Ground Source

Reasons for an Accurate Peak Heating Demand Calculation

An accurate heat (and cooling) loading calculation is often overlooked in the building and/or design process.

We highly recommend that a professional heat/cooling load calculation/modeling is performed for every potential Ground Source installation. The information and recommendations from this exercise will save you money in both on going operating and initial installation cost.

The reasons why:

A Ground Source System in order to run at the highest efficiency must be sized to the application as closely as possible. This is to prevent the Ground Source system from “short cycling” (turning the compressor on and off in a short time frame). Short cycling means less efficiency, higher running costs.
Bigger does not mean better. A larger Ground Source System will not do the job easier and more efficiently.
If the Ground Source System is too small the there will be inadequate heating/cooling for the building.
A Ground Source System that is too large will cost more to purchase, install and operate.
Peak building heat/cooling demand determines the exact size (kw) of the WaterFurnace unit.
The size/length of the ground loop is directly related the size (kw) of the unit(s) selected. Larger the kw the larger theground loop.
Different buildings use very different construction materials and methods. This means the heating/cooling requirements can vary wildly from building to building. H1 (NZ minimum standard) is typically 80-100w/m² - In many cases this can be vasty improved for little construction cost.
If the peak heat demand is guessed there will be a percentage allowance (typically 20-30%) built in to ensure that the system meets peak demand. The result, you pay for a 20-30% bigger system than is required, no matter what sort it is.
An accurate heat load calculation/modeling will normally pay for itself immediately, with the operating savings and reduced installation costs. e.g. a smaller, correctly sized ground loop and WaterFurnace unit
Increased in building insulation and/or sealing is often an option. The capital investment in added insulation and air retention is often less than the captial cost difference between smaller and larger units.
A professional heat load calculation can cost from $300 to over $5000 for a very large multi faceted building.
For an average new building the cost is usually between $300-1700, dependant on the detail of the data supplied by the client.

Example of buildings of the same size with differing heating requirements:

Building Floor Area m² Heating Watts / m² Total Building kW

200 200 40

200 150 30

200 100 20

200 80 16

200 50 10

200 30 6

Yellow = Aprox minimum (H1) insulation for New Zealand new homes.

Annual running cost estimate:

System Size kW Ground Source Diesel Electricity LPG

40 $3,124.00 $8,496.00 $12,496.00 $13,122.00

30 $2,343.00 $6,372.00 $9,372.00 $9,841.50

20 $1,562.00 $4,248.00 $6,248.00 $6,561.00

16 $1,249.60 $3,398.40 $4,998.40 $5,248.80

10 $781.00 $2,124.00 $3,124.00 $3,280.50

6 $468.60 $1,274.40 $1,874.40 $1,968.30

Estimated COP's: Ground Source 4.0, Diesel 0.86, Electricity 1.0, LPG 0.90

Fuel Cost: Electricity$0.22kW/hr, Diesel $1.20/l, LPG $1.35/l

Indication of Ground Source Base Cost:

System size kW	Trench Length m	Loop Estimate	WaterFurnace Unit(s)
40	570	$17,500	$34,000
30	430	$10,500	$26,000
20	290	$8,200	$16,700
16	220	$7,000	$15,000
10	150	$5,700	$13,000
6	90	$4,600	$9,500

Note: Cost is indicative only. Items such as trenching/excavation, travel etc are not included.

This information is produced as a guide only. Although every effort has been made to ensure this information is accurate and up-to-date, Ground Source and/or its principals or representatives cannot be held responsible for errors, omissions or inaccuracies that maybe present.