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Shower power control

I am looking for a way to control the power (the water temperature if
you prefer so) of my shower.

Specifications:
Tension: 220V
Resistance: 11 ohms
Nominal current: 20A

I found solutions using Google but they are some problems on them:
- generates a lot of harmonics
- wastes much power on control circuit

I would like a circuit to analyse/think not a ready product.
I appreciate any idea.

$ flames >> /dev/null

Thanks you,
Pedro Henrique
 
H

Homer J Simpson

Jan 1, 1970
0
I am looking for a way to control the power (the water temperature if
you prefer so) of my shower.

Europe? Why not increase the water flow?


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P

Phil Allison

Jan 1, 1970
0
** Groper Folly Alert !

I am looking for a way to control the power (the water temperature if
you prefer so) of my shower.

Specifications:
Tension: 220V
Resistance: 11 ohms
Nominal current: 20A

I found solutions using Google but they are some problems on them:
- generates a lot of harmonics


** Phase control always does that.

Why should YOU care ?

- wastes much power on control circuit


** A triac will drop maybe 1.5 to 2 volts at 20 amps - not much compared
to a 4.4 kW load.

Use a hefty AC power relay if you cannot tolerate a bit of heat.

I would like a circuit to analyse/think not a ready product.
I appreciate any idea.


** Getting a clue first would be a good start.




...... Phil
 
J

John Popelish

Jan 1, 1970
0
I am looking for a way to control the power (the water temperature if
you prefer so) of my shower.

Specifications:
Tension: 220V
Resistance: 11 ohms
Nominal current: 20A

I found solutions using Google but they are some problems on them:
- generates a lot of harmonics
- wastes much power on control circuit

I would like a circuit to analyse/think not a ready product.
I appreciate any idea.

The general choices are phase control or integral cycle
control. Phase control is finer grained, smoothly variable
and faster responding, but is electrically noisy, ans you
mention. Integral cycle pulse control is a lot quieter as
far as harmonics goes, but creates sub harmonics that can
cause annoying flicker of lights and picture distortions on
televisions. I guess a fast motorized variable transformer
would be the quietest and smoothest as far as the AC line is
concerned.

No particular need to worry about waste heat, since that is
what you are producing. Just heat sink the control elements
to the cold water upstream of the heater.

A PID feedback controller with feed forward (power
predicting feature) capability on either water flow rate or
unheated water temperature or both, would help speed up the
control. Stabilizing such a controller is also easier if
the heater mass is lower (less heat storage inside the
heating element) and the water volume being heated is better
mixed (some backward mixing of heated and unheated water)
and larger.
 
** Groper Folly Alert !

Why folly, hehehe?
** Phase control always does that.

Why should YOU care ?

Why not?
Sometimes, the circuits in a house are not installed/separated
adequately. So it could be a serious problem to others equipments
connected in the shower circuit. Don't you think?
** A triac will drop maybe 1.5 to 2 volts at 20 amps - not much compared
to a 4.4 kW load.

The problem will be the cost and the harmonics. Anyway, It seems to be
the best solution really.

Use a hefty AC power relay if you cannot tolerate a bit of heat.

What relay type do you refer?
** Getting a clue first would be a good start.

..... Phil


Thank you,
PH
 
The general choices are phase control or integral cycle
control. Phase control is finer grained, smoothly variable
and faster responding, but is electrically noisy, ans you
mention. Integral cycle pulse control is a lot quieter as
far as harmonics goes, but creates sub harmonics that can
cause annoying flicker of lights and picture distortions on
televisions. I guess a fast motorized variable transformer
would be the quietest and smoothest as far as the AC line is
concerned.

Can you explain better about integral cycle pulse control please?
Maybe, some book.
:) I will study officially power electronics this year.

The motorized variable transformer will be very much expensive to me.
No particular need to worry about waste heat, since that is
what you are producing. Just heat sink the control elements
to the cold water upstream of the heater.

The water could damage other circuit components. I would like to put
the control circuit in a plastic box with a little opening to a
possible potenciometer.
A PID feedback controller with feed forward (power
predicting feature) capability on either water flow rate or
unheated water temperature or both, would help speed up the
control. Stabilizing such a controller is also easier if
the heater mass is lower (less heat storage inside the
heating element) and the water volume being heated is better
mixed (some backward mixing of heated and unheated water)
and larger.

You have reason.
Anyway, the control speed isn't so important preoccupation to me. I
just would like to adapt the temperature control to common showers
(when there isn't a mixing between heated and unheated water) in the
best way possible and, of course, viable economically.

Thank you,
PH
 
H

Homer J Simpson

Jan 1, 1970
0
Brazil. I would like to control the power/temperature, dear Homer.

You can't make the water hotter except by reducing the water flow. To make
it cooler, you need a 20 amp dimmer control which is safe to use on 220 V.
You will have to adjust it before using the shower - it would be very
dangerous to use one while in the shower.


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G

Gareth

Jan 1, 1970
0
I am looking for a way to control the power (the water temperature if
you prefer so) of my shower.

