Hi. I hope I can get some help with diagnosing a problem with my CH/DHW system. These are the facts.
Boiler is a Potterton Suprima 80 (~ 20 years old but still in good condition)
DHW is stored in Megaflo cylinder (unvented system)
DHW is on a water circuit separate to two CH circuits serving first floor and ground floors. All have zone valves.
Time control on the DHW is by a Honewell timeswitch which is programmed on from 0600 to 2400 daily.
The Megaflo has a cylinder stat set to 55 degrees. I have tested the stat and confirmed it is working. The cable to the stat has two cores connected: L and SL. The SL core gives 0 volts (as expected) when the temperature control is turned down and 230V when it is turned up.
The stat cable SL feeds the Brown core on the zone valve. The one valve also has Grey, Orange and Blue cores.
The problem with the boiler is that it is continually cycling off and then on again after a few minutes. The sequence is as follows:
1. Boiler off. Light flashes green (= Boiler temperature satisfied) (boiler temperature control is set at ~30% round from "Off")
2. After ~ 2 minutes, light solid orange (= No external call for heat)
3. After ~1 second light flashes orange/green (= Air proving & ignition)
4. After ~20 seconds, burner ignites. Light solid green (= Burner on)
5. After ~1 minute burner shuts down. Light flashes green and loop back to 1
If the boiler temperature control knob is turned off, the light is flashing orange (= External call for heat - temperature control set to off)
Given that the stat is working, it seems to me that there must be a wiring such that the boiler is continuously receiving a call for heat.
The results of all this are: (1) DHW temperature is excessively hot (2) excessive gas consumption (3) increased wear and tear on boiler?
My question is, if the following are the wired components, then in what order should I test the various connections:
Boiler
Time switch
Zone valve
Cylinder stat
All comments advice and questions appreciated. I have a 'map' of all the connections at the junction box installed adjacent to the cylinder if that would help analysis.
Boiler is a Potterton Suprima 80 (~ 20 years old but still in good condition)
DHW is stored in Megaflo cylinder (unvented system)
DHW is on a water circuit separate to two CH circuits serving first floor and ground floors. All have zone valves.
Time control on the DHW is by a Honewell timeswitch which is programmed on from 0600 to 2400 daily.
The Megaflo has a cylinder stat set to 55 degrees. I have tested the stat and confirmed it is working. The cable to the stat has two cores connected: L and SL. The SL core gives 0 volts (as expected) when the temperature control is turned down and 230V when it is turned up.
The stat cable SL feeds the Brown core on the zone valve. The one valve also has Grey, Orange and Blue cores.
The problem with the boiler is that it is continually cycling off and then on again after a few minutes. The sequence is as follows:
1. Boiler off. Light flashes green (= Boiler temperature satisfied) (boiler temperature control is set at ~30% round from "Off")
2. After ~ 2 minutes, light solid orange (= No external call for heat)
3. After ~1 second light flashes orange/green (= Air proving & ignition)
4. After ~20 seconds, burner ignites. Light solid green (= Burner on)
5. After ~1 minute burner shuts down. Light flashes green and loop back to 1
If the boiler temperature control knob is turned off, the light is flashing orange (= External call for heat - temperature control set to off)
Given that the stat is working, it seems to me that there must be a wiring such that the boiler is continuously receiving a call for heat.
The results of all this are: (1) DHW temperature is excessively hot (2) excessive gas consumption (3) increased wear and tear on boiler?
My question is, if the following are the wired components, then in what order should I test the various connections:
Boiler
Time switch
Zone valve
Cylinder stat
All comments advice and questions appreciated. I have a 'map' of all the connections at the junction box installed adjacent to the cylinder if that would help analysis.
