View Full Version : HVAC Evaluation - truth or lies??
07-12-2006, 12:53 PM
I just had my 10-year-old Goodman / Janitrol (contractor grade) heat pump system checked and cleaned. My house is almost 10 Years old, I am in Florida and the house is single story, 1350 SQ with high vaulted ceilings throughout and my windows are single pane but small and with little direct sun exposure. I have ceiling fans in almost every room and a programmable digital thermostat. The attic (crawlspace) has R-19 fiberglass batting rolled between the trusses.
The tech that came out says that my electric bill will be cut by more than 50% with a new system and that my current system is failing. I find this difficult to believe.
The system I have now is a 2.5 Ton oudoor unit paired with a 3 Ton air handler. I believe the model numbers to be as follows:
Compressor = CPKE30-1B
Air Handler = A36-10
The guy who checked everything took the following readings:
Compressor Amps = 12.1
Condenser Fan Amps = .8
Suction pressure = 78 PSI
Discharge pressure = 240 PSI
This was in the morning with an outside temperature of around 80 degrees F and the indoor temperature was around 76 degrees F
He also said that the temperature differential from the inlet side of the air handler to the output side is just over 14 degrees and anything less than 17 is bad.
I'll admit that the A/C does seem to run a long time and the temperature in the house comes down REAL slow in the heat of the day, but it does work. He also says that I should have some sort of booster installed in addition to a new start capactitor on the compressor.
My questions are these:
Is a delta T of 14 degrees F really that bad (can anyone even answer that with the given information)?
Before I buy a new HVAC system, would I do better to improve my home's insulation?
Is it reasonable to expect a new HVAC system to cut my electric bill that much (assuming all else is equal)? I just can't believe the claims I am hearing.
If my compressor's start capacitor was bad, would the compressor start at all?
Sorry this post is so long, I just need really need some help and I want to give as much information as I can. I am not trying to throw anyone under the bus - the guy who came to my home was very nice and he seemed to be honest. I just know that sometimes people just regurgitate stock phrases to sell equipment. I need some reference to know if I am hearing truth or not.
07-12-2006, 12:56 PM
Originally posted by pgman
The tech that came out says that my electric bill will be cut by more than 50% with a new system and that my current system is failing. I find this difficult to believe.
I haven't even read your whole post yet and I can tell you right now that's "BS"
why not get a 2nd and 3rd opinion and don't advise these about the conclusions of the 1st?
07-12-2006, 01:12 PM
Thanks, for the quick responses. I thought it very hard to believe that anything (other than shutting the A/C off) would save THAT much energy. When you get a chance, I would sincerely appreciate your thoughts on the rest of the information I included originally.
If there really IS something wrong with my system, I'd like to have it fixed. Of course, I realize you can't tell for sure without looking at it, but I am mostly interested in learning more about this temperature differential issue. I would think it has as much to do with air velocity as anything else. Since he measured it with no filter in the return duct and he measured basically on either end of the air handler enclosure, I am not sure there WOULD be that much difference. Is this a common "trick" to manipulate the data?
07-12-2006, 01:19 PM
How long had your unit been running when he took the TD's?
Also your TD might suffer a tad because your condenser is a half ton less than your evaporator.
07-12-2006, 01:23 PM
You need another opinion.
After 10 years, wild stab in the dark, maybe it needs a bit of freon.
I don't see any issue with how he measured the temps, but I know most of the inpsection reports have more "special" temperatures in them, superheat or something like that.
Things to think about;
Clean fllters and grills.
Check freon level.
Check electrical issues like the capacitor.
A new system could save 50% over what you have.
Of your total bill about 46% is for heating and cooling in a typical Florida home.So at best 50% saving of 46% of the bill ,so 23% of the total bill.Carrier Florida Guaranttes that a 12 SEER replacing a 10SEER ,will save 25% of the 46% or they'll pay the difference ,for the first year,they get very few claims,and when they do,there's usually a cause that can be found.
Your insulation in the attic should be R30 not R19 ,this could reduce the size of the system you need.Also look at tinting east/west glass ,etc. etc.,.
Have a load calculation done ,incorporating the possible changes before getting a new system,as with the changes you may only need a two ton.Two ton is nominal 6,000 btus less ,which is 20% less than your 2.5 ton.So 20% less to operate.Upgrades to insulation etc., provide liftime savings,well worth the money.
07-12-2006, 02:32 PM
Thahks again. I was worried that I was getting mostly a sales pitch. According to this guy, I had pleny of Freon, but I don't know how he knew that from simply checking the pressures. Isn't it possible to have good pressure readings with air in the system?
By the way, East glass is tinted and West is not but that is on my list. Also, I was planning to roll another layer of insulation this coming Winter and add a second gable fan (I only have one right now). The Summer temps in the attic are just too high to do any serious work up there. I had to go up there to change out my attic fan motor in May. That was brutal - even at 9:00 AM.
