Re: Aga temp problem?

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Keep walking, further down the road to Damascus you will be fully enlightened.

I couldn't agree more. The sort of people who buy them are the sort who voted for Britain's best house the other night. That house? Never in a million years. In my mind I never even considered it wondering how it was even in the final. then it won. Or did the gay community all vote for those two old Queens.
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I dismantled our gas 4 oven a few weeks ago as the kitchen was being rebuilt. Took lots of piccies at the time but any advice & tips for re-assembling in a few weeks time would be most welcome. Toby
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Toby Sleigh wrote:

No, but I watched someone build ours from parts...

Get a pro in m8 :-)
All that repacking with insulatuon and gentle filing to get teh parts to fit.
Mind you with gas you don't have to check oil flow etc etc.

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I have only reassembled a few oil fired Agas so my experience of gas fired beasts is zero. However there are many points of similarity and so I will pass on a few tips.
The vertical rods that secure the top to the rest of the structure should be firmly locked at the bottom plate. Six lengths,or four if it is a two oven model, of 10mm copper pipe, about 4 to 6 inches, pushed onto the rods makes the alignment with the holes in the Aga top a simple matter.Although two or even three people makes lighter work!
Don't be in a hurry to re- stuff the insulation until you have adjusted both the hot plates to be absolutely level and at equal heights. Having done the levelling put the top in place and ensure that each hot plate is below it's surround by the thickness of a coin . This is to allow for expansion at operating temperatures. The objective is to have the plates level with or a tiny amount above the surround at working temperature. Note that there are adjusting screws in the top of the hot oven.
Remember to fit the thermostat and oven sensor before you finally fit the top. It is possible to replace and re-fit the thermostat with the top in place but this will not apply in your case.
Get yourself a detailed assembly/Installation manual from the Aga/Rayburn people. I have always found them most helpful.
Take you time and whatever the insulation type wear a mask !
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On Thu, 31 Jul 2003 18:36:21 +0100, "Toby Sleigh"

I have a bunch of pictures of the assembly of a 4 oven gas model if they would be of use to you.
From memory, one of the main issues is adjusting the threaded rods at each stage such that the component being supported is level.
If you have removed the insulation from the left hand oven module, you may need to install fresh. Apparently when new the material is coated in lanolin to allow it to be stuffed into the spaces. That is driven off on first firing and the material is then not easy to remove and replace.
Depending on its condition it may be worth replacing the Vermiculite in the main body.
One final point is to make sure that the surfaces of the plates are approximately 3mm below the cast rings surroiunding them when the unit is cold. When hot, expansion brings them up to the level of the ring.
To be honest, I would suggest having somebody from the dealer put it back together.
.andy
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When was it last serviced? I suspect you have a coking up problem in the burner oilways and possibly the burner underfeed tube. This requires a strip down and clean out together with the remainder of the service schedule works.
-- Please note antispam measures - do not hit reply Horse sense is what horses have that makes them not bet on people - W.C. Fields
Regards, John
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maybe it needs more oil
The Natural Philosopher wrote:

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Greetings, A usefil nugget gleaned froma an Aga engineer: re oil Aga's. If summer you may notice that your Aga runs hotter than in Winter for a set thermostat setting. Apparently this is because in Summer the oil is warmer and hence more "liquid" and runs through the feed pipes faster, so more oil to the burner. In winter the oil is thicker and so flow is slower and hence temp is lower. regarsd M
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came up with is a load of codswallop. The thermostat that controls the high/low flame modulation is installed within the house ,usually screwed to the Aga itself. It is in a room temperature environment but in any case the temperature of an Aga or any other such device is controlled by an internal thermostat which I am sure you will eventually realise does not care if it is Summer or Winter outside.
Richard.
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NOT ALL Agas have thermostatic control. Many of the early models simply regulated the oil input flow via a needle valve from a constant head float chamber into the burner casting. Mind you I think the explanation whilst it "may" have some theoretical physics basis is getting a bit near the edge of the bullshit envelope since the viscosity of kerosine is not going to change all that much over the range of temperatures at the input to the float chamber (BM Box to those folks who have one). Possible other related factors by probable truth are 1. Human impression of heat/humidity 2. Variation of the metal clearances of the internals of the BM Box due to expansion allowing marginal variation in flow (non thermostat type) 3. Reduction of thermal gradient from inside cooker to room temperature giving less "losses" and thus higher oven temperature 4. any other things you can imagine when asked a question you don't have the answer for but don't want to admit it to customer
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I would be very interested to which "early models" you refer that have no thermostat. Even the very early solid fuel to oil conversions had low/high flame modulation controlled by a thermostat. Whether the burn rate is controlled by a needle valve or a metered slit a thermostat has always been the means of control.What is your source of information on Agas without thermostats ? I find it hard to believe that such bits of kit have ever been produced. However I am always willing to learn.
For your information the original solid fuel Agas had thermostats which controlled the airflow entering the fire box and consequently matched the heat supplied ,over time, with the cooking requirements. You are now saying that some early oil fired models did away with thermostats. I find that hard to believe so convince me.:-)
Richard.
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SNIP
I'm sorry but you are wrong in the scope of your statement. I reiterate that NOT ALL Agas have thermostats. I know this because I spent a great deal of time servicing many in my locality when I worked for the area Shell Oil agent. Hands on experience of a number of units is what I speak from

