New Egger - Temp too hot for slow and low.

It's not the chips. They do not catch fire at lower temps. Even 400+ unless there was too much air to begin with, which allowed the temp to rise, and the chips to catch fire as a result. What i mean is, the chips down catch fire and then cause the temps to rise. Instead, the temp rises, and that allows the chips to catch fire

a hot fire is always (and only) due to too much air. 

an hour isn't enough to be sure it's stable. And it sounds like the daisy was off? Keep the daisy on as insurance. Sure, you can run with only the lower vent, but if the lower vent is too open (probably no more than two credit cards thick), the daisy will keep the temp from rising

don't soak chips. That's the reason you were seeing low temps. Then the chips dried out and the fire took off because the vents were set for a fire that was damped by wet chips. No longer wet, the charcoal took off, and so did the chips

i ain't kidding about chips or chinks or twigs or whatever. If my fire is stable at 500, i can throw in chips and shut the lid. And once the extra oxygen (from the open lid) is used up, the chips absolutely cannot cacth fire. There is no spare oxygen. It's used up by the lump. The chips are on top

The fire was artificially low due to the wet chips. They dried, fire took off. 

Could be the heat rising caused more draft, lighting more coals, leading to more draft, etc. 1/2" is a big opening for the bottom vent. It takes a tiny opening for 220 degrees. And once the ceramic gets hot, it takes a long time to cool down.

Where you by any chance using a drip pan with liquid in it?

half inch is too open.

what caused the fire to appear stable with the vents that open is probably a combination of being the start-up of the fire, so it's small for a while, plus the wet chips.

imagine you have a burner on high on the stove but with wet chips on it.  that burner isn't going to be too hot.

then the chips dry out, and the REAL settings of the burner cause things to catch fire.

same for you.  half inch open on the lower vent is pretty wide for a fire you want at 225-250.  except, not at start up, where you might have it open to help get things going faster.

but you couldn't tell it was open wider than it needed to be (to be stable) because your chips were damping the fire.  chips dry off, fire acts like a real fire with a more-open lower vent, and rises to its REAL temp settings, which are higher.

there is no need to soak chips.  chips, or other wood, can NOT catch fire in a stable fire, even if you are at 400+.  if this were an open campfire, of course they would catch fire.  but this is an airtight grill, and a stable fire is consuming all the spare oxygen that is coming in from below the fire.  tossing flammable wood on TOP of the fire doesn't cause flaming because the O2 is being full used.  there's no spare O2 to cause the wood to flare up.  it would need a lot more.

as you get used to the egg you will see this.  you'll open the egg to turn something, and standing there with all that air rushing in, you will see flames start up (whether the lump or wood pieces).  shut the dome when you are done, and that stuff will stop flaming in a few short moments as the egg resumes its stable burn, with the air from below

wood is wood, in the egg.  a pound of chips lasts as long as a pound of chunks.

in fact, you have better control with chips, because you can spread it out.

but that's not the issue.  the issue was: your vents were too open.  your fire was not actually 'stable'. and your fire was being held back by wet chips, which dried out in an hour and the fire (no longer working on drying the chips) was free to grow

...and just noticed what @gamason said too.  that will do it as well.  water pans are a governor, holding temps back, as the energy goes into evaporating the liquid (it doesn't boil at lo/slow temps).  when it is gone, that energy grows the fire.  more draft, higher temps, bigger fire.

fuel and air.  that's all it ever is. if the fire is too hot, it is ALWAYS (always) too much air, no matter how 'shut' you think it is

Holding the temp at 220 is not that easy.  Aim for something around 250 to 260 degrees ... that's the sweet spot for most eggs.  Some folks cook ribs at 375 and claim they are just as good as low-n-slow ones, so the extra 30 or 40 degrees or so will not be noticeable in the final product.  The bottom vent will end up around 1/8 inch open once everything is stabilized.  Utilizing the daisy wheel with the petals open just a crack (again in the 1/8 inch range) is good insurance.  The final openings vary slightly and are affected by the egg size, air tightness, lump, temperature, humidity, wind speed, etc. 

Don't introduce any moisture into the egg ... soaked chips, chunks, or a water filled drip pan.  Spritzing a few times might be the only exception, but again it's not needed.  The egg doesn't need, nor want any additional moisture it in.

Eggs are easy to get hot, they are almost impossible to cool down while still cooking.  Do a hot cook and shut the egg down for the evening with the ceramic cap ... come back in a couple hours and it'll still be hot.

And yes, if they're honest, everyone will tell you that they've had a similar problem when they first got their egg.  It's difficult to come to grips with how little air is necessary to achieve target temps.

Usually small gasket seal problems just mean that the other vents need to be more closed. If the dome is not seated such that you can fit a pencil, or such, in a gap area, then you won't be able to control the temp.

You definitely had an air flow problem. As mentioned, wood can't burn in the Egg at low temps. The burning lump uses all the oxygen, and the wood doesn't reach combustion.

Again as mentioned. 1/2" at bottom is too open. I'd expect at least a 300F dome with an opening like that. I leave the daisy off and the bottom wide open till the dome therm reads 200F. Then I put the daisy on, petal less than half open, and shut the bottom to a little less than 1/4". Typically, that sets in to about 250F. After a few hours, the temp usually creeps up, and I end with both top and bottom all but closed.

Once the ceramic heats up, the heat will stay up for a long time. I measured a few times, and found that after shutting completely down w. a dome around 250, the Egg interior temp stayed above the 140F "danger zone" for between 60 & 90 minutes.

For 250 on my large, the bottom vent is open about the width of 2 stacked credit cards.  Daisy is open about the same.  She will roll like that for 28 hours until the lump is completely exhausted.

Wood chunks run easier when mixed in with the lump during filling the firebox.  All you'd need is about 3-4 fist-sized chunks to cover for smoking.  Once the meat hits a certain temp, it won't absorb/adsorb any more smoke.