Oil Boiler doesn't want to stay on.

jojoffion

We have a Grant Vortex Oil Boiler around 15 years old and it will fire up for around 30 seconds and then switch off.  Plenty of oil in the tank. Pressure is fine, know its getting a signal and recently serviced.  I have tried the overheat button and the reset button but this is hit and miss. Automatic valves changed recently after a similar problem and a few bits were changed in the boiler.

The engineer did say that oil boilers don't have all that much that can go wrong but it seems this Boiler does (has never really worked as it should)

Any suggestions on what else I can try before calling in an Engineer? Another expense we can't really afford!

Thanks 

Reed_Richards

When I had a similar symptom it turned out the pump had failed.  

Apodemus

At 30 seconds in, I wonder if there is a photocell that checks for ignition and if it doesn't find light, it swtiches off the fuel flow?  Photocells give out after a number of years and are cheap to replace, so I think I'd start with that (if the Vortex has such a thing!).

Is the flue clean?  If so, does the Vortex have a pressure switch that only allows firing if the air flow is clear?  I once had a faulty pressure switch, which prevented the burner operating - engineer never managed to track down the fault, but I replaced it "just in case" and it solved the problem.  You can get the same problem if the air tube to the burner-exhaust side of the pressure switch is blocked with soot, but this should have been picked up on Service.

EDIT:  If you manage to track down a Service Manual for the boiler, it might have a troubleshooting guide and also a description of the start-up process (with timings) that would indicate what is meant to be happening at that 30 second point in the process.

lohr500

As per Apodemus suggestions, but could also be something as simple as a blocked fuel filter.

Our boiler has two filters. One at the outlet of the tank and a second one close to the boiler.

Although it may have been serviced recently, I would ask the engineer if the filter/s were changed at the service and check them again for contamination. Sludge can form at the bottom of the oil tank and it is possible for some of this to get disturbed during a tank fill and subsequently get drawn into the filter/s. 

Apodemus

Yes, we are assuming that it was a full Service and perhaps that is not an assumption we should be making!

dunstonh

Having myself been the victim of someone doing a full service only to find out later that they hadn't, it is worth checking.   In my case, the filters and nozzles were not replaced (amongst other things).  Both of which could be potential causes of the problem here.

spannerzone

My 13 year old Grant Vortex combi 26 (outdoor boiler) has had several issues that cause cutting out central heating or hot water:

1/ Central heating / hot water intermittent (two seperate faults, same issue) - all lights ok on the panel but pump stops/starts - this was due to failing speed switch on the motor pump intself (a 3 way switch for low/med/high pump power) - tapping the switch itself made the pump start working so was easy to locate the issue.
2/ Main control panel PCB (circuit board) - went intermittent and caused hot water to be intermittent - The LED lights on control panel flashed all randomly and not as they should - I replaced the entire circuit board (i'm an engineer) cost about £100. (I had tried fault finding on the board but couldn't locate the issue)
3/ Temp sensor going intermittent

This boiler has been the worst investment ever, so unreliable, I've got through 4 expansion vessels, oil pump, main PCB, motors, sensors, inlet water sensor, mains switch (twice) and it's serviced yearly. I am certain many of the problems are due to it being an external boiler that is pretty much airtight - so all that heat cannot escape and cooks the components inside. I know for a fact ciruit boards don't like to be that hot, constantly.

This boiler also required an additional expansion vessel to be fitted - the standard one fitted may not cope as it's not that big. I complained to Grant about the constant failures I had early on and they sent out an engineer who fitted a second vessel which helped a lot.

My plumber suggested a Grant boiler as they were so reliable....well they used to be as they were so basic but combi boilers are far more complex hence more prone to failures.. I'm quite handy so attempt to fault find myself before getting the engineer out.

my DIY Not forum threads in case they help
https://www.diynot.com/diy/threads/grant-vortex-combi-26-random-demand-led.530665/#post-4465110
https://www.diynot.com/diy/threads/grant-oil-combi-pumps-intermittent.506397/

gm0

Tripping out on the ignition startup timer could be a burner sensor part where it doesn't see the stable flame correctly. 
Pump failure also stops it running but I don't know the symptoms

Here are some other common Grant Vortex faults from that era (we have a 2008 model)

The expansion vessel hose blocks with system crud as it is at a low point then w/o the vessel volume being available causes overpressure, PRV exit for that pressere. Lost water = too low pressure. Then poorly or not working and needing cold fill. Then repeats until expansion restored. Changing the expansion vessel without changing and checking the hose is not enough. 
Visible as overpressure when warming up and initial running then PRV discharge.  Then low pressure before next run.

The crap main electrical panel switch (likely underspecified for peak starting Amps) or insufficiently corrosion resistant - burns out becoming intermittent cutting power to the boiler as an odd function of time, scenario and temp - until it fails and the power is just off.  Lots of these were swapped. Believe Grant OEM part was changed for something better later on. 

The thermocouple for the oil fire valve and its placement at installation or putting back after service could also trip the boiler but this would be fairly obvious as the fire safety valve would be tripped outside (easy to check) and so there would be no oil flow.  The burner is then starved and can't start.  This can suddenly happen if the service engineer takes the boiler apart a bit and then refits the thermocouple wire casually where it receives too much heat too quickly

Kiran

Is the boiler firing up at all or failing in the startup sequence? If you have plenty of oil, checking the following, check for water in the oil tank, check the filters, check the fire check valve is open, check for an air lock at the burner and pull the photocell out, check its clean and try starting the boiler with it exposed to the light

Sun-Is-Fun

Similar thing happened to ours. Changed loads of parts on the burner but didn't work. The cure was to get a whole new burner unit, which was about £300 a couple of years ago.

in_my_bumble_opinion

90% of what can go wrong with an oil boiler is in the burner unit.

Yes, it's £300+ (unless you get a second-hand unit) but it's pretty much the silver bullet.