Help me make sense of my HVAC system [Paging JoeyR] (1 Viewer)

[Jason L.]

I have owned my condominium here in Dallas since 1999 and the heating and cooling functionality has been “barely tolerable”. It just doesn’t punch out enough cold/warm air as I would like. I don’t know anything about this – I actually thought the blower above my bathtub was the HVAC unit. Everything is electric. I had the blower replaced around 2001 and it didn’t help at all.

It wasn’t until I got on top of the roof of my complex that I saw my actual HVAC unit. The manufacture date is May, 1983 – quite old. When electricity rates were cheap this wasn’t much of an issue. I now want to get a new HVAC unit that is more powerful and energy efficient but I am clueless about how to go about it. I had a neighbor put a new one in and it cost him $5000 [part of the cost is for a crane to install it on the roof] – which I thought was ridiculous considering how these condo units are small compared to a HVAC unit for a house.

JoeyR, based on the pictures, how does the HVAC/blower work? Tell it to me like I am an 8 year old.

1.What would you guess the SEER rating is for my current unit?
2.What HVAC brands/models would you recommend?
3.What about the padding/insulation that has rotted off the pipes?
4.How much should this cost me [my condo is 926 square feet]?
5.What are the “power ratings” for HVAC units? Are they measured in BTUs? How much power do I need to a 926 square foot, one story condo?
6.You talked earlier about the “R-22 phaseout”. Would any new unit I purchase be R-22 free?
7.On one picture with the blower there are 2 circuit breaker(?) switches. One on the top of the picture for the blower and one below it that is splotched with paint. Is one switch for the blower and the other one for the HVAC unit on the roof?

This is confusing. Thanks in advance for all your help.

 

[ChristopherDAC]

Considering the age, it was probably no better than about 10 SEER equivalent when installed, & if it's as high as 4 now I would be surprised. Undoubtedly, between aging of the motor, wear on mechanical parts, & gradual loss of coolant, it is practically ineffective. With the high price of power these days, if it did cost you $5000 to replace, you could well recoup that in the first two years — and be more comfortable betimes. HVAC units are sometime rated in BTU per hour of heat removed (especially for window AC), but more typically in "tons". This unit, peculiar to the field of refrigeration, corresponds to the amount of heat which will melt 2200 pounds of ice per hour, or freeze an equal amount of 32°F water into ice. As far as I am aware, no new refrigeration systems have been built for some years using R-22 or R-12 ; the phaseout of these chemicals complicates the maintenance of those old systems it is worthwhile to keep running (typically big industrial installations), but your case calls for a completely new system, so it is not an issue. The insulation around the pipes is important because it ensures that the unit is cooling your condo rather than the great outdoors. A thumbnail sketch of the operation of the system is as follows : 1. A heavy gas, the refrigerant, is compressed to a high pressure by a pump in the outdoor unit. As a result of this compression, its temperature rises. 2. The hot, high pressure refrigerant circulates through a coil (like an automobile radiator) in the outdoor unit, and the big fan blows air over it. [In your photos 1, 2, & 4, the condenser coil is hidden behind the louvers which allow air to pass through it, & the cooling fan is easily seen.] Since the refrigerant is hotter than the air, it loses heat to the air, and cools off enough that it condenses into a room-temperature liquid. 3. The liquid refrigerant is forced (by the pressure of the gas behind it, coming from the pump) through a small pipe to the interior of your condo. 4. Inside your condo, the refrigerant passes through a pressure-reducing valve into a pipe of larger diameter. The sudden drop in pressure causes it to expand into a gas, which is cold. 5. The cold, low pressure refrigerant passes through a coil in the indoor unit, and the squirrel-cage blower fan [your photos 5 and 6] drives room air over it. Because the room air is warmer than the refrigerant, the refrigerant absorbs heat and cools the room air down. In the process, because cold air cannot hold as much water vapour as warm air, some of the moisture condenses out as liquid & must be drained away ; the white pipe in your photos 5 & 6 is probably this drain line. 6. The warmer refrigerant flows through a pipe [your photos 3 & 4] into the pump (compressor) inlet on the outdoor unit, where it repeats step 1. The insulation on the pipe mentioned in step 6 makes sure that the refrigerant does not have a chance to absorb heat from the outdoor air — when it does absorb extra heat (since it is probably still cooler than the indoor air, which in any case is cooler than the outdoor air), it has to lose more heat in the condenser, so that part of the compressor power goes to getting rid of that heat instead of the heat inside your condo. The practical effect is that the unit has to run longer for the same drop in indoor temperature.

