I am modelling a 3,000 sqft house which is designed as using two gas powered furnaces to heat the entire house. They are the same model of furnace, one has a capacity of 80,000 BTUh and the other of 60,000 BTUh. I am modelling the 80,000 BTUh furnace in the Type 1 furnace tab of the heating/cooling section, and the other furnace as a supplementary heating source. My problem is that HOT2000 does not seem to be taking the supplementary heating source into account. I have an error message that prompts me to increase the capacity of the heating source. If I model the house as using one furnace with a capacity of 140,000 BTUh I don't have a problem. I am modelling this house for code compliance; does anyone know if I am modelling one large furnace instead of two smaller ones, would HOT2000 assume that the large furnace uses much more energy than the two smaller furnaces? Right now the model is not passing the code requirement and I am wondering if this is the issue.
This screams oversized! Why the two furnaces? Split system for two floors?
I would think 2 furnaces would use more energy than 1. As you have to start up and power two blowers now.
Sorry not familiar with HOT2000. Good Luck!
Hire a professional to inspect the system.
I agree with Daniel, Two furnaces would use more energy than one furnace.
An undersized furnace will work fine for the majority of the time, but every once in a while it won't get the house quite as warm as desired. An over-sized furnace will also be less efficient. A furnace is least efficient when it first fires up and doesn't reach its peak efficiency until the temperature of the air coming out has reached a steady value. An over-sized furnace will keep the house warm no matter how cold it gets outside, but it does so at a cost. First, it will probably make the house less comfortable. When the furnace kicks on, some areas may warm up very quickly, so much so that they get uncomfortably warm before the thermostat has even been satisfied.
If your model is not passing the code requirement and you are still in a confusion you should consult the expertise person having certified license like Furnace Repair Santa Barbara to get the proper solution of your problem.
We do not find many 3,000 square foot homes that require 140,000 BTU's of heat but that is another subject. Could you use one 120,000 BTU fully modulating gas warm air furnace?