2 port and cylinder thermostat

[DIYLover38]

Hi Guys,

I’m trying to figure something out, which I need help with. I have electrical testing equipment and have tested other stuff before, and wanted to know if I’m on the right track?

So I have an issue with hot water being slightly hotter than usual. I have checked and the immersion heater is definitely off. I replaced the cylinder thermostat and still no joy. The 2 port is a Myson, but I can’t work out how to get inside it. If I turn water on at the programmer, and wait for it to heat up, then test if the thermostat is asking for hot water after the boiler has gone off, and then also check the 2 port orange or brown wire?

 

[ianmcd]

which Myson 2 port ?there are a few, post a pic

 

[DIYLover38]

Thank you. Hope this is a good photo

 

[ianmcd]

I suspected it would be a power extra, if it ever worked properly you will need a new actuator,but one of the worst valves for being wired up wrong from install

 

[DIYLover38]

I think it worked properly, and possibly still does. When the water is on, it powers up, boiler kicks in, water heats up, then when water goes off on program it all turns off. Yet hot water is really hot and hotter than when I first moved in.

 

[ianmcd]

check the Hot water cylinder thermostat, your hot water can never get any hotter than the boiler thermostat is set at so turning that down might work for you

 

[DIYLover38]

Thanks, great advice. It’s set at 60, that seems too hot, but a google search tells me it’s so legionaries can’t grow?

edited: you mentioned the boiler thermostat, should I be checking this as well?

 

[DIYLover38]

This is my replacement thermostat, does it look wired correctly?

 

[Deleted member 267285]

60 degrees is required to kill off any legionnaires growth yes, so keep it at that. Wiring looks ok to me. Might be microswitch or motor inside powerhead that may have failed? @ianmcd will know better than me.

 

[JohnD]

50C will kill it, but more slowly. If you have a hot-water cylinder where hot water is stored, it is not likely to be a breeding ground.

The loft tank in summer, however, if not insulated, may be ideal.

• Above 70 °C (158 °F) – Legionella dies almost instantly
• At 60 °C (140 °F) – 90% die in 2 minutes (Decimal reduction time (D) = 2 minutes)
• At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain (D = 80–124 minutes)
• 48 to 50 °C (118 to 122 °F) – can survive but do not multiply
• 32 to 42 °C (90 to 108 °F) – ideal growth range
• 25 to 45 °C (77 to 113 °F) – growth range
• Below 20 °C (68 °F) – can survive, even below freezing, but are dormant

 

[ianmcd]

Yes it is to kill Legionella, your cylinder can never get any hotter than your boiler is set at, double check your immersion is not switched on , you would be surprised how many are adamant that it is not when it is

 

[DIYLover38]

Thank you John, makes me feel better

 

[DIYLover38]

Thanks Ian, yes immersion seems to be off unless the switch is wired wrong? Looked up about the position of thermostat, does mine look ok?

don’t worry electrics turned off and will refit cover

 

[DIYLover38]

Could it be the pump?

 

[ianmcd]

Thanks Ian, yes immersion seems to be off unless the switch is wired wrong? Looked up about the position of thermostat, does mine look ok?

don’t worry electrics turned off and will refit cover

Normally Immersion switches have a red neon to indicate if it is on , are you sure you have the correct switch ?