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I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
I want to model a heat load.-a I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
On 27/09/2025 18:33, Don Y wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Electric fire bars are probably cheaper and much more robust for bigger loads.
US 100v bulbs are a bit more efficient than UK 240v ones.
I have used light bulbs as a heat source for terrariums.
Don Y <blockedofcourse@foo.invalid> wrote:
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Probably more than 90% - and the light will turn nto heat when it is
absorbed by the walls and the contents of the room. You need to measure
the voltage and the current because the resistance of a tungsten
filament lamp increases greatly with temperature, so you can't make assumptions from just the voltage or the current alone.
Industrial fan heaters also make good loads, I have used them as
starters for a three-phase motor with a high inertia load (it took over
45 seconds to run up to speed).
On 9/27/2025 11:09 AM, Liz Tuddenham wrote:
Don Y <blockedofcourse@foo.invalid> wrote:
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Probably more than 90% - and the light will turn nto heat when it is
absorbed by the walls and the contents of the room. You need to measure
the voltage and the current because the resistance of a tungsten
filament lamp increases greatly with temperature, so you can't make
assumptions from just the voltage or the current alone.
I will be controlling the power into the load. But, I need a (cheap)
load that I can easily resize.
Surfaces absorbing heat from light will tend (?) to do so slower than
the radiated heat from the lamps' inefficiencies. (I don't want to have to >"soak" for a long time to get a feel as to the temperature rise in the >volume)
On 9/27/2025 11:09 AM, Liz Tuddenham wrote:
Don Y <blockedofcourse@foo.invalid> wrote:
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Probably more than 90% - and the light will turn nto heat when it is absorbed by the walls and the contents of the room. You need to measure the voltage and the current because the resistance of a tungsten
filament lamp increases greatly with temperature, so you can't make assumptions from just the voltage or the current alone.
I will be controlling the power into the load. But, I need a (cheap)
load that I can easily resize.
Surfaces absorbing heat from light will tend (?) to do so slower than
the radiated heat from the lamps' inefficiencies. (I don't want to have to "soak" for a long time to get a feel as to the temperature rise in the volume)
Industrial fan heaters also make good loads, I have used them as
starters for a three-phase motor with a high inertia load (it took over
45 seconds to run up to speed).
"Fan heater"? A ceramic heating element with forced air over it?
Will it "melt" (degrade) if the forced air was disabled?
On 9/27/2025 11:27 AM, Martin Brown wrote:
On 27/09/2025 18:33, Don Y wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Electric fire bars are probably cheaper and much more robust for
bigger loads.
What's a "fire bar"?
US 100v bulbs are a bit more efficient than UK 240v ones.
Bulbs are cheap.-a If I need to use 10% more of them, <shrug>-a I can put them
on a rheostat and "tune" the actual power dissipated (as I don't care what happens to the light)
I have used light bulbs as a heat source for terrariums.
We use "XMAS lights" (strings of 25 x 9W lamps) on the citrus on winter nights.
Not to keep the trees *warm* but, rather, to keep the air moving around
them
(air that settles on the leaves is COLDER than the surrounding air).
[I've been looking for fans that are capable of being used in outdoor settings (think:-a rainfall) as they would be easier to deploy to
protect such a large volume (~4000-8000 cu ft)]
I will be controlling the power into the load. But, I need a (cheap)
load that I can easily resize.
Surfaces absorbing heat from light will tend (?) to do so slower than
the radiated heat from the lamps' inefficiencies. (I don't want to have to >> "soak" for a long time to get a feel as to the temperature rise in the
volume)
I'm not sure that is correct. The energy input to the surfaces will
start instantaneously - but they will be slow to heat up because the
actual amount of energy input is small and their thermal mass is large.
The same energy flow carried by convected air would actually take longer
to heat them because the air would have to be heated first to establish
the circulation.
Industrial fan heaters also make good loads, I have used them as
starters for a three-phase motor with a high inertia load (it took over
45 seconds to run up to speed).
"Fan heater"? A ceramic heating element with forced air over it?
Will it "melt" (degrade) if the forced air was disabled?
The ones we used had wide-pitches spirals of nichrome wire stretched
back and forth between porcelain insulating plates. If the fan failed
they would take a minute or two to glow red hot, by which time a
bimetallic thermal cutout would have disconnected them. The danger
wasn't the nichrome or the porcelain melting but the effect of high temperature on the motor windings and the possibility of starting a fire
if dust had collected near the element.