 

[Jason L.]

Christopher,

Thanks for helping me out. Do you really think my HVAC unit built in 1983 is a SEER 10? It sound like HVAC technology hasn't changed a lot in 25 years.

Also, what size unit should I get for a 926 sq.ft, one story condo?

 

[Mort Corey]

My house was built in 86 and IIRC, the builders special that was originally installed was an 8 SEER unit. I think the minimum that's sold new today is 13. Five grand for a complete new heat and air system (especially having to use a crane) is not out of line. Have you ever had a professional come and check out/service your unit? It might be worth paying someone to evaluate the entire system (duct work etc) to see what the cost will be in total.......unless you're going to move in the next year or so, then just have it serviced and let the next guy deal with it.

Mort

 

[JoeyR]

Jason, I'm sorry but for whatever reason this is the first time I seen this post(I know I'm 4 days late) again, sorry.

I'm working out of town for the next year and I'm just getting home tonite give me a little bit and I will give you a rundown

 

[JoeyR]

1. It should be a 8 SEER possibly less
2. Trane/American Standard(which now owns GE) or Rheem/Ruud
3. The pipes should be reinsulated on a new install, if not they have not done the install right.
4. Thats a hard call, its been awhile since I've done installs for myself(I'm doing DDC control work full time now). I havent bought a new unit since before the new 13 SEER law went into effect. What is scaring me the most about your pics is the air handler(inside unit). Its going to be next to impossible to find a residential air handler like that(I could be wrong but). According to the model number the condenser is a 2 ton so somewheres in that neighborhood(I would have someone do a load calc, I'm hearing that people in rare instances dont need as much tonnage with the new SEERs). The rule of thumb for sizing is 400 to 450 square feet per ton, but without seeing the whole condo, I again recommend a load calc. Also you could get buy with a ductless split depending on how your condo is laid out. The air handler hangs on the wall and it is cheaper but, here is some info for you.

Mitsubishi Electric - Mr. Slim Split-ductless

Fujitsu Ductless Mini-Splits

Friedrich | Ductless Split Systems | Overview

in my opinion they are the equivalent to central air window units off the top of my head I would figure anywheres from 2500(mini split) to 5000(replacement) dollars(hope I'm wrong though), but I did notice you said crane, was a crane used because of the weight, lack of access, or height? Most cranes we use charge a minimum fee(like 4 hours) even if they finish in 20 minutes.

5. 12,000BTUs=1 ton 400 to 450 square foot per ton(loose rule of thumb)
6. No any unit you would purchase new would have a 75% chance of having R-22 in it. When you make your purchase you need to tell the company you want a unit that has R-410A in it(this will actually increase your price).
7. Those units come in some crazy configurations, this is just a guess but from what I can make out the back breaker with paint on it is for the blowers. The one underneath is in the controls/probably electric heat compartment.

Christopher covered the basics of how it works pretty good.

BTW the unit to the left of yours is a new Trane/American Standard

Let me know if you need anything else

To find a decent contractor in your are check HVAC-Talk: Heating, Air & Refrigeration Discussion - Powered by vBulletin in the residential area(check into how other members regard that member by looking at previous posts)

 

[Jason L.]

Sorry it took so long for me to get back to this.

- The crane is to get the condenser(?) on the top of the roof. The roofs at our condominium have some high slopes and that is the only way to get it up there.

- Do the condenser and the air handler/blower get purchased seperately?

- What is a load calc?

- I don't think a split system would be an option because I live in a condominium and I can't make those type of changes. Does a split system heat as well as cool? I see a lot of these split systems in the Middle East/Africa. They seem obtrusive. I prefer to have my system out of sight.