Damn, to bad about Maria, I didn't know about that.
And yeah, it has slowed down a little. Seems like the fairly typical middle of July lull though. Give it a couple of weeks staying in the high 90's and/or a few 100º days in a row, and we will be swamped with bad run cap + dirty condensor coil calls.
Can anyone explain if this is normal operation: On most afternoons with temps in upper 90's and my upstairs is apparently experiencing lots of heat gain, my upstairs unit will run at 50% cfm on 1st stage for one to two hours. During this runtime the t-stat is holding a 76 degree setpoint. The ylo-o jumper is installed with dips set at 400cfm/ton and comfort-r enabled. I've watched this event repeat itself several times. At other times the unit has ramped up to 80% after one minute then cycled up to 100%, back down to 50% and often run for 20-30 minutes before shutting down. None of these examples are during any t-stat adjustments. T-stat is a visionpro 8k. I thought that in comfort-r the unit will always go to 80% after one minute and then to 100% after 8 minutes if needed before dropping to 50% for a few minutes before shutting down. It has in fact done this at times. My daily run times are about 14-16 hours. I do know this system is oversized, but would that affect the comfort-r run times the way I've described? If anything I would've have thought excessive cooling capacity would shorten my run times. I now have digital humidistats reading 47-50% rh at 76 sp.
Depending on several varriables,a properly sized XL19i system basicly won't ever shut off when it is over around 90º outside.
It will run continuously in first stage, 2nd stage will cycle on and off to maintain the setpoint.
Your system cycling off during mid to upper 90º days is another indicator that your system is grossly oversized. Wich is probably why your RH is running a little high.
With Comfort-R enabled, When first stage cycles on the airflow will ramp to 50% of 1st stage airflow, then to 80%, then to 100%. You likely won't notice the ramping in 1st stage since the airflow is so low anyway.
TWEAKING the air balance requires a HANDS-ON approach with small, iterative changes by an experienced tech...
Originally posted by tmoss
I'm soliciting PROFESSIONAL opinions and possible solutions.
Last year this same guy ran a Manual J and determined I needed between 3.5 and 4 tons.
My electric usage is down 25-30% and I'm keeping my upstairs 3 degrees cooler AND keeping my foyer area cooler as well compared to the old inadequate unit.
16" return he added has a 12X30 inlet grill to a closet. )
Ceiling has a 12X14 return because an existing light fixture prevented the proper size from being installed. He pointed out that the light needs to be removed for him to make it right. He also commented that another 8" return would help the unit when running on high speed. BUT, unless I keep the T-stat on 70 it seldom runs on high.
In fact, it's usually set on 76.
73 get me 50-53% RH but that's too cold for my babies.
Did he run a Manual D? I doubt it.
His service and advise to me has been just fine.
Well, he's pragmatic.
I titled this post air balance because I wanted to know how much ducting this unit needs to run the way it is designed to run.
If I want to add or modify my ducting differently than what he suggests I need to have some intelligent and valid data to support it.
UNLESS you are prepared to
perform an As-Built on the duct system and
have a comprehesive Manual D analysis completed
in order to reduce the number of iterations.
Sounds like you may be satisfied with Variable Speed AHU set to 350 CFM/ton which should deliver < 50% R.H. and decrease the noise.
Also, use MERV 8 or 9 pleated air filters.
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
So what specifically dictates 2nd stage cooling to energize and why?