Great site - tough not cooling question - long

[simpleman]

Thanks Jav for being cevil and yes I do blame other hvac contractor.

Take your price of 60 to 100 dollars,as a hvac contractor
that not alot of money to get a expert and the parts store
into the driveway.

So yes I do blame other hvac contractor that dont charge enough,to take care of there people,to offer the beenie to
keep them,to give them the schooling they need to better
there skill,at the same time being able to give the customer value for there dollar.

I come here to this great site and see many of my fellow contractor that cant afford 250 year to support a site as
this,where the expert come together and share there knowledge,and make it better for all.

Why is that I ask?

[jav]

HVAC3901,

I'm not sure what you mean by "mystery set point"? Are you asking my expectations of inside temperature or what we set our thermostats at? If so, I did post that we normally set the AC to 75 degrees during the summer... I think thats reasonable becuase most people I know go even lower.. like around 72 (which is too cold for me).


Simpleman,

when good people are offering to help me, I'd be a jerk if not civil and appreciative. And, I agree that 60-100 dollars to get an expert and a parts store into my driveway is darn cheap! The probelm is that its 60-100 PER HOUR PLUS TRAVEL to get a NON-EXPERT into my driveway. Thats not cheap or even reasonable.

To give you an example. Just this last Tuesday, I spent $75 to get a guy out. At first glance, that seems cheap. Well I don't think so and here's why. It took 3 weeks to get this guy out. He could not give me a day (or a time) he would come but he was supposed to call the day before to confirm. He calls me at work out of the blue and tells me he'll be driving by my street in 15 minutes and if I can't meet him, he doesn't know when he can come back. Luckily, I work close enough where I was able rush out and meet him. He spent no more than 20 minutes on site, used only a set of guages and determined the system was too small... all before setting foot in the house. And when he heard that I would only consider a new system as a last resort and that I would need to be convinced that the problem was an undersized system with more than just "becuase this one isn't working", he was actually a little tiffed.. like i insulted his intellegence.

So, 20 minutes of his time, no travel (he was passing by my street whether I could meet him or not), and nothing more than guages and his "proffesional opinion".... $75 bucks. That works out to $225 per hour and while cheap, I don't feel I got my monies worth.

[Edited by jav on 06-17-2004 at 05:10 PM]

[simpleman]

You're a good man Jav,but that the problem I talking about,thats what I mean when I say it breed this kind of
contractor,believe me I feel the sting from guys like this
as well.


See if you can get someone else out there,make sure you time it for the heat of the day.Ask him to show you the guages,if its a r22 system and the system not big enough
to handle the load,both suction pressure and head pressure
are going to be way above the norm.

But again we can only guess as to what the problem is,we have no numbers.Do yourself a favor do a load calc and then
you'll know.

Good Luck!

[midhvac]

Hey jav, looks like you've gotten lots of good advice in my absence

A good simple place to start would be taking regular temp measurements (we call these dry bulb) at the returns on the 2nd floor, and at the air handler. Also check the supply temps on the 2nd floor and at the air handler. I think someone touched on the importance of checking the supply heat gain, but not the return. Either one's a killer. I've also seen systems where 10 degrees was picked up in the return and another 10 in the supply on an attic unit. The result was room temp air coming out the supplies into the conditioned area.

There are some *excellent* simple tutorials explaining superheat and subcooling in the "For your interest" forum here. They were authored by some of our best. We have many teachers here and tech reps.

[jav]

To all,

I knew I was in the right place the moment I started reading posts here (well at least some of them.... theres always the "hey solve my problem and use your cyrstal ball cuase I ain't got clue" with the appropriate reply's that follow.

I plan on visiting the local supply house and inquiring about wet bulb measurements or a sling psychrometer... if they aren't hundreds of dollars, I'll likely get something to enable me to provide you guys with some data to work with. I've already gotten enough info from you guys to suspect I'll find I'm loosing some ground in the attic duct work (likely both the supply and return). Next week, I'll post some supply/return air temp measurements at a couple of locations including right at the coil. I'll also get some line temps at the service fittings and if I can swing some guages, some pressures as well. I'll also record outside temps, relative humidity and t-stat info. I'm thinking some air flow measurements might be helpful but we haven't touched on that... is there a tool to determine that? I know what the what blower CFM spec is and what the pressure drop should be at that flow but I can't confirm any of it. I would think that the temp drop accross the coil will tell us if we have too much or too little flow??

Anyway, I have some work to do and some data to collect..

To all those helping, don't quit on me! I need you and I sincerely appreciate your reading this book and you great insight! Thank You!

BTW - Offers still open to any of you pro's in the Masschusetts or rhode island area... I don't mind paying for this kind of experitse!

[rob10]

Do a load calc. Big button at the top of screen.

