Water Heating.

from_atozinc

Hello

In the last few days, We are nearly at the stage where we don't have the oil heating on at all, thanks be to Christ ; )

Up to now the oil heating heated the water, we never had to bother to use the immersion. We do not have a stove.

We have 2 children under 3 years and my wife is at home all day. I Suppose we just need a bit of hot water in the morning and maybe a bit during the day and then more at night for showers........ and baths for children every few days.


What is the best cost saving way to heat the water.

A ) Turn on the oil heating system and let that heat the water. (We have a switch to turn off all radiators)

B ) Turn on the immersion.

Pete67

Oil should be cheaper unless you can use night rate electricity for water heating, in which case probably not a lot of difference.

from_atozinc

Pete67 wrote: »

Oil should be cheaper unless you can use night rate electricity for water heating, in which case probably not a lot of difference.

Thanks for input.
We only have one rate for electricity.......but I switched electricity providers a couple months back so I'm getting cheaper usage for this first year, don't know if that would make a difference to immersion V oil.

If one is only using oil to heat water, would you use way way less oil this way. Sorry for silly question but haven't trained it yet.

I'm sick of buying oil over the last 7 months.

gctest50

Have a look at this and "update" it with newer prices :

http://thehelpfulengineer.com/wp-content/uploads/2013/02/Boiler-or-immersion-heater-to-heat-hot-water.pdf

immersion is 100% efficient - oil boiler a bit less, pumps to run, wear & tear on boiler, heat loss in the pipes from boiler to tank etc

still have to run your boiler now and again in the summer though

Pete67

Good summary but the oil prices are well out of date - the figure used is 90 cents per litre, whereas it is currently about 48 to 50 cents per litre. Electricity at 20c per kWh is not too far wrong when you factor in the standing charges and public service levy. So that would put the cost of heating the cylinder of water at about €1.34 for electricity on the standard day rate, and €0.60 for oil. You will use far less oil per hour if the radiators are off.

from_atozinc

Pete67 wrote: »

Good summary but the oil prices are well out of date - the figure used is 90 cents per litre, whereas it is currently about 48 to 50 cents per litre. Electricity at 20c per kWh is not too far wrong when you factor in the standing charges and public service levy. So that would put the cost of heating the cylinder of water at about €1.34 for electricity on the standard day rate, and €0.60 for oil. You will use far less oil per hour if the radiators are off.

Thanks.

Does having the oil boiler on use much electricity though ?

Pete67

Not a lot, say 200W for the burner and 100W for the circulating pump. The burner does not run continuously, probably well less than 20% of the time when heating water only. The pump runs continuously, so on average about 140 watts - thats about 2.8 cents per hour.

corsav6

Pete67 wrote: »

Not a lot, say 200W for the burner and 100W for the circulating pump. The burner does not run continuously, probably well less than 20% of the time when heating water only. The pump runs continuously, so on average about 140 watts - thats about 2.8 cents per hour.

I highly doubt the system would use 300w when in use. The burner is using feck all as it's only injecting kerosene and the pump may use 100w on its fastest setting but if only heating the tank the the slowest speed setting would be grand.
Our oil usage over the last 1000lt was 1lt per hour, that's with 7 double rads and the hot water tank.
Last summer our electricity bill about 40% higher than during the winter as we used the immersion during the summer to heat water. This year so far we've been using the oil for heating water and the bill has stayed the same, so for us using oil for heating water is far cheaper.

from_atozinc

corsav6 wrote: »

I highly doubt the system would use 300w when in use. The burner is using feck all as it's only injecting kerosene and the pump may use 100w on its fastest setting but if only heating the tank the the slowest speed setting would be grand.
Our oil usage over the last 1000lt was 1lt per hour, that's with 7 double rads and the hot water tank.
Last summer our electricity bill about 40% higher than during the winter as we used the immersion during the summer to heat water. This year so far we've been using the oil for heating water and the bill has stayed the same, so for us using oil for heating water is far cheaper.

