Boiler cycling and radiator balancing

[Johnbobo]

Hi all,
I have a couple of questions about boiler cycling and radiator balancing.

What I'm doing:
I'm balancing my radiators using two multimeters with thermal probes. I have one heat probe taped to the the pipe just below the lockshield and the other just below the wheelhead.

My setup:
The four upstairs radiators have TRVs fitted but for the sake of balancing I've removed the TRV heads. The boiler is an Ideal Classic RS 260 (non-condensing).

What's happening:
The boiler is firing for 3 minutes then resting for three minutes.As the boiler fires up then I've noticed that the temperature of water entering the radiator rises to about 62 degrees celcius then drops down to about 47 before going back up again. The emperature is constantly either rising or falling, even after the heating has been running for about 4 hours.

My two questions are:
Is this continual rise and fall in the temperature of the water entering the radiator normal? Or should the boiler be firing up for longer? -the central heating thermostat isn't satisfied at any point durnig this process.

and assuming it is normal operation:
Should I be trying to balance the radiators at the upper end of the temperature range inflow? Obviously the water leaving the radiator drops in temperature too but there is a short while when the in flow is at it's lowest that it is a degree cooler than the out flow.

 

[ianniann]

You won't fix this by balancing. The boiler is either too powerful for the output of radiators or it has a fault such as partially blocked pipes or the pump not working hard enough. Has it always done this?

I believe the lowest output of the boiler is 15kW. You could work out approximately the output of your radiators and if it is about half that then you've found your problem. The problem can be reduced by turning up the flow temperature so your radiators are hotter and put out more heat.

You haven't said what temperature drop you get across your radiators when the boiler is firing? Can you also read the actual flow and return temperatures at the boiler, again while it is firing? That will give some clues wether you are getting a decent flow rate through your system or whether the heat is just backing up at the boiler.