Central heating not working pump runs

[starfish_001]

I have a potterton MF installed in 2004 it stopped working last Saturday and then started working after I looked at the pump (probably after around 5 hours). not sure that was the problem now?

I got it checked and service on Monday by the heating guy - given the all clear, probably the pump? not so sure know


But now I have the same problem again... heating starts but only one rad gets hot and then it turns off. I have checked the over the boiler electrics seem okay. checked the pump shaft turns under power from the boiler.

Looking at the cold water tanks, I have some white scale indicating excess hot water? checked tank stat it was set to 72 degree seems a bit hot to me?.

so looks like the core temperature control is stopping the boiler? not really sure what to do next

i have turned the boiler down

• room stat up
• tank stat left at 70 seems too high-- turning it up allow ch to start
• seem to have hot water but no central heating

I am wondering if the issue is

• tank stat is causing issue? the HW water seems to be around 50 rather than 70
• The boiler thermistor
• boiler PCB
• some sort of obstruction
• the pump shaft is spinning so think it pumps

 

[75pete]

You say that if you increase the water ( cylinder ) stat to a higher set point, the boiler and the heating comes on.
If this is the case, I would check the mid position (3port) valve.
Have a look at FAQs boiler and central heating Question 10.

 

[starfish_001]

tested mid valve but not 100% sure

tank stat is controlling boiler, room stat does not seem to. With heating and CH on the value goes to mid position which should be correct. A,B and AB all get hot an then it cut off after around five minutes

in manual position it is HW and CH so will try that

 

[starfish_001]

oh I'm think the tank stat is probably faulty? if it is set at 70 then I'd expect the water to be around that but colder. My HW seems to be around 50 something is not right?

 

[starfish_001]

looking at the mid valve wiring the heat call (white) has no voltage indicating a room stat problem

 

[75pete]

Have you also checked out FQAs 17 This gives an overview of this valve and how to check it.

 

[starfish_001]

thanks .....REALLY GOOD FAQs - I have it working now seems to be room stat

I also found this helpful

http://www.diydoctor.org.uk/projects/chfaults.htm

 

[Agile]

Don't know why the FAQ here were not totally sufficient.

What did you think was missing from here?

Tony

 

[45yearsagasman]

Nothing like a second opinion

 

[starfish_001]

When you are unsure about something it pays to looks at multiple references .... the FAQ are very complete