Deep fryer’s got issues

[ectofix]

AHHH!  I re-read what I’d written yesterday and see that I accidentally chopped something out.  This site kept kicking me off yesterday while I was composing that lengthy post.

 

Look back at my earlier post.  The paragraph I’ve highlighted there in red is now rewritten HERE – with additional information I previously left out now added – in RED:

 

“FWIW:  A thermopile can generate UP to 750mV.  On those basic millivolt systems (not yours), the load of keeping the pilot valve coil energized usually drops that to around 600mV.  When a millivolt fryer’s thermostat calls for heat, the additional load of the MAIN valve coil will drop the thermopile voltage to AROUND 250mV – which is considerably lower than power needed for just the pilot valve…but well above the minimum of 200mV that Frymaster had stated.

So…with your fryer only utilizing thermopile output for just the pilot, I would think that your voltage would be WELL above 200mV and read more like 500-600mV.”

[ectofix]

(ORIGINALLY POSTED 7/17/2018)

 

200mV would be the MINIMUM the thermopile is supplying under a load (energizing the pilot solenoid valve coil.

 

olivero, I’m surprised you’re not familiar with a millivolt system.  Then again, the equipment you work on in-house would dictate your experience.  I get it.

Yes, the safety is all based around the pilot.  If the pilot goes out, the main burner goes out.  That’s the safety function of the combination valve.  The combination valve incorporates everything that was once used as a GAS CHAIN….but into a smaller package  Here’s a video about the gas chain:

The gas chain control for gas furnaces – YouTube 

 

Your basic standard commercial range ovens are really the only cooking equipment that still uses THERMOCOUPLES nowadays.  I’m sure you have some of those. 

Millivolt systems (like on some fryers, some old tilt skillets, some deck ovens) use a THERMOPILE instead of a thermocouple.  A thermopile generate 750mV.  A thermocouple only generates 30mV.  As put to me almost TOO simply years ago, a THERMOPILE is just a whole bunch of thermocouples PILED on top of each other.

 

BTW:  Don’t confuse thermocouples used in pilot safety circuits with thermocouples used as temperature probes.  The latter is a whole other topic.  They both generate DC voltage, but for entirely different reasons.

 

SO…many fryers using the millivolt system power BOTH – the pilot valve AND the main burner valve.  Those are the most basic fryers.  No power cord is needed.

That Frymaster just powers the pilot valve ONLY with the thermopile…simply to employ the pilot safety feature.  The main valve is powered from a 24v transformer via the Fenwal thermostat (in your case).  Despite the differing power sources, the PILOT is the master of it all.  If the pilot valve closes, it also shuts down main burner flow.

 

Frymaster said you want 200mV.  That’s because if the thermopile voltage drops much lower, the pilot valve will open.  TRUTHFULLY, lockout normally doesn’t occure until under 100mV.  It takes about 150mV for the valve to hold in while you’re lighting the pilot (my experience). 

 

FWIW:  A thermopile can generate UP to 750mV.  On those basic millivolt systems (no yours), the load of keeping the pilot valve coil energized usually drops that to around 600mV.  When a millivolt fryer’s thermostat calls for heat, the additional load of the MAIN valve coil will drop to only needs to power the pilot.  I would think that your voltage would be WELL above that, since it doesn’t have any additional load.  (NOTE:  This is incomplete info.  See additional post BELOW)

 

If I was in your situation, I’d first check gas pressure to the fryer.  You want 7″WC minimum – whether it’s just with one fryer running, all three…or the whole cooking line.  7″ minimum.

NOW, there’s a pressure regulator INSIDE the combination valve.  Be aware that IT only regulates MAIN burner pressure.  So the pilot should be seeing that 7″ source pressure.  That’s the first reason why incoming pressure is important.

The SECOND thing I’d be checking is the pilot’s flame quality.  If it’s clogged from grease and debris, then the subsequently weak flame might be causing thermopile output to drop over time.

The THIRD thing is wire connections from the thermpile to the valve.  Beings it’s only three-quarters of a volt MAX, keep in mind that such a low voltage may not be capable of punching through any loose or corroded connections.  You DO NOT want any bad connections to cause a resistance to such a low voltage, since the slightest resistance in such a low voltage circuit can be monumental.

 

Once you’ve scrutinized all of that and are satisfied that it’s all good,, then move on to troubleshooting with fryer temperature in mind.  The high-limit is in series with the thermopile’s circuit to the pilot coil.  If the high-limit opens, then the entire fryer shuts down.

 

I’ll continue on your latest post…

[olivero]

Haha, well there you go, makes more sense.

 

The center one was only reading about 250 MV with just the pilot, I Turned up the flame a little and moved the pile closer to the pilot and it went up to 500MV, even when its running with full flame, its about 300-400 MV so I think it’s good.

 

They’ve been using it for about 4 or 5 hours now, no problems.

[ectofix]

The voltages I’d stated might be a bit too optimistic.  If it’s 300-400mV and holding steady under all conditions, then it sounds like you got it.  

[olivero]

I Sure hope so, I’l let you know at the end of tonight.