Specifications:
Tension: 220V
Resistance: 11 ohms
Nominal current: 20A

I found solutions using Google but they are some problems on them:
- generates a lot of harmonics
- wastes much power on control circuit

I would like a circuit to analyse/think not a ready product.
I appreciate any idea.
First, think very carefully about safety before actually doing anything.
Water and electricity can be a dangerous mix, but since you just want
to think about it..

A simple solution would be to have a number of different heater elements
in the shower. If these elements had a suitable power ratings you could
get a large number of different levels with only a few elements and no
additional electrical noise or wasted power. e.g. if you had four
elements you could get 15 power levels by selecting different
combinations (2^4 - 1)

Perhaps not as elegant as a solid state PWM system but I think it would
work.

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J

John Popelish

Jan 1, 1970
0
Can you explain better about integral cycle pulse control please?
Maybe, some book.
:) I will study officially power electronics this year.
(snip)

Phase control involves turning on a latching device, like an
SCR or TRIAC at the same fraction of each half cycle, and
the device remains on till the next current zero crossing.
Power is varied by changing the timing of where in each half
cycle that power is switched on.

Integral cycle control involves turning on the switching
device just after a voltage zero crossing, so that an entire
half cycle of line voltage is passed, so that there are no
fast voltage rises in the waveform. Power is controlled by
changing the number of complete cycles, in some time
interval, that are passed to the load and the remainder that
are blocked. Usually, the cycles that are passed are all
together in a group, and the ones blocked are also together
in a group, but the power control is smoother if the
groupings are eliminated and the ratio of passed and blocked
cycles are mixed as well as possible. With a microprocessor
that has a line cycle input, to synchronize the timing to
the line zero crossings, this process can be done almost
entirely in software, as can the feedback PIC control
function, whose output decides the fraction of power cycles
passed.

While it is not so important that each positive half cycle
delivered is immediately followed by the negative half
cycle, it is important that it is impossible for the
controller to supply only positive or only negative half
cycles, because this would put a DC component back into the
line power source, and that isn't good for the transformers
in the distribution system.

See:
http://www.athenacontrols.com/pages/fund.html
http://www.ccipower.com/support/control_modes.php
http://www.patentstorm.us/patents/6849834-description.html

There are also special purpose solid state relays that
accept a control voltage and generate the variable duty
cycle burst of line cycles in proportion to the control voltage.
http://www.crydom.com//userResources/productFamilies/50/crydom_pcv.pdf
 
H

Homer J Simpson

Jan 1, 1970
0
A simple solution would be to have a number of different heater elements
in the shower. If these elements had a suitable power ratings you could
get a large number of different levels with only a few elements and no
additional electrical noise or wasted power. e.g. if you had four
elements you could get 15 power levels by selecting different
combinations (2^4 - 1)

The UK ones work like that. You have a high / low switch, and further
adjustment is done by adjusting the flow rate.


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The UK ones work like that. You have a high / low switch, and further
adjustment is done by adjusting the flow rate.


There is a similar switch here also but the switch isn't very useful
because:

- that is above the shower, so it is height
- I would like to have a better temperature control. The climate in my
region is very volatile.

thanks you,
PH
 
H

Homer J Simpson

Jan 1, 1970
0
There is a similar switch here also but the switch isn't very useful
because:

- that is above the shower, so it is height
- I would like to have a better temperature control. The climate in my
region is very volatile.

Does this unit have a pump?


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J

jasen

Jan 1, 1970
0
I am looking for a way to control the power (the water temperature if
you prefer so) of my shower.

Specifications:
Tension: 220V
Resistance: 11 ohms
Nominal current: 20A

I found solutions using Google but they are some problems on them:
- generates a lot of harmonics
filter.

- wastes much power on control circuit

bolt the heatsink to the water pipe (with apropriate insulation)
I would like a circuit to analyse/think not a ready product.
I appreciate any idea.

look at some datasheets.
 
H

Homer J Simpson

Jan 1, 1970
0
No, it doesn't have.

Are you european, no? What is used there, handshower or headshower?

No, Canadian but I travelled in the UK for work. Most of theirs have pumps.
In N America, we have high pressure hot water gas fired so plenty of hot
shower water.

You could build a triac type dimmer but you'll need a big triac - 20 or 25
amperes 400 volts.

I'd use a neon lamp to fire it - you don't need to go down to a very low
setting.

http://www.aaroncake.net/circuits/dimmer.htm is a circuit using a neon for
117 VAC. You will need to add resistance to the circuit for 220 volts.

http://www.epanorama.net/documents/lights/lightdimmer.html#1kw230v is a
circuit for 230 VAC. It uses a diac instead of a neon.

Assume 2 VAC across the triac (it'll be a little less than that). At 20 amps
that's 40 W which is HOT. You'll need to be able to get rid of that heat.

Search for (neon lamp triac dimmer 220 volt) for more info.
 
H

Homer J Simpson

Jan 1, 1970
0
The plumbing trade figured out an easy way to do this long ago:

Works in the USA. Not in many other countries.


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