Most crankcase heaters I have seen are a PTC element you place in a socket in the compressor base, with 2 wires leading to the mains supply. They draw 150W when cold, but when it gets to setpoint the draw drops a lot. As here we never have it cold enough to use the units as heat pumps most have them disconnected as ambient is enough to keep the oil warm in any case. Leaving it connected when in use as a heat pump in cold ambient though will help with oil flow.
In most cases the compressor will have a jacket around it, made from an outer neoprene rubber with a fibre lining, held with a strip of hook and loop fabric stitched to it. That is common in split units, though I tend to remove them as they cause issues here with corrosion, and trap moisture on the compressor case from the suction side. I always give the compressor a coat of anti rust paint if possible when new before installation, as there are a few places like the suction elbow and the base plate mounts that always rust, and which eventually leak. Have one going in under warranty today, it has leaked from the compressor. First time though that I found the leak not to be the suction flange or the base plate, this one is leaking from the terminal block. Gas sniffer located area then spray confirmed it. Now to evacuate and pull it out to take in.