Sime Format boiler seems to have stopped modulating

[steves741]

Not much experience with radiator boilers so excuse any ignorance in my question, but our Format 34i boiler seems to be operating in "binary", rather than "modulating" mode for some reason. That is, instead of the burner staying on and holding the water temperature reasonably steady while there is demand from the room thermostat, the burner turns on and off constantly. The temperature range showing on the dial fluctuates between a very narrow range, maybe 70 degrees at minimum when the burner fires, to say 73-74 degrees when it cuts out again. This is with temp dial at max. Naturally, the room never gets anywhere near the set temp (manages about 21 degrees at best after hours of the system being started). Boiler used to operate well, modulating to keep water temp at around 90 while there was demand from the room stat. Can anyone advise where I should start looking to diagnose this, or suggest what parts might be in need of replacing? Sick of cold rooms!

Any hints greatly appreciated

Steve

 

[D_Hailsham]

Which version of the Sime Format do you have?

 

[steves741]

As far as I know it is called a Format 34i (i for internal). Does this make sense?

 

[D_Hailsham]

As far as I know it is called a Format 34i (i for internal). Does this make sense?

Yes.

Is the pressure OK?
Are the green/orange and red lights doing anything?

 

[steves741]

Pressure is where it should be on the gauge, and bottom green light stays on permanently. Top LED is always off.

 

[Agile]

Most water based heating systems are designed for a flow temperature of 62-82 C and not 90 C. The boiler controls might be able to allow it to operate outside the design range. So its possible that you have been operating it outside the design range by leaving the adjustment at the maximum?

A lack of modulation is usually either an electronic or gas related fault.

We dont advise on gas related faults and unless you have considerable experience of electronics its unlikely that you will be able to sort out any electrical fault.

It seems likely that you will need to call a professional to diagnose the fault.

Tony

 

[steves741]

Thanks Tony, I guess I'll give the repair guy a call! Appreciate your help,

Steve