A question about radiation from a microvawe oven

[Titus]

Hello!

 

I'm new to this forum and I have a question concerning an interesting thing that we have seen in our kitchen at home. We were renovating some things and decided to move the microwave for a moment. That is when we discovered that there was an actual hole in the wall, slightly bigger then my palm and half a fingernail deep, at the side od the wall where the oven was sitting for many years. So it was in the corner, the ventilator from the oven was facing the counter, and when in use, both the ventilator as well as the oven did not give away much heat. And we did not use the oven that much. A few times per day for 30 seconds to maybe a minute or two. So I doubt it could have been heat that dug the hole. And mice also couldn't get that high up. 

So is it possible that it was years of daily short bursts of radiation from this oven that dug the hole? I don't see anything else that the wall could have been exposed to but that. 

 

Thank you for any kind of feedback

Titus

 

  

[swansont]

I would think heat is much more likely than microwave leakage. I’m not sure how you eliminated that from consideration. There’s a lot more thermal energy involved as compared to microwave, outside of the chamber.

[Titus]

I wrote that the thing does not give off much heat. Today it was on for about 30 seconds and I held my hands on both sides. I could barely feel any heat at all.

And the walls are not plastered or painted in any way. This is a black kitchen - it means that it's bare rock and the only covering it got was decades and decades of smoke, soot and fry or oil that ended on the walls, eventually turning it all black. This is a very old farm house in the countryside 

Edited April 6, 2021 by Titus

[Ghideon]

1 hour ago, Titus said:

So I doubt it could have been heat that dug the hole.

A guess to start the discussion: would moist and other residues in the vented air interact with the wall material over time? How much moist is vented out from the microwave oven?

[swansont]

28 minutes ago, Titus said:

I wrote that the thing does not give off much heat. Today it was on for about 30 seconds and I held my hands on both sides. I could barely feel any heat at all.

And it gives off even less energy in microwaves, because those are inside the chamber. (unless it’s broken)

A 1 kW microwave that’s 66% efficient at converting electrical energy to microwave energy is dumping 1 kW into the food and 500 W is waste heat, some/most of which is sent off to the outside environment.

 

 

[studiot]

3 hours ago, Titus said:

Hello!

 

I'm new to this forum and I have a question concerning an interesting thing that we have seen in our kitchen at home. We were renovating some things and decided to move the microwave for a moment. That is when we discovered that there was an actual hole in the wall, slightly bigger then my palm and half a fingernail deep, at the side od the wall where the oven was sitting for many years. So it was in the corner, the ventilator from the oven was facing the counter, and when in use, both the ventilator as well as the oven did not give away much heat. And we did not use the oven that much. A few times per day for 30 seconds to maybe a minute or two. So I doubt it could have been heat that dug the hole. And mice also couldn't get that high up. 

So is it possible that it was years of daily short bursts of radiation from this oven that dug the hole? I don't see anything else that the wall could have been exposed to but that. 

 

Thank you for any kind of feedback

Titus

 

  

 

2 hours ago, Titus said:

I wrote that the thing does not give off much heat. Today it was on for about 30 seconds and I held my hands on both sides. I could barely feel any heat at all.

And the walls are not plastered or painted in any way. This is a black kitchen - it means that it's bare rock and the only covering it got was decades and decades of smoke, soot and fry or oil that ended on the walls, eventually turning it all black. This is a very old farm house in the countryside 

 

OK An old farmhouse with a blackened masonry arch (fireplace ?) in the kitchen.

What makes you think the cavity (I see no hole) was not always there ?

If there was a slight spalled cavity on the stonework surface years ago perhaps they filled it and the filling got covered and disguised by the blackening ?

In the days before polyfilla they used to do what was called pargetting - sometimes they literally used pigshit.

Anyway a filled surface cavity or just a bit of surface spalling it could have been the hot moisture from the microwave and its predecessors that 'weathered' it off.

True water vapour is invisible.

[John Cuthber]

4 hours ago, Titus said:

So is it possible that it was years of daily short bursts of radiation from this oven that dug the hole?

No.
 

[Titus]

Hello again and thank you for all your kind feedback! I think you helped me solve this mystery.

You guys asked about moist. No, there was no moist from the microwave oven, of that I am sure. The vent was always turned away from the wall, it was never hot or gave away water. And the reason I know the cavity was not always there is because we refurnished this kitchen years ago and set up the counter, the microwave and everything else. We would surely see the cavity rubble on the floor (the fourth photo) and clean it up. So it all had to fall down after it was all set up.

So where is the culprit? I posted another photo – under the counter and the microwave, in the red circle was a refrigerator. It stood there as many years as the microwave and it did give off moist. And it’s likely that this moist went by the side of the counter, up the wall and through the years dug the cavity.

That I think is the most likely what happened.

Thank you for all of your answers! 

[zapatos]

9 hours ago, Titus said:

And mice also couldn't get that high up. 

As someone who has dealt with mice for years, I can assure you they can get that high up.

[John Cuthber]

11 hours ago, Titus said:

in the red circle was a refrigerator. It stood there as many years as the microwave and it did give off moist.

Is it a gas powered refrigerator?

Most electric ones are practically airtight and don't give off moisture at all.

[exchemist]

1 hour ago, John Cuthber said:

Is it a gas powered refrigerator?

Most electric ones are practically airtight and don't give off moisture at all.

