System not keeping up
System not keeping up
(OP)
I was involve with the HVAC design of a custom home. It is a zoned system, upstairs and downstair. Well two years after the homeowner moved in, we got a call that the cooling was not working. The homeowner did not call until two years after he move in because he does not use the upstairs. It was only noticed when he had company staying upstairs. There are other simular homes that we did and they are not having any problems. The difference is a skylight, but even when I figured it to be the worst case it only add roughly 2000 BTu/hr to the load. The total load is roughly 20,000 BTU/HR. We installed a 2.5 ton condenser and a 3-ton furnace. We have had problems with the manufacturer, so we changed the condense to another manufacturer, but the same size. We also changed out the furnace to a 5-ton to get more airflow. But no matter what we do, it seems like we can only drop the upstairs an intial 4 degrees and then it will just idle there. It stays roughly 10 degrees lower than the outside temperature. If the outside temperature goes up so does the indoor temperature. We have tried everything. It seems to me that maybe we are missing insulation in the house? Any ideas as to what is going on? Has anyone run into something like this before? Please help.





RE: System not keeping up
RE: System not keeping up
RE: System not keeping up
What's the breakdown on the 20,000 BTU/hr? That doesn't seem to jive with a house big enough to only live downstairs.
How is the zoning accomplished? It sounds like there's only one condenser, so is the zone control done by dampers?
TTFN
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RE: System not keeping up
RE: System not keeping up
RE: System not keeping up
Building HVAC systems are some of the worst engineered systems I see. Getting perfect heating in in winter and cooling in summer is a very complicated control problem and cannot be done with one simple thermostat. You get what you pay for.
RE: System not keeping up
Is there unfinished attic space above 2nd floor?
Is there attic ventilation, such as gable or soffit vents and roof ridge vents to let heat out?
RE: System not keeping up
RE: System not keeping up
All my ducting is in the attic, and it's got maybe R15, and it's HOT up there. Nonetheless, there's plenty of cold air getting into the 2nd floor, although we had to twiddle the registers a bit.
A simple thing might be to simply shut all the registers on the first floor and see what happens.
TTFN
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RE: System not keeping up