Most of the solid fuel to oil conversions prior to about 1980 that I worked on relied on a rotating knob on top of the BM float box which was an extension of the needle valve spindle. (You may have regarded this as a thermostat?) In all the cases I can recall, the removal of the solid fuel burning apparatus included the simultaneous removal of the "flap" which controlled the air supply. This was required since a vapourising oil burner requires sufficient (excess) combustion air to prevent carbon monoxide formation and interference with the airflow has high risk of improper combustion. I don't deal with Agas now as age has given me a lower back problem which is exacerbated by trying to lift the cast iron lumps which form the hotplates out of the cooker to gain access to the burner. However, I can definitely assure you that I am correct in what I say about not all Agas having thermostatic control. Later models and some of those manufactured as oil fired rather than conversions from solid fuel were indeed fitted with an electrically operated thermostat which used a low voltage transformer, a normally closed electrical thermostat which opened on temperature rise and a heater element which caused a bimetal strip to deflect and operated on a pushrod which opened or closed the needle valve. If you are really interested I am sure Aga will confirm what I have told you
-- Please note antispam measures - do not hit reply Horse sense is what horses have that makes them not bet on people - W.C. Fields
Regards, John
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Your first post on the subject of aga temperatures varying with the time of year was stated as a generality and was plainly incorrect which is why I felt it necessary to post my comment. You also said that you got this "nugget of information" from an aga engineer. Was this in conversation with an engineer at the Aga headquarters or was it from someone who held himself out to be an Aga engineer in the field? Because which ever it was either he was talking rubbish or you have a poor recollection of what was said.
In your further posts it now is revealed that you are very experienced in the servicing and maintenance of Agas and that the lack of thermostats only applied to some conversions to previously solid fuelled Agas prior to the 1980s If you knew this to be so why did you make the fallacious post that appeared to apply to Agas generally? Or did I miss a smiley at the end of you post ?
In about 1960 my parents had a solid fuel to oil converted Aga and even then it was provided with an electric controlbox that had red and green lights to show the high or low flame state and guess what, this was controlled by a thermostat. this pre dates you reference by a mere 20 years.
I am not familiar with the BM regulator to which you refer and I am not going to waste my time to follow it up with the Aga/Rayburn people because I am quite sure the burning rate was thermostatically controlled. The actual thermostat may not have been in the current form of a sealed vial in the oven.There were I believe some early conversions which used a bi-metallic strip attached to the structure next to the fire box they were none the less thermostats.
BTW your reference to needle valves in later models and purpose made oil fired versions is somewhat inaccurate. The metering slit operating in a tube need an enormous leap to be described as a needle valve. It would be impossible to prick yourself with it for a start!
One final thought, how did the user of a thermostatless Aga manage to avoid thermal runaway or maintain any sort of control over cooking temperatures. What would happen if they were away from home for say 24 hours, planned or unplanned, ?
Richard.
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Richard wrote:

Agas on oil are set up for two flow rates - one is the low flow rate, designed to maintain the minimum useable temperature, and the other is max flow rate, designed to get the aga as hot as it ever needs to be.
They toggle between the two under thermostatic control, and can be manually overridden.
I have manually overridden mine, but it still runs too cool :(
All that having the high flow rate set will do is run the aga at its max useable temperature. They don't do runaway, any more than any other paraffin stove does.