Any idea how much oil you are going through to heat the water only ?

corsav6

from_atozinc wrote: »

Any idea how much oil you are going through to heat the water only ?

We only turned the rads off 2 weeks ago as we have 2 kids under 3 so we try and keep the temp around 19-20c.
We got a fill on the 1st of September as we had just run out. I checked the tank on the 1st of May and I could just see the top of the oil feed pipe so basically out. Since then we've been using the oil to heat water only, 1 hour in the morn and 1 hour in the eve and it's still not ran out completely.
Between September 1st and May 1st we used the oil for 5 hours per day, so that works out at less than 1lt per hour but I'm not sure of the exact consumption.
The tank is practically full after 30 mins using oil but we use hot water as soon as we're up so the oil replaces what we use and leaves enough until bathtime before the kids bedtime so it's on for another hour then which covers showers for us too.

Tldr: not a clue how much it's costing just to heat the water with oil, but it's far cheaper for us than using the immersion.

Pete67

It was just an estimation to allay concerns about the cost of electricity used in running the burner, however out of curiosity I checked a couple of datasheets, and the typical domestic burner consumes around 100W when running, plus the pump consumption, so you're correct, it's more like 200W than 300W, either way, it's not significant compared to the cost of the oil.

The burner blower would take more power than the oil pump, though both are typically driven by the same motor.

corsav6 wrote: »

I highly doubt the system would use 300w when in use. The burner is using feck all as it's only injecting kerosene and the pump may use 100w on its fastest setting but if only heating the tank the the slowest speed setting would be grand.

from_atozinc

corsav6 wrote: »

We only turned the rads off 2 weeks ago as we have 2 kids under 3 so we try and keep the temp around 19-20c.
We got a fill on the 1st of September as we had just run out. I checked the tank on the 1st of May and I could just see the top of the oil feed pipe so basically out. Since then we've been using the oil to heat water only, 1 hour in the morn and 1 hour in the eve and it's still not ran out completely.
Between September 1st and May 1st we used the oil for 5 hours per day, so that works out at less than 1lt per hour but I'm not sure of the exact consumption.
The tank is practically full after 30 mins using oil but we use hot water as soon as we're up so the oil replaces what we use and leaves enough until bathtime before the kids bedtime so it's on for another hour then which covers showers for us too.

Tldr: not a clue how much it's costing just to heat the water with oil, but it's far cheaper for us than using the immersion.

How many litres does your oil tank hold ?

How many radiators had you on ?

My oil consumption since last October is scandalous to be honest.

Fogmatic

Just wondered if you'd considered gas for the water heating (bottled if no mains)?
(Not that I know the comparitive costs).

Idbatterim

does your immersion have a sink switch? If so, it only heats half the tank or so, this can only be done if using electric though afaik...

from_atozinc

Idbatterim wrote: »

does your immersion have a sink switch? If so, it only heats half the tank or so, this can only be done if using electric though afaik...

Yes it does have a sink switch.

How do you mean "this can only be done if using electric though afaik..." ?

Idbatterim

ok so I assume with electric, the immersion only heats half the tank or so, when sink is selected, with oil, I am assuming it heats the whole tank. I am sure someone will be along shortly to clarify...

you are heating way less water if you use immersion, but oil may still be cheaper as the fuel is so much cheaper per kwh than electric...

from_atozinc

thanks for all the comments.

so it seems from the posts so far that using the oil is the best cost saving way to heat the water.

so here are more stupid questions, lets say childrens bath time is at 7pm and parents have showers after 9pm.

How long before I want the water hot would I need to turn the oil boiler on?
How long should I leave the oil burner on for to heat enough water for above?
How long would water stay hot after the oil burner is turned off?

gctest50

from_atozinc wrote: »

...............

We have 2 children under 3 years and my wife is at home all day. I Suppose we just need a bit of hot water in the morning and maybe a bit during the day and then more at night for showers........ and baths for children every few days.
.........

a bit of solar water heating maybe, it might suit your usage ?

http://www.aei.ie/solar-panels

from_atozinc

gctest50 wrote: »

a bit of solar water heating maybe, it might suit your usage ?

