AGA thermostat

Matrixx

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I have an oil AGA with manual oil control, just wondering if i added a auto controller & thermostat would it reduce the oil consumption?
And how difficult would it be to retrofit the thermostat?
 

johnser

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Modern pressure jet burner? Or old float and vaporising burner.

If the latter, don't think I've ever seen a temperature controlled one. Be interesting if you were going to make something. But I don't think there would be a lot to gain as a lot of the inefficiencies are kind of baked into the burning process.
 

Matrixx

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Its the float type, all the ones you see on the net have the oil control box on top, mine you just set up , and away it goes maintaining a steady temp. Its a 2 oven type, the running oil consumption is supposed to be 40L a week, but i think its using more like 50+.
 

Matrixx

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423289BE-1B81-4D61-A4F0-CEC38F3B6E85.jpeg
3A4E56E4-06C7-4003-B5FF-702406B826C3.jpeg
 

Matrixx

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The space to the right is where the stat control would go , but the end of the stat is fitted in the top oven I think.
 

julianf

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When cars etc become more efficient, it's about either converting more of the fuel to energy, or more of the energy to the right type of energy.

As the universe spirals toward maximum entropy, heat is the where its all ending up...

So to increase the efficiency of your aga, you either need to convert more of the fuel to energy (ie less carbon products up the stack) or retain more heat (less heat up the stack).

That's the bottom line. If you think a change is going to alter that, maybe, but I suspect not.

People convert to pressure jets for controllability. So that's a third option really. Less heat (when you don't need it)
 

hotponyshoes

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Like julianf says,
Unless you increase efficiency somehow (add some fins/fan to the outlet flue?) Heat out = oil in at a fixed ratio.

I would think adding a thermostat is just going to give you a ramping cycle of heat up/cool down/heat up again/etc. Overall oil consumption will be the same.

I think the idea with an aga is the heat coming out of it is equivalent to what the house loses. I suppose a thermostat could reduce oil consumption on warmer days though?

Even 40l a week is a lot. How often do you use the oven and hot plates? Would it be worth thinking about fitting electric elements into the oven chambers and induction elements to the hot plates and having the oil on minimum just for the aga glow?
 

Matrixx

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It is efficient, nearly 400deg c on the plates, 230 in the top oven , and only 50 deg c up the flue.
When its on we use it for everything , boil the kettle. Frying and , slow cooking, etc. And it keeps the kitchen warm. Its not on yet. Its normally 55p/ L the last lot I got for 17p/L.

just referbing it at the moment. It seems the manual oil fill is quite rare, so I assumed the auto fill must be a better option.
 

julianf

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400c on the plates seems hot. I would expect more like 330c.

Obviously that's pretty much just user preference but lowering the heat just a bit will probably make a disproportionate difference to fuel consumption.
 

johnser

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If I recall, AGAs were set up to run at full temperature 24/7.

But those oil control boxes do offer a degree of controllability so, you could try altering the knob to have it idle. Overnight, say. If you find "minimum" is still too hot, you can raise the burner a bit or lower the control box, to lower the oil level. Therell be a minimum you can get away with though, the burner needs to be hot enough to properly vaporise.

Best hope no one has mucked about with the little control alteration screws on that oil control box though. Resetting them either involves careful measurement (assuming you can find the setup spec) or very time consuming iterations.

That stuff all looks nearly brand new!
 

julianf

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That stuff all looks nearly brand new!

They draw the air for combustion across that section where the viewing window is. So all the dust collects around there.

What I mean is, someone has cleaned the one in the photo recently! : )

(Or lives in an entirely dust free modern house... But you don't normally get agas in them!)
 

waddycall

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If I recall, AGAs were set up to run at full temperature 24/7.

But those oil control boxes do offer a degree of controllability so, you could try altering the knob to have it idle. Overnight, say. If you find "minimum" is still too hot, you can raise the burner a bit or lower the control box, to lower the oil level. Therell be a minimum you can get away with though, the burner needs to be hot enough to properly vaporise.

Best hope no one has mucked about with the little control alteration screws on that oil control box though. Resetting them either involves careful measurement (assuming you can find the setup spec) or very time consuming iterations.

That stuff all looks nearly brand new!
Don’t adjust the height of the burner or valve! That’s not how the flow rates are adjusted. The cold oil depth is only needed to get the burner lit. The maximum cold oil depth is set to ensure that if the oil level reaches the safety trip level in the control valve that the oil won’t flood over the top of the burner.
The agas usually have an oven thermostat connected to a flexitemp actuator which sits on top of the control valve and switches the flow rate from minimum to the valve setting (usually maximum) by pressing or releasing the pin poking up through the valve. If you talk to an aga spares place they can probably supply one.
https://www.agafixspares.com/store/index.php?main_page=product_info&cPath=215_11&products_id=1011

The temperature of agas is usually fairly constant/stable compared to most appliances. As suggested you could try turning the control knob down a bit from wherever you keep it (I’m guessing you’ve probably done that already).
If you keep it on minimum but it’s using too much oil then the flow rates need adjusting. It’s easy to do on the BM valve. The minimum flow rate for agas is either 3.5 or 4cc per minute depending on age. I usually set them to 4 as 3.5 is pushing it a bit low.

Flow rates are checked by disconnecting the burner, taking the bundy tube of the base of the burner and reconnecting it to the elbow inside the door but with the bundy tube sticking out into the room. Put a tray underneath and turn the oil on. A steady drip will establish and it’s checked with a measuring cylinder and timed for a minute. You don’t need a measuring cylinder though, any accurate volume measure will do even a measuring jug if you’ve got the patience to test it for enough minutes to get an accurate result.

The flow rate is adjusted using the two screws in the white plastic slider that moves backwards and forwards as you turn the control knob (top plate removed). When the knob is set to minimum the low flow rate screw is at 3 o’clock relative to the knob.

Maximum rate is usually 8cc per minute. When the control knob is set to max the high rate adjusting screw is at 3 o’clock relative to the control knob.

I wouldn’t recommend adjusting the flow rates or tinkering with it at all unless you’re used to doing your own servicing.

If the flow rates are correct fitting a stat and flexitemp would be the best option. It won’t make the aga more efficient but will reduce your oil consumption!
 

Matrixx

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I set the temp by the thermometer on the AGA, to keep the mercury on the black line. I had to set up the heights of the vaporiser and the BM float valve, and I do all my own servicing. a new valve, controller and thermostat would be well over £350, I could by second hand, just not sure where the stat lives.
 

waddycall

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I set the temp by the thermometer on the AGA, to keep the mercury on the black line. I had to set up the heights of the vaporiser and the BM float valve, and I do all my own servicing. a new valve, controller and thermostat would be well over £350, I could by second hand, just not sure where the stat lives.
It’s s long time since I built an aga so can’t remember but if you look carefully at the castings you can probably work out the route it would take to the oven. Dependent on age it may have been designed so the stat can be replaced without taking the top off.
These people can probably help. You probably just need the stat, power supply and flexitemp/electric top.
https://www.agadiyservice.co.uk/shop.php#
 

Matrixx

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It seems the Stat lives at the front top of the oven, and had a tube down to the front control section, there is no tube at present as it never had a stat fitted, I am going to have to open up the AGA to fix the backplate of the top oved as it has come apart so will have a good look when the top is off.
 

waddycall

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Funnily enough I’ve had a similar job come up today. A gas aga needing a new gas valve/thermostat. As you say the capillary goes up through a tube in the top rh corner above the burner door and if there’s no tube there you need to take the top off.
 
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