Immersion heater and Hot Water Cylinder pipes (Ed.)

[stender]

I have a honeywell timer in the cupboard with my emersion heater and its set to come on about 4am til about 7am so we have hot water for morning showers. Is it normal that the pipes out of the emersion are still hot mid day? There is no light on the honeywell so shouldn't be on and the electric switch to the emersion is off so it's not on that way either. I just want to make sure its not on all the time for some reason.

 

[Johntheo5]

The DHW outlet pipe will stay very hot if you are drawing off even a litre or so of hot water every hour or so, you speak of pipeS being hot, some systems have a pump that circulates the DHW around the system and back to the cylinder.
You may also have a gas or oil heating coil in the cylinder and a hot cylinder can sometimes cause circulation by convection causing the cylinder to lose heat.

 

[stender]

We are done with showers by 8am and then not really used. is there any way it could be on all the time? if i where to check say 5pm would you still expect it to be hot? there is a pipe out of the top of the cylinder and another out the middle into a shower pump. both are hot. I cant upload photos as too big on phone.

 

[Harry Bloomfield]

We are done with showers by 8am and then not really used. is there any way it could be on all the time? if i where to check say 5pm would you still expect it to be hot? there is a pipe out of the top of the cylinder and another out the middle into a shower pump. both are hot. I cant upload photos as too big on phone.

The simple way, is to check your electric meter. Either watch the disc rotating, if an old style meter, or note the readings, if a modern digital one.

 

[JohnD]

The pipe going up from the top of the Cylinder will be hot from convection of hot water rising. This will not continue where the pipe turns down again on its way to your taps.

If a supply pipe to a tap is hot, water is running through the tap or escaping through a leak.

Some photos of your pipe layout will help.

You can probably edit them to reduce file size, in photo editor or something.

 

[stender]

I cant check on meter when other things will be drawing.
The thermostat on the top of the cylinder - the switch connecting to that is always off. I only had to switch that on when we had a boiler issue. So is it the small box on the cylinder that switches on and off via the honeywell?

 

[Harry Bloomfield]

I cant check on meter when other things will be drawing.

The difference between a 3kw water heater, and a fridge/freezer running is massive on a meter.

 

[JohnD]

In your consumer unit, turn off the Immersion Heater breaker and watch the meter to see if anything changes.

At this time of year, the 3kW immersion heater will be drawing more than anything except your oven or tumbledrier, and more than ten times as much as a fridge, or 500 times as much as a light bulb.

Does your meter have a flashing red light?

 

[stender]

My meter just flashes numbers, it not the old spinning wheel. I just get a 1 or 2 for rate. Also have solar so dont know if that makes a difference.

 

[Murdochcat]

Which type of solar heating for your water do you have?

 

[stender]

Which type of solar heating for your water do you have?

its not for my water. It came with the house. I have about 10 panels which i get a small quarterly fit payment for. I cant see me getting any electric reduction and prices increased when i moved in.

 

[Johntheo5]

To rule out the boiler, take a photo or write down the gas meter reading when you think the cylinder should not be reheating and again before any reheating is scheduled/due to take place.

 

[Murdochcat]

its not for my water. It came with the house. I have about 10 panels which i get a small quarterly fit payment for. I cant see me getting any electric reduction and prices increased when i moved in.

There are diverters on the market that allow you to send surplus electricity to your immersion rather than back to the grid.

 

[ericmark]

There are diverters on the market that allow you to send surplus electricity to your immersion rather than back to the grid.

Yes but as to saving not so sure, mine shows less than 5kWh/week is used, OK only heats top of tank, but I get paid 15p/kWh to export solar, and pay 8.5p/kWh to import 00:30 to 05:30 so cheaper for me not to use solar.

But now we are looking at the tariff, I looked at Octopus Flux, and the rate 4 pm to 7 pm is the problem, in Winter I would likely need to manually boost my battery to ensure no import at that time on some days, and my idea is to set up and forget, so I went for the Octopus Go, after having a year with British Gas and unsuccessful getting paid for Export I am not interested in shopping around.

However in my efforts to get solar sorted, I realised it is not as simple as saying XYZ is the best. Battery size matters, and can make a huge difference to which tariff works out best.

I cant check on meter when other things will be drawing.

This is where my iboost+ gives me the edge, I do know, it tells me. Never been more than 5 kWh for the week, you likely use a little more as we don't use the DHW for showers, I have seen it show under 3 kWh for week, so at 15p/kWh (the export I am not getting as heating immersion heater) we are looking at 75p per week, at £300 for an iboost+ will you get the money back in your life time?

Heat raises, so the pipe at top of cistern will get hot, which is why we lag them. But also all the pipes between the boiler and the cistern will also get hot when the boiler is running, and the boiler itself, so more energy is used heating DHW with gas or oil to using electric, since my boiler does not modulate, and I know to get warm water in summer it needs to run 4 times a week for 20 minutes at a time, 80 minutes x 20 kW / 60 to get it into hours = 26 kWh, so over 5 times the energy used to heat with electric. Also means house being heated with the pipes boiler to cistern which in summer I don't want. Clearly some heat also out of flue, so since electric costs me 8.5p/kWh oil would need to cost 1.7p/kWh or less, so for me electric DHW heating is cheaper.

Lagging pipes boiler to cistern will not really help, in winter you want the heat into the house, in summer the time between boiler burns means pipes will have cooled down completely before next burn, even with lagging.

My tank near same as yours, will keep water hot for 2 days, so adding lagging to the cistern is well worth while, unless using the heat to dry clothes, or as we put it airing them in the airing cupboard.

A simple timer may help

it depends on if you have off-peak, and how much you get paid for export, since the tank will stay hot for 2 days or more, heating it only in the morning as that is when you have a shower is pointless, the timer only helps ensuring you heat when electric is cheap. I would be better off with a simple timer to my iboost+ the iboost+ does have 8 timed heating times which can be used 4 summer and 4 winter, and that 2 at week end, and 2 in the week, so mine does turn on 1 am to 5 am, but it still uses solar which means 15p/kWh lost instead of paying 8.5p/kWh so I loose money by heating with solar. But likely not enough to be worth swapping to a simple timer.