Thanks. I'm in a rented house for now but maybe in the future solar could be an option.

corsav6

from_atozinc wrote: »

How many litres does your oil tank hold ?

How many radiators had you on ?

My oil consumption since last October is scandalous to be honest.

Our tank holds 1100lt but we ordered 1000lt so that's what I'm basing consumption on.

We have 7 double rads off the oil, 10 in total but 2 were turned off. Our timer is set to 5 hours per day and the odd time we'd put it on for an extra hour or 2. Water temp is set to 70c.
The stove heats 5 double rads and 2 single so that's why we get away with 5 hours of oil in winter.
Boiler is a Firebird S90 indoor unit, its uses 160w max when in use and the water pump uses 30w on slowest setting, 52w on medium setting which is what we're using now and 90w on highest setting.
Giving the higher ambient temperature now I'd say the boiler is only active for about 20-30 mins per hour on the timer, so that's approx 130w per hour, meaning 7 hours of oil usage would cost 1 unit of electricity.
Our immersion is 3kw meaning it uses 1 unit of electricity every 20 mins, and we need it on at least 1 hour just for enough bath water and a quick shower.
We also have a top up meter for electricity which tells us the exact usage in real time giving in both kw/h and € per hour. I'll try and do a little test tomorrow with both and see what the results are.

from_atozinc

corsav6 wrote: »

Our tank holds 1100lt but we ordered 1000lt so that's what I'm basing consumption on.

We have 7 double rads off the oil, 10 in total but 2 were turned off. Our timer is set to 5 hours per day and the odd time we'd put it on for an extra hour or 2. Water temp is set to 70c.
The stove heats 5 double rads and 2 single so that's why we get away with 5 hours of oil in winter.
Boiler is a Firebird S90 indoor unit, its uses 160w max when in use and the water pump uses 30w on slowest setting, 52w on medium setting which is what we're using now and 90w on highest setting.
Giving the higher ambient temperature now I'd say the boiler is only active for about 20-30 mins per hour on the timer, so that's approx 130w per hour, meaning 7 hours of oil usage would cost 1 unit of electricity.
Our immersion is 3kw meaning it uses 1 unit of electricity every 20 mins, and we need it on at least 1 hour just for enough bath water and a quick shower.
We also have a top up meter for electricity which tells us the exact usage in real time giving in both kw/h and € per hour. I'll try and do a little test tomorrow with both and see what the results are.

Thanks very much for the detailed reply.

from_atozinc

from_atozinc wrote: »

thanks for all the comments.

so it seems from the posts so far that using the oil is the best cost saving way to heat the water.

so here are more stupid questions, lets say childrens bath time is at 7pm and parents have showers after 9pm.

How long before I want the water hot would I need to turn the oil boiler on?
How long should I leave the oil burner on for to heat enough water for above?
How long would water stay hot after the oil burner is turned off?

Hi,

Any thoughts on this?

I know they are silly questions, but for the last 15 years or more, I have lived in places with only storage heaters.

corsav6

from_atozinc wrote: »

Hi,

Any thoughts on this?

I know they are silly questions, but for the last 15 years or more, I have lived in places with only storage heaters.

Our kids bath is at 6 so oil is set between 5 and 7, this covers showers after 8 also.

from_atozinc

corsav6 wrote: »

Our kids bath is at 6 so oil is set between 5 and 7, this covers showers after 8 also.

oh ok, so you kinda put it on for an hour before and for 2 hours.

and this keeps the water hot for a bit afterwards.

would you always have enough water this way or do you run low, have too much hot water etc.

from_atozinc

Just want to say first of all that I have googled this and downloaded the manual but still cannot find out the answer.

See attached pic which is the basic controls for my firebird 90-120 oil boiler.

My question relates to the button labelled "C pump" What does this actually do ?

