| Author | Message | ||
     Wolfridgerider |
its time to up-grade my system. It was installed in 2002. The heat pump is only rated for 10 seer and is 3 ton. I think its way smaller than I should have. house is 2500 sqft Ranch with about 1500 finished in the basement. Good insulation and windows. I know its a rough guess but.... What size unit do you think I need? | ||
| Ftd |
Rule of thumb in FL is sq ft/500 = tons | ||
| Fast1075 |
The only way to know what capacity the system needs to be is with a heat load calculation. Sorry, but the old "rule of thumb" 500 Sq Ft per ton can be wildly inaccurate. Unless you live in the desert, correct equipment sizing is critical. Make sure the duct system is evaluated and modified as needed to work with modern equipment. Otherwise. you can end up with a new system that doesn't work well, efficiently, or live very long. I will refrain from any long drawn out technical stuff. Just make damn sure that whoever you hire is a professional. Quality is not cheap. And pick a brand, any brand.....they are all equally good in general. The down side is that out of warranty component failure will make a repair at a Harley shop seem inexpensive by comparison. Most units use at least one ECM, or variable speed motor. If you have to have one replaced out of warranty, expect $1,500.00+ cost. BUY THE EXTENDED WARRANTY, 10 YEARS PARTS AND LABOR!!!!!! This coming Tuesday will mark my 30th year in the HVA/C trade. | ||
| Kenm123t |
FAst 30 lol your just a kid I m @ 37 in june | ||
| Baybueller |
Also make sure they size the line set for the new equipt. | ||
| Aesquire |
I'm about to drop the dime on a split system heat pump. I've got the size figured, and the fancy feature list trimmed down, which is easy since the Seer rating is more important to me than fancy packaging, like "artcool". ( nice to have but apparently they don't make it in a high efficiency version ) I'm down to a brand I've never heard of, "Gree" and Mitsubishi. I've pretty much decided to go with the 3 diamonds company, but wonder if I'm being unduly influenced by brand name,????? I'm doing the simple stuff myself, drilling holes and running tubes, with a pro to come and do pump down and connect. | ||
| Kenm123t |
mitsu or Daikin I do a lot large ok Huge Daikin water cooled systems and I m using my Mitsu in the garage right now Gree is Chinese I think Mitsu has good warranty and is a very good unit | ||
| Kenm123t |
PM me guys if you want to get into details I ll send you my cell # | ||
| Wolfridgerider |
Well. I have a guy coming out Sunday morn to take a look and give me a quote and then one on Monday evening. any pointers? questions to ask? BS lines that might get tossed my way? | ||
| Kenm123t |
You want a Manual J load calc done for sizing and a Manual D for duct. If they can do the Whole Wright Soft suite or do a Trane Trace program both are good and you will get a proper sized system that way. As Fast said get the Factory extended warranty Oh and NO X13 ecm motors ECMs are great just not the low end X13 ecm motors If you can do it get a 2 stage system two compressors ala Trane American Standard or a Unloading unit most of the others Better low load humidity control in mild weather Get copy of the proposals and we can go over them | ||
| Fast1075 |
What Ken said. Share what they lay on you with us. | ||
| Blake |
What makes you say the 3 ton is insufficient (way smaller than (you) should have"? Remember the most efficient system is one that has barely enough capacity to do the job. Best to have it run non-stop on the hottest day of the year and not got the temperature inside below 78F. Why replace a system that is working? The payback likely wont be there. The furnace and evaporator in my house were installed in 1982. Lennox. We finally had to replace the condensing (outside) unit three years ago. You might look into doing that. It's tricky though, so you need a very knowledgeable technician to even consider such a plan. Sure can save you some money though. Or add a little split system. Those are really sweet. No ducting required. Ask Ken or Fast about the effect of ductwork. My electricity is just $0.08/KWH here, and the heater is natural gas. | ||
| Wolfridgerider |
the rule of thumb.... but then, because of this thread.... I learned something Sorry, but the old "rule of thumb" 500 Sq Ft per ton can be wildly inaccurate. my whole goal is to save some $$ in the long run. I have a 10 SEER unit. They don't even make that anymore. | ||
| Wolfridgerider |
and just a fyi. My electric bill is $320 bucks a month on the "Budget". my house is all electric. | ||
| Ftd |
