Water not getting hot - boiler cycling

[SBDIY]

The 15mm isn't the issue, there are plenty around with 15mm circ's. They used to do it to balance the coil so it didn't take preference to the heating circuit. It's only 15kw boiler.

i have had a similar problem once before on a heating circuit. The radiators stopped almost overnight. I checked everything and in the end chucked some sentinel x800 jetflo in and within 2 hrs they were working again. Still never found out what caused it and the water was gin clear.

before doing this though, I would isolate a pump valve and carefully crack the nut in the picture with a bin bag underneath to catch the water, this will push water through the bottom of the coil and out the top just to check for blockage or air, the coil could be bend and rising up trapping air although unlikely. Make sure you open the pump valve again.

That's another good suggestion mate and I can do that quite easily, as a non professional, as long as the missus can hold a bin bag 😉.

I have had some X400 in the system a couple of weeks ago and by coincidence today bought some X800 to give it another go.

 

[SBDIY]

you shouldn't be messing about inside the boiler, you could make the problems worse.

Yes, fair enough. I wouldn't mess with a boiler but as an electrical engineer I'm confident to test a Thermistor but you're advice is good and I'll take it.

Also the other point that if it were a Thermistor fault it would happen with the CH also makes sense too.

Thanks.

 

[Nostrum]

I wouldn't trust my misses to hold a door open

 

[Dotty]

Good point - makes sense. I think I will check the two Thermistors though just to make sure they are both responding consistently to changes in temperature. Probably ok but at least eliminates them from the investigation before looking at things more difficult and time consuming.

And to do that you need to be a GSR.

Read the forum rules appertaining to gas appliances.

Thread closed.