Experiences with Geothermal Heating

May 2012

Living in the north-east of Ontario often means that one of the less convenient forms of providing heat for your property, a natural gas supply, is unavailable.  The alternatives for a basic fuel are wood, oil, propane or electricity.  During the recent design of a new 2,000 square foot residence in the French River area the possibility of using one of the above fuels or a combination of them, was studied.  Oil was ruled out due to its cost leaving wood, propane or electricity.

Several types of heating systems are also available and those contemplated were:

  • Convection, i.e. direct heat from a wood stove or electric convection heater
  • Electric baseboard heaters.
  • An electric or propane fired boiler providing hot water for domestic needs and, via a heat exchanger, to an in-house heating system.  The in-house heating system could be either ducted hot air or an in-floor (hydronic) heating system.

The selected system used a propane fired boiler with a radiant floor (hydronic) heating system and a wood stove for supplementary heat.  A radiant floor heating system (water filled pipes embedded in the sub-floor) was installed to transmit heat from the boiler to the interior of the house.  It is important to ensure that as the radiant heating system is installed in the sub-floor, the finished floor materials (laminate, solid wood, carpet, etc. placed on top of the sub-floor) should be selected so as not to provide a barrier for the flow of heat from the pipes to the rooms. A radiant floor heating system cannot provide air conditioning as cold water flowing through the in-floor pipes would cause the floor to sweat.

The system worked well but it was found that after the first year the cost of using propane as the main fuel was not economical.

It was at this time, and thanks to a Government Grant, a geothermal heating installation became a viable substitute for propane.  The geothermal unit is powered by electricity (expensive!!).  One of the advantages of this type of heating is that for every unit (kWh) of electricity consumed by the geothermal equipment, between two and four units of heat are generated.  The geothermal unit selected provides heat for the house and supplementary heat for the domestic hot water system.

The geothermal unit is comprised of a heat pump, hot water tank, and circulatory pumps installed inside the house.  Outside of the house a long loop of 1 ¼” polyethylene pipe is sunk into an adjacent river or lake, or buried in the ground close to the house.  This loop is connected to the heat pump.  The loop must be installed sufficiently deep so that the winter cold does not affect the temperature of the water/ethanol mixture inside the pipe.

The installation of the geothermal system should be done by certified personnel. Often a 10 year parts and labour Warranty can be obtained to cover the installation.

Once installed the main benefits of the radiant floor heating were immediately noticed, warm floors and an even temperature throughout the house and, most importantly, at the end of the first year of operation the heating cost for the house was less than 60% of the cost of the first year when propane alone was used.

From the beginning of operation the system worked well, minor problems were noted initially due to air bubbles entrapped in the piping causing pumps to over-heat.  This was promptly corrected by the contractor and the system returned to normal.

The only negative experiences have been that occasionally the geothermal unit trips on “Frost Protection”; no heat is generated until the power is switched off and on again.  The operation of the Frost Protection signifies that the temperature inside the unit has dropped below a pre-set value. The contractor advised that this seems to be a problem only with those systems that use a pipe loop installed in a river or lake.  Loops directly buried in the ground do not seem to be affected.  Improvements have been made to the installation but as yet it has not been perfected.

A further inconvenience is that when the electricity supply fails no heat is available from the geothermal unit without the installation of a sufficiently large standby generator with capacity to handle the in-rush current required by the compressor and pumps.  The original gas boiler or the wood stove becomes a backup source of heat.

Like most modern day equipment maintenance is important and this should be carried out on an annual basis.

During the summer months the geothermal unit is not required and is therefore switched off, domestic hot water is supplied from the original gas boiler.

Date Added: September 23, 2012 | Comments Off | Filed under: News — Tags: — webedit @ 8:12 pm

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