If you want the elements to operate without the fan-assisted air flow
(which is quite gentle in a large industrial heater) just put pairs of elements in series and lay them horizontally so that they are convection cooled. They are unlikely to overheat at one quarter of their rated
power.
For testing the power dissipation capabilities of a large die-cast box,
I just bolted a couple of aluminium-cased power resistors onto it. From those results I was able to calculate the largest size of audio
amplifier that could be built into that box without needing a separate
heat sink.
On 9/27/2025 1:42 PM, Liz Tuddenham wrote:
I was able to calculate the largest size of audio
amplifier that could be built into that box without needing a separate
heat sink.
Yes, but, as I mentioned above, you likely assumed said box was surrounded
by a 25C ambient "heatsink".-a Put it in your closet and see how it fares. See how the *other* items in your closet fare!
Then, ask how you could locate it there without unwanted "ill effects".
On 27/09/2025 20:12, Don Y wrote:
On 9/27/2025 11:27 AM, Martin Brown wrote:
On 27/09/2025 18:33, Don Y wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of >>>> the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Electric fire bars are probably cheaper and much more robust for bigger loads.
What's a "fire bar"?
1cm diameter 25cm long ceramic former spiral wrapped with ~0.8mm nichrome wire
1kw resistive heating element for an electric fire.
"100% efficient!" at turning electricity into heat. Glow orange in use.
This is a traditional radiant electric fire with modern 600W fire bars:
https://www.chums.co.uk/products/hb813/two-bar-heater
But today fitted with a safety bar glass covered.
Most electric fires now are much more fancy with pretend LED flames.
This one isn't.
https://www.chums.co.uk/products/az971/free-standing-electric-fire
That is a modern one with much longer element glass coated so you can't easily
electrocute yourself. The ones of my youth were bare nichrome wire on a ceramic
former. I still have a couple of bars of that type.
Convenient as indestructible 1kW loads at mains voltage.
US 100v bulbs are a bit more efficient than UK 240v ones.
Bulbs are cheap.-a If I need to use 10% more of them, <shrug>-a I can put them
on a rheostat and "tune" the actual power dissipated (as I don't care what >> happens to the light)
Filament bulbs last a lot longer if you put a small power resistor in series to
limit the inrush current into the cold filament.
I have used light bulbs as a heat source for terrariums.
We use "XMAS lights" (strings of 25 x 9W lamps) on the citrus on winter nights.
Not to keep the trees *warm* but, rather, to keep the air moving around them >> (air that settles on the leaves is COLDER than the surrounding air).
[I've been looking for fans that are capable of being used in outdoor
settings (think:-a rainfall) as they would be easier to deploy to
protect such a large volume (~4000-8000 cu ft)]
You can surround them with a big plastic or ducting tube.
On 9/27/2025 1:42 PM, Liz Tuddenham wrote:
I will be controlling the power into the load.-a But, I need a (cheap)
load that I can easily resize.
Surfaces absorbing heat from light will tend (?) to do so slower than
the radiated heat from the lamps' inefficiencies.-a (I don't want to have to
"soak" for a long time to get a feel as to the temperature rise in the
volume)
I'm not sure that is correct.-a The energy input to the surfaces will
start instantaneously - but they will be slow to heat up because the
actual amount of energy input is small and their thermal mass is large.
The same energy flow carried by convected air would actually take longer
to heat them because the air would have to be heated first to establish
the circulation.
I want to see how the unvented space reacts to the load.-a Take the "amplifier
simulator" you mentioned, below, and sit it in a cupboard.-a Closet.-a etc. "Suddenly", the "die cast box" isn't sitting in a nice, comfortable 25C ambient "heatsink" but, rather, a warmed environment that only loses heat
by convection through walls, floor, ceiling, etc.-a There WILL be some maximum
temperature attained beyond which power injected manages to dissipate out of the enclosure-enclosure.
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
On Sat, 27 Sep 2025 10:33:58 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Halogen/tungsten lamps produce >95% of their luminous output in
the infrared.
Model?
On 9/28/2025 11:40 AM, legg wrote:
On Sat, 27 Sep 2025 10:33:58 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Halogen/tungsten lamps produce >95% of their luminous output in
the infrared.
Yeah, bit they all seem to be higher wattages. And, not as readily available as traditional incandescents. E.g., you could piece together a 4, 10, 20, 40,
60, 75, 100, 150, 200, 300, 500, etc watt "load" with the items that you could find on hand in many homes (even if it meant removing lamps from fixtures).
