Timing a water heater already on economy 10

[djchapple]

I have a water storage tank heated by economy 10electricity which gives 5 hours of heating in the night and two separate periods totalling 5 hours in the day and evening.

I wish to restrict the heating period to a few hours in the night period. This is because (i) the heater now comes on when we are often just going to bed and makes quite a bit of noise and (ii) I believe (though I am not sure) that the off peak use is dearer during the day.

The problem is that there will be no power to the heater and any associated switch for 14 hours a day and I believe that the battery in battery backup switch will not last long with such long and regular breaks.

I am considering using a switch with the clock powered from by normal 24 hours mains supply, one which can then be used to switch the economy 10 supply to the heater.

Are suitable switches readily available and, if so, from where?

 

[ericmark]

There are special switches for the job quick look and I found this advert there are many more try this link for more.

However economy 10 is a tariff not a system and there are different ways to use the tariff so you do need to work out how yours is wired before selecting a product.

 

[JohnW2]

The problem is that there will be no power to the heater and any associated switch for 14 hours a day and I believe that the battery in battery backup switch will not last long with such long and regular breaks. ... I am considering using a switch with the clock powered from by normal 24 hours mains supply, one which can then be used to switch the economy 10 supply to the heater. ... Are suitable switches readily available and, if so, from where?

ISTR that this question was discussed here fairly recently. As you say, the most obvious solution to achieve what you apparently want would be to power a timeswitch from 'normal 24h electricity' and to use the output of the timeswitch to operate a relay or contactor which controls the water heater. However, I do wonder a little about the wisdom and/or necessity of what you are wanting to achieve.

Kind Regards, John

 

[lxboy]

Hi, yes you can purchase a timed hold off or on relay module from RS.

regards,

lxboy

 

[phatboy]

If its noisy, it sounds like there might be some air trapped in the system or something?

If the heater is well insulated, it won't heat for long during the day periods, as it will just top up the heat thats been lost, or hot water used.

I wonder if the cost of a switch for this job outweighs the amount of power thats being used heating the water during the day?

 

[djchapple]

There are two reasons why I want to make this mod

1. The water heater is of the type where the electrical element heats the water in the tank which then heats the water passing through a coil inside the tank and it's much more complex than the standard immersion heater system. (Pulsacoil Response PCR145) It makes clonking noises when the heater is on and I find this distracting when trying to get to sleep.

2. I do not understand the tariff and I am not sure whether the two day time off-peak periods are more expensive than the night time period. As we have our showers in the morning most of our heating will occur during the afternoon.

 

[JohnW2]

There are two reasons why I want to make this mod ... 1. The water heater is of the type where the electrical element heats the water in the tank which then heats the water passing through a coil inside the tank and it's much more complex than the standard immersion heater system. It makes clonking noises when the heater is on and I find this distracting when trying to get to sleep.

Do you mean that the water in the tank heated by the immersion is not used at all, your actual hot water being heated by passing through a coil within it? If so, I have to say I'm not familiar with that system. In any event, I would presume that it's not meant to make significant clonking noises and, if it does,it would probably be better to get that addressed than to consider changing the times the heater is operative.

2. I do not understand the tariff and I am not sure whether the two day time off-peak periods are more expensive than the night time period. As we have our showers in the morning most of our heating will occur during the afternoon.

As has been said, you really need to find out details of your tariff (they vary), since that could have an appreciable impact on your situation. Are you also using it for storage heaters (i.e. why do you have E10?)? What 'on period' for the immersion are you hoping to achieve - are you sure it will be on for long enough to service your morning showers (and don't you require any hot water in the evenings?)?

Kind Regards, John

 

[flameport]

Pulsacoils are thermal stores. There are various types, but in all cases, they have both an on and off peak supply. Some have overcomplex controls, others do not.

They are all grossly expensive to run, generally fail rather often and always cost a fortune to repair, assuming you can find anyone foolish enough to even look at it.

Attempting to save money using an external timer most likely won't do what you expect, and could actually cost more.

 

[JohnW2]

Pulsacoils are thermal stores.

Thanks. I'm struggling to understand that concept. In what way can that sort of 'thermal store' be any 'better', or more efficient than (indeed, even as efficient as!), simply storing the heated hot water that one will subsequently use?

Kind Regards, John

 

[Aragorn84]

Thanks. I'm struggling to understand that concept. In what way can that sort of 'thermal store' be any 'better', or more efficient than (indeed, even as efficient as!), simply storing the heated hot water that one will subsequently use?

Kind Regards, John

Mains pressure hot water i guess is one advantage, without the related PRV's and other safety devices used on unvented mains cylinders.

