HI-SPEC J32, HI-SPEC J50 

(Basic and System E-T versions)

This Hi-Spec J32 warm air heater was introduced as the replacement for the J25-32. It is superficially similar but with major differences, the main being the more modern case styling, the adoption of high voltage 230Vac mains electricity for all the internal controls, thermostats, gas valve etc instead of low voltage 24Vac previously, and the addition of a flue sensor safety device to turn the boiler OFF should the flue not be working correctly. Heat output is adjustable between 7.3kW and 9.4kW.

The HI-SPEC models come in two versions as did their predecessor. A basic model with a conventional room thermostat to turn the unit on and off to regulate the room temperature, and the “System E-T” version with a clever proportional control system which continually adjusts the air circulation fan speed up and down to keep the room temperature stable rather than crudely turning it ON and OFF. 

This is the last of the open flue boilers made by Johnson and Starley for use with an open vertical flue and requiring an air vent from outside, and having a permanently burning pilot light. Later models are all “room sealed” with dual concentric fan assisted flue systems and automatic ignition. 

Common faults and fixes:

1) Air circulation fan failure:

The large, quiet-running fan which blows the warm air around the ductwork to the various air vents eventually fails with age, leaving you without heating. Dust gradually enters the bearings in the motor and they become stiff, and eventually so stiff the motor and fan simply will not spin and the air stops being distributed around the house. The quickest but more expensive fix is to fit a whole new fan unit. For economy the fan assembly can be sent away and a new motor fitted, but this involves some delay. Another mode of failure, completely different from above is where the fan continues to work but emits the most horrifying screeching noises when starting up. If left to run for a few minutes the screeching will sometimes stop, but usually the noise is so intolerable the user calls out a breakdown technician immediately.

2) Pilot light failure:

The pilot light goes out regularly and repeatedly, or will not re-light. 19 times out of 20 this is caused by failure of the safety device called the “thermocouple”. The thermocouple is a semiconductor device that senses heat from the pilot flame and the heat generates an electric current which holds a valve supplying gas to the pilot jet, open. If the flame goes out the thermocouple cools, the current stops and the gas valve closes, shutting off the gas so unburned gas is not escaping. When the thermocouple starts to fail, it does not produce enough current to keep the gas valve open even when hot. A new thermocouple usually fixes the problem. Other causes of the same fault can be a partially blocked pilot jet causing the pilot jet to be too small to properly heat the thermocouple, or a failed coil inside the gas valve. Neither is particularly common but I see each perhaps once or twice a year. 

3) Basic version, main burner failing to light or chattering on/off:

A common problem on the basic, non-System E-T version. This is usually a failed relay on the “relay module”. A new relay module is fiddly to fit but usually fixes the problem.

4) System E-T control panel failure:

The electronic control panel on the System E-T versions has a spectacular repertoire of failure modes, which it is only too happy to implement at a moment’s notice ;) Some odd behaviours including the air distribution fan only running at full speed, the gas burners chattering on and off, or the main burner refusing to light (which is usually 0Vac on terminal 29 instead of 230Vac that ought to be present). Failure of the control panel is the second-most common failure after the air circulation fan expiring. The simplest way (sometimes the only way) to diagnose control panel failure is to fit a new one and see if the fault is corrected. I keep them as stock items. 

5) Thermista-Stat failure:

Either the heating stops working completely, or it operates unreliably or randomly. To eliminate the Thermista-Stat is can be bypassed by disconnecting it from the PCB terminals 7 and 8, then connecting together the PCB terminals labeled 7 and TEST. This introduces a resistor on the PCB which replicates the function of a working Thermista-Stat for fault tracing. (Curiously, the Thermista-Stat wiring although low voltage and only two wires, is polarity-conscious on some of the J&S boilers so if connected with the two wires reversed, some odd fault behaviours can occur.) If the Thermista-Stat has recently been removed from the wall and refitted (by say, a decorator), reversing the two connections may fix a fault. 

If you are within driving distance of me near Hungerford and need your warm air boiler fixing, call or text me on 07866 766364.

Mike

P.S. I have just found a System E-T fault tracing chart given to me by Johnson and Starley many years ago when I did a training course there. A pink laminated A5 document which I photographed and include below. (Hopefully J&S will not mind me including it here.) Zoom in to read the detail.

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