Saturday, 25 March 2017

Was I wrong on the oven?

I am puzzled. I checked the manual for the oven (here).

The instruction is

"Operating the Ovens
Push in and turn the knob controlling the oven to gas mark 9 (Fig.2-22). The oven will light automatically.
Turn the oven knob to the desired gas mark (Fig.2-23)."

OK, no suggestion of delay, or that going to 9 will be a way to get to temperature faster - just to ensure it lights by the look of it. It does not say why.

Fair enough, but I really have to wonder why. The manufacturer of the oven should have a reason for this, surely?

I could understand if there was some aspect of the lighting mechanism that was somehow more reliable if you do this.

But that cannot be the case. The oven has to be able to self light at any gas mark because it can be set for a timer. If you set for a timer, it will not have the "turn to 9 first" aspect. That is why the spark is automatic and not a button like the top burners. So it must have a reliable mechanism to light anyway without turning to 9 first.

Yet, they have put it in the manual.

Perhaps I'll write to them and ask them.

8 comments:

  1. Perhaps to ensure it lights even when it's hot ? ie a re-light

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    1. Not sure I understand - that is instructions for what you would do from cold?

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    2. Yes, but the manufacturer may well be covering themselves by providing instructions that will definitely work whether the oven is hot or cold.

      Turning it up to 9 for lighting certainly can't do any *harm* (other than sending a confusing message about how thermostats work, obviously...) but setting it at a low heat in an already-warm oven might result in a gas flow too low for it to light reliably, and the accompanying risk of the oven going boom.

      It's a reasonable 'fail-safe' procedure for lighting an oven in an unknown state.

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    3. Seriously, no way! They have a lot of built in fail-safes - relying on user operation like that for fail-safe would be practically negligent!

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  2. Not all thermostats are binary! Mechanical thermostats such as those used in engine cooling systems control flow rates effectively like a tap that begins to open as the temperature rises. Car thermostats are usually a wax pellet that allows a valve to progressively open as it melts.

    For really old-school gas ovens the gas mark is a simple flow rate with no thermostat. These are still common in Spain, much to my aunt's annoyance because it means baking requires a thermometer and constant manual adjustments!

    Newer gas ovens are similar but add a regulator, using a thermostat to reduce the gas flow to limit maximum temperature. The maximum flow is controlled by the gas mark, so gas mark 9 will accelerate heating the oven simply because more gas is available.

    I expect modern programmable gas ovens exclusively use a thermostat to regulate flow without the gas mark limiting it; so I'd be surprised if they heat faster at higher gas marks.

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  3. For some reason, the link to the manual appears as "http://here/" to me.

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  4. How much play is in the knob? Could it be simply to ensure that you are on the upper side of the "swing".

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  5. My mum used a gas oven for 40 years before going electric. She always just set it to the desired gas mark and left it at that. No farting about. This was a gas oven you had to light with a match though, the ignition had died decades ago. I singed my hair lighting it a couple of times.

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