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You seem to be confused about the attribution of who posted the initial posts? I suggested in my post that there was a high bullshit factor in the "Aga Enginners" explanation :-)

See above - you will see that my posts said NOT ALL Agas came under the banner of thermostatic controlled units. This by definition does not exclude those that do but please try to understand that ther are many that do not, especially those that vary in temperature during the summer (even if only in their owners "impressions")

Presumably this is an early version of the auxiliary low voltage control which I described. The ones I met did not have the lights but I have already gone over their methodology

Please try to understand that there are others outside your experience of one unit which do not in fact comply with your expectations. Some I agree may have done so.

The original solid fuel thermostat damper indeed had a bimetal strip which moved the position of the air damper but as I explained before restricting air to a vapourising burner is dangerous and this was not used with converted units. I am quite prepared to believe that there is a possibility that somewhere along the line a few models may have been tried with a bimetallic strip acting on the needle valve which is what was done further down the line with the hybrid electrical thermostat system which I described. A heater element being attacched to the bimetal to cause it to deflect.

OK for pedantrys sake it is a metering slit which is in a tube which slides into another tube so opening or covering the "clear" length of slit or orifice but in the context of easy explanation for others to read I think describing it as a needle valve is normally adequate insofar as the further the inner tube is pressed down the less aperture is presented to the oil flow although this desription takes significantly longer to write and is perhaps not as succinct!
Suffice it to say we are talking about the beige coloured, ovaloid cylinder shaped control box bearing the "trip" lever and the flame control knob etc fitted to the Aga range along with a myriad other vapourising burner appliance for dozens of years here?

One of the frequent complaints from customers after a service when the oilways had been cleaned out and the flow was back up to standard was of "overheating" although this was one of those "cooks" impressions rather than one supported by thermometer measurement. The BM box was (is) a clever bit of kit insofar as it contained in one box a fuel filter, overfilling cut off device (if the float control suffered a bit of grit on the seat etc), fusible firestop shut off, fuel level control for constant head feed to the metering valve, low flow limit stop and high flow limit stop. The low and high flow limits were set according to makers specifications and the high flow or high fire setting was designed to avoid thermal damage to the device if not to the cakes and Yorkshire Puddings. The housewife soon came to learn to run the Aga on low for most of its life and turn the burner up in good time for baking day
The system as such worked just fine for many years even if it was a bit crude by a modern control engineers standards. The lack of thermostatic control was never a problem to the early manned burning kit such as on factory boilers, furnaces, steam locomotives, warships etc. All you needed was a decent stoker with a shovel and a strong back on the big uns. I know of a sinter hood in Tilbury which burns waste oil even today and is entirely regulated by the operators adjusting gate valves in the oil suply to the burner nozzles. The thermal mass of the process allows wide(ish) tolerance of the flame to be taken care of without rapid oscillation of the temperature, exactly as is the case with the big lumps of cast iron in an Aga
-- Please note antispam measures - do not hit reply Horse sense is what horses have that makes them not bet on people - W.C. Fields
Regards, John
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John wrote:

I will confirm teh veracity of this. Oil convesrions and early oil agas had no feedback, but mechanical regulators.
Mine has an electrical one however, which is still functioning.

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m.holley wrote:

Shame. Its ruinning cooler :-)

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God I get sick of thread smart ***es and thread hijackers. Hey people if you want to dribble, go somewhere else. If you want to ask another question, start your own thread. Rant over, back to the Aga servicing. I'm not an expert but this is what I do to my own 5yr old oil Aga. If your burner/pipes dont match the description below, you may need to adapt the process. 1. Turn it off and let it cool (instructions inside burner door) 2. Disconnect the oil line at the elbow. Put a rag underneath to catch any drips. Be careful of the elbow/join as you disconnect it. 3. Slide out the whole burner unit on its plate. 4. Note the orientation of the lid and the burner rings as you lift them off. 5. Lift the lid off the oil bowl and you should find it coked up ie. you can't see the inlet hole. 6. The wick may look tired but it will still work fine. 7. Remove the pipe (not the pipe fitting) from the bottom of the bowl. Decoke the bowl, the hole (i use a small drillbit for the hole) and the bowl end of the pipe if necessary. A vacuum cleaner helps clean away the bits of carbon as you loosen them. 8. Reassemble and follow the intstructions on the door to light. 9. Don't alter the levelling screws on the burner plate - the installer will have set the plate level. It may take you a couple of hours the first time you do it. Next time it'll take you less than an hour. Good luck.
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