation on all sides with inner and outer metal. When I put an amp tester on one of the 110 leads going into the box, I am getting a reading of 36 amps, but I should be getting a draw of 41.6 amps. Is this normal? I have a 50 amp service going into the oven. I would appreciate any help on this.

Pete

[dbug10]

Re: Oven Heating Problem

sounds like you dont have enough heat i have the same size oven with 20 kw of heaters 20 min its up to temp

[petshe25]

Re: Oven Heating Problem

What did you end up with for a contactor and what amp service?

[Popeye]

Re: Oven Heating Problem

You should be about 45.5 amps... could be low voltage or bad element

[petshe25]

Re: Oven Heating Problem

I thought that you took the total watts of the elements and divided it by the volts? 20,000watts / 240V = 83 amps or am I incorrect on the way to figure this?

[edwardpic]

Re: Oven Heating Problem

We have the same size oven and use (6) 1500W elements wired 3 phase delta, our oven takes 15 minutes to reach 400. Ours is running off a 40 amp main with a 3 pole contactor. Most people dont have 3 phase, but maybe the info helps a little. Maybe you should run (6) 2500W elements, also a circulation fan helps the oven pre-heat.
Ed

[petshe25]

Re: Oven Heating Problem

Hey Ed,
What voltage are you running with your 3 phase?

[edwardpic]

Re: Oven Heating Problem

We are running 240V 3-phase. The elements themselves are 240V as well.
Ed

[petshe25]

Re: Oven Heating Problem

I guess I can't figure out why you are only running 9,000 watts and are able to get that much heat out of it in 15 min. Dbug10 has 20,000 watts and it takes him 20 min. to get up to temp. Tonight I am going to check the voltage and amps at each of the elements. Since I only have a 50 amp service, I don't want to really go above 44 or 45 amps to leave a safety factor.

[dbug10]

Re: Oven Heating Problem

Ed are you sure you have only 9kw i swear it doesnt seem like that is enough to heat your oven

[Popeye]

Re: Oven Heating Problem

You figured it correctly.
4 heaters at 2500 watt is 10kw or 10,000 watts. You said 110 so I assumed you have a 220 volt service, 10,000 by 220 is 45.45... but now it's 240 which 41.6 would be right

[petshe25]

Re: Oven Heating Problem

Popeye,
You were right, I typed in 240 but it is 220V.

[petshe25]

Re: Oven Heating Problem

I checked my voltage at the element block and I am getting 231 volts. I also checked the ohms on each element and they are around 24 ohms. With 36 amps I am around 8,000 measured watts which I think are low. I looked at the Caswell ovens and the 96 cu ft. one has 15,000 watts and a 60 amp breaker. I think I am going to update my service and give it a try.

[Popeye]

Re: Oven Heating Problem

Yep, the amps are low, you should be around 43amps at 231 volts.. it's normal to for the amps to drop a tiny bit when the element is hot but not that much. You're missing almost 7000 Btuh.
You ohm'ed the elements disconnected, correct? You might want to call the manufacturer of the elements and see what the normal resistance is..

[petshe25]

Re: Oven Heating Problem

Yes, I ohm'ed the elements disconnected. I tried a test last night by adding one more 3200 watt element. I was able to get up to temp in 1/2 hour. Alot better than the 1 hour and 10 minutes. I am going to do an amp test tonight to see what draw I have now with the 3200 watt attached. It looks like if I am only drawing 36 amps with the (4) elements, it is only about 8,000 watts. This should bring me up to 11,200 unless I loose some with this element also. This could bring me to 48.4 amps which is pushing the limit of the 50 amp breaker without a safety factor. Another question about the powder itself. Does the powder start to melt at a certain temp on average? Just wondered if it needs to get to 300 - 350 before it even starts to melt.

Thanks,
Pete