Is it needed when just heating the water only with no radiators being heated.

corsav6

from_atozinc wrote: »

Just want to say first of all that I have googled this and downloaded the manual but still cannot find out the answer.

See attached pic which is the basic controls for my firebird 90-120 oil boiler.

My question relates to the button labelled "C pump" What does this actually do ?

Is it needed when just heating the water only with no radiators being heated.

We have the exact same boiler. C pump is circulating pump, it pumps the hot water from the boiler.

from_atozinc

corsav6 wrote: »

We have the exact same boiler. C pump is circulating pump, it pumps the hot water from the boiler.

Thanks. So essentially it HAS to be on yeah. Otherwise, nothing will be heated ?

Why is there even an option to turn it off ?

Water John

Solar is not remotely value for money, sadly.
With the price of PV panels falling however, they may be worth considering in a few years.

How long the water stays hot depends on the lagging on the cylinder. Is it a loose jacket or is the outside of the tank covered in foam? If either, it should hold the heat for a few hours at least.

from_atozinc

from_atozinc wrote: »

Thanks. So essentially it HAS to be on yeah. Otherwise, nothing will be heated ?

Why is there even an option to turn it off ?

Should there even be an option to turn the circulating pump off ?

from_atozinc

from_atozinc wrote: »

Should there even be an option to turn the circulating pump off ?

Any comments on this?

corsav6

from_atozinc wrote: »

Any comments on this?

I have no idea why it's there tbh, but if u switch it off the hot water won't get pumped from the boiler so it's pointless.
We ran out of oil completely yesterday so that's 5 hours per day between 1st Sept and 1st May with all rads on and 3 hours per day just heating the tank up til now on 1000lt

Wearb

corsav6 wrote: »

I have no idea why it's there tbh, but if u switch it off the hot water won't get pumped from the boiler so it's pointless.
We ran out of oil completely yesterday so that's 5 hours per day between 1st Sept and 1st May with all rads on and 3 hours per day just heating the tank up til now on 1000lt

3 hours per day for hot water only is enormous.

from_atozinc

Wearb wrote: »

3 hours per day for hot water only is enormous.

Can you maybe answer these questions so:

How long before I want the water hot would I need to turn the oil boiler on?
How long should I leave the oil burner on for to heat enough water for above?
How long would water stay hot after the oil burner is turned off?

We have 2 children under 3 years and my wife is at home all day. I Suppose we just need a bit of hot water in the morning and maybe a bit during the day and then more at night for showers........ and baths for children every few days.

Wearb

1. It should be going off just before you need it.
2. That depends on how big your cylinder is and how much hot water you need. For standard cylinder, probably somewhere between 30 and 45 minutes.
3. Depends on the insulation on you cylinder and pipes. Ballpark: 10 or 20 hours.

Pete67

from_atozinc wrote: »

Can you maybe answer these questions so:

How long before I want the water hot would I need to turn the oil boiler on?
How long should I leave the oil burner on for to heat enough water for above?
How long would water stay hot after the oil burner is turned off?

We have 2 children under 3 years and my wife is at home all day. I Suppose we just need a bit of hot water in the morning and maybe a bit during the day and then more at night for showers........ and baths for children every few days.

You might just be over thinking this - why not just start with setting the timer for an hour before you first need hot water, say 5pm to 6pm, and see how that goes. If you need more water increase the time. You will also see how long it stays hot and can make adjustments based on that - for example maybe 30 minutes first thing in the morning followed by 30 minutes in the early evening would work fine for you.

corsav6

Wearb wrote: »

3 hours per day for hot water only is enormous.

1.5 hours in the morn and 1.5 in the eve. When the tank is full we empty it as the oil is running so it fills again and leaving us plenty of hot water for the day. 2 baths in the eve and 2 showers plus a few dishes means we need the oil on again in the eve. 3 hours is probably a bit excessive but we never run out of hot water

Wearb

If you ran it for 1 hour instead of 1.5, would you see any difference ?

corsav6

Wearb wrote: »

If you ran it for 1 hour instead of 1.5, would you see any difference ?

