keston celsius 25 problem.

[spacethegas]

i'm gonna tell you a story.

i installed this boiler & converted the system to sealed 5 years or so ago for my auntie and have been tending to the little blighter regularly ever since. the latest problem to have arisen has been making me scratch my head a little today & i would be grateful for any helpful suggestions.

the fault described to me was that it wouldn't fire up for ch & i also gleaned that the hw was a little erratic too.

ive dropped around on a couple of occasions over the last week, flicked the heating on & boiler fired, rads warmed as i drank my tea. apparently i have magic fingers.

as usual as soon as i drive off problem returns.

had a bit more time to spend on it today. so fired it up & ch started. rads warmed though not completely. all trvs open & free, all lockshields fully open. today bypass fully closed, its a gate valve & i must get round to fitting a proper bypass.

the boiler had appeared to reach temperature & had shut down on time delay. when it attempted to relight, it sparked, it lit ,the bottom 2 or 3 modulation leds began to light up. on ignition the pressure gauge surged from 1 to 1.5 bar, then it went back into time delay. it would continue to repeat this. the pump continues to run. when it lights for this short period the flow & oddly the return by the boiler get very hot.

if i shut the user control off & then on a few times to bring it out of time delay to fire the boiler, the red led lockout will begin to flash once every 2 seconds & diagnostic led 1 comes on. this indicates flow overheat which is associated with a circulation problem.

ive tried it with the bypass fully open too, the same.

i've removed the pump head & cleaned out a tiny bit of muck in the impeller.

i'm thinking it may be the pump but the boiler determines how fast the pump runs, & it does run. also if the pump cannot maintain sufficient boiler water flow to disperse the heat generated the red pump led should flash, & it doesn't.

all suggestions gratefully accepted.

 

[spacethegas]

i have noticed that kestons generally get slagged off.

i'm surprised that i have had no response.

surely someone knows them better than me.

 

[Agile]

It seems to be a lack of flow through the boiler.

If I remember correctly this is a standard pump but they modulate the speed with a triac speed controller.

I suspect that the pump or more likely its control circuit is not working correctly.

IF you can determine that it is a standard pump then I would power it externally and see how the boiler responds.

Tony

 

[spacethegas]

the pump is a gru 1560 but with no speed settings & is specific to this boiler. it has the normal lne + 3 xtra wires.

 

[Agile]

In that case without a scope and details of the waveforms/voltages to expect then it will be very difficult to determine if the PCB or the pump is at fault.

Thats if it is indeed the pump at fault anyway. It could always be a blockage or possibly some other problem!

Being unwilling to spend on new parts unless I am completely confident what the problem really is then I would be fitting a standard pump head and powering it externally to see how the boiler responds.

If that cured the problem then I would leave a standard pump in use for some while before I attacked the next hurdle of finding out if its the pump or the PCB.

Tony

 

[spacethegas]

i was planning to do that. but even if the system effectively works under this test the problem still remains, pump, control pcb or even one or both flow & return thermisters.

im popping round shortly. i will let you know of any developments.

 

[spacethegas]

stuck a new 1560 head on attached to a 3 pin. it worked fine. but this does not really prove anything. i just watched the one attached to the boiler spinning away.

the problem only occurs when the system is hot.

what happens is when the boiler lights, the pump spins fairly slowly & then gradually picks up speed to match the demands of the system using the flow & return thermisters.

my feeling was that the gas valve was possibly at fault causing the boiler to shut down almost immediately sensing that it was up to temperature.

so i did what i should have done first (yes i know), i checked the inlet pressure only 17mb (minimum 18mb req). checked at meter, too low. new meter governor.

checked the burner pressure looking for -3.15mb, found -5.4. the gas valve is factory set & the mi say do not adjust. i figured its more than likely gonna need replacing anyway. the closest i could get it is -4.15mb.

new gv on order. fingers crossed.

 

[Agile]

I would not be surprised if all the special pump does is to bring out the three different windings which normally go to the speed switch.

Perhaps all it does is to switch the supply to each of the three windings thus giving a three step speed control?

You could test that theory by seeing if it provides power to just one of the three at a time.

I always teach my trainees to visually inspect the flue FIRST and test the on load working pressure SECOND !

Tony