Potterton Boiler Cycling

[Longclough]

I have some questions about boiler cycling.

I have a potterton Suprima 40L.

When the boiler has been on for about an hour or so constant and the radiator are really warm the boiler seems to cycle alot. Is this normal?

it generally only stays on for 4 mins and then off for about the same time. This happens for hours on end

In alll this time the room stat is never statisfied.

Thanks for any info

 

[Boilerman2]

turn the boiler thermostat to max if the rooms are still not warm then you have undersized heat emitters!! it is normal for a low water content boiler to "cycle"

 

[Longclough]

thanks boilerman.

I was wondering if it was right for it to cycle that much. What determines how much it will cycle. Can anything be done to stop it cycling so much. House does get warm but I am not sure the boiler is operating that efficiently.

The boiler supplys 1o radiators and cylinder tank.

The radaitors are the following sizes-
5 at 54 x 53 cm
1 at 95 x 53 cm
1 at 75 x 53 cm
2 at 115 x 53 cm
1 at 83 x 53 cm (Double)

thanks for any further info

 

[Longclough]

should the boiler thermostat be set to Max

 

[Longclough]

Just an update and a few extra questions.

I calculated the output of my radiators to be 7.6 Kw in total. I am however not sure what the output of the Suprima 40L is. Can anyone provide this info.

I also found out that the Mechanical stat in the lounge is not that accurate, which wasn't helping. I put a wall thermometer next to it. When the room stat is satisfied at 18 degrees. Thermometer reads 21-22 degrees.

I am going to replace it. Was thinking about the Honeywell CM907. Is this a good Stat? I am right in thinking that I could just leave the current controller in constant for CH and let the CM907 control CH. Control of HW would be as before?

Thanks again for all your help

 

[Agile]

You need to stop and think!

The boiler should be set to a flow of 82° max the knob on that model may take it higher.

Its normal for the boiler to cycle because the output its set to is twice whats the rads are giving out.

The boiler is a nominal 12 kW but what its currently set to could be a lot more. The power output can be reduced a little by an engineer but the manufacturers dont encourage that.

Thats the effect of oversizing a boiler. Cycling reduces efficiency.

When heating up from cold more power is needed so the boiler does need more power for that.

Your room stat is out of calibration but as you know that then its irrelevant. You set it at the lowest temperature for comfort and NOT at a particular figure and then sit sweltering!

Tony

 

[Longclough]

Thanks Agile for your response.

Ultimately I am happy with the temperature in my house.

However I was trying to understand my system and see if it could be more efficient.

I was under the impression that the temp setting on the boiler regulated the flow temp between 55 - 82 degrees. I assume that I am wrong?

I currently have it set at about 3 o clock. What flow temp should it be set to achieve, ie should it be set for a flow temp of 82 degrees

Agile I am not sure that I calculated radiator output correctly. So my output may be more than 7.6 Kw. I also need to add on HW requirement to this.

Maybe I should be happy that the house is warm and stop worrying about efficiency and best operation so much!