The halogens I've seen tend to be in floodlights -- hundreds of watts and up.
Model?
Create a load that mimics device(s) dissipating certain amounts of power
in certain place(s) in a volume. Note how the space responds to the
presence of that load, over time. Explore options to decrease that impact
to "manageable" levels, given the other items that may share that volume.
As I commented to Liz, imagine siting a power amplifier in a bedroom closet. How does the operating condition for the amplifier change as it throws off heat that the surrounding space CAN'T dissipate? How do the items in
the closet react to the presence of this unexpected heat source?
IME, people think nothing of siting a wireless router in such a place.
But, that's a tiny thermal load. Could you similarly site it at the
back of a kitchen/pantry cabinet? How "much" could you site in a space
(in your home or business) that wasn't explicitly designed for such use?
Maybe a PABX in a small equipment closet? A small server in a broom closet?
The more important followon question is "what type of space would you want designed into a residence/business to support a particular size load,
given the cooling requirements it might necessitate?" Your home likely has
a place for "guests" to stash their coats -- and, it's likely not in some far off corner but readily accessible from your main entrance. There is a reason for that.
The more important followon question is "what type of space would you want >> designed into a residence/business to support a particular size load,
given the cooling requirements it might necessitate?" Your home likely has >> a place for "guests" to stash their coats -- and, it's likely not in some far
off corner but readily accessible from your main entrance. There is a reason
for that.
In theory you could measure the thermal conductivity of the different materials or combinations of material the heat energy would have to pass through, then calculate the overall temperature gradient to whatever
ambient you set as your maximum. The problem with large spaces and
objects is that poor convection and conduction give very significant differences in temperature between various parts.
Stirring the air will distribute the temperature more evenly and bring
down the hot spots, but it will still hit a limit imposed by the
conductivity of the various layers the heat has to travel through. You
also have to take into account the certainty that a fan will fail during
the lifetime of the equipment (and may put an end to that lifetime). Convection 'chimneys' are much more reliable as long as the equipment is
only used the right way up.
Even with the most careful calculations, things can be disrupted by unexpected events. I once left an automatic battery charger, in the
corner of a Portakabin, supplying the batteries running a P.A. system
for a large event. When I came back to check, I found it was underneath
a pile of coats and almost too hot to touch. The internal temperature sensing had shut down the output to a level which it could sustain, so
there was no damage but the batteries weren't happy. When I removed the coats, it cooled down and returned to normal operation.
The moral of that story is to assume the equipment will eventually
overheat from some unforseen cause and make sure it degrades gracefully without damage.
There is a tendency, left over from the days of valves and expensive
power transistors, to try to extract the maximum output from a single
device. Two transistors in parallel have half the dissipation and half
the thermal resistance to the heatsink of a single transistor, so the
slight extra complication of using two devices is more than compensated
by the four-fold reduction in the temperature gradient.
On 9/28/2025 11:40 AM, legg wrote:
On Sat, 27 Sep 2025 10:33:58 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Halogen/tungsten lamps produce >95% of their luminous output in
the infrared.
Yeah, bit they all seem to be higher wattages.-a And, not as readily available
as traditional incandescents.-a E.g., you could piece together a 4, 10,
20, 40,
60, 75, 100, 150, 200, 300, 500, etc watt "load" with the items that you could find on hand in many homes (even if it meant removing lamps from fixtures).
The halogens I've seen tend to be in floodlights -- hundreds of watts
and up.
--Model?
Create a load that mimics device(s) dissipating certain amounts of power
in certain place(s) in a volume.-a Note how the space responds to the presence of that load, over time.-a Explore options to decrease that impact to "manageable" levels, given the other items that may share that volume.
As I commented to Liz, imagine siting a power amplifier in a bedroom
closet.
How does the operating condition for the amplifier change as it throws off heat that the surrounding space CAN'T dissipate?-a How do the items in
the closet react to the presence of this unexpected heat source?
IME, people think nothing of siting a wireless router in such a place.
But, that's a tiny thermal load.-a Could you similarly site it at the
back of a kitchen/pantry cabinet?-a How "much" could you site in a space
(in your home or business) that wasn't explicitly designed for such use?
Maybe a PABX in a small equipment closet?-a A small server in a broom closet?
The more important followon question is "what type of space would you want designed into a residence/business to support a particular size load,
given the cooling requirements it might necessitate?"-a Your home likely has a place for "guests" to stash their coats -- and, it's likely not in
some far
off corner but readily accessible from your main entrance.-a There is a reason
for that.
