Virginia "Best" Contracor Quote

I would very much appreciate it if you would share with me comments on the following quote. I like one contractor over the others because of his qualifications and track record.

My home in upper Virginia (about as far north as you can go). The project involves replacing two ASHPs with new GSHPs. My all electric annual cost is about $3500 a year. T-stat setting 65F winter and 75F summer.

~ $33.5k
- Load Determination: ACCA Manual J, using Wrightsoft Software
- Cooling: 91F outdoor, 75F indoor, 50% RH
- Heating: 18F outdoor, 70F indoor
- Upstairs Unit: Waterfurnace Series-5 (2 Stage, with hot water assist), 2 Ton Split, reuse existing attic flex spider ducts
= Downstairs Unit: Waterfurnace Series-5, (2 Stage, with hot water assist.) NDV036, 3 Ton, reuse existing 3-zone ducts.
- Vertical closed loop. Number of wells and depth determined by using GAIA GLD and Waterfurnace GeoLink
- Loop Material: Rehau Cross-linked PE (PEX)
- Grout: 1.2K thermally enhanced
- Flow Manifold: All loops brought to an inside manifold
- Grundfos Pump(s)
- Hot water buffer tank
- Commissioning included
- T-stats: 3 heat, 2 cool Waterfurnace TPCC32U01

Contractor In-house Qualifications: Certified GeoExchange Designer (CGD) by Association of Energy Engineers (AEE), IGSHPA Accredited Installer, Master HVAC, Master Electrician, Master Plumber, Master High Pressure Gas, Master Waterwell Certification, PE, LEED AP.

Seem about right? Any suggested enhancements or changes?

Thanks in advance!

 

Rehau never really took off in a lot of markets due to their claims of performance advantage over HDPE. The connections were what turned off traditional folks, but if all the tails are run inside, no worries.
Eric

 

Appreciate that - I was a little concerned, having never heard of PEX.

 

My existing zoning is controlled by a Honeywell EMM-3U MiniZone. There are three zones. Is it compatible with a WF Series 5 or 7?

 

Your existing HW EMM-3U zone panel does not support 2 stage heat pumps. It can control a 5Series if it is a single stage unit with aux heat but I wouldn't recommend going that route. There are too many advantages stepping up to a 2stage unit especially in a zoned system.

Zone control for the variable speed Series7 requires the WaterFurnace IntelliZone2 system. There are no alternatives.

 

The existing downstairs unit has Honeywell zone panel and will be replaced with a 3-ton Series 5 or 7 (under review). I now know it will need to be replaced with the IntelliZone2. Thank you for identifying that before the contract is signed! We were assuming the HW zoning unit would work with the new WF unit.

The upstairs unit is sized for 2-tons, series-5, two stage compressor. I assume that this unit will not have to be zoned, and if not, should it be zoned? The existing single-zone upstairs unit serves two bedrooms, a bonus room (conditioned room above the garage), and the top level of a two story foyer with open stairs. The second bedroom is only occupied in the summer months and the bonus room is rarely occupied.

 

I don't understand the sequence of controls for WF products. Is everything by the book or is it up to the installer to improvise? Perhaps you could point me to a WF design manual.

For example, does a house with a 2-ton Series-5 and a 3-ton Series-7 require both a variable flow and a constant flow center? How is the flow rate controlled from one flow center to each WF unit?

How is the fan speed controlled - by duct static pressure? Is it plug and play or highly optimized in the field?

 

Sorry - never mind - I found the installation manual. It doesn't answer all the questions, but is a good start.

 

Good luck with that my friend

 

All those engineering degrees and that's the best he can design for your money.
WOW

 

Any suggestion on what have been a better design?

Tom, it strikes me to watch out for the pumping solution. You can have something very efficient, and something very inefficient. Over the years, as soon as there are multiple heat pumps on one loop, I have to become very used to a variable speed central pump, and either modulating valves for the 7 series or on/off valves for the dual stage 5 series.

