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Heater woes - WBP1
virginiacoffee
I was hit tonight with the dreaded repeat of the ni-chrome wire break on my WBP1. After finishing the roast in a stand-by, I proceeded to disassemble the WBP1. Sure enough, broken wire.

Now, this wire has been broken before, and re-hooked back on itself with success. But now, it's not being so cooperative. So, here's my thought. I have another popper, one of the death trap ones (screen on the bottom) at 1200 or so watts, I believe. What would be the ins and outs of placing the wire out of that one in the WBP1? Need to shorten it to make the 1500 watts?

Thoughts? Pitfalls?

Thanks,
jason
 
seedlings
May seem counterintuitive, Jason, but shortening the nichrome wire will INCREASE the current to it and therefore increase the power. You could use the 1200W coil in the 1500W P1, but you'll have to shorten it a little bit. How much depends... measure the resistance of the broken P1 coil. It should be 13 or 14 ohms. Shorten the 1200W coil until it reads the same resistance. You can put one ohm meter lead on the end of the coil and move the other lead down little by little until you get 14 or 13 ohms. If the coils are shorted (touching) anywhere that will give you a bad reading and probably burn your element up in that spot.

Let us know how it goes!

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
virginiacoffee
Thanks Chad. That's what I was thinking, though I may have mis-typed. I had been into my P1 several times by then, having issues reassembling it. And what did happen was the coils touched and fundamentally welded together. Not quite enough to keep going.

And nothing like hitting the middle of 1st and see the temps drop precipitously. I'll hit the bench tonight and see what I can do.
 
bvwelch
It just so happens that I was measuring the nichrome in a P2 recently:

http://photos.bvw.../P2wiring/

But how will you make the connections? That is something I haven't had much luck with.

-bill

 
virginiacoffee
bill-
I'll have to look at the existing connector on the P1 tonight. If I can remember, I'll see about some photos.
 
virginiacoffee
Well, I ripped out the heater coil from a Presto Popper. Coil was too large to fit into the housing of a P1. So, I recoiled it smaller. In place now. But the solder that connects some of the heater pieces together broke. Didn't have an iron handy, so I had to retreat upstairs to help get the kids down. Soldering tomorrow.
 
bvwelch
Soldering-- is that safe? lead? melting point?

Sorry I have no answers, just questions.

The poppers I've dissected seemed to be using a rivet and crimp approach for the nichrome.

-bill

 
virginiacoffee
The P1 links the nichrome to the power via two threaded studs. The nichrome is looped around and screwed down, as well as a raw, uninsulated lead for power (it is sheathed in some fabric, but I don't know what). One of the power leads is screwed down, the other comes from the other side of a thermal bridge. That's where the solder is. I will use silver solder if I have to add any to it.

Maybe I can grab a pic of the wiring tonight.
 
bvwelch
Jason,

I was thinking that you were trying to repair a break up inside the ceramic ring itself. Sorry about that.

-bill

 
Island Addict
Is it safe to use solder? It would make some things easier if it is. I think silver solder melts somewhere in the low 400 deg. F range depending on the composition. I guess maybe it doesn't get that hot near the terminal screws, but it probably gets that hot or more near the thermostat.
Rob
 
virginiacoffee
Rob,
Interesting thought. I hadn't gone there. I'll definitely monitor that.

I did get a roast in just now. The new nichrome is a bit larger so the bottom plate vibrated a bit. It may have caused more turbulence and loss of directed airflow. My roast was down to about 2/3 the volume post roast. I may be able to push it higher, well see. I may also re-use the original nichorme if I'm not satisfied. Or else, look at some new nichrome and a better winding technique.

Jason
 
RayO
Two things- if the element were 13.5 ohms, the power at 120v = 1065w. (That's what my Post Versalog guesses) The HP-35 says 1066.66...7w.

If you must have 1500 watts at 120v, you need 9.6 ohms, 12.5 a load.
Just go for 10 ohms. 120v will give 1440 watts and a 12 ampere load.
Max for a 15a circuit 120v = 1800w (8.0 ohms).

Don't use any kind of solder on a heating element. There's a reason manufacturers always use crimps or compression connectors- they Hate replacing stuff under warranty. Splicing Nichrome [DON'T!] requires absolutely shiny clean wires at the splice; ditto if you want to try brazing them together.

Resistance welding is best for a heater wire but even that is not fool-proof for an open splice.

Nichrome is the same as the "Chromel" wire in a type K thermocouple, [Call Omega Engineering] or you could search online to find a supplier of coiled nichrome wire heating elements [Sears] electric dryer element.

If the heater makes 1800 watts at 120v, it will do 7,200 w at 240v. Don't be scared of the high power ratings of the dryer elements. They're rated at 240 v. Half voltage = 1/4 power, and you can't exceed 15a, 1800w on a standard home circuit.
Cheers -RayO

Got Grinder?
 
virginiacoffee
Thanks Ray. Great wealth of info. I'm going to have to double check things tonight, once the kids are down. The roasts aren't building heat properly. It may be an assembly issue. But right now, I'm not sure.

Thanks for the info again!

Jason
 
virginiacoffee
Got down a bit early and re-seated everything. Better heat flow. Roast in a bit.
 
seedlings
Hopefully a little nip and tuck will do wonders!

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
virginiacoffee
Reseated and roasted a Tanzanian Blackburn Estate to about 440. Nice appearance and flavor for short rest this morning. The only thing that worried me was what felt like a hotter than normal popper housing. Can't be sure, though. Gonna have to check some more. But at base function, all is well. Multi-roasts might be a fire hazard. Need to get the grill running!
 
virginiacoffee
RESOLVED. Things are looking up. Did a double, back to back roast last night. Took a Costa Rica Vino de Arabia to City+, about 435. Didn't notice the time, but the ramp was definitely slower, but not too slow. My biggest gripe with a stock P1 is that the heat ramp was always too fast for something like a Kenya that likes to dwell in the land between 1st and 2nd.

The CR - VdA was followed by more Tanzania Blackburn to about 440. The casing was not too hot to my palm, but a bit hot to the back of my hand under the popcorn chute/handle.

Thanks all for the help!

Jason
 
bvwelch
Jason,

I'm not sure what you mean when you mention a "stock P1", presumably your P1 has been heavily modified?

Regarding the hot casing-- yes I've noticed that too-- when I was shoehorning some mods inside a P1, I considering putting some circuits up high inside the plastic case but decided it was too hot up there. It is much cooler down below where the fresh air enters the P1. But there isn't much room, so I prefer an external box.

-bill

 
virginiacoffee
Stock P1 - I've made no significant mods to my P1. No split wiring, but I've thought of it. Added a soup can and a thermometer. That's it. Plug in, turn on and bingo!
 
EddieDove
Jason,

Glad things worked out ...

I would be really interested in your thoughts on the Tanzania Blackburn (maybe a thread under "In The Cup"). My first roast and trials were last week (I have more of the bean), but would really like someone else's perspective.
Respectfully,

Eddie Dove

The South Coast Coffee Roaster
vita non est vivere sed valere vita est
Home Coffee Roasting Blog and Reference
http://southcoast...gspot.com/
 
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