Boiler information request

oridiusmorphius

Hi,

I hope this is the right place.

I have a standard boiler, that heats on economy 7, probably 4-5 hrs a night when our supplier has the economy 7 times set, the boiler capacity is 210L.

Our showers are normally in the morning 6.30am when economy 7 is still on, over Christmas we have done a lot of nights so have not used the shower until 2pm.

This is when we found a problem, we are getting 1.5 showers, the first person no problem, me, i have been the one that runs out of hot water towards the end, is this normal for a 210L boiler? Surely we should be getting more than this?

Karl

matelodave

I'm assuming that by a boiler, you mean immersion heater in a hot water tank.

It will take around 10 kwh to heat the tank from 15 degrees to 60 degrees so if you run it right out it will take over three hours to reheat it - even longer at this time of year when the incoming water is much colder. Have you checked the timer settings to find out when the heater is switched on - is there a separate timer or is it couple to the E7 meter?

E7 off-peak times are usually around midnight to 7am however sometimes the timers can drift out, so you need to actually check at what time you E7 switches and at what time the immersion switches.

Secondly, if you've got a 210l tank and are managing to empty all the hot water out of it then you must be using excessive amounts of hot water.

Perhaps you should try to spend less time in the shower and fit a flow restrictor to reduce the amount of water it discharges.

A shower flowing at 15lpm will use 150litres of water in ten minutes, so by reducing the flow to say 10lpm and your shower time to five minutes you could save 100 litres per shower - thus making your hot water go a lot further and saving you money as well.

oridiusmorphius

You are probably right it is an immersion heater, it runs straight off the E7 supplied by my energy supplier, there is not timer. It usually goes on for 2 hours late at night, then about 4 more hours in the morning.

The flow i shall check, but it has not really changed, in fact we use it less as there used to be another adult in the house.

I will look through it but we only really managed 1.5 normal showers on three days last week before we run out, no washing up or anything else and online stats implies this size immersion heater should managed 5 adults.

I might just check about getting an expert in to check things over.

Thanks for the reply.

Karl

matelodave

If it takes near enough four hours to heat a tank to 60 degrees from 15 degrees, then only having it on for two hours will only put in half the heat required, so you'll only heat it to about 47.5 degrees. As the incoming water is down to between 5 and 10 degrees at this time of the year the tank probably wont even get that hot.

If you then run off most of that hot water then your four hours in the morning is only just going to manage to heat the whole tank up to it's normal temperature.

Bear in mind that when the tank is at 60 degrees you'll be mixing cold water in with it to make it comfortable so it will go further - when it's at 45 degrees or so you'll just use hot with no cold mixed in so it wont go as far.

You need to try to use less. What sort of insulation ahs the tank got?

Dont forget that everytime you run off the cold water to get the hot water flowing, you'll leave the same amount of hot sitting in the pipework to get cold so dont rinse your hands or other stuff under the hot tap. Use cold where possible and dont let water, hot or cold run down the sink. Put a plug in or use a bowl.

It's easy to check how fast the shower runs - time how long it takes to fill a 10 litre bucket - ideally it should take more than a minute.

System

I suspect that the answer lies in the heating on times and usage. The immersion heater will only heat when there is a requirement to do so. For example, I re-heat my cylinder in the period 05.30 to 9.30 am. My cylinder is usually up to temperature within 45 minutes. It will then re-heat if someone has a shower in the period up to 9.30am. If the the E7 period is midnight to 7 am, and someone is having a shower at 6.30am, then the cylinder will re-heat for 30 minutes. If showers are not being taken until 2pm, then there is no re-heat time unless peak boost is used.

It is also worth remembering that the temperature of the infill cold water is very cold at this time of the year which further reduces the heat/temperature of the mixed water at the bottom of the cylinder.

macman

If this is a dual element immersion, then possibly the longer element has failed and only the top part of the tank is heating up? Impossible to know without the OP giving more details. E7 is a straight 7 hours at cheap rate, typically commencing at midnight or 1am: it is not split into a night and morning cheap rate.

matelodave

usually a dual element unit would have the longer one on off-peak and the upper one for boost from the peak rate and would be separately switched.

I suspect that they are just using more hot water than the cylinder can recover in the alloted time