Stupid questions about water heating
Discussion
We have a Potterton Profile 50E boiler. It's set to 'gravity-fed'. Next to it is a Grundfos pump.
Upstairs in the airing cupboard is an electric immersion heater. It looks ancient, I guess from the 1960s. It's a Santon 3kW model.
The problem we sometimes have is hot water running out after several baths. It would seem, given the gas boiler is 12-15 kW output, that the immersion heater is relatively useless except if the boiler is not working.
Given so, is there any way to increase hot water, I checked the thermostat on the boiler is set to 1 (it goes up to 7 or thereabouts); would this determine the water temperature - obviously if the tank stores say 200 litres, then if the water is at 60C rather than 45C or whatever it is now then it will last longer?
Or is there something else I should be looking at to determine the hot water temperature?
Upstairs in the airing cupboard is an electric immersion heater. It looks ancient, I guess from the 1960s. It's a Santon 3kW model.
The problem we sometimes have is hot water running out after several baths. It would seem, given the gas boiler is 12-15 kW output, that the immersion heater is relatively useless except if the boiler is not working.
Given so, is there any way to increase hot water, I checked the thermostat on the boiler is set to 1 (it goes up to 7 or thereabouts); would this determine the water temperature - obviously if the tank stores say 200 litres, then if the water is at 60C rather than 45C or whatever it is now then it will last longer?
Or is there something else I should be looking at to determine the hot water temperature?
DHW should be over 60DegC as a minimum
60°C is the recommended minimum, as at that temperature Legionella bacteria is killed within 32 minutes. At 66°C, Legionella bacteria dies instantly.
Hot water tanks are sized based on number of occupants and other conditions, there is a handy online tool to check your sizing
http://www.copperindustries.co.uk/cylinder-calcula...
60°C is the recommended minimum, as at that temperature Legionella bacteria is killed within 32 minutes. At 66°C, Legionella bacteria dies instantly.
Hot water tanks are sized based on number of occupants and other conditions, there is a handy online tool to check your sizing
http://www.copperindustries.co.uk/cylinder-calcula...
First of all, as above, if the temperature on the house water isn't that high then turn it up a bit.
Secondly if you're going to have a few baths in rapid succession then why not put on both the boiler and the immersion heater in parallel. The heating coil in your tank won't take the full 15kw output of the boiler, probably takes about 5kw say. Together with the immersion heater it will reheat the hot water fast enough, unless you have multiple bathrooms all taking baths.
Our boiler gets sufficient hot water for a bath from clock cold in about 25 minutes, put the immersion on as well and it's more than quick enough.
Secondly if you're going to have a few baths in rapid succession then why not put on both the boiler and the immersion heater in parallel. The heating coil in your tank won't take the full 15kw output of the boiler, probably takes about 5kw say. Together with the immersion heater it will reheat the hot water fast enough, unless you have multiple bathrooms all taking baths.
Our boiler gets sufficient hot water for a bath from clock cold in about 25 minutes, put the immersion on as well and it's more than quick enough.
thelawnet1 said:
So the thermostat knob on the boiler controls and is the only thing controlling the water temperature?
Usually, yes. I don't think you can adjust the temp on an electrically heated cylinder.What you are running into here is just a capacity issue. The cyl heater is 3kW. That's 1.5 kettles, in the real world. You know how long it takes a kettle full of water to get to a suitable temp for a bath, now work out how many kettles there are in your cylinder and work it out. If it's 100 kettles then it will take 100 times as long, it's that simple. Yes, it's going to take an hour or two. If you run 3 baths then it will be empty of hot water and filled with cold. There is no way that the 3kW electrical boiler will heat water fast enough for you to run cold water in and hot water out. To do this you need serious power, as an example an electric shower is about 8kW, the better ones are more and need special heavy wiring to handle the power.
There's nothing wrong with your cylinder, you won't fix this by turning up the temp by 5 dgerees, if you want 3 baths in a row then turn the heating on and the immersion as soon as you start. The only alternative is a new boiler generating instant hot water. This will burn 15 or 18 kW all day long, but they don't come for free.
OP you'll need a bigger tank, or you need to wait between baths for the HW to heat up. Happens in family houses all the time.
Yes the temperature control on the boiler ultimately controls the temp of the HW, on more modern pumped systems the HW tank would have a thermostat fitted to control HW temp.
You could up the temp on the immersion heater, if you take the cover off there should be a thermostat control inside, usually a small pot with a screwdriver slot. MAKE SURE YOU TURN THE POWER OFF FIRST!
Higher temp HW would mean you use less IF you mix it correctly with the cold.
Yes the temperature control on the boiler ultimately controls the temp of the HW, on more modern pumped systems the HW tank would have a thermostat fitted to control HW temp.
You could up the temp on the immersion heater, if you take the cover off there should be a thermostat control inside, usually a small pot with a screwdriver slot. MAKE SURE YOU TURN THE POWER OFF FIRST!
Higher temp HW would mean you use less IF you mix it correctly with the cold.
This is quite a common modern problem in older houses with traditional heating systems. When your house was built, most people would have a bath once or twice a week so a hot water system with capacity for two baths per evening was more than enough for the average family. Nowadays, most people want to bathe every day.
You can fiddle with controls and get a bit higher water temperature , but you won't improve it drastically.
There are three solutions to your issue.
1. Fit an electric shower if you don't already have one, it'll give you the ability to bathe all day long if you want without touching the hot water in your cylinder.-cheapest option.
