Variable speed?

[gpalasz]

Hello, I currently have a 10 seer RUUD that died. I understand now its all pretty much 13 SEER+ Question. When I get over the 13 SEER range does it "automatically" go to variable speed? Can you get a 15 SEER standard?

Also what is variable speed? Is it the compressor, the indoor fan motor or both? My furnace is only 10 years old and in good shape. I am just looking to replace condenser and indoor coil. Thanks.

[BaldLoonie]

MOST brands require VS to get over 13 SEER. You can find some that don't. Not sure at the 15 SEER point, someone might do it but don't know whom.

Variable speed is just the indoor blower. Those motors use much less juice which is why they are needed for super SEER. They also have the capability of maintaining set airflow as duct & filter conditions change. And have dehumidify capabilities a standard blower can't. They are pricey but seem to be reliable. If you are looking high end, sure worth doing.

[gpalasz]

Thanks Baldloonie. So when you say air handler inside...your not just referring to the blower motor...but the WHOLE furnace...correct?

[gpalasz]

Can they replace condenser, coil and blower motor to have variable speed or do they need to replace all of air handler/furnace. Maybe thats better phrased.

[jayhvac]

if you check around carefully you can find 15 seer in fixed speed condensing units from 2 or 3 brands Carrier, Lennox, etc. When you get to 16+ you will get into vs outdoor units. Trying to keep a 10 seer coil with a 15 seer outdoor probably won't happen so ask the contractor to give you a match verification to prove you will get 15 seer. Otherwise the mismatch might hurt your efficiency.

[gpalasz]

Thanks Jayhac. Does the whole airhandler have to be replaced to get VS? or just the motor in the airhandler?

Can I just keep my furnace..get a 15 SEER coil and 15 SEER condenser?

When you say VS outdoor units it must be matched w/ VS indoor?

[gpalasz]

OK think I have it figured out. I can use say 15 SEER 5 ton condenser and new 5 ton coil WITHOUT a VS airhandler..I just simply wouldnt get the 15 SEER rating?

Why wouldnt someone w/ an older say 10 SEER install a VS furnace?

[danglerb]

Furnace kind of has 3 parts, blower, fire thing, control board. Variable speed is the control board and blower, but all the furnaces I have seen also upgrade the fire thing to a two stage gas valve or variable.

Variable speed has so many nice comfort issues, the stage one will give you almost silent heating with less temperature swings, and you really have little chance of reaching tier 2 energystar as required for tax credits without one.

How much do you use your furance? Whats the fuel efficiency AFUE? New units are 80% and 90%+, which add up fast if you need heating a lot.

[gpalasz]

Thanks for your response. Currently it is an 80%. I really like the sound of the variable speed. Question. you say 2 stage gas heat...is this "standard" in a variable speed, or an addtional"option" I live in central US, use it quite a bit though in winter.

[danglerb]

Originally posted by gpalasz
OK think I have it figured out. I can use say 15 SEER 5 ton condenser and new 5 ton coil WITHOUT a VS airhandler..I just simply wouldnt get the 15 SEER rating?

When people talk about a 15 seer blank, they mean "when used with a appropriate coil and air handler". A condenser by itself might have some associated efficiency, but it isn't a SEER number.

Air-Conditioning & Refrigeration Institute (ARI) http://www.aridirectory.org

ARI has a database you can search with all the tested combinations of condensers and coils and furnaces, and its the combination that gets a SEER rating.

SEER looks at the total heating and cooling costs for an "average" year, so combining an efficient cooling system with an efficient heating system and an efficient blower motor you get a higher SEER number.

[danglerb]

Originally posted by gpalasz
Thanks for your response. Currently it is an 80%. I really like the sound of the variable speed. Question. you say 2 stage gas heat...is this "standard" in a variable speed, or an addtional"option" I live in central US, use it quite a bit though in winter.

All the variable speed furnaces I have seen are at least 2 stage gas (except the electric

If you use a lot going up to a slightly more costly sealed combustion chamber design, 90%+, might pay off for you. Some are rated as high as 96% AFUE.

[BaldLoonie]

Nobody makes a kit to add variable speed blower capability to an existing furnace. Stuff like that messes with the certifications of the furnace too.

In the central US you ought to be looking at dual fuel, pairing a new heat pump with a gas furnace.

[gpalasz]

Gotcha...now i understand a lot better. Thanks for the help!