Boiler help

liamsteven1

Hi

I have just moved into a new property and I am a little confused about the heating controls.

I have a combi boiler which has on-screen options for hot water and CH temperatures, however, I also have a control dial on the wall.

I am confused as to what temperature I should set the CH to and what the control dial on the wall actually does if the temperature is set on the boiler panel.

Any help appreciated!

neilmcl

Well assuming the controller is connected to the boiler then you use that and the thermostat dial to control when your CH comes on and at what temp. Don't bother with the controls on the boiler itself.

If you don't have them I'd suggest you download the manual for both the boiler and the Siemens controls.

RelievedSheff

The controls on the boiler itself will be controlling the water temperature within the system.

The rotary dial sets the room temperature at which you want the heating to heat the room too. The other controller sets the times you want the heating to come on.

As suggested above. Download the manuals and have a read of them.

FreeBear

If 80°C is the set temperature for the hot water, I would recommend turning it down. Contact with hot water & surfaces above 43°C can lead to scalding. The hotter the water (or surface) the greater the risk, and the shorter the time for serious injury. At 80°C, scalding would be instant.

Whilst there is a risk of disease such as Legionella, the bacteria will be killed if the water is over 50°C fairly quickly ( 60°C for a quick kill). So set the water temperature to 60°C - It will reduce the risk of scalds and save money on gas.

Rosa_Damascena

FreeBear said:

If 80°C is the set temperature for the hot water, I would recommend turning it down. Contact with hot water & surfaces above 43°C can lead to scalding. The hotter the water (or surface) the greater the risk, and the shorter the time for serious injury. At 80°C, scalding would be instant.

Whilst there is a risk of disease such as Legionella, the bacteria will be killed if the water is over 50°C fairly quickly ( 60°C for a quick kill). So set the water temperature to 60°C - It will reduce the risk of scalds and save money on gas.

I agree with this, with one caveat - that is if the OP doesn't have mixer taps. 60 deg will still be very hot to the touch so I would set it at 40 for everyday use and crank it up to 60 for baths.

Mickey666

Can the boiler control different water temperatures for the rads and the DHW though?

I agree that 80C, even 60C is potentially dangerous for DHW, but radiators are usually sized for around 70C temperatures and a lower temperature may mean it's a struggle to attain/maintain the room temperatures.

My system is not a combi but it runs at 75C water temperature for the heating and supplies DHW via a separate thermostatically controlled mixer valve which I set to 45C.

As noted, reading the manual is a good idea.

liamsteven1

Thanks for the advice.
I have read the manuals for both Siemens programmer and the boiler but I was curious to know what temperature I should set for CH on the boiler. The 80’C was the CH when I first looked at the boiler and so I have set the CH to 60 and the hot water to 50. 
I suppose it’ll be trial and error to get the temperature just right but it looks like setting the CH to 60 and running the TVR’s on 3 seems to have done the trick.
I am keen to save energy and money. 

Ectophile

If you want to save energy, don't set the boiler temperature higher than it needs to be.  55 to 60C is good for killing legionnaires' disease, and isn't ridiculously hot for water from the taps.

A condensing boiler works most efficiently if the water returning to the boiler is below 55C.  So a central heating boiler temp of about 60C should be right.  If it's too hot, the boiler can't condense anything.

FreeBear

Mickey666 said: My system is not a combi but it runs at 75C water temperature for the heating and supplies DHW via a separate thermostatically controlled mixer valve which I set to 45C.

System boiler here with a hot water cylinder. Off the top of my head, couldn't say what temperature the water is coming out of the boiler (should hook up some more sensors at some stage). The HW tank is set for 50°C, and the temperature peaks at ~53°C every four hours or so. During the winter months, the temperature gets up to around 60°C, and I usually turn it off completely during the summer and only fire it up for bath night. Found a handy graph of Legionella-v-water temp - I might think about increasing the DWH to 55-60°C for the summer...

RelievedSheff

The Potterton Promax Ultra is a condensing boiler so at the temperature it is set it will never drop into condensing mode so will never run at it's most efficient. The return flow need to be at around 55 degrees to get the boiler into condensing mode which means that your boiler temperature needs to be somewhere around 60 degrees depending on how large you system is and how it is set up. You will need to have a play with it when you next put the heating on.

southcoastrgi

RelievedSheff said:

The Potterton Promax Ultra is a condensing boiler so at the temperature it is set it will never drop into condensing mode so will never run at it's most efficient. The return flow need to be at around 55 degrees to get the boiler into condensing mode which means that your boiler temperature needs to be somewhere around 60 degrees depending on how large you system is and how it is set up. You will need to have a play with it when you next put the heating on.

If you are only getting 5° then the pump speed is too high