Sorry, but the old "rule of thumb" 500 Sq Ft per ton can be wildly inaccurate. Yea, I heard all the "experts" say this two months ago when I was getting two new HVAC units. Then after all the calculations my 3200 sq ft house came in needing 5.5 tons (3/2.5). HA Key words I guess are "can be". | ||
| Wolfridgerider |
"Manual J load calculation" how do you go about doing one? | ||
| Blake |
What I was getting at is whether or not the current equipment does an adequate job of keeping the place cool in Summer and warm in Winter. If so, then it's sized appropriately, or at least not too small. No? Snap a photo of your outdoor unit placement and post it up here. Might be some other points to consider. | ||
| Kenm123t |
look On the ACCA web site and you can get the forms and manuals. FTD did they install the required fresh air supply and air balance the systems Orlando isn't So east fla and its Not WVA The key is the latent heat capacity not just total tonnage. We have 4 climate regions in fla alone. I love it when proper engineering and experience are ignored. Love the expert witness fees. Working on redesign of a brand new surgery center So new its never been used can't pass healthcare inspections and maintain required temps and humidity. Get this one a certain HVAC distributer converted air cooled light commercial units Think Strip mall units ' to water cooled since the engineered ignored the fact that there is a roof over top of the 8 units ! This one is going to be fun and a money maker Sweetie wants stone floors and a new kitchen. | ||
| Fast1075 |
That is hilarious Ken. We bid a spec job for an eye surgery center once. You know the ropes. Do the quote by spec and then follow on with advisements. When the engineer (who had specified obsolete equipment and then substituted even more inferior equipment) refused to listen to sound judgment concerning latent control,and the owner who was convinced that all he needed was "air conditioners" and was focused on "value engineering", we handed the project back to them and walked away. They went to another contractor and got what they "wanted". A year later, our Ductz division got a nice piece of the building remediation from the mold issues. In the end, it turned out as so often happens, the equipment selection was made by the local equipment sales rep. Brilliant. Forrest Gump's momma was right. How in the hell does somebody miss the roof over, and then "convert" the units..Some real sound engineering there. How many value line units even have the ability to be converted from fixed metering, with those in coil short orifices? I would love to be a fly on the wall on that one. Maroons. | ||
| Kenm123t |
If every thing goes well the next 18 months sweetie gets the new house on the mountain lake debt free. I get the Float plane. Who said you can't fix stupid Ok what stupid does ! | ||
| Wolfridgerider |
1st guy.... some things he said that I remember. I have over 60 L/F or line set that is 3/4". He said it should be 7/8", he also found a "kink" in the line. Not really kink... more like a squeeze or squished spot. Outside unit is 3 ton. Inside air handler is 4 ton. He measured the duct work and double checked it. Came to the conclusion we didn't have enough return air. All the returns I have are up high. Suggested a 8"x34" floor return that would go in the floor in front of the thermostat. The thermostat is a mercury switch.... need I say more about the thermostat??? When he was looking at the inside unit he also noticed the last "service tech" did not re-install the cover properly and basically air was being pulled into the system from the basement rather than the cold air returns..... this did not make him to happy. He is going to work up a couple of numbers for me and get back to me tomorrow. 2nd dude will be here tomorrow at 5 what say ye so far? | ||
| Oldog |
I have a question for the HVAC peeps, I live in coastal NC, the house was built in 07 I moved in in 09, the house is total electric, with heat pump, In '12, replaced the A coil and 6 pounds of the 9 pound charge, Was told the line set was ok. The heat function has never worked well, Q1. I got tired of the unit running nearly continuously, so early last winter I set the heat to EMG, shutting down the HP, Are the heaters sturdy enough to do that? essentially making it electric central heat? Q2. When the heat pump cant keep up are you not just putting wear on the equipment, trying to get it to heat the house? ( it gets into the 20s for a few days each year...) It is 85~90F today the AC runs about 20 min an hour if that, I presume that the insulation and over all tightness of the house is ok. [ house is white with black roof ] also What is the expected reasonable life of Goodman equipment? where do I find the tonnage? | ||
| Hughlysses |
