Central Heating not working as it should

[clarksonbc]

Please bear with me as I am after some advice.

Our central heating system is no longer working as it should.

Only some of the radiators are warming up to an acceptable level, some are 'lukewarm' while others are stone cold.

My initial thought was a faulty pump as I am pretty sure I used to hear an audible click and a rather noticable hum when the system operated - this does no longer seem to be happening. I am no expert though and any advice is welcome.

The radiators that warm up most do seem to be closest to the immersion heater, although strangely one of the kitchen radiators gets warm while the other, next to it, does not - but this could just be how they have been connected up? Also, if a faulty pump how come some of the radiators get warm? Also, the power switch on the pump when changed to a more powerful setting does gurgle with water as if it is pushing it through...We have no issues with hot water - that is always very warm.

We have been in the house since new (10 years).

I would welcome advice so that I can make an informed judgement on whoever I get in to fix the problem as I am not competent enough with plumbing to attempt any fix myself.

Many thanks in advance.

 

[alan333]

Also, the power switch on the pump when changed to a more powerful setting does gurgle with water as if it is pushing it through

There's a few things you can check. First... Do the "cold" radiators get hot anywhere, ie at the top/bottom? If only cold at the top try bleeding them. Do they get hot when running the pump at a higher setting? Do they get hot if you turn the "hot" radiators off? If you can force them to get hot then it points towards flow, either the pump not strong enough or some sludge in the system (especially common with 8mm microbore pipe). If you can't force them to get hot then it could be faulty valves not allowing flow. Ot could also still be sludge in the system severely blocking flow.

If you can force them to get hot then you can try "balancing" how much water gets to each radiator, using the lockshield valve at the (non TRV) valve on the bottom. Remove the plastic cap and turn the shaft - tightening the valve (clockwise) restricts the flow, so make sure the "cold" rads are fully open, and close off the hot rads a bit to force more flow to the cold ones.

We had similar with our (at the time) 12 years old 4 bed house. We reckon the pump struggles with the number of radiators, together with a bit of sludge build-up was the cause. We drained and flushed the system, added a cleaner, then ran it as per the cleaner instructions for a week or so, then drained and flushed again, this time adding an inhibitor. We also removed and flushed all the radiators with a garden hose but there wasn't any serious sediment in them, and we put on new TRV's as some of the rads weren't coming on/off properly. Doing all this has improved our "bad" ones about 60%.