confused on HVAC choices

[ian930]

Hello all,
I have spent several hours on this forum using the search engine to find answers. While I have not found the answer yet to my specific questions, I have been most impressed with the quality of the responses I have read. I have certainly learned a lot, Thanks! So now that I hope I will not insult anyone with asking questions that have been asked many times previously, hopefully you'll can help in my decisions process.

I have had 4 quotes on a new HVAC system. I am looking for a top of the line type set-up. I know there are proponents of other systems and apologize if I am oustersizing you, but I have zeroed in on a Bryant/Carrier Infinity or Evolution system. My problem is related to these complex systems and different inputs from the bids I received.

I should state that I currently have a 125K Btu Lenox furnace and a 3 ton A/c unit in a house built in 1986 (Argon filled windows, 6 inch walls etc.) and live in Minnesota.

Here are the questions:
1) From the 4 quotes, 2 say I need an 80K BTU system and 2 say I need a 100K BTU one. These are all for the 90+ Bryant or Carrier top line setups with corresponding fancy/high-tech tstats. How do I determine who is correct? It seems for this type of set-up to work efficiently they need to be sized correctly (and I know from reading other postings that installed correctly is key too).

2) This is the one I really can't figure. All the quotes are for either a Bryant 90i (model 355MAV) or equivalent Carrier furnace. Other than question #1 above I am fine with the furnace choice. However, when it comes to the Aircon unit I am confused. One person said to go with the Evolution tstat and the 2-speed Model 598 Evolution unit and another person said not to use the Model 598 with the Evolution tstat as the system becomes over controlled. This person recommended going with the single speed Quantum level Model 550A with the Evolution tstat. Apparently the issue is the two speed 598 system along with the Evolution tstat becomes confused as both try to control (so he says). It seems to me if Bryant and Carrier made the Evolution/Infinity systems they would make them work together well with all components. However I do understand that having too much control could confuse the system. So basically should I use a 2-stage aircon unit or a single stage one with the Evolution/Infinity tstat to achieve better efficiency and not over control.

To confuse it more, one sales person said to use my Current Honeywell tstat with the Quantum one speed 550 model as the two speed 598 model was really for commercial use and a waste for residential use. He also said that I couldn't use the Evolution tstat with a 90i and a Quantum aircon unit so I should use the Howneywell tstat I already have and save money.

Thanks in advance for your help in clarifing all this!
Ian

[jacob perkins]

Originally posted by ian930
Hello all,
I hope I will not insult anyone with asking questions that have been asked many times previously,

dont worry...most of are really too stupid to be insulted

welcome to h-talk.

[jacob perkins]

Originally posted by ian930
Hello all,
However, when it comes to the Aircon unit I am confused. One person said to go with the Evolution tstat and the 2-speed Model 598 Evolution unit and another person said not to use the Model 598 with the Evolution tstat as the system becomes over controlled. This person recommended going with the single speed Quantum level Model 550A with the Evolution tstat. Apparently the issue is the two speed 598 system along with the Evolution tstat becomes confused as both try to control (so he says). It seems to me if Bryant and Carrier made the Evolution/Infinity systems they would make them work together well with all components. However I do understand that having too much control could confuse the system. So basically should I use a 2-stage aircon unit or a single stage one with the Evolution/Infinity tstat to achieve better efficiency and not over control.

To confuse it more, one sales person said to use my Current Honeywell tstat with the Quantum one speed 550 model as the two speed 598 model was really for commercial use and a waste for residential use. He also said that I couldn't use the Evolution tstat with a 90i and a Quantum aircon unit so I should use the Howneywell tstat I already have and save money.




C'mon guys help a bro out here.



I wont get to sleep tonight without knowing the answer

[BaldLoonie]

How did the dealers determine size? Guess? Or did any measure every window, door, ask you about insulation and use a computer to decide size? If so, that's who is right. Usually those guessing guess big to be safe. That's probably the 100K guys!

Minnesoter sure doesn't need super SEER unless you want the ultimate and can afford it. From an economic standpoint, you probably would NEVER pay for a 12+ SEER in electric savings over the life of the unit. If the NSP or whoever the utility is these days has a rebate, that could help on higher SEER. The Evolution control is amazing but much of its benefits is in humidity control, perfect for tropical areas but not as needed in your climate. Again it is what your budget permits. If you want the ultimate, go that route. If you want to be more practical, go with a good 2 stage stat, reasonable SEER single stage A/C and take a great vacation!

[dan sw fl]

Originally posted by ian930
... I have had 4 quotes on a new HVAC system.

... I know there are proponents of other systems and apologize if I am oustersizing you, but I have zeroed in on a Bryant/Carrier Infinity or Evolution system.

I should state that I currently have a 125K Btu Lenox furnace and a 3 ton A/c unit in a house built in 1986 (Argon filled windows, 6 inch walls etc.) and live in Minnesota.

Here are the questions:
1) From the 4 quotes, 2 say I need an 80K BTU system and 2 say I need a 100K BTU one. These are all for the 90+ Bryant or Carrier top line setups with corresponding fancy/high-tech tstats. How do I determine who is correct? It seems for this type of set-up to work efficiently they need to be sized correctly (and I know from reading other postings that installed correctly is key too).

2) All the quotes are for either a Bryant 90i (model 355MAV) or equivalent Carrier furnace.

However, when it comes to the Aircon unit I am confused.

...

It seems to me if Bryant and Carrier made the Evolution/Infinity systems they would make them work together well with all components.
...