On 9/28/2025 11:40 AM, legg wrote:
On Sat, 27 Sep 2025 10:33:58 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I want to model a heat load. I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Halogen/tungsten lamps produce >95% of their luminous output in
the infrared.
Yeah, bit they all seem to be higher wattages. And, not as readily available >as traditional incandescents. E.g., you could piece together a 4, 10, 20, 40, >60, 75, 100, 150, 200, 300, 500, etc watt "load" with the items that you >could find on hand in many homes (even if it meant removing lamps from >fixtures).
The halogens I've seen tend to be in floodlights -- hundreds of watts and up.
Model?
Create a load that mimics device(s) dissipating certain amounts of power
in certain place(s) in a volume. Note how the space responds to the
presence of that load, over time. Explore options to decrease that impact
to "manageable" levels, given the other items that may share that volume.
As I commented to Liz, imagine siting a power amplifier in a bedroom closet. >How does the operating condition for the amplifier change as it throws off >heat that the surrounding space CAN'T dissipate? How do the items in
the closet react to the presence of this unexpected heat source?
IME, people think nothing of siting a wireless router in such a place.
But, that's a tiny thermal load. Could you similarly site it at the
back of a kitchen/pantry cabinet? How "much" could you site in a space
(in your home or business) that wasn't explicitly designed for such use?
Maybe a PABX in a small equipment closet? A small server in a broom closet?
The more important followon question is "what type of space would you want >designed into a residence/business to support a particular size load,
given the cooling requirements it might necessitate?" Your home likely has
a place for "guests" to stash their coats -- and, it's likely not in some far >off corner but readily accessible from your main entrance. There is a reason >for that.
On 9/28/25 5:56 PM, Don Y wrote:
On 9/28/2025 11:40 AM, legg wrote:
On Sat, 27 Sep 2025 10:33:58 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of >>>> the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Halogen/tungsten lamps produce >95% of their luminous output in
the infrared.
Yeah, bit they all seem to be higher wattages.-a And, not as readily available
as traditional incandescents.-a E.g., you could piece together a 4, 10, 20, 40,
60, 75, 100, 150, 200, 300, 500, etc watt "load" with the items that you
could find on hand in many homes (even if it meant removing lamps from
fixtures).
The halogens I've seen tend to be in floodlights -- hundreds of watts and up.
Do a search for G4 halogen 20W 2 pin bulb.-a These run on 12 volts and were (maybe still are?) popular for under-cabinet kitchen lighting.-a I know 10W's
were available, not sure about other sizes.-a Not the standard screw-in Edison
base, but widely available.
Maybe a PABX in a small equipment closet? A small server in a broom closet?
Maybe maybe maybe. What's your problem?
Stick your heaters in a wooden box, the average surface temperature
rise of the outer box wall, above ambient, will be:
Don't forget to measure each centimeter accurately, for averaging.
It's sort of cool knowing what each centimeter is actually doing,
and may give you some useful packaging ideas.
This is, of course, reversible. You can reliably estimate power
dissipation of a surface are with known aveerage rise.
What you can't tell, is what the spot temperature of the internal
radiator. That's modelling for you. The smaller the source gets,
the higher it's temperature in order to dissipate the power being
wasted, and the stupidder the modeling and modeller becomes.
I've had to demonstrate this too many times in the past, to enjoy
explaining the miracle coefficient ' 1 '.
It's drawn from and confirmed by those demonstations and from
ripple current rating charts of phsically dimensioned, thermally
restricted, computer grade aluminium elctrolytic caps. From before
the days of built-in fans for cooling for reliable equipment.. ..........................
Thermal rise of surrounding air is fixed by it's 'specific heat'.
Move volume of such air elsewhere, by any means you desire, to
evacuate volume area requiring cooling. Rates are measurable.
Add conditions codicils or flambools as you will. principals will be
the same.
The more important followon question is "what type of space would you want >> designed into a residence/business to support a particular size load,
given the cooling requirements it might necessitate?" Your home likely has >> a place for "guests" to stash their coats -- and, it's likely not in some far
off corner but readily accessible from your main entrance. There is a reason
for that.
What would you want? You'd follow the mfr's instructions, or draw from
your own experience/observation. There's probably a second hand book discarded from the local library or tech college somewhere
You're not designing a clothes closet or an airing cupboard.