 

Thanks for the help guys, you’r faster than Frymaster, lol.

[olivero]

Look’s like we’re good.

 

Thanks a lot guys.

[olivero]

Nevermind. I lied we’re not good and I want to roll this thing into the dumpster.

 

Center bin is the most troublesome, on and off it shuts off intermittently, no pattern, no consistency and it’s driving me up the wall.

 

I just recently changed the thermopile, then it worked Ok for a week, no problems. THEN it started again so I changed the high limit and the gas valve, because, why not?

 

Worked OK for a week, same thing.

 

Well, dumpster time.

 

So now I pulled the burner down, well, more like dropped it. Pulled the pilot out and gave it my best intimidating stare, then pulled it apart. 

 

One thing i’ve noticed is that these won’t allow you to adjust the pilot flame, you can turn the screw inside but it doesen’t increase. SO, I figured, it’s gotta be something other than the mechanics of it, perhaps airflow or something of the sort is blowing it out in some way, perhaps if I increase the pilot flame it’ll be better. But I can’t.

 

I ended up drilling out the orifice in the pilot so I can get some more flame, just a bit more, don’t judge me so harshly. NOW there’s flame like I want to see it, had to turn it way down BUT It’s very adjustable and I think it’ll have a better chance of surviving now. Only time will tell.

 

It’s driving me crazy though, tried cleaning all the connections, sanding the ground, the stuff I mentioned above and it just won’t stop doing it, this is over weeks and weeks, immediately it looks fine, measures fine, everything’s great and all of a sudden, boom, it’s off.

 

They also had an issue with one of the other compartments today which is why I think it might be an airflow thing, but the center one is habitually more troublesome.

 

Any help is appreciated.

[ectofix]

I’ve rarely seen an airflow problem blow out a pilot on fryers.  It takes allot to blow out a good, clean pilot flame.  Try to do that yourself.

It’d have to be some serious undesirable draft to do so.

 

Pilots on millivolt setups do require some upkeep.  If the pilot flame gets weak due to buildup around its orifice…or air getting to it, then the pilot might appear fine, but could prove to be weak when the circuit is under a load.  Nearby sources of grease (griddles, chargrills, poor ventilation) are sources for air-bound grease to get sucked right in there to clog ESPECIALLY pilot burners.

 

olivero, is that fryer strictly a millivolt setup (no power cord for the actual fryer), or one with the thermopile only powering the pilot valve while the main valve runs off 24vac (has a power cord)? 

Don’t let the existence of a power cord fool ya.  Some “strictly” millivolt fryers might still have a power cord just to run a filter system…if it has one.

 

ANYWAY.  If it’s a strictly millivolt-powered heating circuit, then cleanliness of the pilot becomes especially critical.  In THOSE fryers, the thermopile must power TWO valves (pilot & main).

 

AGAIN, along with making sure the pilot has no blockages, a mVDC voltmeter can tell you what’s going on.  I’ve actually used my mVDC meter reading just to set proper gas flow to the pilot.  A pilot’s burner pressure in a fryer isn’t regulated by the fryer gas valve’s internal regulator, so the adjustment screw is really the only way to set a proper pilot flame.  EYEBALLING it isn’t the way to do that.  The mVDC output of the thermopile while under a load is the correct way.

 

So, once it’s in a heat cycle and the mVDC reading expectantly drops under a load, watch that voltage for awhile.  Monitor it.  It shouldn’t be s-l-o-w-l-y dropping MORE – a volt a time.  It should maintain whatever it first settled at when you turned the thermostat on.

If NOT, then you have a gas or airflow problem supplying the fryer. 

 

I probably don’t need to to tell you this, but I’ll say this anyway.  Make sure you have a minimum of 7″WC coming into the fryer under ALL cook line conditions.  Fire EVERYTHING up from a cold start, then check your main gas supply pressures.  7″ MINIMUM.  Any lower is out of specs for MOST cooking equipment.

 

I’ll add one more thing:  IF…your main line pressure falls within an acceptable 1/2 psi or less (BEFORE any line regulators)…AND – you have a dedicated line pressure regulator just for the fryers – REMOVE THEM.  If your main is already within range, then you don’t need a line regulator for fryers.  The fryer(s) already have built-in regulators, so having an addition line regulator is redundant and just something else that will eventually fail and cause you grief.

[fixbear]

You never said if the main burner is lighting normal or violently.  I have seen a violent ignition extinguish all.  Usually related to a clogged chimney and major flame roll-out..

[olivero]

Let me try to answer everything.

 

I’ve checked gas pressure, it’s fine, there is no redundant regulator, only the ones in the fryer it self.

 

This problem didn’t always exist, the burners don’t blow out the flame from what I can see, it does tend to drag the pilot flame around a little but it doesen’t go out. I Figured if I can make the pilot flame bigger/stronger, it would prevent it from going out. After having replaced the thermopile, gas valve and high limit, there’s not much else in play to keep that flame alive.

 

What is a rough ignition of the main burners? What’s it supposed to look like? I’ve looked at all 3 and they all seem the same to me, none is more violent than the other.