Troubleshooting hydronic control problems

July 1, 2000
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When the first cold weather strikes, calls for service will heat up your business. We’ll review some common hydronic control problems and give troubleshooting tips for each.

In this business, there are at least three ways to solve each hydronic control problem. The idea is, of course, to choose the approach that’s right for the application at hand, for you, and for your business.

One general recommendation is to choose controls that are reliable and simple to use. Look for products that are backed up with toll-free manufacturer support and clear technical and consumer literature.

Consider, too, sharpening your skills by enrolling in a good training program. The best training will bring you up-to-date on trends in oil and hydronic controls, and give plenty of hands-on problem-solving practice with actual residential oil and hydronic heating equipment.

Let’s begin by looking at some general problems and solutions, then move on to room temperature and noise problems.

General problems

Valve end switch does not make connection — This could be caused by an insufficient supply of VA or voltage to the valve due to a faulty transformer or to an excessive drop in district line voltage supply. Change the faulty transformer, if that is the case.

  •  If too many valves are powered by the same transformer, add a transformer.

  •  If the overcurrent is causing an overheated end-switch blade or burnt-out contacts, ensure that the actual current draw is within the specification of the end switch.

  •  If the valve motor is burned out or worn out, replace it.

  •  If the actuator gear or motor gear is worn out, replace the actuator.

  •  If the valve is installed backwards with respect to flow direction, reinstall it correctly.

  •  If end switches are damaged by silicone from lubricating sprays, replace the actuator. Avoid using any lubricating sprays again.

    Premature valve failure — This frequently is due to rubber plug, O-ring, or plug shaft failures. The problem begins when oxygen invades the closed system and damages the guts of the valve. Hydronic valves that are sold for closed-loop hydronic heating system applications cannot handle an environment with oxygen.

    Watch for this problem especially in older solar heating applications. The solar panels and tubing used may not have an oxygen barrier; although watertight, they are oxygen permeable. The oxygen corrodes the inside of the valve.

    If you’re working with an open-air hydronic system or an oxygenated water application, look for valves designed for fresh water applications. (Honeywell’s VC valve is an example.)

    Premature valve motor failure — The lubricant inside the motor can dry out under a combination of over-voltage, over-temperature, and high duty-cycle conditions, causing the valve motor to fail prematurely.

    If the valve motor is constantly energized for more than a few hours per day, reduce the duty cycle of the valve. If the motor is energized for months during a system-off period, turn the valve off, too.

    Insufficient hot water (in combination heating-hot water systems) — Combo systems are designed to both heat the house and supply hot water for showers, baths, and other domestic use.

    If your customer complains of insufficient hot water, install a zoning panel with the domestic hot water priority feature. When there is demand for domestic hot water, the zoning panel turns off the home’s heating system and shunts all the energy into heating the water for the hot water tank.

    Room temperature: too hot, too cold

    Here are some tips for tackling room temperature control problems.

    Temperature swings in the spring and fall — Overheating in the spring and fall indicates an opportunity for outdoor temperature compensation, or OTC. Today’s OTC controls work by varying the hydronic loop supply temperature in proportion to the outdoor air temperature, and solve the problem of excess heating on mild weather days.

    Thermostat location — Is the thermostat located correctly? Make sure it’s mounted on an inside wall. A thermostat mounted on an outside wall is a formula for discomfort. In cool weather, for example, it will be overcooled by the wall, needlessly calling for heat and resulting in too much warmth.

    Thermostats should not be in the sun or where dead air will give a false reading. Here’s an exception: In separately zoned solariums or other sun spaces, the thermostat should be located in the sun.

    Thermostatic radiator valves (TRVs) — TRVs can be used to rezone a room or space without having to repipe. Most contractors tend to use a centrally mounted or room-mounted thermostat versus one mounted on the radiator. Keep TRVs in mind as a potential solution where you have one thermostat controlling a large area or number of rooms.

    Install TRVs to trim heat from overheated areas and get better balance without running room wires and installing extra thermostats.

    Zoning — A zoning (or zoned temperature control) system helps maximize comfort in any type of home. Zoning can help eliminate problem areas that are too hot or too cold by delivering heating when and where it is needed.

    Bedrooms, for example, may be kept at an energy-saving setting when vacant or used for sleeping, while the main living areas are kept warmer (or cooler) when they are in use.

    Zoning also can compensate for dynamic load changes (i.e., solar gain on the south and west sides of a home).

    Noise

    Use good plumbing practices to help eliminate noise problems and associated ills. Here, we’ll reinforce some fundamentals and give a few pointers to help quiet the system.

    Pumps and valves — With modern high-head pumps, noise can occur in larger installations with long pipe runs and multiple zones. Here are some ways to reduce noise:

    • Secure the long pipe runs properly.

    • If you have more than three zone valves supplied by one pump, add a bypass loop with a throttling valve or a differential pressure regulator. This allows the water to bypass when only one zone valve in the group is open.

    • Rezone using more than one pump.

      Water hammer — Water hammer noise can be a nuisance. Here are pointers to consider:

    • Make sure zone valves are installed correctly (not backwards).

    • Move the valve from the supply to the return side of the loop.

    • Slow down the closing speed of a motorized valve, or use a TRV.

    • If the differential pressure across valves is too high, make sure the pump is properly sized, or slow the pump speed while providing adequate flow.

    • A water hammer arrester installed next to the inlet of the valve is also effective in reducing water hammer noise.

    You can encounter condominiums or larger commercial buildings where the zone valves near the pumping station have to deal with the greatest system pressure. Look for valves designed specifically to handle these punishing circumstances (i.e., capability to handle high close-off pressure, as well as providing a “soft close-off”). The Honeywell VC valve is one example.

    Air in system — Make sure you’ve got proper air removal with an air separator in the common supply piping and with air vents on the boiler and radiators.

    Pumping away or pumping into the boiler? Pumping away is the best, but most important is that you locate the expansion tank near the intake side of the pump.

    It is preferred to have the expansion tank on the high-temperature supply side of the boiler. This arrangement increases the pressure in nearly all parts of the system when the circulator operates, and prevents problems with air in the system.

    Locate the air separator on the supply side too, because that’s where most of the air is generated. It comes out of the water at its highest temperature.

    Conclusion

    Most hydronic control problems, whether related to temperature, noise, or the catchall “general” category, can be solved in a number ways.

    When you’re familiar with the range of solutions, you can select the approach that’s best for the application and your business.

    To learn more about troubleshooting, take advantage of a good hydronic control training program that emphasizes hands-on learning.

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