sometimewoodworker

The assumption of an inexperienced poster can often be made when not every scenario has been explained in the detail and manor that someone who has seemingly only ever been exposed to a subset of situations is expecting. From experience as well as the knowledge of the basic physics that @JBChiangRai has well explained, the cure suggested of larger cabling could be a part of the problem that @zlodnick is experiencing, this is unlikely to be the fix as the PEA has visited on 4 consecutive days, and while there is a significant lack of belief by some in the competence of the training required to become an electrician for the PEA this is a canard, the PEA has excellent well trained employees, though I don’t know if they also have muppets, it is less likely that all of local staff are incompetent. The statement that the the only other “fix” than larger supply from the meter to the house, would be to move the house closer to the supply is a possible answer but again is fanciful, impractical, likely impossible and does not guarantee a cure. There are other, more likely, correct answers that have not been thought of but @zlodnick will have difficulty getting implemented. The first, least likely answer, is that the PEA were incompetent in their calculations and the mains cables are too small. The situation is much more probably that when the current low voltage transformer (low voltage, in that it is suppling 220v) was installed the PEA load calculations assumed the usual load demand for Thai houses. Over time the households gained wealth and now are making a significantly larger demand. Also likely foreigners have built or upgraded houses. This means that in the daytime when many are out of the houses the PEA calculated load is not exceeded, but come evening when the microwaves, IR cookers, TVs, hot showers and AC units are all getting used there is insufficient PEA power or the installed transformer was undersized so isn’t able to cope with demand. If the second scenario is correct the only people who can fix the problem are the PEA who likely don’t have the budget (though reducing tea consumption could help). One of the fixes the PEA may be able to do is to change the transformer tap. Commonly there are 3 available on the transformers this may be an answer unless the transformer is maxed out already. Another fix that is possible is to change which phase the transformer is on, this is dependent on the location of the 3 phase supply (usually at 22k) A third fix, though the most expensive, and dependant on the PEA load availability, is installing, at the customer’s expense a new transformer (this then becomes PEA property and can have other users added without consent from the person paying for it. All in all an AVR is a relatively cheap answer to test and while it will increase the load on the current section of the network it maybe enough for @zlodnick. It may also make the voltage drops for other users annoying enough that they will put more pressure on the PEA and persuade them that your section is higher on the list for upgrading.

That is precisely one of the fundamental functions of an AVR/AVS, it regulates over and under voltage to maintain the optimum (220v, other voltages are available, ) output. There are certainly some extremes that it can’t fix but then usually has a Hi/Low voltage cut contactor for the extremes, if not they are simple enough to fit.

Again you are misquoting I said Exactly the opposite Corrected wording That is absolutely true but irrelevant Again it is true but it fails to address the point It not only holds the heat for very significantly longer but because of that it gives a greater total heat load into the roof space. If your insulation, ventilation etc doesn’t allow your ceiling to heat up at all the fact that you get a greater heat load above the ceiling means that any roof material is perfectly OK. That however would be a very unusual situation as usually nobody bothers with that level of insulation

Of course it’s rather expensive to insulate any Thai roof so that you get no daytime heat gain. However it’s not at all difficult to insulate any roof be it metal or concrete to reduce the heat gain to a manageable level. The problem with concrete is that you get the heat gain during a rather unfavourable period. My roofing is all metal and I can assure you that it is not only a theoretical possibility to insulate to a good level but I have done so and my roofing is an example of how easy it is to do it. FWIW Without AC the interior of the house is on average 10C lower than the daytime high, and with an AC unit that most would consider to be significantly undersized (316 BTU sqm) it’s not difficult, given enough time, to drop the temperature by 20C, I don’t drop the temperature to be polar bear or penguin friendly but could if I wanted to.

You miss understand the meaning of equilibrium. A roof has in essence 2 sides the top receives heat, the bottom (if you are sensible has insulation so radiates little heat. Once equilibrium is reached the top side will be loosing heat by radiation and convection at almost the same rate as the sun is radiating heat to it, not quite the same as some is being lost into the roof. The quality and thickness of the insulation on the underside some heat will be transferred to the house though the percentage will be much smaller than the heat lost from the top. The heat transfer from the metal roof stops very shortly after it stops being heated by the sun. _—————-_ with a concrete roof the amount of heat being transferred into the house is smaller at the beginning of the day while the roof is heating up. However the heat transfer to the house extends hours into the night while the thermal mass of the roof cools down

No that is not correct. The insulated metal roof doesn’t magically take on more heat than the insulated concrete roof The heat received by both is equal, the metal roof will reach equilibrium faster than the concrete roof (equilibrium being the point at which heat leaving the roof is equal to that arriving at the roof) take away the heat source (sun down) and the temperature will drop immediately. The concrete roof will reach equilibrium much slower that the steel one due to the much greater thermal mass of the roof, this however is a problem in countries like Thailand where the thermal mass, that is a great benefit in cold climates, stores and releases the daytime heat long into the night. We have just recently roofed the outside kitchen and dog house with these. They trap heat generated from under the allow little to be transmitted from above. The significant advantage is that the insulation doesn’t deteriorate as it is enclosed. Our previous roof had the insulation drop off after a few years while the roof rusted through.

