Which thermostat should I adjust for the hot water?

[Ackoman]

Hello,

I've got a system boiler supplying central heating and hot water, via an unvented cylinder.

This may seem like a daft question, but if I want to change the temperature of the water then presumably I should do it using the thermostat on the cylinder, and not the water temperature adjuster on the boiler? Should the boiler one be set to maximum permanently?

Thanks,

Ackoman

 

[DP]

Set cylinder thermostat to 55 or similar what you want. Set boiler to higher temperature else boiler will always be on demand to heat water to temperature that is never reached to cylinder thermostat set point

 

[Ackoman]

Set cylinder thermostat to 55 or similar what you want. Set boiler to higher temperature else boiler will always be on demand to heat water to temperature that is never reached to cylinder thermostat set point

As I thought - thanks.

The boiler is displaying a solid tap symbol, even with the cylinder thermostat set low, which supposedly indicates a demand for heat - to me this implies the cylinder thermostat is not wired up correctly.

 

[Echo the husky]

What model boiler do you have?

 

[Iamchamps]

Mine did that on the new boiler I just had installed (vaillant 418) turns out the electrictian forgot to remove a little jumper wire inside the boiler. When boiler on always demand for heat for water regardless of what the thermostat was set to, since it been taken out thermostat works fine.

 

[Ackoman]

What model boiler do you have?

Vaillant 618 ecotech

 

[Ackoman]

Mine did that on the new boiler I just had installed (vaillant 418) turns out the electrictian forgot to remove a little jumper wire inside the boiler. When boiler on always demand for heat for water regardless of what the thermostat was set to, since it been taken out thermostat works fine.

Thanks for the heads up!

 

[hertsboilers]

Vaillant 618 ecotech

Solid tap? Unusual!

It is a system boiler, and heat only, unless you have e-bus controls.

 

[Ackoman]

Just did a little experiment - I turned the cylinder thermostat to minimum, had a shower and listened out to see if the boiler was coming on (too lazy to go and see what the display was saying - the boiler is in the garage and you have to go outside to access it), and it wasn't. I then turned the cylinder thermostat up until it clicked, and a few seconds later I heard the boiler come on - so I guess it is working as it should.

 

[Ackoman]

Solid tap? Unusual!

It is a system boiler, and heat only, unless you have e-bus controls.

Forgive my ignorance - what are e bus controls?

 

[Ackoman]

Vaillant 618 ecotech

Actually, it's a 618 ecotech plus, if that makes any difference?

 

[The831Bunny]

The early ecoTECs (with two control knobs) will show a tap symbol if the hot water knob is turned up. As you probably don't have Vaillant's own controls/programmer/thermostat (as @hertsboilers said eBus controls), then the hot water knob can be turned to minimum and the the tap will disappear.

Leave the heating knob set around 70C. The radiator symbol will then appear when the boiler fires for either heating or hot water.

 

[Ackoman]

The early ecoTECs (with two control knobs) will show a tap symbol if the hot water knob is turned up. As you probably don't have Vaillant's own controls/programmer/thermostat (as @hertsboilers said eBus controls), then the hot water knob can be turned to minimum and the the tap will disappear.

Leave the heating knob set around 70C. The radiator symbol will then appear when the boiler fires for either heating or hot water.

Ahhh OK, so the tap thermostat on the boiler itself is redundant? And the temperature of the water which runs through the heating loop in the cylinder is determined by the setting of the radiator knob?

 

[The831Bunny]

Ahhh OK, so the tap thermostat on the boiler itself is redundant? And the temperature of the water which runs through the heating loop in the cylinder is determined by the setting of the radiator knob?

That's it. Best to keep that temperature about 10-15C above the stored water setting to ensure good heat transfer and efficient HW heating, hence 70C. If this is set lower than the required store temperature, then the cylinder thermostat would never be 'satisfied'.

The HW temperature can be set at the boiler if you have Vaillant controls, it's just redundant if you have standard 240v time clock, stats etc. It's not very clear in the instructions, doesn't cause any problems if turned up though.

 

[Ackoman]

That's it. Best to keep that temperature about 10-15C above the stored water setting to ensure good heat transfer and efficient HW heating, hence 70C. If this is set lower than the required store temperature, then the cylinder thermostat would never be 'satisfied'.

The HW temperature can be set at the boiler if you have Vaillant controls, it's just redundant if you have standard 240v time clock, stats etc. It's not very clear in the instructions, doesn't cause any problems if turned up though.

OK great, many thanks


Derby