It is as important to understand the space you're heating as it is to know the unit you are heating with. Examine your home and rooms. Remember that south-facing rooms may overheat during the day and call for extra heat in the evening. Bedrooms may be closed off or out of use during the day, but create high demand at night. While zoning will answer many of these issues, two-stage or multi-stage furnaces are the ideal solution since they can deliver high, medium or low levels of heat depending on demand, without creating excess. When designing heat zones or controlling heat through registers, excess heat must always be taken into consideration. If it is not dumped into an excess heat zone, such as a spare room, workshop, basement or garage, the heat can back up into the furnace, causing damage.
If you’re painting over an old semi-gloss paint, check to see if it has become hard and brittle. Try to pick off a piece from an obscure area with your fingernail. If it chips, it probably needs a light sanding to improve the “tooth” for a new coat of paint.