Lag Lead System??? what is it?

[Viper Gas]

Hello chaps,

i came across a 'lag lead' system.
ie two heat only boilers working together to heat up a whole house and provide hot water via two indirect hot water cylinders.
The boilers are keston 28.

the lag lead is controlled via three switches which im not sure what they do. I.E one makes the 1rad symbol appear, another makes 2rad symbol appear.
has anyone installed on like this and if so what do the three switches do?

cheers
DD368

 

[Ray Stafford]

I haven't been involved in one of these for a while, but my (very limited) understanding is this.

Your lead boiler comes on first when there is demand. If it can satisfy the demand alone, thats fine. If it can't satisfy it, the lag boiler comes on to support it.

There is usually/sometimes a sequencer switch that reverses the lead/lag in order equalise wear on the boilers, so if you start with Boiler A = lead, boiler B = lag, the sequencer changes it to B=lead, A=lag.

Do you have a pic of the three switches?

 

[stani]

We're the kestons on a jig from the manufacturers into a low loss header?

 

[Dotty]

I haven't been involved in one of these for a while, but my (very limited) understanding is this.

Your lead boiler comes on first when there is demand. If it can satisfy the demand alone, thats fine. If it can't satisfy it, the lag boiler comes on to support it.

There is usually/sometimes a sequencer switch that reverses the lead/lag in order equalise wear on the boilers, so if you start with Boiler A = lead, boiler B = lag, the sequencer changes it to B=lead, A=lag.

Do you have a pic of the three switches?

Pretty much covers it!