2. Change your cylinder for a bigger one.
3. Change your heating system to a combi-boiler which heats the water as you need it.
I used to work for a largish landlord with a huge stock of 1950's and 60's houses all with similar problems to yours. We had a program of fitting electric overbath showers to every property as a short term fix till the existing boilers became due for replacement with combi systems. We only ever went down the route of increasing the cylinder size if there was a medical reason not to fit a shower.
You can fiddle with controls and get a bit higher water temperature , but you won't improve it drastically.
There are three solutions to your issue.
1. Fit an electric shower if you don't already have one, it'll give you the ability to bathe all day long if you want without touching the hot water in your cylinder.-cheapest option.
2. Change your cylinder for a bigger one.
3. Change your heating system to a combi-boiler which heats the water as you need it.
I used to work for a largish landlord with a huge stock of 1950's and 60's houses all with similar problems to yours. We had a program of fitting electric overbath showers to every property as a short term fix till the existing boilers became due for replacement with combi systems. We only ever went down the route of increasing the cylinder size if there was a medical reason not to fit a shower.
Yeah it's a rented house, so we can't do much; the immersion heater is often on 24/7 but that seems very wasteful so I wanted to leave it off tbh.
It seems in theory like the only time the immersion heater could be useful is after someone has already had a bath, as the tank should be full and at temperature after 30-40 minutes using the gas boiler alone.
I have an instant heater in my house in Indonesia - it's much easier there, the water comes in at 20 Celsius, and I heat it to around 40. Doesn't take much gas nor a very fancy heater. (Though I still wouldn't use electricity, the average house over there has a 10 amp supply and everything pretty much has to be backed up with a generator).
It seems in theory like the only time the immersion heater could be useful is after someone has already had a bath, as the tank should be full and at temperature after 30-40 minutes using the gas boiler alone.
I have an instant heater in my house in Indonesia - it's much easier there, the water comes in at 20 Celsius, and I heat it to around 40. Doesn't take much gas nor a very fancy heater. (Though I still wouldn't use electricity, the average house over there has a 10 amp supply and everything pretty much has to be backed up with a generator).
thelawnet1 said:
Yeah it's a rented house, so we can't do much; .
Most landlords would be quite happy for you to fit an electric overbath shower at your own expense. If you're planning on staying there any length of time, it would probably cost you less than the savings you'd make on heating water for baths.Bear in mind that it's been bloody cold the last couple of weeks, and that means your cold water will be colder than usual, so you'll need more hot water to get the bath the same temperature. Setting the hot water to the highest temperature possible means you'll need less of it to get the bath up to temperature.
brrapp said:
This is quite a common modern problem in older houses with traditional heating systems. When your house was built, most people would have a bath once or twice a week so a hot water system with capacity for two baths per evening was more than enough for the average family. Nowadays, most people want to bathe every day.
You can fiddle with controls and get a bit higher water temperature , but you won't improve it drastically.
There are three solutions to your issue.
1. Fit an electric shower if you don't already have one, it'll give you the ability to bathe all day long if you want without touching the hot water in your cylinder.-cheapest option.
2. Change your cylinder for a bigger one.
3. Change your heating system to a combi-boiler which heats the water as you need it.
I used to work for a largish landlord with a huge stock of 1950's and 60's houses all with similar problems to yours. We had a program of fitting electric overbath showers to every property as a short term fix till the existing boilers became due for replacement with combi systems. We only ever went down the route of increasing the cylinder size if there was a medical reason not to fit a shower.
Or you could have the hot water converted from the gravity system (which are slow to recover the hot water) to a fully pumped system with independent control of the heating and hot water. Much better than combi boilers or electric showers which just about allow you to wash each shoulder in turn.You can fiddle with controls and get a bit higher water temperature , but you won't improve it drastically.
There are three solutions to your issue.
1. Fit an electric shower if you don't already have one, it'll give you the ability to bathe all day long if you want without touching the hot water in your cylinder.-cheapest option.
2. Change your cylinder for a bigger one.
3. Change your heating system to a combi-boiler which heats the water as you need it.
I used to work for a largish landlord with a huge stock of 1950's and 60's houses all with similar problems to yours. We had a program of fitting electric overbath showers to every property as a short term fix till the existing boilers became due for replacement with combi systems. We only ever went down the route of increasing the cylinder size if there was a medical reason not to fit a shower.
I don't know much about gravity systems specifically, but if you have gas heating/water then the immersion heater is provided as a backup, or for heating hot water during the summer if the hot water used is moderate (basin/sink volumes only). As mentioned it will have almost no effect at quickly heating a bathful of water after a bathful has been emptied.
Start by understanding your hot water temperatures by actually measuring it with a thermometer.
Then look for the tank thermostat that calls the boiler for heat.
Then as suggested increase the boiler temperature- but only after carrying out the above to understand what problem you are trying to solve.
However, having successive baths on a 200L tank is easily going to drain it.
I have an unvented 250L tank with a 35kw boiler set to maximum and it would get drained if you had 3 baths.
Then look for the tank thermostat that calls the boiler for heat.
Then as suggested increase the boiler temperature- but only after carrying out the above to understand what problem you are trying to solve.
However, having successive baths on a 200L tank is easily going to drain it.
I have an unvented 250L tank with a 35kw boiler set to maximum and it would get drained if you had 3 baths.
forest07 said:
Much better than combi boilers or electric showers which just about allow you to wash each shoulder in turn.
Nothing wrong with a combi boiler as long as it's big enough. I think mine is 20-some kW and it will run the shower in the main bathroom fast enough to blast you across the room. It will run 2 showers in fact, albeit it doesn't actually rip your skin off with 2 running.Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff