Hot water can run out quickly in an oil-fired furnace system due to factors such as inadequate tank size, high demand for hot water, or an insufficient heating capacity of the furnace. If the hot water tank is too small for the household's needs, it can be depleted rapidly during peak usage times. Additionally, if the furnace isn't operating efficiently or has maintenance issues, it may struggle to heat water quickly enough to keep up with demand. Regular maintenance and ensuring the tank size meets household needs can help mitigate this issue.
Not if it was disconnected properly
have baseboard heat boiler runs off furnace want to shut off furnace to save oil will it hurt anything
an electric furnace runs off of 208/230 Volts while a typical gas furnace runs off of 120 also a gas furnace will have a valve for the gas relay where the gas enters the furnace.
The water being held in the water tank when the furnace shuts off is at a set temp, the water tank hopefully is insulated, as time passes, the water temp has to drop because the furnace has not come on to maintain the set temp, also the controller could be faultly that controls the water temp for the hot water heater, the only time you have hot water is when the furnace runs.
Gas tankless water heaters use high-powered burners that quickly heat water as it runs through a heat exchanger. It is 22 percent more energy efficient on average than the gas-fired storage-tank models.
Hot water runs out quickly in your shower because the water heater may not be large enough to supply a continuous flow of hot water for an extended period of time. The capacity of the water heater and the rate at which hot water is used in the shower can affect how quickly it runs out.
a furnace
A blast furnace runs continuously, and input materials are continually dumped in at the top to make their way down through the furnace. Shutting down a blast furnace for relining or other work is a major event in its life.
check to see if drain to unit outside in draining may be clogged
A resistance furnace runs on electricity so it will be some type of electrical transformer.
To make electricity, the most common way is to burn something that heats water that creates steam that runs a fan/turbine. Coal fired electricity is when the thing that is burnt is coal.
The coal heats water into steam the steam runs turbines connected to generators.