Time lag then switch on.

[Yvonne]

Hi,

We have a problem in a hostel where some of the 'guests' stay far too long in the electric power shower so that the hot water gets drained too quickly and the late-comers have to shower cold. This causes a lot of grief.

So, what I'm looking for some sort of timer that can be wired into the electrical supply to the power shower pump. This would start the timer and after a pre-set time lag, the timer will switch on another circuit to activate say a buzzer (or whatever). The idea is that the buzzer will let the guest ( and the others) know that the recommended time has elapsed.

Ideally, the time lag before switching on the circuit (buzzer) should be adjustable but be in the range of 4 to say 10 minutes.

Now, there's a challenge for you guys. Any ideas?

Yvonne

[Piers Finlayson]

You could fit one of those vacuum light switches that switch themselves off after a few minutes - and fit it outside the shower room. Then your 'guests' have a choice of showering in the dark or finishing up.

[Will Dean]

So-called 'Smart Relays' (e.g. Telemecanique Zelio, Mitsubishi Alpha, loads of others) are quite good for this sort of thing. About 50 quid, though you'll need to put it in a box, and you'll need to buy some kind of starter-pack for the first one so that you have the programming bits.

See RS or Farnell for proper list-price offerings, though they come up on ebay sometimes.

Dunno if that's anything like the kind of budget you were thinking of.

Will

[Owain]

On-delay timer relay from RS. Someone will be along with a part number "real soon now". In fact, you could have one that after x minutes sounds a buzzer for 30s as a warning for people to rinse off shampoo, then cuts off the pump until reset by a button outside the shower room.

However, if you turn down the speed of the pump, and use a low-water shower head, you can probably resolve the problem in a way that will appear less miserly to the inmates. Installing low water showers can help you get points towards a Green Tourism award too. :-)

Owain

[Guy King]

The message from "Yvonne" contains these words:

I'd use another thermostat on the side of the hot water tank. Use it to run a "Plenty of hot water" light.

[John White]

You could use a flow switch (RS 257-076) in the cold pump->shower pipe to detect when the pump started. The output from this could trigger a

555 timer delay circuit and a buzzer.

This would have two advantages:

- You would not need to connect anything to the pump internals - The whole thing could be run from batteries rather than the mains.

If your guests ignore the buzzer, you could also arrange to shut off the shower's hot water supply when the buzzer sounds. :-)

John

[David Hansen]

On 17 Sep 2006 05:03:49 -0700 someone who may be "Yvonne" wrote this:-

Then the hot water system is not correctly designed for the use it is getting. Has the use changed, or was it not designed properly in the first place? Cure the problem at source, the best cure.

Presumably the storage capacity is not adequate. This could be increased, with due consideration to recovery time. An alternative would be instant generation of hot water for the shower, either from an instant heater or a thermal store. It all depends on the usage pattern.

[Dave Liquorice]

A PLC (Programmable Logic Controller) is a bit OTT for this. Most PLCs can be programmed from their buttons but it's a lot easier on a PC with =

an emulator to make sure you have your logic right. B-)

A simple time delay relay would do it, around =A320 to =A330 and enclosu= re.

[Dave Liquorice]

Well a relay to sound a warning and/or do things with pump/water supplies is treating the symptoms but not the root cause, ie lack of hot water. Strikes me that the boiler is undersized for the load and a single shower shouldn't be that great a load for a decent boiler with stored hot water. Is the cylinder a fast recovery one or standard? How big is the boiler?

[SantaUK]

Potential accident waiting to happen, then a hefty claim. Careful with this one!

[ARWadsworth]

Rename the hostel with a suitable name (Auschwitz-Birkenau, Treblinka, Butlins etc) post guards at the door and time the "guests" as they take a shower. Impose strict punishments for non complient guests

Or buy a bigger HW tank

Adam

[Yvonne]

Super responses from you all and it will take me a while to evaluate them all but I do like this last one :-) Thanks Yvonne

[Douglas de Lacey]

Lateral thinking is your friend. (1) turn down the thermostat so that showering is not such a pleasurable experience; and/or (2) increase the stored volume of the hot water (and/or (3) make the unit cold-shower only)

Douglas de Lacey

[David Hansen]

On Sun, 17 Sep 2006 15:17:06 +0100 (BST) someone who may be "Dave Liquorice" wrote this:-

Power showers can gobble up as much hot water as a bath, much of the capacity of a "normal" domestic sized hot water cylinder. They also suffer from the problem that the occupant doesn't spend 15 minutes or so not drawing off water before the next occupant, giving time to recover the cylinder temperature.

I suspect that someone has installed domestic type equipment, without understanding or caring about the duty cycle. Hostels are not the same as houses, but this tends to only become apparent to those that don't know what they are doing when something like this happens.

If the OP can give some indication of the duty cycle then someone might feel like giving a little more help. However, this is the sort of area where engaging the services of someone well versed in building services on more than a domestic scale is advisable.

The best choice between the various forms of storage and instant hot water generation depends on the use to which the installation is to be put. How many showers, used how often, for how long, the consequences of hot water not being available and so on. "It depends" is not a useful answer.

[David Hansen]

On Sun, 17 Sep 2006 15:45:14 GMT someone who may be "ARWadsworth" wrote this:-

Three different establishments. Birkenau involved slave-labour or murder. Treblinka was simply a place of mass murder, very, very few survived. Butlins camps were very many bad things, but I don't think it funny to mention them in the same sentence as the other two.

[Owain]

You could probably charge a supplement for the strict punishments :-)

Owain