You did rather ignore the fact that a concrete roof will continue to radiate heat for a much longer period than metal one. And while insulation will reduce the amount radiated into the roof spaces it doesn’t eliminate it. The rain noise will be greater on metal than concrete but you will still get some.

It actually shows that while you may have studied roofing you neglected, forgot, or never learned basic physics and are attributing statements to me that I never made. Also from the sun in the usual Thai weather. Metal roofs do not store heat (or at least the thermal mass is so small the heat storage is minimal) Metal roofs will quickly transmit heat. in direct sun A metal roof with sufficient insulation will not heat up the interior at any greater speed than than a properly insulated concrete (cement tile) roof With no sun and a low air temperature (Thailand after sunset) The metal roof will almost instantly (in a few minutes) be at ambient air temperature. Conversely it will take hours for the concrete (cement tile) roof to loose the heat it has gained I will use the option that is suitable for myself. you are welcome to continue the your your night storage heater roof

my post got eaten

That goes to show that the information printed on it is not enough as you must have an air gap between the silver side and the roof, it could be completely correct if it is designed to lay on a ceiling.

You are getting confused by the difference between a reflective barrier, where the reflective side goes up And a radiant barrier where the non radiant (shiny side) goes down. There are 2 different laws of physics involved radiation (shiny side down) and reflection (shiny side up) The silver film sold in Thailand is either shiny on one side (cheapest) where it is important to have it shiny side down on the underside of a roof as it is a good radiant barrier. Or shiny on both sides where it can act as a reflective barrier on one surface and a radiant barrier on the other surface The problem with reflective surfaces is they quite quickly get dirty/dusty so loosing effectiveness The benefit of non radiant surfaces is they face down so dirt and dust has little effect so maintaining effectiveness

FWIW There is a very simple experiment you can do to demonstrate the effectiveness of a radiant barrier. materials required; black surfaced frying pan, a spatula and aluminium cooking foil. NB insulation foil will not work method heat the frying pan to just under the smoke point of peanut oil hold your hand a close to the surface of the pan as you can for at least a minute (without burning yourself) this will be several to many cm above the pan surface (is it isn’t the pan is not hot enough or you have no nerves) take a piece of aluminium foil that is at least 5cm large on all sides than the pan, place it dull side down, using the spatula (don’t use a plastic one) press the foil down to the surface of the pan hold your hand a close to the surface of the pan as you can for at least a minute (without burning yourself) this will be Very much closer than in number 2. You can avoid the use of the spatula by forming a bowl shape to fit into the frying pan before heating the pan. The foil can be touching the frying pan’s surface so at or close to the same temperature as the pan. This demonstrates that a polished aluminium surface is a poor radiator of heat, while a black surfaced frying pan is not. A demonstration of a reflective barrier is a rather more complex process.

It seems that your studies did not include anything to do with night storage heaters! If it did you would know that cement is a good storage medium for heat. The mass of the cement tiles will nicely absorb the heat from the solar furnace AKA the sun, and then radiate that through the night keeping you nice and toasty warm. So in fact metal roofs are far better than cement, as they don’t store anything like the amount that cement does.

Regrettably that post very much glosses over the difference between using aluminium foils as a reflective barrier and using them as a radiant barrier. Given that in Thailand the heat is virtually always from the roof, a radiant barrier with the high gloss surface facing down in contact with the underside of the roof is extremely effective, there is a need for the underside to face an air space, the topside doesn’t need an air space.

I agree No they don’t. You missed the full information in your physics classes, or you’re really confused in your wording. Radiant barriers function by NOT radiating heat, they can be hot (very hot) but they don’t radiate heat well. Reflective barriers function by being good reflectors of heat so don’t get hot. Correct You are confusing the 2 different functions (this is not helped by the double sided silver film sold in Thailand) a radiant barrier needs a relatively clean surface the reverse side has no effect on the functioning of the radiant barrier. This is only if you have double sided film and want to allow reflection back to the roof surface. You can use single sided silver faced plywood boards with the silver face down and they will be as effective. I used single sided foil in my install as it was half the cost, as effective and I did remember my physics lessons 😉