Chimney crackles and pops

What does it mean when I hear crackles and pops from my chimney?

I have a newly installed (by professionals) VC Encore cat that has a straight double skin SFL Nova SF chimney pipe running up through the living room ceiling, bedroom ceiling and roof (no bends). It finishes in a reclangular chimney with further pipe and top. The draught is fine. It is about 5-8C outside nowadays when I start the fire.

I start the fire as usual, with a firestarter, kindling and a few small logs/sticks. I add a few more small logs and bring it up to 230C and then engage the catalytic combuster, as per the manual. As it is heating up, from say 140C up to 230C I hear cracks and pops from the chimney. I usually open the ashpan door very very slightly to get the fire burning hotter. I don't open the front doors at all, except when adding more logs. The damper is open until engaging the cat.

Are the sounds I hear soot and creosote building up on the inside of the chimney pipe or are they just normal sounds? Should I refrain from trying to heat the fire up and let it do so on it's own? Is this normal or am I clogging up the chimney unnecessarily?

Someone put my mind at ease, please. Ask me for further details if I've left something out.

Chime in guys...

Oh yes, the sounds totally stop a few minutes after the cat is engaged.

Well,...when I'm upstairs I can hear some muffled crackles from, what I think is inside the chimney pipe.

If the ashpan door is cracked open a tad the fire burns more vigorously and the noises are more profound. I don't have an air intake valve on the front as I've seen some stoves do. I suppose I could try leaving one of the front doors cracked open a touch instead or not at all and see the difference.

???????

I think that must be what it is. I shall keep my ear to the pipe, well, no, not really.

But you've put my mind at ease, many many thanks!

Much appreciate the advice,

Okay, then today I'll leave the doors shut tight and see the difference. I suppose as the outside temps are lower now than last month there isn't any need to open a door.

I did see on that 'sticky' video posted that they advise to open the front stove door a little initially. Is that just for the first 10 minutes?

My stove gets up to cat opperation temps after 30/40 minutes, so I shall refrain from opening any stove doors now. Wonder if I'll get those noises? As posted, I suspect it is the chimney pipes expanding as they heat up.

Will check tonight...thanks for all the guidance,