Jim- Q1- yes, the heaters should be capable of running full-time. By turning it to the emergency position you're making it straight electric heat. Q2- if the compressor's running continuously and the heat's not keeping up, yes, you're just putting wear on the equipment. It'd be worth having the charge checked though; I'd think a heat pump shouldn't have any problem keeping up for most of the year where you live. 20 minutes out of an hour sounds about right; how does it do during July/August? IIRC, expected life of home grade HVAC system is about 15 years. Depending on how close you are to the water, it could be a lot less. Salt water spray will eat uncoated condenser coils which greatly compromises the performance and efficiency of the unit. Most of the manufacturers offer "seacoast" packages now that include a coating on the coils that greatly enhances their life. | ||
| Oldog |
Thanks Hugh, No the A coil was replaced a year or two ago the tech said that my decision to run on Aux probably saved the compressor. as there was only about 3 pounds of gas in system when it should have been 9, My outside unit does not show any issue that i can see I rinse it off once in a while, and shut it down and cover it when cleaning that side of the house ( bleach ) and rinse it as I finish that side of the house. is the poor performance on heating caused just by gas issues or can valves etc cause issues? | ||
| Fast1075 |
On the heatpump issue, heat pumps pretty much go over the curve at 35 degrees, meaning that below that the amount of heat in the air falls off. Heat exchange depends on the difference in temperature between the ambient air and the temperature of the gas vapor inside the outdoor coil. the colder it gets outside, the the delta T drops. I have no idea what the codes are in your area. Some restrict the amount of auxiliary heat in proportion to system capacity. Some codes require what is known as an outdoor thermostat to inhibit aux heat above XXX temperature, prohibiting aux heat unless it is below the threshold temp of the ODT. When you switch to EM or Emergency heat (a hold over and redundant mode from years gone by when heat pumps were not reliable at all), you shut down the heat pump and run only the aux heater, which may or may not be enough to provide the heat. In any case it is generally more expensive to heat with electric strip heat if the outdoor temp is above 35 degrees (this figure varies with age, equipment design, and type of refrigerant). If the control system is properly engineered, the aux heat will be called automatically by the t/stat as a "second stage" unless inhibited by the outdoor thermostat. If the climate gets cold below design standards for the outdoor unit you have, it would be set up with a second outdoor t/stat that inhibits automatically the outdoor unit during extreme cold. In most cases a system installed in those conditions will be "dual fuel" where below the threshold temp, the heat is provided (usually) by a gas or oil furnace. As for your system, a failed indoor coil is almost always caused by either air flow problems (by far the most common) or formicary corrosion in which airborne contaminants corrode through the very thin copper tubing in the coil. The most notorious contaminant is from "chinese drywall" (no insult intended to anyone of asian descent, look it up). The largest A/C company in New York did a study in which every system service by them was checked for mass air flow. 80% were found to be substandard. My 30 years experience in the trade mirrors their findings. Also, the "old" heat pump systems that used refrigerant R-22 have far lower heat output than those using the newer R-410a refrigerant. | ||
| Fast1075 |
Mark, to answer your questions. The line set needs to be upgraded for best performance. it is also a good idea, since you will be going from R-22 to R-410a refrigerant. The old system uses mineral oil for compressor lubricant, and the new system will use Polyol Ester synthetic oil. It is generally not a good idea to mix the two kinds of oil, and the new refrigerant does not mix well with the old oil. Benefit/Benefit. You cannot have too much return, generally speaking. The fan that moves air inside the house is commonly called a "squirrel cage" fan. It is quiet, inexpensive and does a pretty good job of blowing air. I does however suck at sucking air, so it needs a nice open unrestricted return. On returns, even on those that are properly designed and installed, too many people choke them back up with "permanent" filters or "pollen guard pleated filters". You have two choices, use standard filters and have the system cleaned regularly. CLEANED, not CHECKED or INSPECTED. Cleaning requires actual tool and material use and actual labor and work. OR go ahead and spring for an electronic filter. You can service that yourself monthly, it is easy. If you buy an electronic filter, do not buy a filter with a honeycomb core. by a traditional Honeywell with the plate and wire cells. They are far more reliable. And spring for the extended warranty on that also. When the cells wear out they are very expensive, as is the "power pack". | ||
