Friday 14 December 2012

Hot Water Not Getting Hot, Heating Getting Too Hot

I was asked to look at a heating system because the lady was not getting any hot water when the boiler was on, and the only way she could get the hot water to heat was to put the immersion heater on. Also, she had also been struggling to control the temperature of her radiators. Even with the room thermostat turned down low the radiators were still heating up.

Looking in her airing cupboard there was a Honeywell V4073 three-port valve. The hot water was set to be on and the room thermostat was turned down low. Feeling the flow and return to the cylinder both pipes were only slightly warm. Feeling the lever on the valve head it was loose, and moved easily from side to side with no resistance. This indicates that the valve was open for the heating. 

After removing the casing from the valve I attempted to move the mechanism back to the hot water position manually. I was unable to do so and so removed the head from the valve body. As soon as I removed the valve head it sprung back to the hot water position. I felt the spindle on the valve body and that appeared to be moving with little resistance.

I replaced the motorised valve head with a new one and tested it's operation. The valve was operating correctly and heating was restored to the hot water cylinder.

Potterton Suprima Red Flashing Reset Light

Was called by a gentleman today who I had done work for in his previous house. He had moved to a new property but had been having trouble with the boiler and thought it needed servicing. I visited to service the boiler and look into any issues he was having with the boiler.

The boiler was a Potterton Suprima and the gentleman was regularly having to press the reset button as the red light was often flashing and the boiler was not running. The fault had been happening for the past six months but was gradually worsening. There didn't appear to be any set pattern as to when the boiler would lock-out and the red light would start flashing.

Pressing the reset button would get the boiler going again and it would carry on working for a few days without issue. However, being the winter, the problem was getting more of an issue as the gentleman would get up to find he had no heating or hot water just when he needed it.

I looked over the boiler and serviced it at the same time. The electrode looked to be clean and have the correct spark gap. The ceramic on the electrode looked to be in good condition. The ignition lead was not the original and it may have been that both the electrode and lead had been replaced in the past. The old electrode lead were prone to breaking down and causing ignition problems, they are sheathed with red insulation. The new electrode leads are sleeved in clear plastic, and thicker black plastc where the lead passes through the case.

It is a possibility that the boiler was overheating due to a fault with the thermistor and/or overheat thermostat but in my experience these generally fail and the boiler will lockout every time it runs. I have also experienced the gas valve failing to open which prevents the boiler from lighting. Again, I have found that this usually fails and cannot be resolved through pressing the reset button.

I dropped the panel down to reveal the PCB and could see that there was some signs of scorching to the PCB near the centre of the board. This is common on these PCBs and I expect is related to the lockout issue. There is usually a manufacturer's sticker on the PCB either on a relay or a semiconductor chip which has a sate code on it. This particular PCB was made in 1998 and has lasted well. There is also a date code in the bottom right-hand corner of the data plate, which again was 98, indicating that it was the original PCB.

I replaced the PCB with the new upgraded PCB kit, 5111603. This comes with a new PCB, housing, wiring loom and ignition leads. After fitting this part the boiler has been working well with no issue for the past fortnight.

Tuesday 11 December 2012

Heating and Hot Water Won't Turn Off

I received a phone call from a concerned customer because her boiler was running continuously and her hot water seemed to be exceedingly hot even though both the heating and hot water were turned off on the programmer.

A colleague of mine was in the local area and so he went round to check it out. Sure enough the boiler was still running when he arrived and the house was like a sauna. My colleague removed the programmer from it's baseplate and the boiler went off. Assuming that the problem was with the programmer he replaced it, tested the operation of the three-port valve and left as everything was working fine.

A couple of days later and I receive a phone call from the same lady because her heating and hot water won't turn off again. I went round straight away to find the boiler constantly running and the house like a sauna. The lady had turned the room thermostat right down and both the heating and the hot water off on the programmer.

I looked at the electrics and checked what voltage were where. There was 230 volts at the grey, 24 volts at the orange and on the white wire of the Drayton MA1 three-port valve the voltage exceeded the scale of my Fluke T3 Electrical Tester. It would seem that 24 volts is enough to power the switch live of the Worcester 15 Ri boiler which was fitted.

I disconnected the orange wire and hot water calling from the switch live to the boiler and the boiler went off.  The voltage was coming from the orange wire of the three port valve. I replaced the head on the motorised valve and re-tested the operation of the heating system, which has been working correctly for the past week.

Disclaimer:
The works described in this blog are a record of work undertaken and should not be taken as guaranteed to solve your problem.

Work should only be carried out by persons qualified and competent to do so.