I see where your coming from but please understand, I know I have a problem and my principle goal has always been to determine where that problem lies. As I see it, there are really 3 possibilites; 1) the existing system, 2) the installation or 3)my house/yard. The house and yard haven't changed. The installation hasn't changed. the sytems older but otherwise, hasn't changed either. I obviously trusted the sizing calcs becuase I bought the system. However, since the system never worked right, even when brand new, I think it would be foolish to ignore a possible sizing problem in light of more than one opinion of undersizing. If you read back, a few have suggested that I should to the calcs myself. I didn't know how and didn't even try until someone pointed out the program to do it... I'm just trying to follow up on any advise that may help.
The humid1 & marko1,
I've heard similar opinions more times than you know. I guess I understand why you might think that but I'd bet you haven't read the whole post, or maybe just not carefully enough. AND, I don't blame you for that.. its awfully long and boring to be sure.
With all due respect (and I'm trying to calm the cord you struck), picking the best guy and leaving him alone is what got me here. AND, blindly following similar advise hasn't served me much better. So I'm not doing that anymore.
There are two sayings that I'm growing very fond of these days "once bitten, twice shy" and "if you want something done right, do it yourself". I'm not an HVAC engineer and didn't desire to become one. I didn't size the system, and admitted I didn't know how. I just wanted to be sure I would be comfortable once it was done. After all, I didn't low ball this... but this quote, though higher, didn't have as much tonnage as some other cheaper quotes...hence I questioned the size and was assured it was optimal by "the best guy" that I left alone.
If this system had initially worked and then slowly gotten worst, I would agree with you. If it had worked until the lighnting strike then started acting flaky, I would agree with the next poster. If I had replaced the t-stats and caps and not had both electricians and HVAC guys out, I too would question the incident. But the facts indicate otherwise. There are still so many details that would just take too long to recount but the main ones are all here.
The symptoms and their history are not facts easily erased by foundless blame on incidents or beliefs perpetuated by protectionism of craft. In fact, foundless blame, given the facts, serves to cloud the issue and fosters ideas that the main "chief" (that would be me), is part of the problem. At least thats how I took your comments....And you know what, I'm used to that from many in your profession. They are the smae ones that when things go wrong can't even consider the possibilty that they may have made a mistake. They'll go to great lengths to blame eveything but themselves. Well let me be so bold as to tell you my thoughts on that. Respect for men, be they proffesionals or craftsmen or garbage collectors is earned by their conduct, not given freely becuase of a sign on a van or an ad in the phonebook or even a name on shirt. I have more respect for an honest man that admits to a mistake and asks for help covering the costs to fix it than the guy that covers up his mistakes, tries to shift blame to equipment or subs or suppliers or manufatcures then tries to look like the hero becuase he didn't charge to fix what was messed up on his job.
I treat others like I want to be treated. If a prospective customer wants to test your knowledge of your craft and you get upset, what kind of message does that send? Do you think it would make the customer trust you more or less if you got upset at the mere question? Logic suggests you would only get upset if you didn't know the answer and got caught... in which case, I wouldn't want you in my home anyway. I've read most of the articles on this site about theory and I would bet you dollars to donuts that if I called every HVAC company in my yellow pages and had them send out a tech for a service call and I asked that tech questions on superheating, subcooling, saturation and "proper" charging methods, many if not most, would be unable to answer one if not all the questions... Do you think I'm wrong?
Sorry for the rant but unless you read all the facts you can't minimize the problem.
[Edited by jav on 06-18-2004 at 09:40 PM]
I have the homeowner version of HVAC-Calc, and my copy has expired. It will save your work and allow you to open, tweak, save another version, etc., for the 30 days. It will do anything a homeowner would need during that time (it's not a crippled version of the software or anything). It takes some time to do it completely, but 30 days is plenty. Then just make sure you print your results, because it shuts down completely once your time is up.
I am VERY happy with the results I got from using it and consider my $50 well spent.
This isn't to contradict any of the pro opinions posted or to argue that you need another load calc. I am just clearing the air on the HO version of the software and what it will/won't do.
