Oil burner lock-out

steve097

Bentone ST 108 Sterling 40 burner. Hit reset, motor runs for ten seconds and then burner ignites, all as usual, but it only burns for 5 seconds and locks out again.
I have cleaned the boiler, the photocell, the filter and replaced the jet. Oil bleed done.
Took out the cell when burn started and shone a bright light on it but still locked out.
Anyone got a diagnosis?

Outkast_IRE

maybe its the control box , have you opened it and checked for anysigns of corrosion ? I dont reccomend it unless your fairly handy at this sort of thing make sure power is off before .

steve097

Haven't done that yet. Hoping its a bad cell.

JamesM

Sounds like the photocell or control box. Try it one more time - hold the cell in your hand, darkened. The minute the burner ignites, shine the light on the cell, you may not be doing it quickly enough, if you have to take out the cell each time.
Make sure that the cell is covered before you press the reset button. If that works, then the light of the flame is not reaching the photocell - the cell might be turned away from the flame, or you have a bad flame - or dirt or fluff in the draught tube.

The different control boxes work slightly differently, but try this.
Try shining the light on the cell before you switch on the burner. Switch on the burner. If it does not try to fire until you cover the cell, then the cell is working and the fault is probably in the box. If the extra sound of the ignition spark comes on and off when you cover and uncover the cell, then the cell is working. Just something to try.
Jim.

Micky Dolenz

JamesM wrote: »

The different control boxes work slightly differently, but try this.
Try shining the light on the cell before you switch on the burner. Switch on the burner. If it does not try to fire until you cover the cell, then the cell is working and the fault is probably in the box. If the extra sound of the ignition spark comes on and off when you cover and uncover the cell, then the cell is working. Just something to try.
Jim.

Good advice Jim.

You 100% the burner is getting a good flow of oil?, line isn't kinked, fire valve failure, near empty tank, isolation valve at tank fully open, partically block line?

OP, spend the 20 quid and get a cell, replace it, this is most likely to be problem, unlikely to be control box in my opinion.

steve097

Took off the control box and saw that it was wet. A slight roof leak had dropped a little water on it. Hair dryer and away she went.
Another problem now. A lot of black smoke at start-up and an awful smell of kerosene. I think I just need to seal it better:).
Thanks for the suggestions lads.

JamesM

If you are getting black smoke every time on startup, there is a problem with the mix, oil pressure, air etc. Did you replace the nozzle with the exact same one ? No blockage in the boiler, flue ?
Jim.

steve097

Exact same nozzle. Cleared up the black smoke/smell by sealing burner to boiler but now the problem is back to square one, i.e. cutting out after 5 seconds burning exactly.:(
Used ohmeter on cell seems OK so now I am going to replace the control box as it did seem to have something to do with the original problem.
Landis-gyr LOA 21 173A27.
Seems there's a LOA 24 that replaced this model. Will that fit the existing base? Where can I buy these boxes in Mayo area. Dublin next choice.
Thanks in advance boys. This is turning into a marathon but I'll win in the end.:)

JamesM

You don't clear up black smoke by sealing the burner to the boiler. Was there smoke from the flue or vent outside ? If there is black smoke, it is likely that there is soot - have you opened the boiler, removed the baffles and cleaned the boiler.
The smoke may now have darkened the photocell.
Of course it could still be the control box :-)
Jim.

steve097

Yeah, cleaned out boiler fully, identical new nozzle, recleaned cell. Just have to try a new box now. It had worked perfectly without being touched for 5 years previously, not a sign of soot when I opened it.

Pete67

A new controller is 70 to 100 euro, a photocell 10-15. I would replace the photocell first. From the sympthoms you describe, it sounds like the burner is igniting, but the flame is not being detected. This could be either the controller or the photocell, but the photocell is a lot cheaper.

If you have a multimeter, you can check out the photocell, I don't have data for the Landis&Gyr models, but for Danfoss ones, the current through the photocell should be 2-4 micro amps when dark, and approx 60 micro amps when illuminated. This test is done in circuit.

