Grant Vortex 15/21 non condensing - overheat stat?

[Bunker]

I went to this external Grant yesterday as it wasn't firing up. It wasn't locked out but controls seemed to be functioning - prog moved the control valve and got power to the boiler but no firing. The overheat stat nipple was extended as shown below and wouldnt reset (that is out isnt it?). The control panel of the boiler was slightly buzzing too which stopped when I pushed against the cabinet?! Anyhoo - I took the lid and control panel screws off and it suddenly started to fire up, seemingly all on its own. On arrival the boiler was completely cold, having been off for 24 hours so it wasn't the boiler stat settling and on arrival I threw the test switch but still didn't fire up.

Thing is, if the overheat stat is u/s - Id expect it not to run atall unless I bypassed it, I wouldn't expect the boiler to fire up with it stuck out.

Any ideas chaps?

Thanks.

 

[Roger Welton]

I'd probably put my money on the on/off switch had a few of them play up.

 

[Bunker]

Thanks for that Roger, does the oh stat look 'out' to you? it would go back in but not stay in.

 

[Roger Welton]

Nope, looks normal, when they trip there is more 'resistance' to them when you push them.

 

[kimbo]

I agree with roger

 

[kimbo]

A grant vortex 15/21 is a condensing boiler, it is basically a multipass with a secondary heat exchanger. It was called a vortex because of the turbulators in the secondary heat exchanger.

 

[Bunker]

Just had a call that's its gone out again. Thinking it through, I wonder if its the boiler stat going off but not auto re-setting....that sounds plausible eh? Ill get the meter on it.

 

[kimbo]

The boiler stats on these do not auto reset

 

[Bunker]

What makes the boiler run again after its gone out on the stat then?

 

[kimbo]

Presume we are talking about the overheating stat or have I missed something

 

[Bunker]

Probably a terminology thing, a 'boiler stat' to me is the adjustable one on the front panel, the 'over heat stat', to me, is the secondary 110 degree one (with manual reset button).

 

[Dotty]

Try control stat and limit stat.

Confusion endeth. Peace and harmony resume.....

 

[Bunker]

Try control stat and limit stat.

Confusion endeth. Peace and harmony resume.....

Bootiful, thanks chap.

 

[Balmoral]

did one 2weeks ago with similar fault ended up with new pcb seams to be a common fault if that helps

 

[Balmoral]

trying to upload pictures of an install done on rhino system 90 by polish plumbers will make ur hair stand on end no cold feed just a garden hose and gets a lot worse lol

 

[SJB6]

It is not uncommon for boiler stats or limit stats to malfunction.
If power has come from valve/valves indoors then check wiring and connections within the boiler control panel. Power should run through on/off switch, then limit stat an then the boiler stat so check the connections there, the test switch has a permanent life as you know but will then run through the stats before burner, the fact that it randomly fired when you took the control panel casing off could mean the incoming boiler live, neutral and earth was moved slightly and wasn't making a solid connection., also check the stat sensors are in the files on side of water jacket properly.
With regards to the stats themselves when they stop working or the limit stat trips power won't go to the burner or if they go out of temperature calibration the same will happen.
Another thing to consider, it has been very cold and wet recently and you did say the boiler casing was lose so it could be something like the contactors within the stats or switch frooze up preventing power to the boiler, its unlikely but it is worth spending 10 minutes thinking outside the box.

 

[SJB6]

It is not uncommon for boiler stats or limit stats to malfunction.
If power has come from valve/valves indoors then check wiring and connections within the boiler control panel. Power should run through on/off switch, then limit stat an then the boiler stat so check the connections there, the fact that it randomly fired when you took the control panel casing off could mean the incoming boiler live, neutral and earth was moved slightly and wasn't making a solid connection., also check the stat sensors are in the files on side of water jacket properly.
With regards to the stats themselves when they stop working or the limit stat trips power won't go to the burner or if they go out of temperature calibration the same will happen.
Another thing to consider, it has been very cold and wet recently and you did say the boiler casing was lose so it could be something like the contactors within the stats or switch frooze up preventing power to the boiler, its unlikely but it is worth spending 10 minutes thinking outside the box.
Also a loose neutral in the wiring centre would cause problems.