How to time Flash MAT Heater

[UI_Paddy]

Simple question this time, but can anyone give me a step by step of how to time the immersion switch in the photo below to heat a house at a certain time every day?

 

[Harry Bloomfield]

Simple question this time, but can anyone give me a step by step of how to time the immersion switch in the photo below to heat a house at a certain time every day?

Start by pulling all of the plastic 'fingers' around the circumference out with a finger nail, they will click. Then just push the ones in for the times you want it to be on for. There are four fingers per hour, one per 15 minutes - note you may need to rotate the dial, to adjust some of the fingers and it can only be rotated clockwise. Then set the time to the correct time, against the pointer on the left.

Below the dial is a slide switch, which allow you to override the times of switching, it will have three positions - on all the time, off all the time and normal operation based on the time clock.

 

[ericmark]

time the immersion switch in the photo below to heat a house

That does not seem to make sense, the standard immersion heater heats domestic hot water (DHW) not the house. This diagram shows how many heat sources can be used both to heat domestic hot water (DHW) and central heating (CH) so there are cases when the immersion heater can heat the house.

But in the main it is only used for DHW, my boiler is programmed to heat DHW every other day, except for weekend. There is in the main no point in switching an immersion heater on/off with timer, the thermostat does all the control required.

With a C plan central heating system it also heats the pipes between boiler and storage tank, so I use a timer, and with off peak power we want to use power when on cheap rate so again we us a timer.

But I fail to see why a timer is used an a standard immersion heater, they heat and cool so slowly seems pointless.

 

[Harry Bloomfield]

But I fail to see why a timer is used an a standard immersion heater, they heat and cool so slowly seems pointless.

Even with a stat, the bill to keep one running unnecessarily 24/7 can be quite substantial, so a lot can be saved by just having it up to temperature when you intend using it. Personally, I would be installing something a bit upmarket from a basic 24 hour time clock. I interpreted the mention of 'house', as a mistype.

 

[ericmark]

My boiler runs for approx 20 minutes even when programmer allows 1/2 hour, it is 18 kW and clearly also heating pipes, so 24 kWh per week, so at 15p per kWh using electric looking at £3.60 per week to maintain DHW at a reasonable temperature.

So maximum saving is £3.60, i.e. have cold water in the hot taps. So using a timer is unlikely to save more than £1 per week, I would not call £1 per week as

quite substantial

I would call that insignificant.

Clearly the insulation around the tank and size of tank will make a difference, when living in a caravan I had a 7 litre tank and a 1 kW immersion heater which was so well insulated I could not detect any extra heat in the cupboard under the sink where the heater was located. This house with a 40 gallon tank, and only the insulation sprayed on the tank the cupboard gets quite warm, I want this as it airs my cloths.

When my dad had a combi boiler fitted, he had a radiator to replace the water tank so he could continue using the cupboard as an airing cupboard. Not having the tumble dryer giving bone dry cloths can have a "quite substantial" saving.

 

[Harry Bloomfield]

My boiler runs for approx 20 minutes even when programmer allows 1/2 hour, it is 18 kW and clearly also heating pipes, so 24 kWh per week, so at 15p per kWh using electric looking at £3.60 per week to maintain DHW at a reasonable temperature.

You checked energy prices recently?

 

[ericmark]

You checked energy prices recently?

Even if you double it, not really quite substantial.

 

[Harry Bloomfield]

Even if you double it, not really quite substantial.

Surely that depends on how much money the OP can afford to waste? You, like me sound as if you are comfortably off. Not everyone is in that comfortable financial position. Whilst I am comfortably off, I do hate to see wastefulness and have always tried to minimise my impact.

 

[ericmark]

I would agree, I am not short of the odd pound, however if you look at the timer shown the on/off times are about the same as a thermostat would switch it on/off.

It takes 20 minutes to re-heat my 40 gallon tank with 18 kW, so 6 times that time with 3 kW, so around 2 hours every 2 days, tank is never cold, so around one hour per day.

The Willis system

can use time, it heats from the top of the tank down, so does not matter if on for 15 minutes or 2 hours you get hot water, and using a timer means either just enough to wash hands, or enough to have a bath, however the rest of UK does not use the Willis system, and if the immersion is only one for 15 minutes you only get luke warm water.

So whole tank needs reheating, and the time it takes will vary on how much water used and how cold the replacement water is, so we need the thermostat to control the water temperature, so the time needs to be long enough to fully re-heat water, so around 2 hours, and the thermostat does have quite a difference between on and off, so if left on all the time, it would run about the same time as using a time clock.

For top entry immersion heaters the duel element is the answer

it only heat top bit normally and all only when second element used, which is only used when one wants a bath, way to save money is tank jackets, and lagging, not timers. Unless using off peak.

 

[UI_Paddy]

Start by pulling all of the plastic 'fingers' around the circumference out with a finger nail, they will click. Then just push the ones in for the times you want it to be on for. There are four fingers per hour, one per 15 minutes - note you may need to rotate the dial, to adjust some of the fingers and it can only be rotated clockwise. Then set the time to the correct time, against the pointer on the left.

Below the dial is a slide switch, which allow you to override the times of switching, it will have three positions - on all the time, off all the time and normal operation based on the time clock.

Thanks, set it to heat from 11am to 1pm every day.