I got my unit price quote along with heat load calc and I need to decide if this installer is on the mark.

The Facts:

 - 3500 sq foot ICF colonial in Cleveland Ohio (internal sq foot - measured from the out dimension it is closer to 4000 sq foot)

 - 10 degrees of of due north south with window mass concentrated on the south

 - probably R 40 cellulose blown into attic - few or no cans in the top ceiling. 

 - the installer has done geothermal before but never in ICF

 -heat load calc is 51,151 BTU/hr - cooling load calc is 36,775 BTU/hr

 - unit is a Climate Master tranquility 27  (064 model) with desupersaturator and vertical loops

 - he sized it as 3.3 tons (064 model) 

My questions:

1. is 3.3 tons about right?

2. The average efficiency is listed as 3.81 COP - my other quote is going to be from another installer (Water Furnace envision COP listed as 5.0) - should I go with higher COP instead? 

3. His quote lists "Air changes/hour as 0.40 in heat mode and 0.20 in cooling" - I have seen on this site that ICF is closer to 0.1 air changes per hour - but then on the web I have seen it listed as 0.5 Air changes per hour at 50 paschals with a blower test. Is my installer using too high a level of air changes for his calc or is "air change per hour" and "air change per hour at 50 paschals" different units?

4. Do I need a preheat tank?  The quote lists an "80 gallon std electric water heater - 450$) - Why an electric water heater?  I thought electric was inefficient? 

5. Is there one COP for a unit  since the COP varies with conditions?  Is there a std set of conditions that all units can be compared at to compare apples to apples?

Thanks so much in advance for your help. 

Todd

COP is totally dependent on the temperature of the water coming out of the ground and into the heat pump  (EWT).  The standard is to rate heat pumps at 32° EWT.  I doubt that the Water Furnace unit has a COP of 5 on a EWT of 32.  Compare both units   at 32° and see what you get.

1) I'm a bit confused about 3.3 tons, approx 40kBtuh, in reference to a CM 064. That's a nominal 5 ton unit. It would be very helpful to know the designed Entering Water Temps (EWT) for summer and winter. COP and EER and capacity for a wide range of conditions can be read off published performance charts for either CM or Waterfurnace.

2) See 1). Compare COPs between manufacturers units only at identical loop water temperatures and flows. WF is a tad (~5-10%) more efficient than CM under some conditions.

3) ASHRAE 90.1 covers IAQ and air changes. I don't have it in front of me but I believe it calls for 15 CFM per person or .35 ACH. Blower door tests are a bit funky and don't relate well to real world occupation for two reasons: 50 Pascals pressure differential corresponds to an atypically windy day, and tests are often conducted with bath vents, dryer vents, and rangehoods blocked. This is done to isolate and evaluate the rest of the building envelope. The test result relates little to actual occupied performance of the structure on a day to day basis.

4) Preheat tank is necessary for good performance of desuper. I've written elsewhere here at length on this - do a search. Electric is very efficient but sometimes more costly to operate. There are various combinations of tank and tankless, gas and electric options, but the bottom line is that a desuper needs an un-energized preheat tank sized at about a day's hot water use to be most effective. Where the water goes after the preheat tank is up to you - electric, gas, propane, tank or tankless, whatever your wallet, space, and available fuels allows.

5) The "one COP" for any unit should be at ARI- standard conditions - the same incoming water temps and flows per ton are used for all units to get ARI-rated conditions. This Engineer concurs with 183EEj's reply.

I have and like WF Envision. Both CM and WF are great units. Far more important to successful outcome than brand will be quality of design and execution of installation. Given the burgeoning interest in geo, its complexity and cost, it is important to use a good installer who can provide several recent good references.

An 064 is a two stage 5 ton unit. So you need to find out where the 3.3 tons come from. ( as others have said ) Maybe it is 3.3 tons on first stage?

It appears that the unit is sized to provide 100% of the heating needs. You could save some money by going with a smaller system and letting the backup heat give you a boost on the really cold nights. The idea is that you can save thousands in install costs and pay less than $50 per year for back up heat.

COP is definately affected by data entry bias and software. Hard to find apples to apples comparisons, but single stage Bards made right in OH operate for <$100/yr more in most applications. It sounds like both installers are oversizing equipment likely due to the fact that us old timers tend to equate square feet to load. Fact is with ICF and other insulation upgrades, we can do with 3 tons what used to take 5. ATTV049 (4 ton Climatemaster) may still be too large, but if the load is correct there is definately no benefit to the 5 ton (TTV064). Worry less about the COP and more about the referrals of your bidding contractors. If other (waterfurnace) contractor quotes 3 or 4 ton I'll like him better than your first guy but his throwing out a 5 cop without running the operating cost data (as I'm sure he didn't suggest an average COP of 5) is a little disingenuous.
J