I understand yourlogic perfectly and your right, I don't know anything for sure at the moment (other than I'm not getting the cooling I expect and that my epectations are reasonable (75 degree set point in the northest).
I think what your saying better than I was understanding (...sorry, I'm a little defensive these days) is that with so many unknown variables, I have to pick an approach to the problem and work in one direction, or the other, but working it from both ends may just confuse things... and your right there too!
I'm not the expert, you are... I don't feel comfortbale enough doing the calcs to trust the results. I'm sure the programs great but the operater is admittedly green. Taking measurements, I know I can do. I'll start there and see where the data takes us. From there I'll be picking your brains for some interpretations or direction on what more I need to do.
Thanks for the help!
if you haveent already plz post the charge info the tech took and if this is a piston coil or exp.valve.
what was the pressures, super heat, subcool ,out door amb, indoor wb and dry bulb!
beleive it that most high eff are not charged right.
Hope this correspondence finds you well, thanks for the opportunity to provide service - although I wish it were under better circumstances. Other than this forum, I realize you have NOT experienced the best customer service in the past and I’d like to change this, if you will me help.
First, I’d like to thank you for putting forth the effort to become an educated customer! Educated customers like yourself are few and far between and if HVAC contractors knew how important educating customers is to THEIR bottom-line profits, they would be climbing over each other in their efforts to educate every new customer they encountered.
Second, I know you have already expressed it in one way or another but let me reassure you that you are dealing with some of the best folks in the business and I say this without really knowing any of them personally (just reading your story was enough to convince me).
Third, there is one concern on your part that I’d like to straighten out if I may. Most of the folks on this forum probably already know it but I haven’t seeing it specifically mentioned yet, although Lmtd touched on it a bit. Having an UNDERSIZED unit is not necessarily a bad thing. If an air conditioning unit is undersized, the unit will run longer; but should still obtain the human comfort goal; an air conditioning unit only dehumidifies when it’s operating and dehumidification can make higher temperatures more comfortable. In other words, the temperature might be higher than desired, but the humidity will be much lower than if the unit were OVERSIZED. This all assumes that the unit is operating near its peak performance. Bottom-line, a slightly undersized unit is preferable to an oversized unit any day of the week – all other things being equal.
Forth Item is NOT a sales pitch, I do NOT nor will I benefit in anyway, shape, form or whatever. You have a big problem and I’m just trying to help.
Forth, please don’t give up on me yet! We still have the dollars to donuts challenge to workout. Specifically, seems like the finding a qualified technician issue is still an ISSUE. Here is how to find the technician you’re looking for (stay with me ‘cause you might think I’m NOT serious). Look in the phonebook, it’s still your best resource. Select a contractor based on the following criteria: a. Licensed, bonded and insured contractor; b. if it’s a big job get at least 3 bids (and never take the lowest bid); c. ask your neighbors friends and relatives for referrals; d. check all prospective contractors out with the Better Business Bureau AND ….E. always - always - always use an air conditioning contractor that employs ONLY RSES or NATE certified technicians!
Why RSES or NATE certified technicians? Because they are some of the best-trained technicians in the industry and they have to attend class, get CEUs and re-certify every few years. Most technicians go through a 6-month college class followed by testing and never open a book or get tested again for their entire career. Now I’m not going to say RSES or NATE Certified technicians are perfect and I’m not going to say they get the problem fixed the first time - every time. But it only makes sense, if you are going to pay for the best you might as well get the best.
Now I know absolutely no HVAC contractors in Ma, however, you can locate them fairly easily by going to the NATE website: http://www.natex.org/natex/consumer.asp and tab down to the C3 locator. I live in a town of about 886,000 people and there were only 3 companies listed at the NATE site (out of about 150 contractors); then go to the phonebook, go thorugh the process I described above and tell the selected contractor you want a NATE certified technician and you want to see their credentials before they work on you unit. Get a NATE certified technician (make sure, ask when he/she shows up) ask your questions if he/she can not answer your questions, let me know (offline) where to send the check, and I’ll buy you donuts! Sorry for the long e-mail, JMM
Jav, I couldn't agree more with lmtd that the diagnostics should be the first thing done. It's highly possible that the system has never been charged properly if only gauge pressures were used, *especially* if a very high load was present, which is highly probable in this case. The higher load would make the gauge readings higher, so the system would appear to be properly charged even if it was undercharged. It could also be overcharged depending on the circumstances. This is why both the temp measurements and pressures are vital.
