Grant indoor boiler

Dtp1979

A customer rang me today saying her boiler would heat the rads and once up to temperature it seems the rads start to cool down but she says the boiler is still going but sounds like it not firing. Why isn't it going to lockout?

shane0007

Dtp1979 wrote: »

A customer rang me today saying her boiler would heat the rads and once up to temperature it seems the rads start to cool down but she says the boiler is still going but sounds like it not firing. Why isn't it going to lockout?

You really need to be in front of it to see what it is doing.

Dtp1979

shane0007 wrote: »

You really need to be in front of it to see what it is doing.

I know ye was just hoping it sounded familiar to somebody. I've never came across a burner where the fan ran continuously. I'm assuming dodgy photocell or control box

shane0007

If it's heating the rads, it's firing.
If it's running & running without firing & not going to lock out, it could be photocell, solenoid coil, control box or incorrect return voltage (50v +/-3) back from the motor.

jimf

Dtp1979 wrote: »

A customer rang me today saying her boiler would heat the rads and once up to temperature it seems the rads start to cool down but she says the boiler is still going but sounds like it not firing. Why isn't it going to lockout?

dtp you seem to get all the easy ones

jimf

shane0007 wrote: »

If it's heating the rads, it's firing.
If it's running & running without firing & not going to lock out, it could be photocell, solenoid coil, control box or incorrect return voltage (50v +/-3) back from the motor.

I wonder is it going through the first cycle ok from cold and then failing to ignite when hot

something not adding up here

DGOBS

Would do that on a faulty PE cell, or a solenoid as it heats up and goes open circuit (as per Shanes post above)

Dtp1979

jimf wrote: »

I wonder is it going through the first cycle ok from cold and then failing to ignite when hot

something not adding up here

Ye I know!! Lookin forward to going to it (sarcasm)

jimf

I would go with shane and dgobs suggestion first p cell is the usual culpit ive often seen them faulty and motor running constantly

but ive never seen 1 go faulty mid cycle without lockout

jimf

heres a chance for another question lads sorry dtp

what happens is the p cell seeing false light or what thus thinking burner is lgnited and goes no further with the start sequence

shane0007

jimf wrote: »

heres a chance for another question lads sorry dtp

what happens is the p cell seeing false light or what thus thinking burner is lgnited and goes no further with the start sequence

Photocell sees what it sees. The control box interprets the lux of the photocell as resistance. During it's 12 sec purge, if it sees light, the CB will go immediately to lock out as it only wants to see darkness.
If after the ignition period, it wants to see light, i.e. a flame but if the flame is too bright or too dim, the resistance will not be within the parameters the CB wants to see & will also go to lock out.

jimf

shane0007 wrote: »

Photocell sees what it sees. The control box interprets the lux of the photocell as resistance. During it's 12 sec purge, if it sees light, the CB will go immediately to lock out as it only wants to see darkness.
If after the ignition period, it wants to see light, i.e. a flame but if the flame is too bright or too dim, the resistance will not be within the parameters the CB wants to see & will also go to lock out.

so this would explain when you disconnect the faulty p cell from the cb it then ignites and goes to lock out

shane0007

jimf wrote: »

so this would explain when you disconnect the faulty p cell from the cb it then ignites and goes to lock out

Absolutely.
If you are getting a continuous running without firing, disconnect the photocell & if it goes to lock out, the photocell is 100% the issue. If it continues to run, next test the resistance of the solenoid coil, etc.

jimf

shane0007 wrote: »

Absolutely.
If you are getting a continuous running without firing, disconnect the photocell & if it goes to lock out, the photocell is 100% the issue. If it continues to run, next test the resistance of the solenoid coil, etc.

in 4 years ive never had a faulty coil on an rdb am I just lucky

plenty of gammy p cells with issues as discussed above

shane0007

jimf wrote: »

in 4 years ive never had a faulty coil on an rdb am I just lucky

plenty of gammy p cells with issues as discussed above

I've replaced a few but not on a regular basis, perhaps a couple per year.

