Radiators randomly not heating up fully

bizguy

Hi,

I have a 10 year old semi-detached house, heated by a BAXI gas boiler, which is serviced every year. The central heating usually works fine but a good few times, randomly over the past year, the heating can be on for 6 hours and the radiators are only lukewarm.

Knowing nothing about the workings of the system, I normally do the following...either some (and give up) or as many as it takes to fix itself:

-Bleed rads...little or no air comes out
-I bleed the one shown as number 1 in the attached photo, little or no air comes out
-I turn off all rads except one downstairs, then turn them all back on in turn
-I turn number 3 in the photo to the fully up position, leave it maybe 30 minutes, then fully down for maybe 30 minutes and then bring it back to where it was
-I turn number 2 in the photo almost all the way to the left, wait maybe 15 minutes and turn it back to its original position of one turn short of fully to the right

In the photo, what looks to be water on the floor is a dry stain which was there when I bought the house and hasn't been added to.

Usually doing some or all of the above will sort the problem, there'd be a bit of banging in the pipes as if an air lock has been removed. The plumber I normally use just says "jaysus that could be a tough one to pin down".

For this reason, I'm on here hoping someone can offer some help.
Many thanks

Dtp1979

bizguy wrote: »

Hi,

I have a 10 year old semi-detached house, heated by a BAXI gas boiler, which is serviced every year. The central heating usually works fine but a good few times, randomly over the past year, the heating can be on for 6 hours and the radiators are only lukewarm.

Knowing nothing about the workings of the system, I normally do the following...either some (and give up) or as many as it takes to fix itself:

-Bleed rads...little or no air comes out
-I bleed the one shown as number 1 in the attached photo, little or no air comes out
-I turn off all rads except one downstairs, then turn them all back on in turn
-I turn number 3 in the photo to the fully up position, leave it maybe 30 minutes, then fully down for maybe 30 minutes and then bring it back to where it was
-I turn number 2 in the photo almost all the way to the left, wait maybe 15 minutes and turn it back to its original position of one turn short of fully to the right

In the photo, what looks to be water on the floor is a dry stain which was there when I bought the house and hasn't been added to.

Usually doing some or all of the above will sort the problem, there'd be a bit of banging in the pipes as if an air lock has been removed. The plumber I normally use just says "jaysus that could be a tough one to pin down".

For this reason, I'm on here hoping someone can offer some help.
Many thanks

Close valve no. 2 ( fully clockwise )and turn the heating on for an hour. Does the heat in the rads improve? When you bleed the rads is the water black or discoloured? When rads are heating, is the bottom of the rads cold or a lot cooler than the top?

bizguy

Dtp1979 wrote: »

Close valve no. 2 ( fully clockwise )and turn the heating on for an hour. Does the heat in the rads improve? When you bleed the rads is the water black or discoloured? When rads are heating, is the bottom of the rads cold or a lot cooler than the top?

Today was a day where no amount of trial and error could get the rads to their warmest. Water is clear when bled. There's no obvious difference between top and bottom of a rad. Turning valve 2 clockwise makes no difference to the heat. Boiler thermostat is exactly at the halfway mark, same as always.

Turning valve 2 anti-clockwise leads to a whole load of water rushing into the pipe, or maybe its rushing to fill the cylinder.

On the photo I attached, what position should number 3 be in to heat downstairs only? What might the red handle without a number do?

Thanks again

Dtp1979

bizguy wrote: »

Today was a day where no amount of trial and error could get the rads to their warmest. Water is clear when bled. There's no obvious difference between top and bottom of a rad. Turning valve 2 clockwise makes no difference to the heat. Boiler thermostat is exactly at the halfway mark, same as always.

Turning valve 2 anti-clockwise leads to a whole load of water rushing into the pipe, or maybe its rushing to fill the cylinder.

On the photo I attached, what position should number 3 be in to heat downstairs only? What might the red handle without a number do?

Thanks again

The valve 3 and similar valve beside it are to turn off upstairs and downstairs. Which one is which I'm not sure

bizguy

Dtp1979 wrote: »

The valve 3 and similar valve beside it are to turn off upstairs and downstairs. Which one is which I'm not sure

The far off one looks to be the downstairs, number 3 being upstairs. I turned up the thermostat a tiny bit and all the rads got very warm. Will try this over the next few days and see if this is the workaround

RJF

No 2 is the balancing valve for the hot water coil (DHW). This controls the rate of flow of water through the coil which transfers the heat to the hot water in the cylinder - separated systems. This needs to be set open to allow flow through it - how much will depend on the rest of your system. For now turn it closed (clockwise) and then open it 1 1/2 turns. The two red lever valves are the isolation valves for the two radiator circuits. When open (in line with pipe) they allow hot water to flow through relevant radiator circuit. If closed (perpendicular to pipe) there is no flow to the relevant rads. You can close them during the summer and use your boiler to heat only the domestic hot water (DHW). No 1 is a manual bleed valve to release air in the system, this one usually seen on a rad. I suggest replacing it with a automatic air vent - get a good one (10-12 euro) not the more popular rubbish ones (4-5 euro). Is your system an open or sealed system and is it fed from a header tank or a mains filling loop. You need to check the pressure in the system, there should be a gauge on your Baxi (what model is it?). If a sealed system the pressure vessel will need to be checked. Should be done during service but often is not. If your system is operating properly all the rads should heat quickly and evenly and you should not be able to keep your hand on them for more than a few seconds, both top or bottom.