| Oldog |
Fast, The system exhibits no such behavior, I have seen days with the outside air temp in the lower 20's, HP running and cold air being discharged from the vents. ( yes the HP was set to heat ) after about 20 minutes of run I checked the air discharge it was sorta warm. I went and switched to AUX, outside unit shut down, warm air came from vents after another 10 minutes or so the house was warm and the system shut down. Its a Goodman system, I doubt that it operates in stages as I have not seen any thing that indicates that it does. What can I do to help prevent corrosion of the A coil, I used to use some thin ( see thru ) crappy air filters, I changed to 800 micron filters, my hope being that I keep the crap out of the system. ( my home is dusty ) is there a service routine for cleaning the coil to prevent the corrosion? the new one is ally vs copper I was told it was better and copper was not made any more. | ||
| Hughlysses |
Jim- I forgot to answer your question about the tonnage. It varies from manufacturer to manufacturer, but generally, you can figure it out from the model number. 1 ton = 12,000 BTUH, so (for instance) a 2 ton unit will usually have a "24" in the model number, a 3 ton will have "36" and so on. If in doubt, you can usually just google the model number and get an answer pretty quickly. | ||
| Oldog |
Thanks Hugh, it never even occurred to me to google the model # to get specs. | ||
| Fast1075 |
There are times when a heat pump does intentionally blow cold air in heat mode, and that is when it goes into defrost. In heat mode, the unit is collecting heat from the outside air. It does so by operating the outdoor coil at a temperature below the ambient air. Below around 40 degrees or so, the coil runs cold enough to form frost. Left unattended, the coil will ice over, stopping air flow and heat transfer. The frost must be removed regularly to prevent icing up. The unit has a defrost board that counts accumulated run time. At the selected interval (generally set up at 60,50, or 30 minutes) the board looks for a closed circuit in the defrost thermostat (yay, another thermostat!) that is attached to the outdoor coil on one of the tubings to sense coil temperature. If the coil temperature is below 25 degrees (average defrost t/stat setting), the unit will go into defrost. You need heat to defrost the coil, and the unit steals it from indoors. Basically, the unit goes back into cool mode, except for a couple of differences. The outdoor fan shuts off (we want the stolen heat to melt the frost), and the board turns on the aux heater to temper the air coming from the vents inside, otherwise the air would be frosty cold inside. So in defrost, the heat will not be working at all, hence the cool air from the vents. The unit stays in defrost until one of two things happen. In a normal defrost termination the coil warms up, and the defrost thermostat gets to approx 55 degrees. At that point the defrost board reverts back to heat mode, and the timer begins to accumulate again. If there is a refrigeration problem, or the defrost interval has been set so long that the frost does not melt, and the defrost t/stat does not see 55 degrees, the board terminates on a safety timer at around 10 minutes, other wise nasty $$$$$ things happen to the compressor. A defrost malfunction will result in a highly visible accumulation of frost and/or ice. The problem is easy to diagnose, and is one of the first things taught to a trainee HVAC tech. Often, the problem is the default interval is left at the factory 90 minutes. In post rainy cold front conditions, it is easy to ice up a coil in 90 minutes to the point where you have a safety trip before you have comlpete defrost. Another thing, is old R-22 heat pumps are notorious for having a low temperature rise. That is the difference between air going into the return vent compared to air coming from the supply. Typical is only around a 14-16 degree difference, so if it is 68 inside, the air from the vents will be well below your body temperature, and in will not feel "warm". The high efficiency air filter you are using, will kill the new coil, and may be a contributor to the heat issue by causing head pressure trips. On most Goodman equipment, the h/p safety is auto reset, so the failure may be transparent. Heat pumps are not at all good at heating up a cold house. You need to anticipate the need and let the unit KEEP the already warm house warm, especially in cold weather. |
