central heating pump update

[Stephen]

Hello,

A few weeks ago I posted about my CH problems. Sorry for the delay, I have been working away and only had the weekends to attempt repairs.

The replacement 1.6A fuses arrived but they kept blowing too.

I bought a replacement pump, this one:

and that seemed to fix the problem. I had CH but no HW.

The following weekend, the CH was working when I went to bed but I was woken up by noises that sounded like air bubbles. I thought perhaps the radiator needed bleeding. I found that the pressure gauge was showing 0. I'm not sure how this was lost; I haven't found a leak anywhere.

I repressuried (it's a combi boiler) but the CH never came back on. The boiler fires and then cuts out. I think the pump is not circulating and the overheat cut out gets activated.

This pump had three green leds to show pump speed and none of them are lit, which is why I think this pump has failed. Perhaps it is too new and advanced for such an old system?

I have now bought this one:

which I am hoping to fit and hoping it will solve the problem.

Regarding the HW, it is only liukewarm. This happened some years ago and I the diverter valve was not working and I had to replace the internal washer and spring. I'm not sure whether a gentle tap or disassembly/reassembly will cure it this time or whether I will have to buy a replacement again.

Seems these things do not like to be switched off when you go away!

[Fredxx]

It does seem the pump has failed. Have you checked power is getting to it? With either HW or CH demanded the system might require the diverter valve to be correct position for power to reach the pump.

Check you can move the valve manually. If necessary remove the motor body. If removed you can also check if the motor works and the corresponding microswitches.

[alan_m]

No, it has 6 operating modes 3 of which are the same as an old pump (3 off fixed speeds). No LEDs may/will just indicate no mains power getting to the pump. As previously mentioned supply some mains power from a separate source to see if the LEDS come on and the pump runs. If your pump is similar to my mine of the same make pressing the setting button multiple times cycles through all the motor speeds/modes with different number of LEDs illuminating as you select each one.

There should be nothing wrong with the pump you originally purchased.

[alan_m]

The LEDs will only be lit when there is a call for heated water and your boiler supplies (switched) mains power to pump. If there is no call for heat then the boiler switches off the mains power to the pump. No mains power to the pump and no LEDs. The boiler may/will also supply power for a pump overrun so that when the boiler heater matrix is still very hot water is still flowing thorough it.

[alan_m]

That should be 9 modes 3 of which are fixed speeds.

For fixed speeds keep pressing the setting button until one or more of the LEDs flash (assuming that there is a call for heat and the boiler has switched mains power to the pump) This means that its in one of the proportional differential pressure modes which can be determined from the number of LEDS flashing. Repeatedly press the setting button until out of the proportional setting sequence. The next Three settings will be the fixed speed modes with the 3 LEDS indication which speed.

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[Muddymike]

In the last system I installed the pump was powered from the three way valve. Central heating or hot water calls for heat, activates motorised valve accordingly, valve activates pump.

So I believe your fault is at the valve. Try replacing the motor.

Mike

[John]

What make of combi? Combi pumps are rarely off the shelf items.

[alan_m]

In what way? Performance or physical size?

[John]

What make?