Those are really tricky.
On 9/29/2025 6:07 AM, Carl wrote:
On 9/28/25 5:56 PM, Don Y wrote:
On 9/28/2025 11:40 AM, legg wrote:
On Sat, 27 Sep 2025 10:33:58 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of >>>>> the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Halogen/tungsten lamps produce >95% of their luminous output in
the infrared.
Yeah, bit they all seem to be higher wattages.-a And, not as readily
available
as traditional incandescents.-a E.g., you could piece together a 4,
10, 20, 40,
60, 75, 100, 150, 200, 300, 500, etc watt "load" with the items that you >>> could find on hand in many homes (even if it meant removing lamps from
fixtures).
The halogens I've seen tend to be in floodlights -- hundreds of watts
and up.
Do a search for G4 halogen 20W 2 pin bulb.-a These run on 12 volts and
were (maybe still are?) popular for under-cabinet kitchen lighting.-a I
know 10W's were available, not sure about other sizes.-a Not the
standard screw-in Edison base, but widely available.
But, what advantage over just using OTS incandescents?-a No need to
purchase special "holders", etc.-a And, when I'm done gathering data,
I can put the bulbs back on the shelf (or, return them to their fixtures)
for later use.
When Liz designs her amplifier, does she include notes telling the user
how large a volume of space must surround it, for any given ambient?
Or, does she just specify the ambient and leave it to the user to
resolve that problem?
Don Y <blockedofcourse@foo.invalid> wrote:
When Liz designs her amplifier, does she include notes telling the user
how large a volume of space must surround it, for any given ambient?
Or, does she just specify the ambient and leave it to the user to
resolve that problem?
I am normally the only user, so the problem doesn't arise. I designed
it so that with a 30% overload, the casing temperature would rise to 50
C in a 20 C ambient. Above that temperature the operator woulld burn
their fingers on the controls, so would be inclined to take some action
to reduce the load. (It is a combined mixer and P.A. amplifier, so the operator would be constantly handling the controls.)
Even at that case temperature the output transistors would have their junctions well below the maximum-allowable temperature because they are
run in paralleled pairs, so the thermal resistance between the junctions
and the heat sink is much lower than it would be with a single device.
The drop in current gain with output current is also reduced, so the
driver stage has less work to do.
I once had to use it badly overloaded, in emergency, for an evening
dance in a large hall. Before we started I went to the rubbish area and
tore a flap off a large cardboard box. Two of us took it in turns to
sit in the 'wings' all evening, fanning air past the casing to prevent
it overheating. It survived the event but one of the dancers told me
the next day that he had seen what we were doing and had spent the whole dance with his fingers crossed for us.
In an amplifier with separate inaccessible heat sinks I would
incorporate some form of thermal shut-down or power reduction. One
excellent method is to use a thermistor as one element of a voltage
divider in the signal path; as the temperature rises, the gain starts to reduce. I precede it by a soft clipper which doesn't operate on normal
input levels. If the user tries to restore the excessive output by
winding up the signal level, the clipper starts to operate and the
output begins to sound distorted.
Under 'field' conditions, this is a reasonable compromise because the
system doesn't sudenly stop working. A bit of soft clipping can
actually make the amplifier sound as though it is delivering more power
than its undistorted rating.
On 9/29/2025 2:37 PM, Liz Tuddenham wrote:
If the user tries to restore the excessive output by
winding up the signal level, the clipper starts to operate and the
output begins to sound distorted.
Under 'field' conditions, this is a reasonable compromise because the system doesn't sudenly stop working. A bit of soft clipping can
actually make the amplifier sound as though it is delivering more power than its undistorted rating.
But what you really want is to know that it will be operated as you
intended and not unduly stressed -- even if it can protect itself.
[There is actually no space here that is truly "closed" that could
be suitable for siting kit. Most homes aren't designed with such
spaces -- other than "basements" or "attics" (non-living spaces).
It's reasonable to assume the same applies to most (residential)
floor plans. Closets tend to be located in bedrooms -- which tend to
be hard to ventilate AND "off the beaten track" in terms of utility
for such kit. Garages are great catchalls, but you have to design for
40C ambients and hope the occupant doesn't decide to pile crap
in the way of your hoped for air flow]
Don Y <blockedofcourse@foo.invalid> wrote:
On 9/29/2025 2:37 PM, Liz Tuddenham wrote:
But what you really want is to know that it will be operated as you
intended and not unduly stressed -- even if it can protect itself.
