Knowing your central heating system can make the difference between fixing issues independently or calling a professional. Simple tasks like bleeding radiators and replacing them can be done on your own, while more complex ones like power flushing require a professional’s help. One question that may arise is the significance of the flow and return of water in your radiators and whether the TRV (Thermostatic Radiator Valve) position affects it.
Check out our guide below to understand how flow and return affects your radiators.
RADIATOR FLOW AND RETURN – WHAT DOES THIS MEAN?
Radiator flow and return pertains to the operation of a wet central heating system. This is the typical heating system found in most households across the country, wherein a boiler supplies heated water to the radiators. Whether you have designer radiators, vertical radiators, or the classic design of column radiators in your home, they all rely on the flow and return of water to work.
A heating system with a hot water cylinder uses a timer, cylinder thermostat, and motorised valve to circulate water from the boiler to the cylinder and back. Combi boiler systems don’t have a cylinder and heat water on demand. If a tap is turned on while using hot water, the flow to the radiators may be disrupted, leading to cold water in the shower.
SHOULD BOTH PIPES ON A RADIATOR BE HOT?
Ideally, both pipes on a radiator should be hot when your central heating system is turned on. Hot water flows through the flow pipe, enters the radiator, and releases heat into the room. The water then returns to the boiler through the return pipe to be reheated.
If the return pipe is cold or lukewarm, there may be an issue such as trapped air or a blockage preventing proper circulation. This can cause the radiator to be inefficient and lead to uneven heating. Bleeding the radiator or seeking professional help to diagnose and fix the problem is recommended.
DOES FLOW AND RETURN MATTER ON A RADIATOR?
Flow and return does matter on a radiator. The direction of flow and return pipes in a heating system is crucial for a radiator’s proper functioning. Incorrect connections can cause inadequate heating, increased energy bills, and reduced efficiency. It can also lead to air trapping in the radiator, which may cause corrosion and damage over time. As such, it is important to ensure that the flow and return pipes are connected correctly for a radiator’s optimal performance and lifespan.
HOW TO TELL WHICH IS FLOW AND RETURN ON A RADIATOR
It’s quite simple to work out which side is flow and which is return, and you’ll be able to tell when you turn your central heating system on. Both pipes should be cold if the heating has been off for a while, so when you turn it back on, one side will get hotter much quicker than the other.
- The flow pipe is the one that gets hottest first, as the water is coming from the boiler
- The other colder pipe side is the return pipe.
Depending on the size of the radiator, it should be easy to tell which is flow and return on a radiator by touching both pipes, for example, on large radiators, as it will take time for the hot water to go through. Smaller radiators may do so much quicker, so you may need to hold both sides to be able to tell in this way.
RADIATOR FLOW AND RETURN SIDES – DOES IT MAKE A DIFFERENCE?
Most central heating systems have two pipes: one that carries water to the radiator and the other that returns it to the boiler. The flow and return sides of a radiator can be determined easily when turning on the heating from cold. Typically, TRVs are placed on the flow side, where water enters the radiator, but they can be installed on either side.
Some TRVs are unidirectional, while others are bi-directional. It’s generally recommended to place the TRV on the flow side to avoid any issues, such as loud and vibrating noise from the return side. Check the type of TRV before purchasing and fitting to ensure it’s bi-directional.
WHICH SIDE OF A RADIATOR DOES THE THERMOSTAT GO?
When it comes to fitting a thermostat to a radiator, it’s usually recommended to place it on the flow side of the radiator. This is because the flow side is where the hot water enters the radiator, and the thermostat can better regulate the temperature of the radiator from this position.
However, it’s worth noting that modern thermostats can be bi-directional, which means they can be fitted to either side of the radiator. If you’re unsure which side to fit your thermostat to, refer to the manufacturer’s instructions or consult with a professional.
DO THERMOSTATIC RADIATOR VALVES GO ON FLOW OR RETURN?
Thermostatic Radiator Valves (TRVs) can be fitted on either the flow or the return side of the radiator. However, it’s generally recommended to fit them on the flow side, as this is where the hot water enters the radiator, and the TRV can better regulate the temperature of the radiator from this position.
If a TRV is fitted on the return side, it may cause a vibrating noise when the water flows through. In addition, some older TRVs may only work effectively when fitted on the flow side. If you’re replacing a TRV or installing a new one, check the manufacturer’s instructions to see if it can be fitted to either side or only the flow side. As always, if you’re unsure, it’s best to seek professional advice.
WHAT IF THE RADIATOR FLOW AND RETURN SIDES ARE FITTED WRONG?
If you suspect that the flow and return sides are fitted incorrectly, or if you notice that the TRV is making noise when fitted to the return side, it’s best to call a heating engineer for investigation. If you have bi-directional TRVs, then it won’t matter if it’s installed on the flow or return side.
Reversing the flow and return pipes could cause inefficiency in the heating system, resulting in cooler water and a potential increase in the heat output of a combi boiler. The installation pipes may have red and blue tapes to indicate the flow and return sides to avoid confusion. It’s helpful to understand your heating system’s setup in case of any issues, but it’s recommended to consult a professional if anything unusual occurs.
For more information about installing radiators, or if you have any queries, please contact us.
