Automatic Bypass Valve Query

[Tigermad]

I had an automatic bypass valve fitted to my unvented system yesterday and it was left at 0.4. Goes from 0.1-0.5. Anyhow I thought I would set it today according to the instructions. So I closed it off completely to th 0.5 mark and then turned all the trvs on. I then began turning it until the pipe started to get warm. Problem is the abv is in the airing cupboard and it is fitted to the pipes marked flow and return. The flow pipe is hot but the return pipe remains stone cold. Even after leaving the heating on for 10 minutes. So turning the valve makes no difference. Am I doing something wrong? Why is the return pipe stone cold?
I just tried turning the heating off and the pipe from the ABV got red hot even though the ABV is turned off

Ignore the non copper pipes. These are from the old system and are redundant.

 

[Aire]

I presume the pipe to the zone valve is the flow? If it is then the abv looks to fitted the wrong way.

Is the abv fitted before or after the zone valve?

 

[Tigermad]

I presume the pipe to the zone valve is the flow? If it is then the abv looks to fitted the wrong way.

Do you mean the horizontal one? The horizontal one is coming downhill from the flow to return. Is this wrong? The return is on the left of the bypass and the flow is on the top (horizontal), the one with the arrow. The zone valve is attached to the return.
The unvented hot water cylinder is in the loft so the abv is before the zone valve from the boiler but after the zone valve coming down from the cylinder.

 

[SimonG]

I presume the pipe to the zone valve is the flow? If it is then the abv looks to fitted the wrong way.

Is the abv fitted before or after the zone valve?

Glad it wasn't just me. Thought I'd had too much beer last night.

 

[Tigermad]

So is it right or wrong after my reply?

 

[Aire]

Sounds like it's fitted ok, unless the valve is faulty or blocked then you shouldn't have any issues setting it up.

 

[Tigermad]

So which pipe do I have to feel getting warmer. The very small piece on the left going to the return?

 

[John.g]

I had an automatic bypass valve fitted to my unvented system yesterday and it was left at 0.4. Goes from 0.1-0.5. Anyhow I thought I would set it today according to the instructions. So I closed it off completely to th 0.5 mark and then turned all the trvs on. I then began turning it until the pipe started to get warm. Problem is the abv is in the airing cupboard and it is fitted to the pipes marked flow and return. The flow pipe is hot but the return pipe remains stone cold. Even after leaving the heating on for 10 minutes. So turning the valve makes no difference. Am I doing something wrong? Why is the return pipe stone cold?
I just tried turning the heating off and the pipe from the ABV got red hot even though the ABV is turned off

Ignore the non copper pipes. These are from the old system and are redundant.

View attachment 36343
View attachment 36344

I had an automatic bypass valve fitted to my unvented system yesterday and it was left at 0.4. Goes from 0.1-0.5. Anyhow I thought I would set it today according to the instructions. So I closed it off completely to th 0.5 mark and then turned all the trvs on. I then began turning it until the pipe started to get warm. Problem is the abv is in the airing cupboard and it is fitted to the pipes marked flow and return. The flow pipe is hot but the return pipe remains stone cold. Even after leaving the heating on for 10 minutes. So turning the valve makes no difference. Am I doing something wrong? Why is the return pipe stone cold?
I just tried turning the heating off and the pipe from the ABV got red hot even though the ABV is turned off

Ignore the non copper pipes. These are from the old system and are redundant.

View attachment 36343
View attachment 36344

The 0.1 to 0.5 settings are 0.1 bar to 0.5 bar or 1 M (meter) to 5 m.
The purpose of the ABV is to to maintain a minimum flow rate through the boiler on pump over run and also to maintain a minimum flow rate in the event of a very low heat demand where some/all of the TRVs are throttled in.
I presume that you were just testing its functionality with the above test with all TRVs ON (open??) and a setting of 1 M (0.1). Now the circ pump, depending on its speed setting may or may not be producing 1 M head with a large flow rate (all TRVs open) so you may not have got any flow rate due to this (pump head < 1 M) and maybe a circ pump speed setting of only 1?.
You could look at the pump make/model & current speed setting, then assuming that you need say 0.3 M3 per hour flowrate, by looking at the pump speed curves you can see what pump head is required, for example if the speed setting is 2 then the pump head at this speed required might be 3M so you would set the ABV to 0.3, and so on, you can then test it by shutting off the TRVs and ensure it is then opening.

 

[John.g]

Here is a example of one ABV setting.

 

[Tigermad]

Hi folks me again. Something is not right since the bypass has been fitted. Nearly every night at 6.40pm there a crackling /gushing water sound through the lounge radiator valve. This rad is nearest to the boiler. I have the hot water cylinder programmed on my evohome system to turn off at 6.40pm so I think it’s linked to this. Any ideas why this is happening?