EXCELLENT Choice.

http://www.bryant.com/Files/Bryant/Local/US-en/consumer_resources/6.pdf

Does your current furnace (perhaps ~100,000 BTU OUTput) handle < 15'F well or does it short cycle somewhat?

Send/post house plans
_______, MN
( i.e., 2,000 Sq.Ft, one-story,
1986, R-19 walls, R-38 ceiling),
house orientation (front faces south ?),
window details (i.e. argon-filled, U-value 0.3),
total window area (i.e. ~ 250 sq. ft)

Review all information on ACCA Manual J calc
and compare to operating data [current ( last 2 years) gas usage].

My first inclination is that
100,000 BTU 2-stage should be selected
unless you are certain that current furnace has a significant short cycle problem.

[dash]

For the most part contractors seldom if ever undersize as they will have to replace it,they oversize and the symtoms usually let them get away with it.

So I'd guess the 80,000 is all that's needed.Detailed load calculation will tell for sure.

[bluetooth751]

Originally posted by ian930
Hello all,

Here are the questions:

2) One person said to go with the Evolution tstat and the 2-speed Model 598 Evolution unit and another person said not to use the Model 598 with the Evolution tstat as the system becomes over controlled. This person recommended going with the single speed Quantum level Model 550A with the Evolution tstat. Apparently the issue is the two speed 598 system along with the Evolution tstat becomes confused as both try to control (so he says).
To confuse it more, one sales person said to use my Current Honeywell tstat with the Quantum one speed 550 model as the two speed 598 model was really for commercial use and a waste for residential use. He also said that I couldn't use the Evolution tstat with a 90i and a Quantum aircon unit so I should use the Howneywell tstat I already have and save money.

Thanks in advance for your help in clarifing all this!

Ian


The 598 is a good unit, but like previously stated you may not get your payback. With the 598 your comfort should be slightly improved and the VS drive will run at lower RPMS making it more quiet.

As for the Evolution Control getting confused when used with the 598. That is not true. The 598 is not a commercial specific unit and in my area almost rarely used in comercial mainly do to the lack of low ambient control.

As for sizing like Dash said the smaller is propably better suited.

How does your current furnace keep your home now? Will the duct system be replaced?

[mayguy]

Originally posted by BaldLoonie
How did the dealers determine size? Guess? Or did any measure every window, door, ask you about insulation and use a computer to decide size? If so, that's who is right. Usually those guessing guess big to be safe. That's probably the 100K guys!

Minnesoter sure doesn't need super SEER unless you want the ultimate and can afford it. From an economic standpoint, you probably would NEVER pay for a 12+ SEER in electric savings over the life of the unit. If the NSP or whoever the utility is these days has a rebate, that could help on higher SEER. The Evolution control is amazing but much of its benefits is in humidity control, perfect for tropical areas but not as needed in your climate. Again it is what your budget permits. If you want the ultimate, go that route. If you want to be more practical, go with a good 2 stage stat, reasonable SEER single stage A/C and take a great vacation!

I think Baldloonie made a good point on this.. Our Minnesota summer do get warm. but the Higher SEERS not needed. Check with Xcel (NSP) to see what type of rebate they off it it helps on the cost of higher SEER unit.

Not knowing the sq ft of your home. My guts says anywhere 60 to 80k furnace.

[Midwest]

You are looking at systems which are high tech, very efficient, quiet and a little pricey over the next models down. The contractors may have guessed at sizing but if they did their own calcs, ask to review a copy if they will let you. I recommend you click on the red tab in the upper right corner of this site page and perform a heat loss/gain calc of your own. Have some data ready: take measurements of your wall lengths/heights, window dimensions and type, insulation levels- attic and walls, orientation of each wall (North, South, etc.) and then you should be ready to perform your own calculation.

These furnaces are 93/92% AFUE depending on vertical or horizontal installation. If your calculation ends up with needing 70MBtu for example, stay with the 80MBtu input models. Avoid all temptation to oversize. Keep a copy of your calcs to show the bidders. The first one who balks at doing a load calculation or says he can size your needs by 'experience' loses automatically. Frankly I would start discussions with the ones who recommended smaller furnace models. I sense they're right, but I'm only speculating.

The 598 condensor may be overkill and increased installation price might never be overcome in energy savings alone. On the other hand, it will run on low stage much of the time, removing more humidity thereby providing better comfort than a single stage model. If you decide to go with the 598, have the Evolution controller added. If you opt for the 550/552 condensors, at least have a quality two-stage thermostat installed for better heating control. I like the concept of staged heating & cooling equipment. It only makes sense at providing improved comfort over those units that operate full-blast only.

[Irishmist]

Albeit, I could probably have put anything in my own home, and in the past have had Lennox Pulse systems (both G14 and G21), and currently have a Bryant evolution system with a 2 stage variable speed furnace and 2 speed heat pump (dual fuel). Very pleased and just this past month received my utility bill that was $154!! Neighbors and friends all complaining about their $300 and $400 utility bills. I don't think I have ever heard the phrase 'over controlled' when it comes to our industry. It's all about control, man! Anyway, make sure anyone you are considering has performed a load calculation and is willing to provide you a copy of that load calculation (upon completion of the work) for your records. Sounds like any of the systems you are considering will be good, high efficiency systems. I strongly recommend the dual fuel system as the best hedge against fluctuations in either fossil fuel (lp / nat gas) or electrical rates. All the best, John.