How long should it take to preheat?

I’m in my garage in Chicago and it’s a bit cold and will be getting colder. I don’t want to overtax this thing (new user) so I’m wondering how long it should take to preheat to like 428 or so. I’m trying to determine what ‘normal’ is and what to expect going into winter.

My room isn’t all that cold probably around 20 deg.C(really need to get myself a thermometer) but when I’ve been pre-heating to 230-250 deg.C(above 428F) it usually switches to charge-mode within 20-25min.

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I always do a 30 min warm up routine to make sure the roaster has good thermal energy throughout. After turning it on I take it up to max temp (310 C), then bring it back down to the needed preheat temp.

Before first roast of the day sometimes I run the machine empty for a few minutes. I wait for “Charge”, then I remove the bean chute plug and wait for “Roasting Started”. I let it go for about 5 minutes.

I don’t let it get extremely hot. I try to keep the IBTS near the PH setting. I use lots of fan. I guess I could make a recipe for this.

As a generalization the criteria might better be temperature than time.

For the first roast I use a very long pre-heat watching BT for when it becomes a flat line (the BT Predictor will guide that). On subsequent roasts BT will initially be too high for this criteria, so after beans are dropped I have to let BT decay to about the same point where I started the preceding roast.

With the pre-heat of 392°F I often use, BT will stabilize at somewhere around 290°F and that becomes the point where I charge the beans for all the roasts (room ambient becomes involved with weather extremes).

My pre-heat is pretty low compared to what many here want to use so it may not work for you. And it takes more roast time than some want to invest waiting for temperature to settle. The lower pre-heat also dictates a longer roast (nearly 15 min to 2C) to get the same end temperature as a slightly higher pre-heat would have allowed. Also I’m using what’s referred to as a heat-soak which dictates slower increases of roast heat.

It’s complicated. Just something to chew on till the next roast session.

Bruce