Can't run it all now we're out
I'd say an hour in the morn and same again in the eve would be grand so when I fill up again I'll prob just reduce the timer.
If your only heating the tank then you could have the oil on constant and still use very little as the burner wouldn't be on much because the water that's circulating would be hot.
Not saying it's what to do though as it's a bit pointless.

from_atozinc

Hi

So my oil heating will be out of action for at least a week. So I need to use the immersion to heat the water - I can see everyone running for panic buttons......your electricity bill is going to be 5000 euro etc etc ; )

anyway, trying to work out how long to switch on for and should I put at sink or bath.

Like if I put it on sink for an hour, I presume that's a waste as its only heating a small amount of water anyway and this should be heated in half an hour, so am I best just to leave it on bath


We have 2 children under 3 years and my wife is at home all day. I Suppose we just need a bit of hot water in the morning and a bit during the day and then more at night for showers........ and baths for children every few days.


any tips on how long to put it on for and whether to use sink or bath ?

Wearb

from_atozinc wrote: »

Hi

So my oil heating will be out of action for at least a week. So I need to use the immersion to heat the water - I can see everyone running for panic buttons......your electricity bill is going to be 5000 euro etc etc ; )

anyway, trying to work out how long to switch on for and should I put at sink or bath.

Like if I put it on sink for an hour, I presume that's a waste as its only heating a small amount of water anyway and this should be heated in half an hour, so am I best just to leave it on bath


We have 2 children under 3 years and my wife is at home all day. I Suppose we just need a bit of hot water in the morning and a bit during the day and then more at night for showers........ and baths for children every few days.


any tips on how long to put it on for and whether to use sink or bath ?

You would use the bath setting if you find that even after having the sink on for an hour, you run out if hot water a couple of hours after turning it off.

I would start off with turning it on sink for about an hour twice a day. You might find that one of those periods will need to be on the bath settings.
After you get that going the way you want it, you could try reducing the time in 10 min intervals, to see what the minimum time period should be.

Well insulated cylinder and pipe work will always improve economy. Make sure not to destroy your comfort of having hot water on demand by skimping too much on savings. The difference between having just enough and a little extra will be in the order of about 10 minutes more and won't cost very much extra.

Water John

With a well insulated tank, I'd say leaving it on all day won't make little if any diff.
Switch on in the morning, turn off before last shower or bath at night.

from_atozinc

Water John wrote: »

With a well insulated tank, I'd say leaving it on all day won't make little if any diff.
Switch on in the morning, turn off before last shower or bath at night.

Hi. Is leaving it on all day just wasting electricity though ?

from_atozinc

Wearb wrote: »

You would use the bath setting if you find that even after having the sink on for an hour, you run out if hot water a couple of hours after turning it off.

I would start off with turning it on sink for about an hour twice a day. You might find that one of those periods will need to be on the bath settings.
After you get that going the way you want it, you could try reducing the time in 10 min intervals, to see what the minimum time period should be.

Well insulated cylinder and pipe work will always improve economy. Make sure not to destroy your comfort of having hot water on demand by skimping too much on savings. The difference between having just enough and a little extra will be in the order of about 10 minutes more and won't cost very much extra.

Thanks for reply.

I suppose the thing in asking is, if I have it on sink for 1 hour V having it on bath for 1 hour, are the results going to be that much different as regards hot water produced ?

Wearb

The sink element is about half the length of the bath element, but (afik) uses the same power. The sink element only heats about the top one third of the cylinder, while the bath one heats about two thirds. Therefore, if having the sink element on for a half hour gives X temperature to 1/3rd of a tank, then the bath element will need to be on for 1 hour to give the same temperature to 2/3rds of the tank. (because it is heating twice as much water)

Hope that helps.

Water John

Wearb is right there on the diff between sink and bath.

Not sure leaving it on during the day will make much diff to electrical use.
with well insulated tanks, Des Bishop's line on 'who left the immersion on' may be redundant.