agusta

My thinking would be if the photocell was faulty,ie, see light, which is giving back lower resistance than the parameter it should be to the control box.The burner will not go to lock out.It will run continuous.By disconnecting photocell from control box the control box only sees darkness[high resistance],so the burner will start and then go to lock out because it dosent see light on ignition.Is this not correct..

jimf

shane0007 wrote: »

I've replaced a few but not on a regular basis, perhaps a couple per year.

and you would be seeing a lot more burners than me so not a big consumable
part then

shane0007

agusta wrote: »

My thinking would be if the photocell was faulty,ie, see light, which is giving back lower resistance than the parameter it should be to the control box.The burner will not go to lock out.It will run continuous.By disconnecting photocell from control box the control box only sees darkness[high resistance],so the burner will start and then go to lock out because it dosent see light on ignition.Is this not correct..

Other way around. No light = no resistance. Light will increase the resistance.
If CB doesn't receive back a reading within its parameter, it doesn't know if there is a flame or not. So it takes no chance & runs fan continuously.

jimf

did you get to this yet dtp

Dtp1979

jimf wrote: »

did you get to this yet dtp

Funny u should ask Jim cause I'm just in from it. When I got there burner was goin flat out but not firing. Turned it off and on a few times and same. Changed photocell and away it went! Thanks again to all who helped

jimf

glad to hear that

thanks for letting us know the outcome

shane0007

Dtp1979 wrote: »

Funny u should ask Jim cause I'm just in from it. When I got there burner was goin flat out but not firing. Turned it off and on a few times and same. Changed photocell and away it went! Thanks again to all who helped

Just remember the simple test to do before changing. Just disconnect the photocell lead from the CB & if it goes to lock out, the photocell is the issue. Saves messing about with new one if another component is at fault.

Dtp1979

shane0007 wrote: »

Just remember the simple test to do before changing. Just disconnect the photocell lead from the CB & if it goes to lock out, the photocell is the issue. Saves messing about with new one if another component is at fault.

No lead on this photocell but I know what ya mean Shane!

shane0007

Dtp1979 wrote: »

No lead on this photocell but I know what ya mean Shane!

What burner was it?

Dtp1979

shane0007 wrote: »

What burner was it?

G3
And yes I'm well aware of the air issue too as I had to inform the customer today

esox28

What's the air issue if you don't mind me asking?

Great posts on pcell lads.

shane0007

Dtp1979 wrote: »

G3
And yes I'm well aware of the air issue too as I had to inform the customer today

G3, just remove the photocell & click back on the control box.

Dtp1979

esox28 wrote: »

What's the air issue if you don't mind me asking?

Great posts on pcell lads.

On the indoor boiler it's not a balanced flue that I have. So basically the burner is taking the air from whatever is inside the casing

shane0007

Dtp1979 wrote: »

On the indoor boiler it's not a balanced flue that I have. So basically the burner is taking the air from whatever is inside the casing

What model Grant is it?
Boiler casings are designed to take air for combustion from the room it's in as long as there is a suitably sized non-closable vent in the room, it should be fine.

Dtp1979

shane0007 wrote: »

What model Grant is it?
Boiler casings are designed to take air for combustion from the room it's in as long as there is a suitably sized non-closable vent in the room, it should be fine.

'Twas the grant multipass Shane

shane0007

Dtp1979 wrote: »

'Twas the grant multipass Shane

What is your concern with it? The indoor casings are vented to the room.

Dtp1979

shane0007 wrote: »

What is your concern with it? The indoor casings are vented to the room.

The only holes I saw Shane were the ones for the wires. Plus there isn't a vent in the room itself

shane0007

Dtp1979 wrote: »

The only holes I saw Shane were the ones for the wires. Plus there isn't a vent in the room itself

The casing are designed to be able to intake sufficient at inducing air for combustion under extreme conditions, i.e. burning gas oil at highest boiler output with full air intake open.

My only concern would be an open flue appliance with no room fixed vent. For adventitious air, you can disregard the first 5kw if the boiler is pre, I think 2006 or 2003. I usually disregard adventitious air due to future proofing of houses.