 

The design has changed. If fact, much has changed. I have a few minutes to type an update:

- Contractor looks at a horizontal loop instead vertical as first proposed. I cautiously agree to anything that could be a cost-effective solution.

- Confirmed 5T block load by Manual-J. The calcs show some aux heat required (around an additional annual electric cost of $5 electric) under design conditions.

- Asked what the cost increase would be for a Series7 3T downstairs, 2T Series5 upstairs. Calcs show an almost insignificant operating cost reduction as modeled. WF territory manager thinks op cost should be lower but does not take the time to double check calcs. WF pointed out that the Series7 has increase comfort and reduced sound levels.

- Two flow centers (one per WF unit). Reviewing one variable flow center.

- Conveyed that the existing Honeywell zoning would not work (thanks “geoxne”). Design revised to include Intellezone2 and new dampers.

- Asked if we could zone upstairs Series5 unit too.

- All these “what-ifs” increases the cost by over $12K. Proposed cost greater than available funds. Panic. Not much time left in 2016 to do the work and get the tax credit.

- Suggested we replace existing downstairs five ton unit with WF five ton Series-7. Counting on the consolidation of equipment and economy of scale to reduce cost. One variable speed flow center (thanks docjenser). Add performance monitoring package. I will add ductwork (DIY project) from new basement unit to attic later. It turns out that there is a non-interfering and straight path for ducts from the basement to the attic with few changes to the house. Will tie into ducts in attic and add three three upstairs zones (six total). Advantage: Cost increase only slightly higher by about $3K over initial proposal (within budget), not including duct materials, zone dampers and recommissioning. Disadvantage: No joy for having a complete project for two or three months. Potential of finger pointing at re-commissioning. Warranty issues to be discussed.

- Signed contract. Full design package will be provided later with partial payments as follows:
Consummation of Contract
Completion of Design
Completion of Loop Field
Delivery of 1 WaterFurnace Packaged Unit
Installation of Flow Center and Commissioning of Loop Field
Final Commissioning and Start-Up

- Determined that horizontal loop is not as feasible as vertical loop. Septic field and reserve field is too restraining. Well application filed. Cost increase – another $2K. It could be argued that the contractor is taking advantage of changes to increase the price. However, I have to admit that he is working with me and within budget to make a working system. I believe the one Series-7 five ton unit with the additional upstairs zoning is a better design. Fortunately, the cost is still under the majority of initial bids. Unfortunately, I am at the end of contingency funds.

We have about four weeks to complete the project before year end. So far, on track.

 

Good choices. For some reason I was always under the impression that you could not route the ductwork upstairs. Having said that it is likely the better solution.
Things to watch out for:
1) The 2 pump flow center from Waterfurnace is not a good solution. The 7 series will run forever, and having a constant speed 26-99 come on as first is very inefficient. Make sure the loop field is designed for low pressure drop so the 32-140 variable speed pump is sufficient. Part of that might be methanol as an antifreeze instead of glycol. Don't be fixated solely on the numbers, or wether a territory manager could confirm them. Wf design software only gives ballparks. At the end, a generously sized series 7 is the most efficient and most reliable solution out there.

 

How does this look?

Borehole Length (ft): 480.0; two vertical GHEX 240.0 each calculated - (installing 260 feet each)
Ground Temperature Change (°F): -0.1 cooling and heating
Unit Inlet (°F): 76.6 cooling; 36.1 heating
Unit Outlet (°F): 84.4 cooling; 31.1 heating
Total Unit Capacity (kBtu/Hr): 52.3 cooling; 52.1 heating
Peak Load: 37.2 cooling; 52.1 heating
Peak Demand (kW): 1.7 cooling; 4.0 heating
Heat Pump System 21.9 EER; 3.8 COP
System Flow Rate (gpm): 10.9 cooling; 15.2 heating

Fluid
Flow Rate: 3.5 gpm/ton
Fluid: 6.3% Methanol
Specific Heat (Cp): 1.03 Btu/(°F*lbm)
Density (rho): 61.7 lb/ft^3

Soil
Ground Temperature: 56.2 °F
Thermal Conductivity: 1.80 Btu/(h*ft*°F)
Thermal Diffusivity: 1.20 ft^2/day

