Last updated on Oct 3, 2024

How do you troubleshoot and repair problems with the pump and the expansion vessel?

If you have a solar thermal system, you know how important it is to keep the pump and the expansion vessel working properly. These components are responsible for circulating the heat transfer fluid and maintaining the pressure in the system. However, sometimes they can malfunction or wear out, causing problems such as overheating, leaks, noise, or low performance. In this article, you will learn how to troubleshoot and repair some common issues with the pump and the expansion vessel, and when to call a professional.

1 Check the power supply

The first thing to do when you suspect a problem with the pump or the expansion vessel is to check the power supply. Make sure the system is switched on and the fuse is not blown. If the power supply is fine, you can use a multimeter to test the voltage and resistance of the pump and the controller. The pump should have a voltage of 230 V and a resistance of 50-100 ohms. If the readings are out of range, you may need to replace the pump or the controller.

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Paul Hind

Operations Director at Secon Renewables, Independent specialist supplier to the renewables industry.
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You can’t use the resistance method of testing modern pumps…they’re all electronically controlled. Resol can supply a PWM tester.

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Ken Mwangi, GEng, MSc

Mechanical Engineer |Technical Sales Engineer | Researcher | Tooling Engineer | Renewable Energy Consultant | Solar Engineer |
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To troubleshoot and repair problems with the pump in a solar thermal system, first check the power supply for any issues such as tripped breakers or blown fuses. Inspect electrical connections for security and corrosion. Listen for abnormal noises or vibrations indicating mechanical issues and ensure there is adequate flow through the system by clearing filters or addressing airlocks. For the expansion vessel, begin by checking the pressure using a gauge to compare with recommended operating levels. Inspect for leaks around the vessel and connections. Verify and adjust the air charge if necessary using a tire pressure gauge.

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Ayush bajpai

Senior Consultant ESG/Sustainability/Carbon Accounting/GHG /15K+ Followers/Content Writer Master of Business Administration - MBA Energy Management from School of Energy and Environmental studies DAVV, Indore
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To troubleshoot pump issues, start by checking for power supply and ensuring the pump is receiving adequate voltage. Listen for unusual noises indicating wear or blockage. Inspect for leaks or air locks in the system, and verify that the pump is properly primed. For expansion vessel problems, check the pre-charge pressure using a gauge; it should be within the manufacturer’s specifications. Look for signs of waterlogging or corrosion. If necessary, replace the vessel or recharge it. Regularly maintain both components to prevent future issues, ensuring all connections are secure and the system is free of debris.

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2 Inspect the pipes and connections

The next step is to inspect the pipes and connections for any signs of damage, corrosion, or leakage. Look for cracks, bends, or loose fittings that could affect the flow of the heat transfer fluid. Also, check the insulation of the pipes and make sure it is intact and not wet. If you find any problems, you should repair or replace the affected parts as soon as possible to prevent further damage or heat loss.

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3 Test the pressure and temperature

Another important step is to test the pressure and temperature of the system. You can use a pressure gauge and a thermometer to measure these parameters at different points of the system, such as the expansion vessel, the pump, the collector, and the storage tank. The pressure should be within the range specified by the manufacturer, usually between 1.5 and 3 bar. The temperature should be consistent and not exceed 100°C. If the pressure is too high or too low, you may need to adjust the pressure relief valve or the expansion vessel. If the temperature is too high or too low, you may need to check the thermostat, the collector, or the heat exchanger.

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4 Clean and flush the system

Sometimes, the pump and the expansion vessel can get clogged or contaminated by dirt, debris, or scale that build up in the system over time. This can reduce the efficiency and performance of the system and cause problems such as noise, vibration, or overheating. To prevent this, you should clean and flush the system regularly, at least once a year. You can use a special cleaning solution and a pump to circulate it through the system and remove any impurities. Then, you should rinse the system with clean water and refill it with fresh heat transfer fluid.

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Paul Hind

Operations Director at Secon Renewables, Independent specialist supplier to the renewables industry.
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You only need to replace the fluid if it needs replacing…once a year is too often, a well designed system will look after the fluid, my system is 15 years old and has never had the fluid changed. Ph tested yearly and is a clear as the day it went in.

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5 Replace the pump or the expansion vessel

If none of the above steps solve the problem, you may need to replace the pump or the expansion vessel. This is a more complex and costly procedure that requires professional skills and tools. You should not attempt to do this yourself unless you are qualified and experienced. You should also consult the manufacturer's instructions and warranty before replacing any parts. To replace the pump or the expansion vessel, you will need to drain the system, disconnect the power supply, remove the old part, install the new part, reconnect the power supply, and refill the system.

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Paul Hind

Operations Director at Secon Renewables, Independent specialist supplier to the renewables industry.
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You will not need to drain the system to replace a pump or expansion vessel. Pumps are easily isolated above and below. Our expansion vessels are always fit with a quick release couple for easy changing.

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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How do you troubleshoot and repair problems with the pump and the expansion vessel?

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1 Check the power supply

2 Inspect the pipes and connections

3 Test the pressure and temperature

4 Clean and flush the system

5 Replace the pump or the expansion vessel

6 Here’s what else to consider

Solar Thermal

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