[hvac3901]

75 degrees set point and ten degrees offset while running and trying to keep up. ouch! the argument of it's a/c not refrigeration is a mute point.

[simpleman]

Shoot my feeling are hurt,and I thought I was being helpful.

[marko1]

sometimes the problem is that technicians look too hard because the homeowner tells them they have a major issue, and sometimes the answer is right in front of the techs nose. My opinion, of course is easy to give because im sitting here but with a 10 degree split out of the duct that he mentioned is , duct leakage, refigerant problem ie. overcharge, orfice not seating, undercharge , no orfice, wrong orfice, unit cycling on safties , t stat dropping out, or my vote, no flow control or problem with flow control from boiler, or low voltage wiring problem. good luck. It may be easy for someone .

[AllTemp]

Looks like your issues are being well addressed by my colleages. I have read the thread from start to finsh and heat gain has been brought up in reference to the ducts, ect.

Attic FANS are great as long as the make up air is avialble and your not creating a negative pressure in the house. m You actually may bring the attic temperture down but at the cost of occupied space. You literally can pull the conditioned air out thru the attic. Follow any manufactures recommendatiosn for their fans, allowing ample intake air for the balance...

I once installed a very nice 3-1/2 High efficent System to have the home owner call and complain it couldn't keep up. All the ducts were in the attic as usually are here in California. I couldn't help but notice the air around me rush in when the homeowner opened the front door. When my helper left me at the FAU and exited the front door I heard above me a slight thud... The crawl hle lid was dropping into place and when the door shut, was lifting up..

This homeowner had installed 3 large electric whole house attic fans. each fan was rated for 2000 sq ft , a total of 6000 . This home was a modest tract home 1400-1600 sq ft :-)

Didn't mena to ramble jsut thoguht I'd throw that wor dof caution out there. Coolingthe attic temps is a good idea but you need the system to be balanced and I'm sure you can tell my this stroy why ... :-)

[rookie903]

Originally posted by simpleman

Right now,I know of several company in my area that do things by the book,and they are setting at the shop with
nothing to do,but there hardnose in maintain there ethic
on doing it right.

We reap what we sow,when price is the only issue,then it
pushes out the contractor that have highly skill tech and
gives way to the I dont know parts changer.Sad but true.

How can we as hvac contractor send our people to schools,
to make them better at there skill and be more efficent at there jobs,when no one is willing to pay for it?

The techs that do it the right way are sitting on their butts because they only have to go out and fix it once.

[jav]

Thanks for all the great info. Lmtd... your 2 questions are right on. I don't claim to know how to do a heat loss calc but I see there is a tool to help do one?... I'll try it and tell you how confident I am with my input... after all - Sh*t in usually equals sh*t out.

I will take all measurements as accuratly as possible and document all test conditions. I take it by the comments that the 75 deg. set point is OK and that the 10 degree delta is not (I kind of figured but its nice to have confirmation from the experts).

Here are some obvious things that I have checked just so you know I'm not overlooking the trees becuase of the forest.

1) Low voltage wiring has been checked. The T-stats (Robertshaw 9000 series) are less than 1 year old (replaced due to lightning strike... and no, this probelm didn't start after the lighting). Capacitors in condensing units were also replaced (same reason). All equipment, relays and controls verified operational at that time. Handler fan relays and fans clearly audible and air flow verified but not measured. No overloads tripping or controls releasing... the system just runs and runs but doesn't cool well.

2) Ducts don't appear to be popped off - Been in attic and confirmed all visible vents are intact. Some are not visible but connections verified by register flow (using smoke).

3) The attic is freakin hot! I would expect that if there were a substantial leak in the duct work, it wouldn't be as hot as it is?

4) All ducts are very close to roof sheathing due to vaulted ceiling design. Radiant heat infiltration has me really concerned... I will confirm with duct temp readings.


5) Air handler could use some sealing... the entry point for lines as well as fliter and access panels are not sealed very well. Filter panel seems to be sucking some air and other holes appear to be leaking some cool air.

6) Working in the attic SU**s! I don't envy you guys!

[midhvac]

All Temp brought up an excellent point about attic ventilation fans.

They can sometimes cause more problems than they solve. I think most people use them *instead of* correcting the problem of inadequate attic vents. You have to remember that the fans need to draw the air they're moving from someplace. If the intake vents in the attic aren't adequately sized and the floor of the attic isn't air tight, the air is going to be drawn from the conditioned space below.

2 attic ventilation fan efficiency studies have been done and both concluded that the power usage of the fans exceeds the energy savings realized by the a/c system. The exception to this was the voltaic (solar powered) attic fan. But the initial cost of the voltaic unit was so high that a 20 year payback period was estimated.