Forget about load calc for now.
I really think something is wrong with the system. Especially in light of your earlier comments:
"He was here less than 30 minutes at mid afternoon when it was around 86 degrees outside. Pressures were 275 high side, 70 low (but spiking to 80-90 psi on occasion). He told ME to clean the condensing coil, "the units too small"... gave me a quote to install a 3 ton condensing unit using the existing 2.5 ton evap coil and charged me $75. I asked about the low spikes and he siad condening unit may be going, might be some moisture in the lines but no definetives."
A 20 lb swing in the suction pressure is highly abnormal if the unit has been running for over 10 minutes. How many feet of rise is there on the refrigerant lines, and approximately how long are they?
[Edited by midhvac on 06-19-2004 at 09:40 AM]
I think you will find performance of a unit is based on proper installation and set up of a system.
The other week I did a capacity check on a 2 ton system rated at just below 24,000 with the match up. The unit was lacking airflow by about 120 cfm. After performing a cpacity test, we cam up with roughly 16,000 btuh's. Now I was in no position to correct the airflow but if I just changed the airflow in my calculation to the correct 800 cfm and adjusted the H1 by 1 degree (an assumtion based on more airflow) the capacity would have read right at the spec of just below 24,000. Thats about 30%
In addition to that, there was a 2 degree rise in return temp from the grill to the unit and a 4 degree rise in the supply from the plenum to the registers from the attic heat.
An 18 degree drop across the coil became 12 from return grille to supply register. Considering the performace drop from the airflow, and the heat gain in the ducts, this unit was seriously handicapped from the get go. I still think it was undersized but non the less you can see the drop in capacity due to installation. Frankly it was a decent installation but I think the ductwork was choked a bit and it could have been insulated better or the attic ventilated better.
Hi folks... sorry I've been away for a while. Great replies...You guys are just tops!
We had an absolutly beautiful weekend which helped me get my boat ready, but did nothing for my AC diagnostics. I did find a decent set if Richie gauges for $50 and a Psychrometer for $110 so I'm ready for some good measurements as soon as we get some heat back.
I think somethings wrong too. From an automotive background, the fluctuations on the low side left me puzzled... AND that unit had been on steady for hours (remember this was mid afternoon). The lines run perhaps 22 feet in elevation to the attic and the total run (round trip liquid and return line)is perhaps 80 feet. BTW, the return line is 3/4" and everything is hard soldered but no inline filters... some say thats normal on a new install others say no.
I would not be the least bit surprised if I have several smaller problems that are all contributing. Like, reduced flow perhaps because of having the heating coil in the air stream and any accumulated dirt that effects both coils... the ducts being as they are, so close to the roof sheathing in a very hot attic and maybe even something going on in the condensing unit too (perhaps over charged or so something goofy with pressures).
I suspect my application will end up having very similar problems to your example. I can't imagine that I'm not loosing ground in my attic ducts.
2.5m tons up and2.5 tons downstairs.
How do they matchup,square ft,and widow exposure?
if you take the great room as a first floor only room,then they match up pretty evenly by sq ft and window loading.
BUT, if you figure the great room extends to the second floor and that the windows, sylights and open ceileing stratify heat to the second floor not the first, then I would say the second floor is under a higher cooling load. This seems accurate given the performance of both systems but then hind-sight is always 20/20.
I don't know how they dealt with that room in the calcs.
Is the Greatroom "open" to the second floor space?Which unit serves the greatroom?
Both units service the great room.
Sounds like the second floor unit is too small,since it has all or most of the heat gain from the attic.
Temperature drop across the coil ,sonds like something is wrong wuth the equipment as well.
After solving the equipment problem,I would close off the second floor registers to the greatroom,if it's not open to the second floor.This will let that space get too warm,but if it's unocoppied ,it won't matter.
[Edited by dash on 06-21-2004 at 05:46 PM]