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Discuss Setting the oil control valve on an Aga in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

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I recently moved to a house with an oil fired Aga. After it sooted up, I adjusted the settings on the BM-30 type oil control valve but am struggling to get it settled again. The Aga is overheating even when the low fire is set at the lowest setting.

I couldn't find a clear set of instructions online so wrote my own in the hope it will help others. Grateful to anyone who can review my guide and let me know where I'm going wrong.

Any ideas anyone?

Attachment.jpg

Control
  • For both high fire (H) and low fire (L): turning anticlockwise increases the flow rate.
  • The screw is very sensitive and each adjustment should be only a quarter turn.
  • Wait up to 15m between each adjustment to allow flames to settle

High fire vs low fire
  • The high fire setting controls the flow rate when the temp is lower than the thermostat setting.
  • The low fire setting controls the flow rate when above thermostat setting (overheating).

Troubleshooting
  • If orange flame: turn high fire [anticlockwise] .
  • If overheating: check thermostat then turn low pass clockwise.
  • If underheating: check thermostat then turn high fire anticlockwise.

Principles
  • HF is the default operating mode.
  • LF is only activated when the Aga is overheating and is activated automatically by the thermostat triggering the lever to drop.
  • The HF should be set to achieve a steady blue flame with no sputter.
  • The LF can be set with minimal flame, so that the flow is just enough to keep the Aga alight.
  • As LF controls the flow only when overheating, LF should only be adjusted when the thermostat is on the lowest setting.
  • The centre pin reflects the height of the slit valve - the higher the pin, the more fuel flows
  • This is because the slit valve is sprung open (up) by default which is its highest flow rate setting
  • The HF represents how high the slit valve can go.
  • The LF represents how low the slit valve can go.
  • So max setting is high fire fully anticlockwise
  • This will produce an orange flame, so keep turning clockwise until a steady blue flame occurs
  • If the Aga overheats (according to the thermostat setting) the lever will drop, pushing the pin down to trigger LF and reduce the opening of the slit valve (the low fire setting determines how closed it goes)
  • The Aga is either at the low or the high fire rate, there is no in-between.
 
I found this guide very helpful for learning how to service the Aga

 
Why did you adjust the flow rates because the cooker sooted up? These archaic beasts regularly soot up and is why they should be serviced at least twice a year. You are correct about leaving the flame to settle after adjustment before adjusting again but have you even measured measured your flow rate on low and high fire? Should be around 4cc on low and 8cc on high. These will vary vary on each appliance though.
 
As SBJ060685 has said regular servicing required minimum of twice a year.
As has been said can soot up also shut down in high winds if they overheat.
I hate the dam things but my oil service engineer loves them! But he carries just about every spare you need including bases we send to be shot blasted.
Get yourself a engineer who understands them .
As you are a new owner get ready for the high running costs.
 
Wont touch them, far too much hassle. Might move into them when I retire and nothing better to do. That is if they haven't been Thundberg'd.
 
Thanks for comments.

The issue I have is that the Aga is overheating, even with the high and low fire flow adjustment screws turned fully clockwise. Thermometer is in the red and i don't know how to bring it down.

My local Aga engineer takes ages to respond and I feel this is something I should be able to fix myself.

I am getting to the conclusion I need to adjust the height of the oil control valve relative to the burner bowl, but nothing has changed so I can't see the logic in that.

I have turned the Aga off to see if I can capture some oil and measure the flow rate.
 
I really would wait for aga engineer
Far too many variables wicks - carbon build up on base - dirt /water in control valve - flue draft can make a lot of difference.
Get it badly wrong and it's happily going to fill your kitchen with fumes or worse.
 
It's possible the metering stem is not closing properly. The oil depth needs to be checked first though and flow rates measured. I really would turn this unit off until the problem is found and rectified. I've seen the hot plates glowing red because of a similar problem!!!!
 
Thanks SJB, I turned the Aga off and removed the oil outlet from the bottom of the oil valve so I could monitor the flow. Seems there was a problem with the metering stem (slit valve) as the oil was flowing at a fair rate even on the lowest setting. It may have been the o ring on the metering stem leaking, but I had a spare unit so swapped the metering stems and all is now working well and I have a happy wife again.
 
Thanks for comments.

The issue I have is that the Aga is overheating, even with the high and low fire flow adjustment screws turned fully clockwise. Thermometer is in the red and i don't know how to bring it down.

My local Aga engineer takes ages to respond and I feel this is something I should be able to fix myself.

I am getting to the conclusion I need to adjust the height of the oil control valve relative to the burner bowl, but nothing has changed so I can't see the logic in that.

I have turned the Aga off to see if I can capture some oil and measure the flow rate.
The quickest way is to buy into the service offered by AgaDIYservice. All the information, knowledge and help is available there. All very do-able and you don't need special tools etc.
 
I found this guide very helpful for learning how to service the Aga

 

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