Category Archives: Low Temperature District Energy Sharing Systems

Scale in Water to Water Heat Pump.

Water quality has come up as a major issue this year for the heating systems in Cheakamus Crossing.  High mineral content in the well water has created higher concentrations of minerals in the closed loop heating. The minerals of biggest concern, are calcium and iron.

The water supply is from the Whistler potable water supply, not, the District Energy System or Waste Water Treatment Plant, as some have asked.  It is certainly safe for consumption and people will even pay money to get the health benefits from mineral water, however, for a closed loop heating system, these minerals are a problem.

image of used copper piping
Calcium buildup on copper pipes

The copper pipes shown here, were recently cut out of a unit that had several leaking fittings. Water had been slowly seeping out through poorly connected pipe fittings.   As water leaks out, it is replaced by the boiler feed which adds fresh water and minerals to the system .   The pipe with the thick layer of calcium shown above, shows the bottom of the pipe, where heavier particles collect.  A  quick swipe along the inside, easily removes the layer of calcium, exposing the bare copper.  The calcium did not bond to the pipe, as  it would if on a  heated surface, however, it is still stuck.

The calcium can be removed or at least reduced from collecting in the piping with water treatment but not, by flushing.  It would take very high velocities to flush the calcium off the walls of this pipe.  Velocities, much higher than what can be achieved by draining the tank.

However, draining the buffer and adding fresh water,  will create more problems down the road.   For example,1-IMG_3098  the mineral scale shown here, is just some of  what was taken from one system that had a slow water leak that went unnoticed.   The build-up eventually caused the unit to shut down.  Now, a lengthy clean up process would have to be performed to remove all the scale.  Until then,  the scale will slowly build on to the heat exchanger plates, where it bakes onto the plates  and hardens,  like limestone.  Eventually, the unit shuts down on high pressure.

There have been contractors trying to sell flushing, as part of an annual preventive service which will actually have the opposite effect.  Flushing, is one thing that should be avoided except in extreme cases.

Fresh water contains oxygen, a key ingredient to rust.  Air bubbles trapped in the fresh water, can become trapped in various locations, adding minerals that  will build up over time.

For those that can actually access the drain at the bottom of the buffer tank, it may be possible, to bleed off some of the water with higher mineral  concentrations, from the bottom of the buffer tank but only after, it has settled over a long period.  Such as, September, after the water pump has been off all summer, there may be some sediment that can be removed.  Only drain off a few liters, at the most.   If the water has visible particles, then it may have helped.  If it is clear, then you may have done more harm than good.  If you break off that cheap little plastic valve, used as a drain fitting,  ( on some of the tanks) you will have definitely done more harm.

The piping practices are of concern on some units, which can affect the  life of the equipment, due to electrolysis.  This can shorten the life of the buffer tanks,  hot water tanks and other components.  I expect the  buffer tanks to last 20 years+ if properly maintained.   The larger hot water tanks, will be shorter due to the fresh water.

There are non-toxic ways to treat this water and to reduce the need for cleaning the heat exchangers.  However, you cannot flush your trouble away.

Water quality is key to the long term operation of these systems.   With proper treatment, the water can be improved at a reasonable cost and these heat pump systems, can run a very long time with very little or no maintenance.

 

 

Cheakamus Crossing Fall Maintenance

Many residents in the Cheakamus Crossing, ask about the maintenance required for their heat pumps. These heat pumps, do not have items that require annual service, there are no filters to change, motors to oil or belts to replace. Having the units inspected every year is not necessary but couldn’t hurt, if inspected by a qualified refrigeration technician. Anyone else, and it just may hurt, the heat pump and the wallet. A qualified technician can identify hidden issues such as overheating, control problems, circulation problems and other issues, preventing future issues.

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Buffer Tank – Heat Pump – Hot Water Tank

In the past, there have been number of problems which had nothing to do with maintenance. Most of which were manufacturer issues with the equipment, installation issues that have been corrected or operator issues.

The only, “maintenance type” item that has been an issue, is the cleaning of the load heat exchangers, the frequency of which is undetermined.

These units have run since the fall of 2008 and, several of these units have been tripping on high pressure. The load heat exchangers, that transfers heat from the refrigerant, to the heating water, have built up scale on the interior surfaces which cause the unit run higher pressures. These units trip on high pressure at 610 PSI. Pressures this high can do serious damage and is not something that can be resolved by a DIYer or unqualified service tech safely. If you see a red screen that reads E2 High pressure fault, call a qualified technician for service. Resetting the control, will restart the unit for a while but it will run hotter than normal. Resting the control multiple times can lead to compressor damage.

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Scale from Cheakamus Crossing heat pumps

There are no access valves on the heat exchanger which makes cleaning difficult and there is a limited number of choices for cleaning and treatment. The heat pump is used for potable water which places several restrictions on what treatment that can be used. If a potable water system, is even at risk of being contaminated, it is considered a serious issue and very expensive to resolve.

There are two other heat exchangers, one for the potable hot water and one the source water. It may be necessary to clean these heat exchangers as well in the future. Several source heat exchangers required cleaning, in the first two years of operation, due to DESS water quality issues, which has since been resolved.

The two storage tanks have aluminum anodes which will need to be replaced in a few years, even sooner if you live in the upper rise. This image was taken last year and shows some corrosion but will be several years before it needs to be replaced.

Image of anode in a hot water tank
Buffer tank anode