He's got the blower cranked up to the highest setting... and it did rapidly drop the temp.
Last guy set it on the lowest setting... this guy sez go to highest (450?) cfm setting, and this may be a little noisy every once ina while, but he said it wouldn't burn the handler out or cause any other issues.
He's still here for a few minutes... does this sound ok? Vents are definitely noisy, but I have no way of knowing how much noise is ok.
You have issues and they are with your contractor.you need 350cfms per ton .Face it the old sytem was handling your temps,and you know it moved less air .
450 is too high, unless you are in the dessert.
i'd go 400, and make sure the dip switch is set at tonnage of system.
The enhanced mode is "Comfort-R", I don't know the air hander if it needs a jumper or not. But on my furnace, it needs a jumper to get the full blower profile.
I run mine at 350, and has no problem at all.
OK, so this guy had "enhanced" totally backward? He said enhanced was no ramp-up, but he reset it to do delayed ramp... so now it's on comfortR but before it wasn't?
As for the 350... It was definitely not getting the house cooled properly... so what's the issue here? Is it just a question of moving the stat?
Right now as I'm typing, stat is set to 75, but temp reads 77. It's not hot out. It's past 11pm, and the blower is blowing like crazy. No one has opened a door in hours. I can see no legitimate reason why system should be unable to hit it's target.
... and, there's NO WAY it's 77 degrees in here. Temp reading is definitely at least a few degrees off. Is it possible this is one and the same problem? If the stat was moved, would this be ok?
I guess I'm not understanding what I should do here. If it needs to go back to 350, fine, but then the system isn't cooling the house. So when they say "maybe you just have leaky ducts or bad windows", and I say "well, the 25 year old system that was in here managed to hit it's target just fine up until a week ago"...
... what's gonna keep it from being a dead-end conversation? What do I need to suggest or ask about?
Yes Ithinktherefore, according to your description the tech got Comfort-R (aka Enhanced Mode) completely backward.
Am I not right in thinking all this money was spent without feeling the need to do Manual J, to select equipment using Manual S, to check duct adequacy with manual D? Yes I can see how there might be shortcuts that an experienced tech can legitimately take -- the ACCA template is more often honored in the breach than in the following. But this is beginning to look like an object lesson in how "same label ton size" can fail to work. The techs almost to a man, eschewed doing things the ACCA way.
At this stage the homeowner is being told he has a Hobbs choice: accept 450 cfm/ton and overloud ductwork, or accept inadequate cooling. Is this not wrong? This also illustrates why techs who don't really know how to predict the outcome of their actions, will want to resort to oversizing. At least with oversizing it will coverup something as obvious as under-cooling -- humidity is more subtle and often the customer lets them get away with it.
I guess this was a rant, and the rant part is over. Sometimes it is so damn frustrating, reading the "high road" of ACCA methods on this board and then learning that 95% of techs don't want anything to do with that.
According to some research I have read, running 450 cfm/ton gets you about 6% more sensible capacity then 400 cfm/ton, and running 350 cfm/ton gets you the same amount less (I have the research abstract on paper, can supply a link if you really want). If everything were working properly, which I suspect is not the case, that would explain the airspeed setting choices a tech might make in a borderline situation.
Hope this helps -- Pstu
Now would be a good time to either do the heat gain calculation yourself or pay someone (the current contractor?) to do it for you.
Then you will know if the current system is adequately sized for your required design temperatures or not and also what kind of duct changes you may need. By twiddling with the input factors you can see how much reduction in heat load you'll be able to get by adding insulation, changing out windows, adding window tint, etc.
As I've said before it is sad that you didn't get this done BEFORE system selection, but such is the cost of being in a hurry.
By the way, call the owner and tell him or her it is time to train the techs on the equipment that they are installing and/or servicing.
"I asked him if comfor R is enabled. He has no idea what comfort R is. " I would have shown him the door.
What did the tech's thermometer say about the accuracy of the thermostat reading? Did he plug the hole behind the thermostat?
Originally posted by ithinktherefore
... and, there's NO WAY it's 77 degrees in here. Temp reading is definitely at least a few degrees off.
If you've got a handheld thermometer than check the temperature for yourself.
I didn't just ask one of the contractors I got about calcultations... I asked all 6. I got blown off 6 times.
As for the thermometer, the tech had a handheld. At one point, when he placed it 8 feet away, it was 4 degrees off. When he placed it on top of stat, it was about 2 degrees off.
