I recently had an old pulse furnace replaced with Bryant 915SB42060E17. The temperature rise spec is 40 to 70 F. I found it was 68 and got the contractor back. He increased the blower speed so now it's 56 f. Seems very good but now when I calculate the static pressure it has jumped from 0.65 to 0.8". The filter is a new 5". The contractor said duct sizes are good. No vents are closed. He thinks the evaporator coil (2 ton AC) 35 years old. Is likely restricting flow. If we reduce the blower speed between new and old speed the pressure would drop to about 0.72" but the temperature rise would increase to about 64f. Otherwise everything works well.
Is 0.8" too high? Is 62f too high? Which is more important for the life of the furnace?
The furnace is tested at a .5'' but designed to work with over 1'' external static if you check the specs for that unit. So it's fine but it will sound louder than normal with the higher fan setting. You'll have to keep up with filter changes because it will be harder on the blower if the blower has to speed up and draw higher amperage because of the filter is plugging up.
Quote from: tenletters on March 15, 2022, 06:53:31 PMYou'll have to keep up with filter changes because it will be harder on the blower if the blower has to speed up and draw higher amperage because of the filter is plugging up.
The blower will speed up if it can't move as much air, but this means it will end up doing less work by moving less air, which will draw less amps, not more.
And I almost never get a static pressure of .5 or less, so since your blower increase is helping it be well within spec, I wouldn't worry about the static.
Quote from: Porcupinepuffer on March 16, 2022, 04:20:49 PMQuote from: tenletters on March 15, 2022, 06:53:31 PMYou'll have to keep up with filter changes because it will be harder on the blower if the blower has to speed up and draw higher amperage because of the filter is plugging up.
The blower will speed up if it can't move as much air, but this means it will end up doing less work by moving less air, which will draw less amps, not more.
And I almost never get a static pressure of .5 or less, so since your blower increase is helping it be well within spec, I wouldn't worry about the static.
That's a PSC motor. The PSC blower speeds up slightly, but not enough to move more air when restrictions happen. Since you move less air, amperage goes down.
You can't get those with new furnaces anymore anyway.
An ECM variable airflow or ECM constant torque will draw higher amperage when restricted to move the airflow it's designed to move. They're designed to work at around 1.25" ESP before any damage can be done to the motor by running too high.
Lots of systems are not designed for .5 static pressure in at least the last 25+ years. The .5" esp stamp on the furnace means the manufacturer tested at that. It doesn't mean you need to have that setup. They don't know your coil, filter selections, accessories, return and supply duct design, etc
So what your saying is the temp rise is within the specs (even though it's at the top end of it) and everything seems to be working fine and you still call yourself hvac guy back? Your type of customers are the ones us hvac guys and gals just love lmao! Sit back, relax and enjoy your heating system. They don't make em anymore like those old pulses and please make sure you don't call me on your next install unless we agree on a curbside warranty lol
Well if the temp rise is practically right at the max spec and the guy has a brand new filter, it will go over spec when that filter gets dirty. I think with current static and temp rise from the increase in blower speed, it will be perfectly fine.
Quote from: Hvacpimp on March 17, 2022, 08:09:45 PMSo what your saying is the temp rise is within the specs (even though it's at the top end of it) and everything seems to be working fine and you still call yourself hvac guy back? Your type of customers are the ones us hvac guys and gals just love lmao! Sit back, relax and enjoy your heating system. They don't make em anymore like those old pulses and please make sure you don't call me on your next install unless we agree on a curbside warranty lol
I'd call them back too. I'd never want a furnace set up with a brand new filter to be at the highest possible point of the temp rise. You don't have a buffer for the filter/coil to even be dirty.
Setting up a system that just works in that single set of conditions is not a good job and nothing to be proud of or make jokes about.
Quote from: tenletters on March 19, 2022, 06:13:05 AMQuote from: Hvacpimp on March 17, 2022, 08:09:45 PMSo what your saying is the temp rise is within the specs (even though it's at the top end of it) and everything seems to be working fine and you still call yourself hvac guy back? Your type of customers are the ones us hvac guys and gals just love lmao! Sit back, relax and enjoy your heating system. They don't make em anymore like those old pulses and please make sure you don't call me on your next install unless we agree on a curbside warranty lol
Setting up a system that just works in that single set of conditions is not a good job and nothing to be proud of or make jokes about.
You must be a huge blast at parties. I guarantee the ladies love it when you show up!
Quote from: Hvacpimp on March 24, 2022, 08:02:32 PMQuote from: tenletters on March 19, 2022, 06:13:05 AMQuote from: Hvacpimp on March 17, 2022, 08:09:45 PMSo what your saying is the temp rise is within the specs (even though it's at the top end of it) and everything seems to be working fine and you still call yourself hvac guy back? Your type of customers are the ones us hvac guys and gals just love lmao! Sit back, relax and enjoy your heating system. They don't make em anymore like those old pulses and please make sure you don't call me on your next install unless we agree on a curbside warranty lol
Setting up a system that just works in that single set of conditions is not a good job and nothing to be proud of or make jokes about.
You must be a huge blast at parties. I guarantee the ladies love it when you show up!
They love me because I fixed your equipment and now they have heating and cooling equipment that works as designed after I leave the dwelling.