Automatic Bypass Valve Query

[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?

 

[John.g]

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]

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]

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]

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]

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.

 

[John.g]

Both sides of the AAV got red hot??

OK' it looks as if it did, now can you set the AAV (temporarily) to index setting of 0.2 with boiler on, then stop the boiler and see if you are still getting that whooshing sound from the rad.

 

[Tigermad]

Both sides of the AAV got red hot??

OK' it looks as if it did, now can you set the AAV (temporarily) to index setting of 0.2 with boiler on, then stop the boiler and see if you are still getting that whooshing sound from the rad.

Thanks. Yes red hot. It only makes the crackling sound now and again. I can't make it do it so will have to test over a few days. Just for info when the boiler fired up the water loudly gushed around all the pipework for about 30 seconds or so.

 

[JTplumbingservices]

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

From what I’m gathering from your info the flow is on the right hand of the pic and the zone valve is on the return. If this is the case then B has to go to the boiler for it to work the way it’s been piped.

 

[John.g]

Thanks. Yes red hot. It only makes the crackling sound now and again. I can't make it do it so will have to test over a few days. Just for info when the boiler fired up the water loudly gushed around all the pipework for about 30 seconds or so.

Gushing sound; sounds like air in the system.

 

[Tigermad]

From what I’m gathering from your info the flow is on the right hand of the pic and the zone valve is on the return. If this is the case then B has to go to the boiler for it to work the way it’s been piped.

Yes that's correct.

 

[Tigermad]

Gushing sound; sounds like air in the system.

There's nothing coming out of the rads when I bleed apart the from the towel rail that needs bleeding every week or so because the toprails don't get as warm. Lots of air comes out when I do that which is strange for a sealed system. Been doing it for over a year.

 

[JTplumbingservices]

There's nothing coming out of the rads when I bleed apart the from the towel rail that needs bleeding every week or so because the toprails don't get as warm. Lots of air comes out when I do that which is strange for a sealed system. Been doing it for over a year.

If the towel rail constantly needs bleeding and nothing else does then it could be an issue with the towel rail which is quite common

 

[John.g]

Is there a AAV (automatic air vent) or a number of them in your system, if there is just check if the little cap on the air nozzle(s) on top of the AAV is open or shut, some prefer just to open these occasionally just to check for any air once all the air has been expelled after a drain down/refill of the system.

What pump/model have you got and what setting is it on?.

 

[Tigermad]

Is there a AAV (automatic air vent) or a number of them in your system, if there is just check if the little cap on the air nozzle(s) on top of the AAV is open or shut, some prefer just to open these occasionally just to check for any air once all the air has been expelled after a drain down/refill of the system.

What pump/model have you got and what setting is it on?.

Hi. No aavs on system. The only pump I have is inside the boiler as far as I know. Is that right for an unvented system?

 

[John.g]

That's correct (gas boiler) and you can't access it (not GSR) , post #57 above suggests that it could be a issue with the towel rail.

I meant to ask you this before, why did you decide to fit a ABV??, was it because the boiler manufacturers require it or some other reason.

 

[Tigermad]

That's correct (gas boiler) and you can't access it (not GSR) , post #57 above suggests that it could be a issue with the towel rail.

I meant to ask you this before, why did you decide to fit a ABV??, was it because the boiler manufacturers require it or some other reason.

Yes the boiler recommend it even when there is one built in. This is if all there wasn't a bypass rad. Also since the unvented system was fitted the radiators make a loud hissing noise so the installer recommended he try this to see if it helps. Since the bypass was fitted and inhibitor put in it is now have hissing and crackling. Wish I didn't bother to upgrade now. Cost me over £6k

 

[John.g]

You would think the installer should sort it out if these problems are there from the time of the upgrade but you probably know all this, I'm afraid I can't offer you any other suggestions.

 

[John.g]

Hi. No aavs on system. The only pump I have is inside the boiler as far as I know. Is that right for an unvented system?

The boiler probably has one, there should certainly be at least one more installed in the system, this is often on a T piece where the cylinder coil enters the cylinder top and before any MV.

 

[Tigermad]

Will have to see if I can see one on any of the pipework. Never told about it anyway.

 

[John.g]

I have a feeling that the ABV when opening is allowing trapped air in your system into the return and causing all sorts of issues (not the ABVs fault) , if a AAV or manual air release isn't fitted then how was the air in the system initially released on refilling the system I wonder, the boiler AAV is fitted to remove air from the boiler and not the system but may do so over a prolonged period but I wouldn't bet on it.
One other query, if there is a pressure gauge in the boiler display, it should read ~ 1bar when cold and ~ 1.5 to 2.0 bar hot.

 

[Tigermad]

I have a feeling that the ABV when opening is allowing trapped air in your system into the return and causing all sorts of issues (not the ABVs fault) , if a AAV or manual air release isn't fitted then how was the air in the system initially released on refilling the system I wonder, the boiler AAV is fitted to remove air from the boiler and not the system but may do so over a prolonged period but I wouldn't bet on it.
One other query, if there is a pressure gauge in the boiler display, it should read ~ 1bar when cold and ~ 1.5 to 2.o bar hot.

Had a look and can’t see one on any pipework. Yes pressure is fine under 2 when hot and a tiny bit over 1 when cold.

I think the air got in when refilling and wasn’t released.

 

[John.g]

Would advise then to get your installer or plumber to install one ASAP.

 

[Tigermad]

Would advise then to get your installer or plumber to install one ASAP.

He’s been installing for over 30 years. Surely he would have put one there?

 

[Tigermad]

He’s been installing for over 30 years. Surely he would have put one there?

Would advise then to get your installer or plumber to install one ASAP.

Replied above about the pressure question.

 

[John.g]

He’s been installing for over 30 years. Surely he would have put one there?

He’s been installing for over 30 years. Surely he would have put one there?

Can't answer that one, is he aware that you are still having problems after the fitting of the ABV?, if not just pick up the phone and ask him to return and sort things out, your system never seems to have been right since the upgrade.