Is it best to remove the existing insulation and replace it with R30 or should I just add another layer (as planned). If so, would a second layer of R19 get me up to a total of R30? Sorry if this is getting off-topic.
I forgot to mention that the A/C had been running approximately 30 minutes when he checked the temperatures.
[Edited by pgman on 07-12-2006 at 02:36 PM]
Thinking blown in would be easier.If you add r19 then it's R38,as I understand it,plus if adding a batt ,I think it should be without a Vapor barrier,just insulation.
When checking the coil inlet temp. they should compare that to the inddor temperature,to see if there's much difference.Higher at the coil inlet can indicate return duct leaks.
Also removing the filter will increase air flow,not much with a standard filter ,but can be a lot with a pleated one,more air flow equals less temp. difference.
07-12-2006, 03:14 PM
The insulation value is an addition calculation. If you have R19 now and add another layer of R19, you now have R38. Just be sure the insulation you add doesn't have a vapor barrier. I.e. Fiberglass insulation with a paper or foil face should not be used. Just put in fiberglass only rolls or blow in fiberglass or cellulous would probably be the logical options.
07-12-2006, 03:48 PM
Thanks, everyone, for your input. I think I may have to go with fiberglass rolls because of the pitch of the ceilings. The whole house is vaulted and I don't know if blown-in will lay properly. The current insulation is encased in plastic. I know I am not supposed to ask "how to" questions here but, if I may bend the rules just a little, can I put plain fiberglass (or anything, for that matter) over that? Also, I am concerned because the space between the roof deck and the drywall ceiling shrinks as I reach the perimeter of the building (the roof pitch and ceiling pitch are different). I don't know how close I can get to the edges before I create airflow issues with the soffit vents.
Finally - back on topic - I am wondering if Dash could clarify something for me. You say that a new system could save me 50% of the cost of operating the system I have now. Do you mean that I will see this savings if I go from what I have now (A 10 SEER, I believe) to the current state-of-the-art? I think I saw a Trane with SEER 19 at the Home Depot (on display). Should I go "all the way" when I do this to make it worthwhile? I plan on staying in this house for a long time so I wouldn't mind waiting seven or eight years for a return on my investment.
You have all given me very good food for thought. I am beginning to realize that I should probably add the extra insulation and a second gable fan before I do anything else. Assuming I reduce the heat load by doing that, I might realize an even greater savings when I replace my current system (because I might be able to go smaller). In the meantime, I expect I will see at least some savings with my current system.
07-12-2006, 04:02 PM
My house is the same size as yours, and just a little older.
We keep it very comfortable with a 2 ton system, which most of the time runs on low speed (which equates to 1 ton).
Set point lately is ~75 degrees, 46% RH, and the system maintains pretty close to that under a variety of conditions.
Now, we're in Maryland, which is not Florida but nevertheless we get plenty of days in the high 80s or low 90s (occasionaly higher) with humidity nearly to match (70-80% RH). Our typical winter lows go down to around 10 degrees (and have been as low as -15).
But we have about R50 in the attic, double pane low-e glass, and my only exposed west-facing window is solar tinted. Pleated cellular shades cover many of our windows.
Insulation is relatively cheap. Add that first? When you're ready to replace the heat pump, invest in a high-end system for good humidity control. Relatively small houses like ours are a big advantage for HVAC as long as you're not squeezing in the neighborhood for a party.
Your 10 SER is not likely working at 10SEER due to age ,airflow ,etc..
So going to a properly operating 16 plus SEER will likely save 50% of what you are spending to heat(heat pump) and cool your home today.
Going with two stage will add more comfort,due to loer indoor humidity,and msot of those will be high SEER systems.
Definately do the upgrades and have a load calculation done to see if a two ton will handle it.Or do it your self for a small fee here;
07-12-2006, 06:31 PM
if you're gonna add insulation you might as well stop the infiltration. Getcha a couple of .99 cent tubes of culk, remove the supply grills and caulk between the sheetrock and supply boot. Make sure the ceiling <spell check>"I" before "E" except after "C"<spell check/> is sealed around the plenum if your airhandler is in conditioned space. And if you're really feel'n spunky, caulk the boxes behind the light fixtures and electrical outlet on the exterior walls. Get that house so tight, when you slam the door your toilet will flush!
[Edited by rickboggs on 07-12-2006 at 06:35 PM]
07-13-2006, 08:15 AM
Actually, I have the air handler (and the whole interior of the house) pretty tight already. I spent a couple days about a year ago with a can of great stuff and two tubes of caulking. The OEM installation was so sloppy on this air handler that I'd say less than 40% of the air moving through it was actually passing through the filter.