No, he didn't cork the hole. He said that might help, but I think he just got frustrated when I said that wouldn't fix the problem because it doesn't explain why the system would cycle down before hitting it's target. In the end, all he did was crank up the airspeed.
If this truly was a marginal case, I'm gonna kick the salesguy's a$$, because when he came over, I told him right off the bat I was pretty sure what I wanted... a 4 ton xl19. I explained that current system was 3 ton, but we might be adding 600 sqft, and we had leaky windows, old ducts, etc. Half our discussion was me asking whether being a little over on the size was a problem. I said I thought it would be ok in marginal situation because it wouldn't short cycle because of 2stages and variable speed. He just told me my ducts couldn't handle the 4ton blower, so it was out of the question without redoing all the ductwork, but that wouldn't do it, because unless we were absolutely sure we were doing addition, they'd refuse to install the 4ton system because they didn't want to be liable for installing the wrong size unit.
If, it turns out that calculations DO indicate 4 ton unit, I'm gonna have to put my foot in his a$$. Maybe I'm not seeing this right, but if they're cranking the system up into hyperdrive on the blower to try to get enough cooling, couldn't I have done the 4ton on a normal blower... or even it's lower setting... AND still been ok with some tweaks if we do the addition? I asked him these exact questions and told him I wanted the 4ton... then went through 20 minutes worth of questions with him to make sure there was NO POSSIBLE WAY the 4 ton would work.
Maybe he was right... maybe 3 ton is the right size, but if that's the case, what is the problem here? Stat in wrong place? Fine, I'll move it... but then what? System should be able to cool to target at normal setting, so what ELSE is wrong?
Ducts a bit on the restrictive side? OK, I'll buy that, but the old 25 year old 3ton system managed to hit it's target, and the tech can talk circles around that all he wants... it proves they are at least capable of handling enough airflow to get the house to target IF the system is running properly.
As you said the old 3 ton had no problem.This indicates there is a problem with your new install.
If the stat is in the same wall space as the return thru to the stand(wiil actual suck air around the stat),and/or the wall is uninsulated ,that can account for the temp difference.
Moving it to a nearby interior wall,that isn't in the path of a supply grille, is best.
I don't see anyway you will need 4 tons,the new system maybe a few btus short of the old one(not uncommon at all),worst case increase attic insulation,which is worth the money regardless if needed to get to setpoint or not .
[Edited by dash on 06-09-2006 at 10:22 AM]
Yeah... even if it's a bit marginal, the old system was 3ton, and could cool the house on a hot day... I gotta think the new system is MORE adequate... I mean I don't have any stats on the old system to back this up, but it was 25 years old... shouldn't a brand new top of the line system be able to do as much cooling at the same size?
Sounds like a given the stat needs moving. I turned it up to 77 last night because everyone was shivering. When we went to bed it read 77, and all 4 adults in the house were talking about how cold it was. Whe I got up this morning, it was hot... stat still read 77.
I could go get a handheld if I knew where to buy one, but I don't need to to tell you the stat is wrong... and not consistently up by 3 degrees or anything like that... because the differential with outside (garage) temp is not always the same.
So, stat's gotta move... maybe ducts kinda leaky too... but there's a lot of air movin' through them right now.
One other thing struck me... when tech was over here the other day, system was in stage 2 for the entire time he was here (2hours or so) All these other people keep saying system runs in low most of the time. System's cranking right now too.... maybe I can chalk all that up to needing duct insulation, better windows.
... still, old system could hit target and this one's struggling... and other system had stat in same place... so what's the OTHER problem here? I feel like it's useless to call them back over if I can't point them in a productive direction.
They old stat may have been sealed of(air wise)from the wall,it's sensing device may have been farther off the wall,it may not have been as sensitive ,etc. ,etc..
Seal the wall opening,if that doesn't do it ,move the stat.
Have the system set for 350 cfm per ton,that's what you need in Florida .
We all as a whole have to remember that all this new technology is just that "new" it took many years to basically perfect the older systems, now were into a different age and newer technology and it will take many years of trial and error just like the past to get it all figured out, so this will require a lot of patience of both the Homeowner and the Contractor, I feel that anyone that expects perfection at this point is just asking to much, in 10 years yes maybe.
“Experience is a hard teacher because she gives the test first, the lesson afterwards". - Vernon Law
"Never let success go to your head, and never let failure go to your heart". - Unknown