Condensing Boiler temprature

RazBurley

Hi,
We have vaillant eco tech plus condensing bioler with a hot water cylendir. Max operating temp for heating is 68 degree. Last night heating was on at full temp for 4 hours and it used 4 cubic meter of gas (£2.81 cost). 

I have seen lots online that condencing bioler can be more effcient if used on proper temp.

My question is what is the best flow temp to run to get best efficiency. Our house is 2 bed mid terrace with extention on the back and fairly insulated. We have six radistors.

Any advice will be appriciated.

Thanks

QrizB

RazBurley said:

My question is what is the best flow temp to run to get best efficiency.

As cold as you can, while still being able to heat your house.

RazBurley said:

We have vaillant eco tech plus condensing bioler with a hot water cylendir. Max operating temp for heating is 68 degree.

How clever are your controls? A modern boiler might include weather compensation, which will turn the flow temp up and down as the weather changes?
If you don't have any clever controls, you'll have to adjust it yourself.

My 20-year-old Worcester Bosch (which is in no meaningful way "clever") is currently keeping my home warm with a flow temp of around 50-55 degrees C.

tacpot12

My condensing boiler needs to have a flow temperature of 65C to heat out house when its -5C outside like it was last night. However the return temperature is 45C (I have a pipe thermometer so I can check this) so the boiler is definitely running efficiently - the boiler will condensing the flue gas to increase efficiency. It can do so if the return temperature is less than 55C. Our boiler was running all last night and will be running all tonight. I don't know how much gas we have used, but I can check and report back tomorrow.  

RazBurley

QrizB said:

RazBurley said:

My question is what is the best flow temp to run to get best efficiency.

As cold as you can, while still being able to heat your house.

RazBurley said:

We have vaillant eco tech plus condensing bioler with a hot water cylendir. Max operating temp for heating is 68 degree.

How clever are your controls? A modern boiler might include weather compensation, which will turn the flow temp up and down as the weather changes?
If you don't have any clever controls, you'll have to adjust it yourself.

My 20-year-old Worcester Bosch (which is in no meaningful way "clever") is currently keeping my home warm with a flow temp of around 50-55 degrees C.

Our controls are just normal ones and boiler has tobe set manully. I am trying to figure out what will be best temp to keep the house heated.  I was thinking to set the te.p to 55 degree and see how it goes with gas usage and house heat up. 

Mostly online info says boiler has max temp of 80 degree and keep it to 65 degreeto get best efficiency but our bioler has max temp of 68 degree so was thinking to put on 55 degree to check. 

Is that you think will work out?

RazBurley

tacpot12 said:

My condensing boiler needs to have a flow temperature of 65C to heat out house when its -5C outside like it was last night. However the return temperature is 45C (I have a pipe thermometer so I can check this) so the boiler is definitely running efficiently - the boiler will condensing the flue gas to increase efficiency. It can do so if the return temperature is less than 55C. Our boiler was running all last night and will be running all tonight. I don't know how much gas we have used, but I can check and report back tomorrow.  

our boiler has max temp of 68 degree so was thinking to put on 55 degree to check.  I don't have a way to check return temp so just have to check the usage to see if it makes any diffrence.

Lorian

OP has a cylinder so it's S plan or Y plan. So he needs to keep his flow set high enough to heat his water.  He might want to heat his water above 60c if he is concerned about legionella. Still a little scope to come down from 68c though, but probably wants to reduce cylinder thermostat a bit too depending what it's on.

55c is probably a leap too far 

Remember reducing the flow will slow down how fast your house warms up in the morning so you may need it to come on earlier 

grn99

With a hot water tank (as I have) I don’t think going below a flow temp of 65 is realistic if you’re to heat the water tank sufficiently. I’m running a max flow of 69 and get a return temp of around 48. Tinkering with slightly lower flow temps hasn’t given me any benefit, but that’s just my experience. I found a  circa10 degree differential between max flow temp and target HW cyl water temp being achieved…so 69 flow can achieve 59 H/W temp.

RazBurley

Lorian said:

OP has a cylinder so it's S plan or Y plan. So he needs to keep his flow set high enough to heat his water.  He might want to heat his water above 60c if he is concerned about legionella. Still a little scope to come down from 68c though, but probably wants to reduce cylinder thermostat a bit too depending what it's on.

55c is probably a leap too far 

Remember reducing the flow will slow down how fast your house warms up in the morning so you may need it to come on earlier 

Hi,

Our boiler has seprate temp control for hot water which we have put on max  as we only do it twice a day. 

Its just about the heating which we want to run as efficiently as possible to keep the house warm and the bill down as well.

Thanks

grn99

RazBurley said:

Lorian said:

OP has a cylinder so it's S plan or Y plan. So he needs to keep his flow set high enough to heat his water.  He might want to heat his water above 60c if he is concerned about legionella. Still a little scope to come down from 68c though, but probably wants to reduce cylinder thermostat a bit too depending what it's on.

55c is probably a leap too far 

Remember reducing the flow will slow down how fast your house warms up in the morning so you may need it to come on earlier 

Hi,

Our boiler has seprate temp control for hot water which we have put on max  as we only do it twice a day. 

Its just about the heating which we want to run as efficiently as possible to keep the house warm and the bill down as well.

Thanks

Ahh, I misunderstood  - disregard my comment as that’s for a single temp control boiler with a hot water tank. 

matelodave

It really isn't rocket science and you dont need a lot of expertise. Neither do you need precise temperatures.

As said above adjust it down to the lowest temperature that you can, until you are either not warm enough or the heating takes too long to get the place up to temp and then add a degree or two.

Same with the hot water, you dont need it at silly temps, 50-55 degrees would be hot enough for most people.

Northern_Wanderer

It depends on your house, the radiator/ room sizes etc. A couple of years ago I experimented with reducing the boiler temp. At 55C, it took a very loooooong time for my house to heat up with the boiler running full whack. At 65C it gets warm nice n quick (I think this temp is within the "eco" range of temp settings on my boiler where it runs most efficiently). Obvioulsy in these sub zero temps it is taking a bit longer to heat the house from cold but I'm not running up to the loft to change boiler temp each week.....it's trial and error for your house I'm afraid.

Re hot water - no point heating it so much that you have to add cold water. No point heating it at times it's not used, so timing the water heating to coincide with just prior to showers or baths important.