After researching attic ventilation a bit, I think that there are cases where the fans may actually work, but sizing and placement would be critical, and the attic space would have to be well sealed from the conditioned space below. These would be special cases which weren't part of the 2 efficiency tests.

From what I've been reading, conventional wisdom about the nuts and bolts of the thermal draft mechanism of attic ventilation may be flawed. The effect of it may be much less than previously thought. Wind driven cross ventilation from the lower inlet vents may be a much greater factor than previously thought. In other words, the cfm of hot air removed from the attic by outside air entering the inlets and moving the air up through the roof vents may be less significant than wind driven air entering the lower inlet vents on one side of the house and exiting the lower inlet vents on the other side of the house. This is making me rethink attic ventilation fan applications.

[jav]

Midhvac - I read the same study that concluded attic fans failed to perfrom from an energy stand point, But, wasn't that study evaluating energy savings only? In my case, the primary goal is more effective cooling without re-inventing the wheel. If an attick fan improves cooling and saves no energy, or even uses slightly more...I would still consider that a success. Obviously, I'd like both but, with such little attic space and such high temps, my situation can't be helping things.



Ok - downloaded trial version of program and did quick tutorial - looks very detailed and no problem using it BUT -
Being a trial version, it doesn't look like you can save your work... I may just buy the homeowner version if there is way to deal the following.

Here's my problem - I have one room that has always been problematic for HVAC design... and as far as the program goes, its no different.

The room is a first floor- sunken great room measuring 32' x 18' but, the ceiling starts at 13 ' on the first floor and slopes up to over 22' high, ending over a second story balcony. The southeast outside wall extends to the second floor as well and has 4 trapazoidal windows that span from the first to second floor. The ceiling (northeast facing) has 2 large skylights. Being open to below, there is no floor. Obviously this room needs to be included in both the first and second floor calculations but how would you do that??? I don't see a simple method to deal with this large open area.

Just so you know... this space of conditioned by both the first and second floor HVAC systems.

Any suggestions??

[Edited by jav on 06-18-2004 at 10:09 AM]

[Shophound]

Just had a thought about your ductwork. Since they are close to the roof decking, it's a sure bet they're picking up some radiant heat if they aren't wrapped in a reflective foil backed insulation.
You asked earlier about radiant barrier after the fact of construction. I've heard of a radiant paint that can be sprayed on the underside of the roof decking, but I don't know how effective that is. I think Sherwin Williams sells that paint, but I'd like to meet someone who's actually used it to see if there's any real world benefit from it.

As for your large room that spans two floors, I would try treating it as having two separate floors. Imagine an invisible floor separating below from above and compute sq. feet, solar load, etc, from there. Maybe Don Sleeth (author of the program) might have a better suggestion.

[jav]

Shopgound,

even painting the sheathing isn't an option. If you can picture it, my ceiling cross section is a sandwich as follows:

Outside air
-------------
asphalt shingles
Felt paper
5/8 plywood sheathing
airspace
styrofoam air space baffle
insulation batt
insulted rigid oval duct
3/4" strapping
1/2" blue board
1/8" plaster skim coat
--------------------
inside air

this whole sandwich is about 14" thick so I can't access anything other than the outside surfaces. In the center od the attic, there is some room above the collar tie which is where the air handler and main trunks are. So you see, my options up there are limited.

[simpleman]

And that the problem with this type envelope,the upstairs
system become over loaded because the heat from the first
floor make it way up,and the cool air from upstair wants to
go down.This is why the downstair run less while the upstair
never shut off.

The type of enevelope you have would be idea for one system on a zone damper system,put the btus where they are needed.

If I had to do that house I would add the load of those two room to my upstair zone,for me the vent that are there now
would be more for heat,even tho They would supplement the
cooling in that room,if it would run long enough to help.

But thats the problem imho ,and that why the upstair is being overloaded.










[Edited by simpleman on 06-18-2004 at 03:03 PM]

[thehumid1]

The real problem is there were too many chiefs " an engineer, supply house, a manufacturer, and a contractor." All them minds and they didn't even think of making the unit accesible for a replacement. I suggest try to put your faith in the best contractor you find then leave him alone and let him do his job. I have walked away from a few customers who kept saying "well don't ya think ...this , that, or the other thing..." NO I told you what i thought its on your proposal If you want to design your system go ahead and install it while your at it.

[marko1]

i agree completely to the last thread.Find a referenced guy to troubleshoot, and leave him alone . And the lightning strike comment and the replacement of caps and thermostat is exactly what i was fearing he would say. That means this new system has taken a jolt in the control wiring and high voltage. FOr me , if you told me that, i would assume that the stat and caps are not the only damage. And the system running all the time, is that just the air handler or the condenser 24 hours a day. This doesnt sound like a complicated problem. please somebody come to this guys house hhhhhelp him

[jav]

Lmtd,

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]