Tag Archives: Whistler

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.

 

 

If all else fails, read the instructions

Buildings have always been changing, new material, new techniques and improved environments, that are slowly evolving to meet our needs.  In the past 10 years, the push to reduce greenhouse gases has accelerated this rate of change. In BC, the LEED standards mandated by municipalities, and the recently adopted ASHRAE 90.1-2010, are bringing some of the biggest changes in construction since the invention of Air Conditioning or the Elevator.  Most of these changes have also increased the complexity of the structure, and with any complex system, comes the increased probability of failure. Whistler

Take for example, this major high end hotel in Whistler. In the first two years, the owners of this property paid out over $100,000 in repairs because of problems with the mechanical system, that was not properly commissioned.  I was called to this site, to look at an issue with a make-up air unit ( MUA ) which was locking out on flame failure. On inspection, I noticed air blowing out of a sealed combustion chamber when the supply fan was on. This air pressure, was interfering with the burner ignition and causing the lock out. If the unit was 20 years old, this kind of issue can be expected, but this unit was only two years old. When I looked at the heat exchanger, the top part looked fairly new, while the bottom was a very dark colour. The duct work that was attached to this unit, looked normal and large enough to do the job.  However, how it had been connected, was a problem. The air flow over the heat exchanger was not even, it was creating a dead space over the bottom section of the heat exchanger. This difference, created thermal stress that warped the heat exchanger, just enough, to bend the tubes and open the seams. The manufacturer installation manual, did, provide proper instruction for the duct connection and, detailed the need for even air flow.  Although, due to how it was connected, it is highly unlikely the installer ever read the instruction. And so, I say thus, “When all else fails, read the instructions!”

 

Eng Air Make Up Air Unit
Eng Air Make Up Air Unit

The MUA, is used to pressurize the hallways and supply ventilation air to the building with outdoor air. Gas heating is used to warm the air in the winter and a chilled water coil is used for cooling the air in summer. A fairly common configuration for this type of building, but, there was also something unusual about how the chilled water was piped in. The Mechanical engineer, wanted to improve the efficiency, and use the cooling coil in the MUA, as an economizer, to cool the chilled water supply, when conditions allowed. This would reduce compressor operation and save energy. The design used a 3 way valve, to bypass the chiller barrel, and send the water to the MUA for cooling, instead of flowing to the chiller for mechanical cooling. When the economizer could not be unused, the compressor would cool the water and then flow to the MUA if the air required cooling. It would have worked too except for one little issue.

The mechanical drawing showed a 3 way valve, or at least that is what it tried to show. The symbol used for the valve on the drawing was a little unusual and was not very clear. The scale on the icon, may have been wrong when it printed and may have looked normal on a screen, but when printed, it did not come out right. There are a lot of little details in 2 dimensional mechanical drawings, and some can be confusing. I was told the plumber thought it was a thermometer and not a 3 way valve, so he  installed a tee instead, with a thermometer next to it. The construction plumber has no expertise in a Chilled water design, their skill is running piping. This little mistake, eventually resulted in a failed compressor, in the first 2 years, on a large chiller and, after the warranty and, long after the contractors hold backs were paid.

So why did two major pieces of equipment fail within two years?

Did someone forget to test the equipment? Did anyone inspect the workmanship? Who should pay for it? This is when the litigation phase of construction starts.

Had a Commissioning Authority been included on the design team, these problems would have been detected.