I'll try and dig out the Landis & Gyr test data.

steve097

The cell appears to be working based on the ohmeter readings in light and dark so I think it has to be the controller.
The 5 second burn is now as clean as a whistle.

steve097

I put in a new control box but there is no spark. If I light it with a weed burner it is going fine(out of the boiler).
With the old box, there is a continuous spark during the purge, then it lights but goes out after 5 secs.
The cell is a bit rare and hard to source but I'll try that next.
Any ideas boys?

Micky Dolenz

It's the photocell, the control box is probably ok.


Photocells at under €15 is always worth a bet.

JamesM

steve097 wrote: »

I put in a new control box but there is no spark. If I light it with a weed burner it is going fine(out of the boiler).
With the old box, there is a continuous spark during the purge, then it lights but goes out after 5 secs.
The cell is a bit rare and hard to source but I'll try that next.
Any ideas boys?

If it continues to burn when you light it, the cell is probably working OK. You may have messed up the contacts in the base or the electrodes or ignition leads.
Jim.

steve097

Just put in a new cell and no change from above.
Going to check all connections and ignition circuit.
Electrodes must be ok as I can see them through the cell hole sparking like billy-o as soon as the button is pushed with the old box in place but not with the new one

I lit the burner last night with the new box fitted using the weeder and pushed it back into the boiler. It ran long enough to heat all the rads. I think the thermostat cut it out eventually.

JamesM

Very odd It could be the transformer contacts in the control box base - you said that it was wet at the beginning.
I would say that there was a problem in the old box, but now with the new box, everything is working, except that there is a problem with the ignition - are you sure that the spark is happening right out at the tips of the electrodes, not back in the body of the burner.
Jim.

steve097

I am just on my way out to have a good look at the electrodes since it finally dawned on me that the only thing really missing is the spark when the new box is in. The old box malfunctioning might have burned them to bits.

Great minds:D. Will this plan come together and will I love it? Tune in tomorrow for the next thrilling episode of "Steve and the Burner that wouldn't."

steve097

Electrodes are fine.
New box is missing pin nos.9 and 7 which is the live to the coil thingy. Only pin no.9 is missing on the old box which is why it still sparks with the old one.
Old box is Landis-Gyr LOA21.173A27
New one is Danfoss BHO72.10 057H6102
So I need to move the coil live to the correct no. pin for this box. Anyone know what it is?

EDIT. just found out from the Danfoss site that he gave me the wrong box. Correct replacement is BHO73.10 057H6104

Pete67

According to this, the live to the ignition transformer is pin 6.

But if you have to rewire the terminals, the Danfoss controller is not a direct replacement - were you told it was? According to the Danfoss Service manual the correct Danfoss replacement for the LOA21.173 is type BHO 64A which is for a two stage burner. BHO72.10 is for a single stage burner.

steve097

I have the model no off this site:
http://heating.danfoss.com/PCMPDF/DKBDPS000A802.pdf
on page 66. (another 6 and we're about right.:D) So I'll be ordering the replacement tomorrow.
I think if I changed from 7 to pin 6 it might work but I'll wait for the right box. I might do damage otherwise. Let ya'll know what happens.

Pete67

BHO73.10 is the replacement for BHO64A so either would be fine. I guess you were looking at a newer version of the Danfoss manual. Hope you get it sorted, bit nippy these days!

steve097

Guy said two wks for new box so I did the 6-7 switch and its working fine this evening.

JamesM

steve097 wrote: »

Guy said two wks for new box so I did the 6-7 switch and its working fine this evening.

I had assumed that you were supplied with the correct box - that's why it was so puzzling. The box you have seems to to be for an industrial burner (I'm not too well up on those). It has 2 solenoid coils - 4 and 5, therefore 2 nozzles. Also 2 ignition circuits - 6 and 7. So, using 6 would seem to be fine.
Glad you got it going.
Jim.