The CBX27UH isn't variable speed - has a fixed speed ecm motor.
Do you have a specific need for air conditioning at cooler outdoor temps (below 55f)? If not, wonder why they're providing the low ambient kit?
I would ask them for an alternate estimate with an XP14 and CBX32MV.
There should be no need for air conditioning if the temp is below 55. I guess I assumed the low abient kit had something to do with the heat pump and cold weather conditions. When I initially spoke with him he mentioned something about using a more economical unit and adding some components to it to make it do the same thing as a more expensive unit. What is the advantage/difference of the xp 14 and the cbx32mv?
Originally Posted by RyanHughes
I would use a GREENSPEED 3 ton (See Page 11 of Attachment).
I might may even be tempted to use a 4-ton (page 12) in a climate with > 6,500 Heating Degree Days.
It seem like a 4-ton may be hard to justify at only $0.08/kW.
Of course, this unit is quite efficient + New, so it comes with a pri$e.
However, it is owners responsibility to try to determine Best Value.
Life_Cycle_Cost (initial cost + operating and maintenance costs) comparison with the Lennox may indicate GREENSPEED should be selected.
Ask each contractor how much it will cost to buy, run & maintain for 5 years.
Need an opinion after you get to that phase ... you have my e-mail address in my profile.
I am a bit ambivalent in attempting to validate whether your 48,000 BTU-hr is appropriate to your structure and locale.
Off hand, it seems a bit high.
What was the Air Change per Hour (ACH) selected?
Is the design temperature you used in your calc in the range of -3'F? ASHRAE 99% design temp.
Thermal Balance Point is 20'F assuming 48,000 BTU/Ht at -5'F
( Balance Point = meaning no aux. heat is needed > 20'F, except in defrost mode).
Aux Heating needed will be about 8 kW at 0'F
with use of a 3-ton Greenspeed.
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
Its an X13/ECM blower. Its not a VS blower. but it is very efficient.
Non Lennox dealers pay a higher price for the parts then a Lennox dealer does.
Performance wise, won't see much difference between a 14HPX and XP14. Both have similar efficiency ratings. Both have scroll compressors with high/low pressure protection. Adding a low ambient kit won't make the 14HPX anymore like the XP14, which would also require a low ambient kit for low temperature cooling (rarely needed in residential). I recommended you at least look into upgrading to the XP14 simply because it's a better built, quieter unit. XP14: nicer cabinet that opens up easily for service, quieter operation, and a unit made in the US. 14HPX: same bare bones, louder operation, made in Mexico -- designed to be a base grade/budget replacement unit. They aren't bad units, but consider all of your options.
Originally Posted by burhead
CBX27UH vs. CBX32MV: both are fine air handlers and will match up well with either outdoor unit. The 27 can't do any special dehumidification without a relay kit. High efficiency, fixed torque motor, so if you have a restrictive duct system or filter starts to get dirty, your airflow will begin to drop, lowering capacity/efficiency. These motors certainly do better than PSC motors and can handle a reasonable amount of static pressure while still providing an acceptable airflow range. With the variable speed blower, it can be set up to run a ramping profile for better dehumidification in addition to doing dehumidify on demand with the right thermostat. It will deliver a constant CFM up to around .8" ESP and will adjust its rpm as needed.
Ok one more question. Would it be a good idea to make this a dual zone system? The contractor has proposed to put a damper in each trunk line but I got to thinking about having them put automatic dampers in with two T stats, one upstairs and one down. It sounds like a great idea but I wonder what happens if the downstairs isn't calling for heat or AC and the damper is closed. It would seem that this would not be a good thing. Any opinions?
That is what a bypass damper is for.
You will like the Zoned (automatic) system much better than manual hand dampeners. It is code here that one system on a split level house must be zoned (automatic dampers and controls). I only like zoning with a by-pass when there is only 2 zones and the loads are fairly close. More than that I like to use variable speed w/ modulating dampers, no by-pass.
agree with Rodney, go with the automatic zoned control system.
Ok I am going with this contractor and he will be here on monday to measure for all of his pre fab stuff. I am going with a varible speed air handler cbx32 I believe. I spoke with him on the phone this morning and mentioned that I would like to add zoning eventually (not in the budget right now). He said he could make the single speed unit work but that I would be better off going with the variable speed unit. This put me at the upper end of my budget so I didn't ask about the xp14 upgrade. He also said that by going with the variable speed air handler I wouldn't need the bypass dampers. Does that sound correct?
That would only be true if the smallest zones load was the same as the capacity of the unit in first stage.