Service Frequency Advice
The frequency of scheduling service calls for a solar hot water system depends on multiple variables. Generally speaking, we recommend having a service call for a general check up of your system every two years. Depending on the system type and the observation capabilities of the system owner, four years and longer are feasible.
During a service call, the basic components which are checked are the antifreeze quality and solar loop pressure if applicable. The pump or multiple pumps operation. The system controller and the tank and roof sensor functions. The expansion tank and air relief valve are also frequent sources of failure which are checked. Additionally, it is quite common for water piping valves to be turned in the wrong direction or a critical valve is open or closed, which prevents the proper function of the system.
If you only go down to your cellar to check on your system when you run out of hot water then you should be on the two-year service interval. It is highly possible for your solar hot water system to fail and you can still have hot water at the tap from your back up system. For example, if you have electric back up for your hot water you may see a jump in your electric bill due to the solar component of your hot water system failing.
If you are somewhat technically minded and can do basic system evaluations on your own you can go up to 4 or 5 years between service calls. All you need to do is check your system pressure when applicable and make sure your system is turning on during a sunny day and shutting off at night. You also need to determine if the system is actually putting heat into your storage tank. Sometimes a valve can be turned the wrong way and even though everything is working fine you are not accessing you solar hot water.
Frequently we are called in to check a system soon after a plumber or boiler technician has visited. Often the other service person opens a valve which must be shut for the solar hot water to pre-heat the backup water tank. The solar tank needs to be in series with the back-up system for the pre-heat function to work properly.
It is innocent on their part but this happens all too often due to their lack of understanding of how a solar system interacts with the conventional hot water backup system. It is sad to encounter a situation where a solar system is producing plenty of hot water but the water is not directed through the system properly due to a simple valve being opened which should normally be closed.
Worth mentioning to you is the situation where it seems like the solar system is not producing hot enough water to the tap in spite of good solar conditions. In many cases it is the Tempering Valve or Mixing Valve, which has failed and is mixing too much cold water with the sufficiently hot solar water. Often we change just the replaceable element on the Mixing Valve and the problem is instantly cured.
A situation related to Mixing Valves is encountered where the cold water supply to the back-up hot water heater is the hot water output of the solar system. We sometimes encounter the incorrect configuration where the cold water input to the mixing valve is branching from the original cold water supply, which is now the hot water output from the solar hot water heater and feeds into the back-up water heater.
This means that the final output of hot water to the household cannot be correctly regulated because the cold water varies in temperature depending on solar conditions.
To correct this problem a separate dedicated supply of cold water to the Mixing Valve must be configured. Sometimes this mistake is overlooked during the original solar hot water system install and sometimes it occurs later during service to the back-up hot water system. It is often observed and should be checked to ensure the proper operation of the Mixing Valve
Another situation we encounter is when the lower limit temperature setting on the oil-fired boiler is set to about 140 degrees or even higher. The solar system may be putting out satisfactory 110 degree water but when it preheats through the tankless heater on the boiler the boiler increases the temperature to 140 degrees! This is a complete waste of oil and money especially during the summer months when the solar system can provide all of your hot water needs. The boiler should not be configured to “fight” against the solar system. I tell people to turn the lower setting back up for the winter months if their Boiler Technician determines it is needed for proper winter operation.
This same principle also applies to Electric and Natural Gas fired water heaters that have their temperature settings higher than 110 degrees. Frequently the proper energy efficient settings are modified by unknowledgeable service people who do not understand how a solar system should interface with a conventional hot water system.
In general, Reynolds systems need shorter service intervals due to two reasons. First, the weak link in the design is the rubber hoses on the roof connecting the solar panel to the aluminum pipes running to the heat exchanger. These hoses are usually old and can spring leaks causing gradual or sudden loss of pressure.
Secondly, Reynolds systems have external Crown Top heat exchangers and often one of the two pumps fails. The system sounds like it is running fine but one pump may have failed and the system is not transferring heat properly.
Most other types of systems have copper pipes and therefore use soldered connections between the solar collector and the supply and return pipes. These systems are less prone to leaks on the roof.
Pressurized solar hot water systems generally utilize non-toxic polypropylene glycol for the heat transfer fluid. Single wall heat exchangers such as the ones used in Vaughn Sepco solar tanks must use non-toxic antifreeze since if the heat exchanger leaked, non-toxic antifreeze would not poison your drinking water.
Reynolds pressurized systems utilize ethylene glycol which is the same as automotive antifreeze. This fluid is toxic but is allowed due to the Reynolds system having a double wall heat exchanger. The toxic antifreeze would have to leak past two walls of metal and the domestic water loop is under higher pressure than the solar loop so there is no way the toxic fluid could enter your drinking water.
Drain back systems are not pressurized and generally use plain or distilled water for the solar loop. The water drains out of the panels and into a drain back tank when the system shuts off. This prevents freezing of the pipes and there is generally no need to mix antifreeze with the water. Drain back systems generally have less maintenance than pressurized systems since the water does not deteriorate over time like the antifreeze solutions do. If your controller fails on a drain back system DO NOT put a timer on the system to keep it running during the day. On a cloudy freezing day the water can freeze the pipes on the roof and created a costly repair job. I encountered one of these situations just recently.
Antifreeze deteriorates over the years due to the heat it is subjected to as a heat transfer fluid. It can break down chemically very rapidly if there is a system failure and the fluid in the panels stagnates and “cooks” the fluid under high temperatures. When antifreeze breaks down it looses its freeze protection qualities. Also it becomes acidic. This acidity can slowly eat away at the aluminum or copper material of the collectors and connecting pipes. The life span of the solar collectors can be significantly diminished. Most collectors installed during the boom years of the 80’s are no longer available from their manufacturer. Used panels are available for some of the more common brands but some brands can be difficult to locate. It is therefore highly advisable to maintain heat transfer fluid quality to extend the life of your system. We should briefly mention the Bray oil which was used in Novan systems. We do not support Bray oil. We will replace it with non-toxic antifreeze if we service that brand of system.
One other related concern about degraded antifreeze is the way it can become sludge like and clog up the solar collector tubes. We have seen some systems where it comes out like molasses and we need to give your neglected system a thorough flushing.
In closing, your total cost of ownership and your final energy savings are determined by not only by fuel costs but my maintenance and repair costs. We do not want to see you spend money any sooner than you need to but we also want to make sure that your system is not neglected which can cost you more in the long run than if you had a regular service schedule.