Identify your Suprima:

When fixing a Suprima it is important to know the exact model and version being worked on as spare parts for the different versions are not all the same or interchangeable. All gas boilers (including the Suprima) are supplied with a data plate identifying the exact model. On most Suprimas this is on the control board chassis and visible behind the tall hinged door on the right hand side, just above the user controls. If you ask me to repair your Suprima I am quite likely to ask you to photograph this data plate and text it to me.

A problem can arise when the PCB upgrade kit has been fitted. The original controls chassis including the data plate is discarded during the upgrade. The new controls chassis has a new, blank data plate and the fitting instructions require the technician to copy the data across from the old data plate being discarded, onto the new data plate. Sometimes this does not happen. The new data plate is left blank for any number of reasons - couldn’t find a pen, laziness, in too much of a hurry, etc etc.

This leaves any future technician in difficulty because the data on the plate gives information needed for safety checking during repairs and servicing, and for ordering replacement parts.

A number of clues to help identify the exact model are usually present. The size (heat output) of the boiler can be determined by a number label on the gas control valve. The number will be 30, 40, 60 etc on a label stuck on the original gas valve. If the gas valve has ever been replaced this label will have been lost though.

A second way is to carefully read the tiny data label attached to the fan motor. Most of these include the Potterton part number for the fan, and a reverse look-up of the fan part numbers can tell you which exact models of Suprima that particular fan is for.

To determine whether the Suprima is an original non “L” or an “L” version, look at the wiring diagram on the inside of the slide-off controls cover. This may say which versions the diagram covers. Another clue is to count the number of fixing screws holding the fan in place. If there are only two the Suprima is definitely a basic or non “L” version. If three, it could be either. A further indicator is the presence (or not) of a flow switch in the flow pipe. Flow switches were only ever fitted to the L version as far as I can determine.

Using all these pieces of information the actual model of Suprima can usually be worked out.

One final way of determining the size rating of a Suprima is to measure the diameter of the hole in the main burner gas jet or injector. Only something a Gas Safe Registered technician should really be doing as it involves dismantling the boiler and removing the burner assembly for access to the jet. Measuring the hole size is not that easy either, but here are the injector hole sizes and the corresponding boiler size, obtained from the boiler manuals:

2.8mm dia = 30

3.1mm dia = 40

3.5mm dia = 50

3.7mm dia = 60

3.9mm dia = 70

4.1mm dia = 80

3.2mm dia = 100

2.8mm dia = 30L

3.1mm dia = 40L

3.5mm dia = 50L

3.9mm dia = 60L

3.9mm dia = 70L