Gas meter sizing
Just as it is important for the heater to be sized properly, it is also important the gas meter is sized appropriately for the heater. Assuming the pool heater is using natural gas, the meter must be sized—at minimum—to the capacity of the heater itself. In other words, if one is using a 400,000 Btu heater, the meter should be capable of providing 400,000 Btus. Always remember there may be other items pulling gas from the same meter so this must be calculated when making sure the gas meter is properly sized. Low gas pressure can cause damage to the internal components of a heater, causing build-up that leads to blockage of the heat exchanger.
Propane tank
If the pool heater is propane-fuelled, the tank must be large enough to supply the proper amount of gas to the heater. Improper gas pressures to the heater—while in operation—will cause less efficiencies in the heater and possibly a build-up of soot, which could cause damage to the burners, as well as the heat exchanger.
Gas line and venting
Once again, sizing is very important. The gas line to the heater, as well as the venting of the heater, need to be sized and vented properly.
When venting pool heaters, it is important to maintain proper clearances (152 mm [6 in.]) from combustible surfaces on the top and side of the unit. Check the heater manufacturer’s manual for recommended clearances.
When considering requirements with respect to how far a heater can be vented, or how far ductwork can run to pull intake air, each 90-degree elbow reduces the maximum horizontal polyvinyl chloride (PVC) air intake run by 3.6 m (12 ft). Each 45-degree elbow reduces the maximum run by 1.8 m (6 ft).
The minimum requirements for air supply specify the room in which a heater is installed to be equipped with two permanent air supply openings: one within 305-mm (12-in.) of the ceiling and the other within 305-mm (12-in.) of the floor for combustion air. This installation procedure is in accordance with the Canadian Standards Association (CSA) B149.1, Natural Gas and Propane Installation codes and the American National Standards Institute (ANSI) Z223.1, National Fuel Gas code, as applicable, and any local codes that may apply.
Air supply openings should directly, or through a duct, connect to outdoor air. In the past, venting and air intake ducts had to be in balance and be the same length; however, with newer heaters, they draw combustible air from outside the structure and flue gases are forced out.
The colour of the heater’s flame is a good indicator of whether or not the unit is receiving enough combustible air to function properly. A clear, blue flame indicates the unit is burning 100 per cent of the gas. If the flame is not getting enough air, it becomes orange and releases carbon that turns to soot and clogs heat exchangers.
One of the more common mistakes that occur when installing a new heater is upgrading the size of the unit without having a large enough gas supply. For example, if the pool previously had a gas line for a 200,000 Btu heater and the new unit is rated 400,000 Btus, the gas line also needs to be bigger to accommodate the increased output.
Troubleshooting heater problems
The symptoms associated with heater failure can generally be narrowed down to issues with a burner or with the heat exchanger. The following are a few troubleshooting tips to consider for common problems experienced with pool heaters.
Loud, high-pitched whine
This symptom is generally associated with a burner issue; specifically with the flame being too ‘rich.’ To remedy this, check the pressure tap between the gas valve in the blower inlet and verify the gas regulator setting is -0.5 cm (-0.2 in.) water column (wc). In some cases, it might be necessary to replace the gas orifice.
Flame is ‘fluttery’
Again, this is symptomatic with a burner issue and can be accompanied by an acrid smell from the exhaust. However, in this case, the cause is most likely the result of the flame being too ‘lean,’ and the burner may even fail to remain lit. As noted earlier, check the pressure tap between the gas valve in the blower inlet and verify the gas regulator setting is -0.5 cm (-0.2 in.) wc.
Flame does not stay lit
Sometimes the combustion on the heater appears to be normal, but the flame does not stay lit. The cause is most likely a result of the flame not being detected. To remedy this situation, check the igniter to see if it is wet or possibly damaged. This may require the igniter to be replaced.
Further, verify the burner flame holder is properly grounded. This might also require the ignition control module to be replaced. Finally, be sure to inspect the manifold pressure. In doing so, check the gas supply line pressure when the heater is operating.
Boiling and ‘bumping’ sounds
The heat exchanger within the heater can also be the cause of several problems. One of the most common issues is the boiling of water accompanied by ‘bumping’ sounds. This is commonly caused by low water flow to the heater. This problem can also be caused by a plugged heat exchanger or a bypass valve that is stuck open.
The best way to fix this problem is to ensure the pump and filter are working properly so the water flow is sufficient to the heater. If the heater is not getting good flow, first check to make sure the filter is clean (as it may need to be backwashed or the element may require cleaning). A dirty filter can reduce proper flow through the heater as well.
The heat exchanger could also be plugged because of improper water chemistry, resulting in scale formation. More often than not, this is because the water is out of chemical balance. If this is the case, the water should be tested to ensure the proper corrective measures are taken to get the water back in balance.
Reduced water flow
It is all about water flow. If it is too fast, it results in condensation. If it is too slow, the heater is not warming the water efficiently. In some cases, when a pump is not working properly it can contribute to heater inefficiencies due to irregular water flow. If this is the problem, it might be a good time to consider a variable-frequency drive (VFD) to ensure the water flow through the pool heater remains consistent.