Most of the (electric) fridges I've seen have a water drain to remove condensation from the cold panel (evaporator). This is typically connected to an exterior evaporating trough at the back, warmed by the heat exchanger (condenser) that rejects the heat. It's not a lot of moisture, obviously, but there is a little. And there is certainly warmth. Perhaps it could be primarily an effect of warmth, combined with the natural damp in the walls, or something. 

 

P.S. On the subject of gas fridges, I remember someone's girlfriend being conned into thinking that, for caravans, one could have a gas television.😊

[John Cuthber]

1 hour ago, exchemist said:

 

P.S. On the subject of gas fridges, I remember someone's girlfriend being conned into thinking that, for caravans, one could have a gas television.

You can.

Most of the UK’s electricity is produced by burning fossil fuels, mainly natural gas (42% in 2016)

from
https://www.energy-uk.org.uk/our-work/generation/electricity-generation.html

 

Fridges move moisture about, but they don't "produce" much.
A lettuce doesn't steam as much as a roast.

[studiot]

2 hours ago, exchemist said:

Most of the (electric) fridges I've seen have a water drain to remove condensation from the cold panel (evaporator). This is typically connected to an exterior evaporating trough at the back, warmed by the heat exchanger (condenser) that rejects the heat. It's not a lot of moisture, obviously, but there is a little. And there is certainly warmth. Perhaps it could be primarily an effect of warmth, combined with the natural damp in the walls, or something. 

 

P.S. On the subject of gas fridges, I remember someone's girlfriend being conned into thinking that, for caravans, one could have a gas television.😊

Yes I don't think there are many fridges or freezers on the market without this system +1

You got there before me, but I'll just add my diagram anyway, which shows the back of the device.

Most of these have the drip collection and evaporation tray mounted directly on top of the motor to use the small amount of heat the motor generates.

The drip tube coming out of the cold compartment is a frequent source of blockage and water collecting inside the device.

 

But the important point here is the word evaporation.

I already mentioned that water vapour is invisible in connection with the microwave, which also gives off water vapour despite the Tiitus' protestations to the contrary.

Not only this but with typical vapour generation rates for both devices, the vapour will be warm not hot so near impossible to detect by touch.

So it is quite reasonable to think that the evaporating water vapour from not only these devices but the rest of the kitchen activities of cooking and washing will disperse and finally condense on that large cold slab formed by the exposed masonry arch.

I note from the pictures that there appears to be some scour on the black coating on that region.

15 hours ago, Titus said:

You guys asked about moist. No, there was no moist from the microwave oven, of that I am sure. The vent was always turned away from the wall, it was never hot or gave away water. And the reason I know the cavity was not always there is because we refurnished this kitchen years ago and set up the counter, the microwave and everything else. We would surely see the cavity rubble on the floor (the fourth photo) and clean it up. So it all had to fall down after it was all set up.

 

I also take it that Titus did not blacken the arch at the original refitting, so it was quite possible that an older bodge was concealed under a more complete black coating at that time.
If that is the case then no 'cavity rubble' would have been evident at the time of the first refit.

Condensation deterioration inside old chimney stacks that have not been used (ie heated) for a long time is a well known phenomenon.
The masonry not only provides a massive cold sink but also often as moisture absorbant one to boot.

 

As regards gas televisions, back when the UK converted to natural gas, my brother was heavily involved and had an interesting isuue to resolve.
British Gas at the time was legally bound to convert all existing gas devices free of charge.
There were some gas powered radios (not televisions as I recall) in the remote North of Scotland that therefore had to be converted.
This caused much head scratching at the time.
 

Edited April 7, 2021 by studiot

[Titus]

I have no idea about fridges but ours ran on electricity. It could be rather loud and cold  

[exchemist]

3 hours ago, studiot said:

Yes I don't think there are many fridges or freezers on the market without this system +1

You got there before me, but I'll just add my diagram anyway, which shows the back of the device.

Most of these have the drip collection and evaporation tray mounted directly on top of the motor to use the small amount of heat the motor generates.

The drip tube coming out of the cold compartment is a frequent source of blockage and water collecting inside the device.

 

But the important point here is the word evaporation.

I already mentioned that water vapour is invisible in connection with the microwave, which also gives off water vapour despite the Tiitus' protestations to the contrary.

Not only this but with typical vapour generation rates for both devices, the vapour will be warm not hot so near impossible to detect by touch.

So it is quite reasonable to think that the evaporating water vapour from not only these devices but the rest of the kitchen activities of cooking and washing will disperse and finally condense on that large cold slab formed by the exposed masonry arch.

I note from the pictures that there appears to be some scour on the black coating on that region.

 

I also take it that Titus did not blacken the arch at the original refitting, so it was quite possible that an older bodge was concealed under a more complete black coating at that time.
If that is the case then no 'cavity rubble' would have been evident at the time of the first refit.

Condensation deterioration inside old chimney stacks that have not been used (ie heated) for a long time is a well known phenomenon.
The masonry not only provides a massive cold sink but also often as moisture absorbant one to boot.

 

As regards gas televisions, back when the UK converted to natural gas, my brother was heavily involved and had an interesting isuue to resolve.
British Gas at the time was legally bound to convert all existing gas devices free of charge.
There were some gas powered radios (not televisions as I recall) in the remote North of Scotland that therefore had to be converted.
This caused much head scratching at the time.
 

Bloody hell, a gas radio! And it's not April 1st any more, either.

I'll have to look that up!