The next logical step (to me, anyway) would be to focus on reducing the heat load (I hope I am using that term correctly). It seems to me that it would make the most sense to insulate and tint before I look at a new heat pump. Of course, this means that I will have to go through another Summer with the status quo. To that end, I am wondering if the numbers I listed in my original post are cause for concern.
compressor is drawing 12 Amps
condensor fan is drawing 800 mA
suction pressure is 78 PSI
discharge pressure is 240 PSI
A temperature differential of approximately 14.6 degrees F was measured between the hot and cold side of the air handler AFTER the system had been running for about 30 minutes. This was measured with NO air filter in place.
Again, this was tested in the morning with an ambient temperature around 80 degrees F and interior temperature around 76. I am not sure what the relative humidity was. I personally looked at the inside of the air handler and everything in there seems to be in good physical condition. There is a little rust on the A coil, but it is nothing structural and all the fins on the outside unit are clean and straight with no significant rust.
Can anyone offer any opinions as to wether these numbers are REALLY bad or just normal for the age / model I have?
I am a common sense type of person and it just doesn't seem to me that this stuff is "on it's way out". If someone here knows from experience that the compressor should be drawing 7 Amps and I know it's drawing 12, that obviously means something isn't right. However, I honestly didn't think 12 Amps was that bad and I am not having any problems other than the fact that the system seems to be using a lot of power. I am guessing that this is mostly due to long run times. For example, I know that it is not uncommon for my system to run almost three hours at a time in the Summer months. This is to keep the inside temperature at 79 during the day. My thermostat calls for cooling when the temperature goes 1 degree over the set temp and it is satisfied when the temperature falls 1 degree under the set temp. I understand that a longer run time will dehumidify better but is this excessive? The run times are also rather long in the Winter months (in heat mode), though I don't notice the electric heat kicking in extremely often.
I know that all my ducts are intact so I don't think I am losing a lot of BTUs in the attic.
07-13-2006, 08:46 AM
the technician was right if you went 16 seer or higher you would see those energy savings so he was not lying to you it was a sales pitch but still not a lie. if you want to see some low energy bills get a trane 16i or 19i and watch them drop
07-13-2006, 09:01 AM
put your filter in to take your measurements.
There are some simple test you can do simply by touch and sight. The question here is "IS THERE SOMETHING WRONG" and "IS MY UNIT ON IT'S WAY OUT" right?
<opinion>The outside unit pressures at 80 degrees seem high... but not too high. Lay holt(that's redneck for grab that thing) of that there little line (on the outside of the unit). Is it hot? If so, have the coil cleaned. Now sometimes you came have some nice looking coils only to find out they're corroded where the copper and fins meet. You check this by using your fingers to gently push the fins back and forth. If they're loose, and corrosion comes falling out, the coil is shot. Remember, this is if your little line, that you laid holt of, is hot.<opinion/>
Now that suction pressure.... <opinion>it seems high, that's a 50 degree coil! Lay your eyes on that there compressor (Just look, it could hurt if really laid your eyes on it)is it sweating on the compressor? You may have an overcharge (the refrigerant, not the tech's bill, which it my be but we're not talk'n about that)
It could even be that the 3 ton coil could use a 2.5 ton piston<opinion/>
Fact is, you need a good tech, one that you trust.
07-13-2006, 10:45 AM
Thanks again for the info. You are correct - my question is "what, if anything, is wrong with my current system?" You are also correct in saying that I need a good tech. THAT part is going to be a challenge, I'm afraid. I will keep trying. Until then, I need to educate myself a little bit more about this. After reading everyone here, I am beginning to think my system is suffering from a basic inefficiency, inherent in its design (the condenser / compressor being 2.5 Ton and the air handler being a 3 Ton). Add to that the age of the system and the fact that my home is not isulated well enough and I think it might begin to explain the long run times and the high bills. I don't think there is anything wrong with my system beyond a questionable design and its age.
No one has balked at the power consumption figures so I am guessing that is farily normal. I have a temperature probe for my DVM and I am going to test the Delta T myself with the filter in place. Considering the air handler is moving a volume of air commensurate with a 3 Ton system, it seems to me that the evaporator coil would NEVER stay as cold as it would in a matched system. This probably, in part, explains the extended run times, but I think it has as much to do with the heat load as it does the system efficiency.
Am I on the right track???
FWIW, when I say the outside unit is good, the fins all seem secure and there is no corrosion visible on the coil at all. Also, the small line coming out of the condenser housing has never been HOT (when I've checked it). It is definitely very warm but not so much that I can't hold on to it for a long time. If I understand this correctly, that line should not be too hot to touch? If it was, it would indicate a faulty condensor or an over-charge, correct? The other line is covered in insulating foam but it does sweat a lot at the point where the insulation ends (at which point it enters the condenser housing). I guess that line, being the suction line, should be cool, but how cold SHOULD it be?
[Edited by pgman on 07-13-2006 at 10:56 AM]
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