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.

 

[doitmyself]

Hi. Thanks for the reply. Did you see my pic and post number 3? Does the position looks wrong ?

If pipe A in the pic below goes to the boiler, it's piped wrongly. But if pipe B goes to the boiler, it's correct.

 

[John.g]

If pipe A in the pic below goes to the boiler, it's piped wrongly. But if pipe B goes to the boiler, it's correct.

View attachment 36944

Correct, and of course also assumes that B is on the boiler flow, that test above should prove it one way or the other but surely it should be also possible to trace those lines, if not already done so.

 

[Tigermad]

Hi. Pipe a and b are the same pipe. If you mean directions then a goes into the loft to the unvented cylinder and b goes down towards the boiler. The whole pipe has return written on it.

 

[John.g]

Hi. Pipe a and b are the same pipe. If you mean directions then a goes into the loft to the unvented cylinder and b goes down towards the boiler. The whole pipe has return written on it.

Can you just do one thing please and post back, turn up the cylinder stat to max (normal setting should be 60C) and see which one of those pipes gets hot first.

 

[John.g]

Hi. Pipe a and b are the same pipe. If you mean directions then a goes into the loft to the unvented cylinder and b goes down towards the boiler. The whole pipe has return written on it.

Reading your reply again, literally, the (and as I suspected) zone valve if fitted on the SUPPLY or FLOW to the hot water cylinder coil, the RETURN is the vertical pipe so the ABV is the wrong way round?.

Here is your image with arrow.

 

[doitmyself]

Hi. Pipe a and b are the same pipe. If you mean directions then a goes into the loft to the unvented cylinder and b goes down towards the boiler. The whole pipe has return written on it.

A and B are actually two separate pipes which connect to the motorized valve; but that's not important. Your second sentence answers my question as pipe B goes to the boiler, so the bypass is installed correctly.

As for checking if the bypass is set correctly, yes, it's the short length of pipe between the bypass and pipe 'B' which you need to feel. However, if the motorized valve from the HW cylinder is closed so there is no flow coming through the MV from pipe A, then you can feel pipe B to check if the ABV is opening.

If pipe B is the HW return to the boiler, where does the heating return connect?

 

[JTplumbingservices]

If pipe A in the pic below goes to the boiler, it's piped wrongly. But if pipe B goes to the boiler, it's correct.

View attachment 36944

Where is the boiler and pump in relation to this pic?

 

[Tigermad]

Where is the boiler and pump in relation to this pic?

Hi. Sorry for the late replies I did not get notifications. The boiler is downstairs under the stairs directly below the airing cupboard. The pump is in the boiler I don't have one seperatesl as far as I know

 

[Tigermad]

A and B are actually two separate pipes which connect to the motorized valve; but that's not important. Your second sentence answers my question as pipe B goes to the boiler, so the bypass is installed correctly.

As for checking if the bypass is set correctly, yes, it's the short length of pipe between the bypass and pipe 'B' which you need to feel. However, if the motorized valve from the HW cylinder is closed so there is no flow coming through the MV from pipe A, then you can feel pipe B to check if the ABV is opening.

If pipe B is the HW return to the boiler, where does the heating return connect?

Not sure where the heating return connects sorry

 

[Tigermad]

Straightforward enough.
1. Shut off the ABV, turn the setting knob clockwise to o.5
2. Ensure all zones (if fitted) on, and all TRV.s fully open.
3. Turn any/all room stats to max. (my suggestion)
4. Ensure boiler is actually firing or cycling on/off.
5. Very slowly turn ABV setting knob anticlockwise until the outlet pipe starts getting warm/hot.
6. Turn ABV setting knob clockwise by 1/2 a turn.
Forget the rest of the instructions for awhile and you can revisit them later.
Re 5 above. IMO, you can expect the pipe(s) to start to get warm at ~ setting 0.3 to 0.2.

Hi. I've done your test and the pipe only stats to get very slightly warm at around 0.25. Even when fully open the pipe is only slightly warm is that correct? By slightly warm I mean nowhere as hot as the flow going into it.

 

[Tigermad]

I thought it was thrashed out re the ABV positioning and the consensus was that it is installed correctly, my only slight unease concerns the vertical "return" pipe, this has a motorized valve attached which I would have thought is a bit unusual as they are normally installed on the flow.
I will just repeat what I said in some other post above, with the boiler firing normally and up to temperature, open (anticlockwise) the ABV fully to index 0.1, if the pipes on both sides of this don't get "red" hot in less than say 1 to 2 minutes then you have a problem. Just re close (clockwise) the ABV fully to index 0.5 after the test.

Just tried this. The pipe on the return side doesnt get red hot just slightly hot when fully open. I have waited a good few minutes.

 

[John.g]

Not sure where the heating return connects sorry

Thanks, if the pipes on either side of the AAV are/were cold, the HW MV closed. With boiler on to CH, if you opened up the AAV fully do the pipes then get hot on both sides of it within a minute or less?. if they do then the AAV is operating/installed correctly, if they don't the there is something wrong.
I appreciate the question was asked a few times but not sure of your reply.

Edit: Just saw your other posts, thanks.

 

[Tigermad]

Thanks, if the pipes on either side of the AAV are/were cold, the HW MV closed. With boiler on to CH, if you opened up the AAV fully do the pipes then get hot on both sides of it within a minute or less?. if they do then the AAV is operating/installed correctly, if they don't the there is something wrong.
I appreciate the question was asked a few times but not sure of your reply.

Edit: Just saw your other posts, thanks.

Just done it. The small return pipe is only slightly warm. Nowhere near as hot as the flow pipe.

 

[John.g]

Just tried this. The pipe on the return side doesnt get red hot just slightly hot when fully open. I have waited a good few minutes.

There is definitely something amiss then, if the boiler and system contents are up to near normal running temperature of say 60 to 70C then both sides of the AAV should get equally very hot in a very short time when opened fully as you are effectively short circuiting the flow&return pipework.

 

[Tigermad]

There is definitely something amiss then, if the boiler and system contents are up to near normal running temperature of say 60 to 70C then both sides of the AAV should get equally very hot in a very short time when opened fully as you are effectively short circuiting the flow&return pipework.

The radiators had been fully on for only 10 mins. My boiler is set at 65. Maybe I didn't leave it long enough?