Automatic Bypass Valve Query

John.g · Feb 11, 2019

Tigermad said:
Here you go. Thanks
View attachment 36907 View attachment 36908

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.

doitmyself · Feb 12, 2019

Tigermad said:
the abv is before the zone valve from the boiler but after the zone valve coming down from the cylinder.

The ABV must be fitted between the flow and the pipe between zone valve and boiler. If it's on the wrong side of the valve there will be no flow to the boiler when the valve is closed, which defeats the purpose of the ABV.

Tigermad · Feb 12, 2019

doitmyself said:
The ABV must be fitted between the flow and the pipe between zone valve and boiler. If it's on the wrong side of the valve there will be no flow to the boiler when the valve is closed, which defeats the purpose of the ABV.

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

Tigermad · Feb 12, 2019

The first vertical pipe is the return. This has the zone valve attached. The furthest right says flow from boiler on it. The abv is on a pipe from the return to the flow. I am not sure what the other horizontal pipe is below the horizontal one with the abv. This joins to the flow but has its own pipe going to the boiler on the other end.

John.g · Feb 12, 2019

Tigermad said:
The first vertical pipe is the return. This has the zone valve attached. The furthest right says flow from boiler on it. The abv is on a pipe from the return to the flow. I am not sure what the other horizontal pipe is below the horizontal one with the abv. This joins to the flow but has its own pipe going to the boiler on the other end.

View attachment 36925
View attachment 36926

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.

doitmyself · Feb 13, 2019

Tigermad said:
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 · Feb 13, 2019

doitmyself said:
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 · Feb 13, 2019

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 · Feb 13, 2019

Tigermad said:
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 · Feb 13, 2019

Tigermad said:
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.

d83f4fdb-703c-4a88-9d98-fa16adbaca14-jpeg.36345

doitmyself · Feb 13, 2019

Tigermad said:
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 · Feb 13, 2019

doitmyself said:
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 · Feb 23, 2019

JTplumbingservices said:
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 · Feb 23, 2019

doitmyself said:
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 · Feb 23, 2019

John.g said:
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 · Feb 23, 2019

John.g said:
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 · Feb 23, 2019

Tigermad said:
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 · Feb 23, 2019

John.g said:
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 · Feb 23, 2019

Tigermad said:
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 · Feb 23, 2019

John.g said:
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?

John.g · Feb 23, 2019

Perhaps, but you did say that the return is cool in comparison to the flow, try again after say 20 minutes, and let us know the result.

Tigermad · Feb 23, 2019

John.g said:
Perhaps, but you did say that the return is cool in comparison to the flow, try again after say 20 minutes, and let us know the result.

Thanks. So do I have to turn all rads fully on our can i just do it to 1 to make the boiler fire up and stay on? Bit of a pain having to keep going round them all

Tigermad · Feb 23, 2019

Hi. Another question. This isn't my cylinder but I have one of the little white cylinders too. But mine is at floor level. What is it?

John.g · Feb 23, 2019

Just 1 will do, just make sure the boiler is firing, thats all, or if you go to the boiler now and feel the Flow (top) pipe it should be quite hot, once it is just open up the AAV and both sides of it should get very hot as well in a very short time.

The "white cylinder" is a expansion vessel.

Tigermad · Feb 23, 2019

John.g said:
Just 1 will do, just make sure the boiler is firing, thats all, or if you go to the boiler now and feel the Flow (top) pipe it should be quite hot, once it is just open up the AAV and both sides of it should get very hot as well in a very short time.

The "white cylinder" is a expansion vessel.

Thanks. Just ran it with 1 on for literally a few seconds and it got red hot straight away. Wonder why it didn't do that earlier.

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