Vaillant EcoTec 838 and hourglass

[bruce_miranda]

To put my theory to the test, I set up a manual schedule this morning where most of the radiators came on from cold at exactly the same time. This allowed a higher flow rate and my flow temperature took 25 mins to get up to the max set on the boiler. So almost in line with everyone else. Also my Block Time didn't kick in until 45 mins since starting and that was when the Return Temperature had risen up to within 2C of the max Flow - which is what this question started with. So the hourglass (block time) starts when the boiler thinks that Return temperature is already too high and stops the boiler from firing for a certain period. The Block time is a timer that starts and ticks down unless there is a new target temperature set within that time which causes the timer to be reset.

I currently have my Block Time and Pump over run set to 20 mins.

[DBMandrake]

To put my theory to the test, I set up a manual schedule this morning where most of the radiators came on from cold at exactly the same time. This allowed a higher flow rate and my flow temperature took 25 mins to get up to the max set on the boiler. So almost in line with everyone else.

That is including you recently turning down the max power output though right ?

[bruce_miranda]

yes. Just winding it down to 18Kw wasn't enough. Because just a few zones open don't create enough of a flow for the heat to move away from the boiler fast enough. I know my pump is too small too for a 36Kw boiler, but for an 18Kw boiler should be OK.

[mtmcgavock]

yes. Just winding it down to 18Kw wasn't enough. Because just a few zones open don't create enough of a flow for the heat to move away from the boiler fast enough. I know my pump is too small too for a 36Kw boiler, but for an 18Kw boiler should be OK.

Is your Automatic Bypass opening too soon?

[bruce_miranda]

It probably is. The issue I have is if I set the ABV pressure too high my boiler will give me an S.53 first thing in the morning because it's only a single zone calling for heat. But now that I have an 18Kw boiler I should reset the ABV too.

[bruce_miranda]

Today was back to a normal schedule where only one zone started up first and again my boiler was back to reaching flow temperature max set in about 2 mins of starting up.