Shower power control

Europe? Why not increase the water flow?

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Brazil. I would like to control the power/temperature, dear Homer.

PH

** Groper Folly Alert !

** Phase control always does that.

Why should YOU care ?

** 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.

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

..... Phil

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.

Why folly, hehehe?

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?

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

What relay type do you refer?

Thank you, PH

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.

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.

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

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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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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To reply to me directly:

Replace privacy.net with: totalise DOT co DOT uk and replace me with
gareth.harris

snipped-for-privacy@gmail.com wrote: (snip)

(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:

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.

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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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

Does this unit have a pump?

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filter.

bolt the heatsink to the water pipe (with apropriate insulation)

look at some datasheets.

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Bye.
   Jasen

The plumbing trade figured out an easy way to do this long ago: http://66.102.9.104/search?q=cache:mSP9VGAX0fkJ:

No, it doesn't have.

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

PH

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.

is a circuit using a neon for

117 VAC. You will need to add resistance to the circuit for 220 volts.

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.

Works in the USA. Not in many other countries.

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