With portable P.A. work it is highly unlikely that the operator will
bother to read any installation instructions or even be aware that they exist. I've never seen a P.A. operator consult a handbook (or its
online equivalent). The equipment is put in a place that is convenient
- if it doesn't work there, it is deemed faulty.
Even with permanent installations I think the best you can hope for is
to specify a maximum ambient temperature and the total wattage to be dissipated - that covers your back when it breaks down. Unless this is
to be a major industrial installation, I doubt if anyone will bother to
read what you have written (or understand what it means in practice).
Your best bet is to assume the worst and leave lots of thermal headroom
for when even-worse-than-the-worst happens..
[There is actually no space here that is truly "closed" that could
be suitable for siting kit. Most homes aren't designed with such
spaces -- other than "basements" or "attics" (non-living spaces).
It's reasonable to assume the same applies to most (residential)
floor plans. Closets tend to be located in bedrooms -- which tend to
be hard to ventilate AND "off the beaten track" in terms of utility
for such kit. Garages are great catchalls, but you have to design for
40C ambients and hope the occupant doesn't decide to pile crap
in the way of your hoped for air flow]
It sounds as though you are thinking of dumping kilowatts of heat into a domestic environment - or are you looking at two possible different uses
for the equipment: single domestic units and bulk industrial ones?
On 9/30/2025 12:40 AM, Liz Tuddenham wrote:
Don Y <blockedofcourse@foo.invalid> wrote:
On 9/29/2025 2:37 PM, Liz Tuddenham wrote:
But what you really want is to know that it will be operated as you
intended and not unduly stressed -- even if it can protect itself.
With portable P.A. work it is highly unlikely that the operator-a will
bother to read any installation instructions or even be aware that they
exist.-a I've never seen a P.A. operator consult a handbook (or its
online equivalent).-a The equipment is put in a place that is convenient
- if it doesn't work there, it is deemed faulty.
You can remove the item if it fails to work -- lift it and
place it in the back of your truck/car/van and be done with it.
On 9/30/2025 12:40 AM, Liz Tuddenham wrote:
Don Y <blockedofcourse@foo.invalid> wrote:
On 9/29/2025 2:37 PM, Liz Tuddenham wrote:
But what you really want is to know that it will be operated as you
intended and not unduly stressed -- even if it can protect itself.
With portable P.A. work it is highly unlikely that the operator will bother to read any installation instructions or even be aware that they exist. I've never seen a P.A. operator consult a handbook (or its
online equivalent). The equipment is put in a place that is convenient
- if it doesn't work there, it is deemed faulty.
You can remove the item if it fails to work -- lift it and
place it in the back of your truck/car/van and be done with it.
When an HVAC system is installed, here, the installer is *supposed*
to do a "Manual J" calculation to verify the plant is sized (heating + >cooling) appropriately for the site.
Don Y <blockedofcourse@foo.invalid> wrote:
On 9/30/2025 12:40 AM, Liz Tuddenham wrote:
Don Y <blockedofcourse@foo.invalid> wrote:
On 9/29/2025 2:37 PM, Liz Tuddenham wrote:
But what you really want is to know that it will be operated as you
intended and not unduly stressed -- even if it can protect itself.
With portable P.A. work it is highly unlikely that the operator will
bother to read any installation instructions or even be aware that they
exist. I've never seen a P.A. operator consult a handbook (or its
online equivalent). The equipment is put in a place that is convenient
- if it doesn't work there, it is deemed faulty.
You can remove the item if it fails to work -- lift it and
place it in the back of your truck/car/van and be done with it.
...leaving the customer and hundreds of punters with no P.A.?
Always carry at least two spares and be prepared to improvise or repair
on the spot if things go wrong.
When an HVAC system is installed, here, the installer is *supposed*
to do a "Manual J" calculation to verify the plant is sized (heating +
cooling) appropriately for the site.
That appears to be unique to the HVAC industry (at least in the UK) and
to structural engineering - everything else, apart from major
engineering projects, appears to be rule of thumb.
On 27/09/2025 18:33, Don Y wrote:
I want to model a heat load.-a I'm assuming I can simulate about 90% of
the power delivered into a 100W bulb as being thrown off as heat?
This, a cheaper alternative to lots of high power resistive loads...
Electric fire bars are probably cheaper and much more robust for bigger loads. US 100v bulbs are a bit more efficient than UK 240v ones.
I have used light bulbs as a heat source for terrariums.