Tips for fixing an unbalanced radiator heater

June 30, 2015

Hot water from your boiler is pumped to the radiators via a flow pipe; cooler water is fed back from the radiator to the boiler through a return pipe. Each radiator has two valves: a handwheel valve, or thermostatic radiator valve (TRV), allows you to control the flow of hot water into the radiator, while at the other end, a lockshield valve controls the flow of water out of the radiator.

Tips for fixing an unbalanced radiator heater

1. To adjust the radiator valves

  • Open the hand wheel valve fully by turning it counter clockwise, or if you have a TRV, turn it to its highest (warmest) setting.
  • Open the lock shield valve fully.
  • To do this, remove its protective cap and turn it counterclockwise with an adjustable wrench.

2. The thermostatic valve won’t turn

Thermostatic radiator valves (TRVs) are prone to sticking closed, so avoid turning them off completely (to zero) during regular use — set them to one or two to reduce the heat output.

  • If the valve sticks, remove its plastic head from the brass body by unscrewing the ridged ring or nut.
  • This will reveal a small pin that controls the valve. Normally, this can be pressed down against a spring and will spring back up when released. If the valve is stuck, try freeing it with a gentle tap from a hammer; don't pull the pin out as it can be hard to refit.

3. Balance the system

Do the radiators closest to your boiler get much hotter than those farthest away? If so, you need to balance the system to even out flow differences. This requires a little time but is not difficult and will make your house feel much more comfortable. Start with the heating system cold and switched off, and make sure you have bled all the radiators.

  1. Fully open the handwheels, or TRVs, on all the radiators.
  2. Turn on the heating system and make a note of which radiator starts to warm up first, which is the last to heat up, and the approximate order of those in between. Recruiting a few people to help with this task makes it a lot easier.
  3. Fully open the lockshield valve on the radiator that warms up last.
  4. Next, work on the radiator that warms up first. Fully close its lockshield valve, then open it up by just a quarter turn.
  5. Adjust the lockshield valves of the radiators in between proportionally — wider open for the cooler radiators.
  6. Open or close the lockshield valves of the radiators until they are all around the same temperature. It helps to use an inexpensive radiator thermometer to do this (you can buy one from your plumbing supply store), but you can get reasonable results by judging relative temperatures with your hand. Remember to take the temperature of each unit in the same place — at the top right of each radiator, for example. This adjustment is a process of trial and error, so be patient!
  7. When the temperatures of the radiators are as consistent as possible, adjust the TRVs to set the desired temperature in each room. Your system is now balanced.
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