Piping:
Pipe Type: 1 in. (25 mm) - RAUPEX
Flow Type: Turbulent
Pipe Resistance: 0.081 h*ft*°F/Btu
U-Tube Configuration: Double
Radial Pipe Placement: 1 in. (25 mm) - RAUPEX
Borehole Diameter: 6.00 in
Grout Thermal Conductivity: 1.20 Btu/(h*ft*°F)
Borehole Thermal Resistance: 0.127 h*ft*°F/Btu

One WF Series-7; five ton unit.
Variable Flow Center

 

What is it? Where is it from? Many things don't add up in my book here.

Specific flags: only 6.3% methanol? Your heat exchanger will freeze.

Not the biggest fan of pex pipe in the ground.
There is a limit for heat exchange when you think you can use a linear heat transfer model, 1.2 ground and dual pipe in the borehole, and shorten the borehole to less than 100 ft/ton when ground conductivity is only 1.8. Again, things don't add up for me.

 

When you write, where is it, do you mean the site location? It is in Lovettsville, VA. I'll ask about the things that don't add up.

 

No. I meant who wrote this up, which would help me understand why they don't add up.

Is the flow center with one or 2 pumps?

 

Well, I took the PDF printout and transposed it to the forum. The software used was GLD. Designer was REHAU Construction, LLC.

Some of the printout seemed repetative, but is included as follows:

"Calculations were based on the peak heating and cooling loads and other information provided.
REV1: Revised fluid type and total gpm.
-52.1 kBtu's/Hr Peak Heating
-37.2 kBtu's/Hr Peak Cooling
-1" PEXa Double Ubend w/Spacers
-56.2F Soil Temp
-1.8 FTC
-1.2 Grout TC
-36F/76F MIN/MAX EWT's
-6% Methanol"

The flow center is two pumps, one constant flow and the other variable. I shared your input docjenser. It seems the designer thinks the two pump flow center is better. Perhaps you can help me with details that justify your suggestion. I appreciate the help.

 

Rehau is a plastic pipe company which manufactures the pex pipe as an alternative to high Density Poly Ethylene pipe, but as mentioned before, it never catched on.

The 2 pump flow center has an (relative) inefficient constant speed and a very efficient variable speed pump. The 7 series due to its capability to modulate down to 20% of max load through 12 stages, will significantly increase the run time, usually from 2500 hours of a dual stage heat pump to 5000-6500 hours annually.

The flow center is set up to have the inefficient constant speed pump on first to run all the time using 235 watts all the time, followed by the very efficient pump coming on only at stage 7 and above using between 9-190 watts depending on the stage.

Thus they have combined the most efficient heat pump with the least efficient pumping solution. The variable speed on the single pump flow center is strong enough to power even a 5 ton 7 series if the loop field is design for low pressure drop. Your designer might understand this. Bigger and much less efficient is not better.

Another big flag is the 6% Methanol. Your heat changer in the heat pump will freeze.

 

I'm reading the Geo-Flo Catalog differently. Refering to http://www.geo-flo.com/downloads/Geo-Flo_Catalog.pdf:

Page 16, the Geo-Flo 2014 Product Catalog shows the pump curve for the Grundfos Magna GEO 32-140 Performance Curves (Single Pump). On the bottom of page 16 there is a paragraph that reads: "*Above pump curves are for a single pump. When the Magna GEO pump is used with a second pump in series,the second pump is constant speed. The Magna GEO (variable speed) pump adjusts speed (when used with a controller) to maintain flow rate or temperature difference. The controller energizes the constant speed pump(UPS26-99 or UP26-99) when the Magna GEO cannot meet setpoint, and adjusts the Magna GEO pump accordingly. See pump curves on the following pages for two pump variable speed Magna GEO flow centers."

Page 17 shows the Grundfos Magna GEO 32-140 and UP(S)26-99 (pumps in series).

So I read this to mean the variable flow pump is the first stage used. The constant speed pump is energised if more flow and head are required.