CH Automatic Bypass and Short Cycling Question

[WhatNext]

Hi

I was wondering if you could help me ?

I have a Vokera Mynute 20HE gas boiler which is controlled using a standard S Plan system ( 2 x 2 port motorised valves ) together with a programmable room thermostat for the central heating and a single channel programmer for the hot water. Each radiator has a TRV.

There is a 22mm automatic bypass valve ( ABV ) connected between the 22mm flow and return pipework.

The ABV is faulty in that it is stuck in the minimum setting – it can not be adjusted.

When the majority of the radiators shut down on their TRVs I can hear ( and feel ) hot water circuiting through this faulty ABV which causes the remaining radiators to stay cooler than they should be before these particular rooms are up to temperature.

Now I understand that there is an automatic bypass valve fitted inside the Vokera Mynute 20HE.

Can I therefore simply remove this faulty external valve, blanking off the associated pipework and rely on the automatic bypass valve in the boiler ?

I did speak to Vokera and they advised that I removed the external ABV as there is already an ABV inside the boiler, however they suggested that I fit a manual bypass in place of the external ABV so as to prevent boiler ( short ) cycling ?

I am confused - I would have thought that a manual bypass would cause a higher chance of short cycling ??

 

[oldbuffer]

Try downloading the fitting instructions for the ABV. It will be adjustable, but with some form of locking to prevent disturbance after setting. It may well be a Honeywell DU145.

 

[WhatNext]

Hi

No it is not DU145 - it is a cheap one - I had a look at an identical one to see if I was doing something wrong when I was trying to adjust it - this is why I know it is broken and stuck on the minimum setting.

 

[fezster]

When the majority of the radiators shut down on their TRVs I can hear ( and feel ) hot water circuiting through this faulty ABV which causes the remaining radiators to stay cooler than they should be before these particular rooms are up to temperature.

This is how it is supposed to operate, though, to maintain the required circulation through the boiler.

Not saying it's not adjusted incorrectly but if you read some past posts on setting up ABVs, they often say it should just barely pass water with all rads operating, and then a quarter turn to close it (i.e. the ABV will open the minute one rad shuts down).