Worcester Danesmoor - lots of DHW but trouble with CH

[evensparrows]

Hi, I've looked through the forum and I'm sure that this question must have been answered somewhere, the problem is with about 100,000 posts its a bit of a challenge finding the right one so sorry in advance.

I have a 3½ year old Worcester Danesmoor oil fired boiler and a megaflow tank. A few months ago (maybe as much as a year) we started to notice problems with the DHW getting very hot and the CH running when the programmer for CH was off. The plumber/engineer who installed the system (who is much too busy to look at a little job like this) said that it was the danfoss HPA2 motorized valve sticking and I should replace it! (I'm not a plumber!!)

Things seemed to settle down a bit without doing anything at all until recently. Now the CH refuses to kick in unless the DHW is running and often the radiators do not get hot even with the DHW and CH "on" on the programmer. The boiler fires up to heat the DHW but will not fire up on CH alone.

Is it likely the danfoss two way valve? Looked at closely the top of the plastic housing is a little discoloured (slightly brown probably due to some component overheating / burning out).

Is there another obvious cause that I'm missing?

 

[oilman]

It's the actuator which needs changing. Relatively easy if you can deal with connecting 4 wires. It is easier to buy a 5 way connector marketed by Regin to make an inline connection. Turn off the system power before you cut through the cable.

 

[evensparrows]

That sounds more like it, I can manage wires. I assume I can buy a suitable actuator easily enough?

 

[oilman]

Try google.

 

[evensparrows]

Thanks, got the part just need the time to do the job.

 

[evensparrows]

OK So I replaced the Actuator on the DHW valve and this made no difference to the way the system was missoperating (is that a word?)

FYI when I replaced the actuator on the DHW valve I shut everything down. Fired up the boiler with neither the DHW or CH programmed to be on the burner and pump remained stubbornly off.

I switched the CH to on and nothing happened at all (turned the room thermostat up to 30deg just to be sure and the temp dial on the boiler up to max), I ran off loads of hot water and still the system would not kick in. I switched the programmer to put the DWH on and both the DWH and CH started to run.

I then put the actuator that I had removed from the DHW valve on the CH valve just to see if that made any difference........

I now seem to be in a position where the DHW runs continually as well as the CH but still the CH will not kick in without the DHW being on.

Have I jut moved a bad actuator round and shifted the problem or is it likely to be a fault in the programmer.


Oh for a few twigs and a flint and steel.

 

[gasandoilman]

I would send the bill for the actuator to oilman for telling you to replace it
Why not call an engineer out as its easier to make a fault diagnostic while on site

 

[oilman]

If the central heating was running when it was selected off, then it's the CH actuator that needs replacing. If you have a problem with the Megaflo, then you need someone G3 certified to work on it, otherwise it's illegal.