You can also use the store as a sort of "centre point" for various heat inputs, so you could have solar thermal array, a wood burner, and the electric elements all feeding into the store, and in some installations the main central heating is run from it as well (though usually with a boiler as the heat source)

 

[JohnW2]

Mains pressure hot water i guess is one advantage, without the related PRV's and other safety devices used on unvented mains cylinders.

Yes, I suppose that's one potential advantage. Mind you, the main advantage of mains pressure hot water is a high flow rate, and I would imagine that it would have to be a pretty extensive 'coil' to heat water to the desired temperature at high flow rates. What sort of temperature does such a 'heat store' run at?

You can also use the store as a sort of "centre point" for various heat inputs, so you could have solar thermal array, a wood burner, and the electric elements all feeding into the store, and in some installations the main central heating is run from it as well (though usually with a boiler as the heat source)

Again, that makes sense. However, particularly if it's not being used for central heating, I would imagine that one could use multiple heat sources to heat a tank/cylinder full of hot water that one was actually going to use, couldn't one? Many of us (including myself) have at least two ways of heating the water in our HW cylinder, and that could theoretically be extended to more than two. Is it that such a store runs at a very high temperature (with attendant greater problems of heat loss!), far higher than one wants for DHW?

Kind Regards, John

 

[Aragorn84]

I dont think you can use a wood burner (or other similar "uncontrolled" heat sources) with a unvented cylinder, so if mains pressure hot water was a requirement then the thermal store wins out.

Mains pressure hot isnt neccesarily about flow rate. Using a thermostatic mixer with mains cold and gravity hot water often doesnt work very well for instance.

 

[JohnW2]

I dont think you can use a wood burner (or other similar "uncontrolled" heat sources) with a unvented cylinder, so if mains pressure hot water was a requirement then the thermal store wins out.

I thought we were talking about a vented cylinder - is that not the case?

Mains pressure hot isnt neccesarily about flow rate. Using a thermostatic mixer with mains cold and gravity hot water often doesnt work very well for instance.

Very true - but, again, I thought (possibly incorrectly) that we were talking about a vented cylinder,in which case there would presumably also be a cold water tank to provide gravity-fed cold.

It sounds as if I may have misunderstood you.

Kind Regards, John

 

[flameport]

You can also use the store as a sort of "centre point" for various heat inputs, so you could have solar thermal array, a wood burner, and the electric elements all feeding into the store, and in some installations the main central heating is run from it as well (though usually with a boiler as the heat source)

That is true for normal thermal stores.

However Pulsacoils are totally electric. There is NO facility for heating the water any other way.

The simpler ones are just a cylinder of hot water with a coil inside, through which the mains cold water is passed to heat it up. They have an external blending valve, and the instructions usually require that flow restrictors are fitted on every outlet, in a vain attempt to conceal the astoundingly poor performance of the thing.

Other satanic designs in the range have an external plate heat exchanger which then requires a pump, multiple temperature sensors and a control panel which is located at the top of the cabinet, ensuring it gets as hot as possible to maximise the chances of failure. You can connect a couple of tiny radiators to some of them, which of course requires another pump and a hoard of other equipment.
Some even have the electric heating element in a can on the outside of the cylinder. This of course requires yet another pump and more temperature sensors.

 

[djchapple]

There are two reasons why I want to make this mod ... 1. The water heater is of the type where the electrical element heats the water in the tank which then heats the water passing through a coil inside the tank and it's much more complex than the standard immersion heater system. It makes clonking noises when the heater is on and I find this distracting when trying to get to sleep.

Do you mean that the water in the tank heated by the immersion is not used at all, your actual hot water being heated by passing through a coil within it? If so, I have to say I'm not familiar with that system. In any event, I would presume that it's not meant to make significant clonking noises and, if it does,it would probably be better to get that addressed than to consider changing the times the heater is operative.

2. I do not understand the tariff and I am not sure whether the two day time off-peak periods are more expensive than the night time period. As we have our showers in the morning most of our heating will occur during the afternoon.

As has been said, you really need to find out details of your tariff (they vary), since that could have an appreciable impact on your situation. Are you also using it for storage heaters (i.e. why do you have E10?)? What 'on period' for the immersion are you hoping to achieve - are you sure it will be on for long enough to service your morning showers (and don't you require any hot water in the evenings?)?

Kind Regards, John

The water heater system comprises a cylindrical water tank, looking like a normal water tank fitted with two immersion heaters. The top one is used for topping up the hot water any time of the day using electricity at the peak tariff. The bottom one uses the off-peak tariff.

The tank is fed by water from a small tank sitting on top o the cylindrical tank. This small top-up tank has to be manually topped up from the mains when it reaches a certain level.

The hot water supplied to the basins, showers etc is heated as it passes through an internal coil inside the cylindrical tank.

This water, I presume, the electrical heating elements do noy get clogged up.