What is a good reasonable priced accurate manometer to measure my barometric damper? My furnace should be 0.025 and my flue should be -0.02. Looking at the gauges for sale i see accuracy (read inaccuracy) ratings that would make readings in the range that I need almost useless. Exp: 0.3% of full scale 55.00wc (0.003x55=0.165) Does that mean that a reading of 0.02 could be off by as much as 0.165? +/-0.3% of full scale 83.02 InH2O NKTECH NK-L3 (0.003x83.02=0.249) ±1.5% of full scale 4.00wc Dwyer 478A-0 (0.15x4=0.6) Am I doing something wrong here? tks, pa

I feel like I've read most of the threads related to this issue, but can't find anything that quite fits. And I've had several HVAC guys out, but nobody has been able to fix this. [B]Here's the scenario:[/B] This is a relatively new (4 years) high efficiency Heil furnace. It periodically short cycles and after three tries locks out with an error code (three blinks) that says the pressure switch did not open or close. It will occasionally run for a while before cutting off or sometimes if cuts of relatively quickly, but it always light up. Once it's up and going it will run well until the temperature is reached, but sometimes that takes several lock out cycles to get to this point (I power cycle the furnace to get it going again after lockout). The problem is significantly better with the door off, but it still short cycles. Condensate seems to be draining and the furnace always lights. But the short cycling seems to be getting worse as time passes. One of the HVAC guys replaced the pressure switch, which didn't help. Another examined the intake and exhaust piping, but couldn't find anything wrong. One other thing — I'm not sure if this is normal or a symptom of the problem — the furnace makes a gurgling sound when the inducer motor starts up. Previous HVAC guys thought maybe there was a lot of water in the motor housing, but when removed, it was just a little damp in there. I'm at a loss to understand what could be going on in such a way that the furnace occasionally will run for a long time without issue, but other times locks out after only a few minutes. Any ideas? I am really at a loss and am thinking about just replacing the darned thing.