Bypass valve

[D_Hailsham]

vaillant 620E

pump in boiler

There's more than one model called the 620E. Can you be a bit more specific? The GC Number would help.

 

[AndyPRK]

turboMAX plus, thermoCOMPACT

 

[D_Hailsham]

turboMAX plus, thermoCOMPACT

Thanks for that information. Yours must be the thermoCOMPACT;the turboMAX is the combi version of your boiler.

I don't understand why an automatic bypass valve has been installed as there is already one built-in to the boiler. (See 4.8.7 in the boiler manual.) I would ask the installer why he did this.

You mentioned that the indicator stayed on 1. This is because you need to turn the red knob about 10 times to get it to move from 1 to 2 -this allows fine tuning of the valve. If there was no bypass built-in to the boiler, the ABV would need to be set to about 3.

 

[AndyPRK]

Thanks for the information.

I will try turning it round and round.

I TXT the installer yesterday, but no reply.
He did like installing lots of things.

He didn't look at my boiler before installing tank, although he worked on it 2 years ago.

 

[AndyPRK]

Turns out I had managed to adjust it to 2.5 but it’s still bypassing.

Have set to 3 now.

 

[D_Hailsham]

Turns out I had managed to adjust it to 2.5 but it’s still bypassing.

Have set to 3 now.

3 is only an estimate. You may have to experiment.

 

[AndyPRK]

It's good to have a starting point though, thank you.

3 and 3.5 no good

 

[ScottishGasMan]

The thermocompact does have an internal bypass as stated. However at its age its not a terrible idea to have an external as the internal may well not be in great working order now.

In those scenarios, I typically close the external bypass right down. Turn on the hot water heating till flow and return to cylinder are hot. Turn it off so the zone valve closes. then open the bypass until heat can be felt flowing through it. That way you know it will be open in the event of a zone valve failure or for the boilers pump overrun.

 

[fezster]

For pump overrun and zone valve failure, that works. But there are cases where the bypass maintains the minimum flow rate through the boiler too. With Vaillant's, if the boiler cycles, it takes 30-40s to modulate down after firing up again, and the bypass may need to be opened further to allow minimum flow, especially if TRV's are closed or if the CH pump or pipework is undersized.

 

[AndyPRK]

Anyone know this Tower APV that I have?

I've gone past 6 (max) and its into a shaded area.
When will the thing stop by passing ? and be completely blocked?

 

[D_Hailsham]

Anyone know this Tower APV that I have?

I've gone past 6 (max) and its into a shaded area.
When will the thing stop by passing ? and be completely blocked?

Two possible causes: Valve faulty or something is keeping it open, e.g muck in the pipe.

 

[fezster]

If it's anything like the honeywell one, it'll break if you turn it beyond its maximum setting.

 

[AndyPRK]

note to self.

I have turned off the 2 rads in the front bedrooms, and now have the dining room rad working. (this is how I always used to have it)
but turned them on to get the air out the system.

 

[D_Hailsham]

I have turned off the 2 rads in the front bedrooms, and now have the dining room rad working.

The system needs to be balanced.

 

[AndyPRK]

my plumber tells me the higher the number or MAX the more it flows/bypasses .
Looking at the instructions/graph I think he has a point.

So trying the other direction now.