Really stupid question about automatic bypass valve

[jmac88]

I think my one is Kaput. We added a radiator a bit far out and it never warmed up. But I also noticed that the boiler would go on and off regularly even when the radiator return pipe was still cold. But the flow from the ABP was always hot and the boiler sensing the hot water coming in would then shut off even thought the demand was still there for heat.

I tried to adjust the valve and had no idea how to make it change - same issue as described above - but I wasn't smart enough to see that it did change slowly after several turns. I went to city plumbing and they showed me another and we figured out how it worked and theirs was the same as mine. So back home I tried to shut it off but it just turns and turns. I turned at least 20-30 turns in either direction and never a hard stop so I think it is just rotating inside and is non functional so have to replace it. But I have 2 questions:
1. It is located only 2-3 feet from the boiler. There are branches off to the bathroom radiators immediately after so it is the furtherst point from the boiler before a split. I know it needs to be before any branching but is this far enough?

2. Honeywell have one - I think the original is Honeywell - but its GBP50-60. There are similar looking ones - one is Corgi and others in Toolstation or Screwfix for a lot less. They are a paid to fit as no shutoff valves so will drain the boiler in the process. Should I go for the Honeywell or are the cheaper - identical looking ones really the same. Don't want to save on the valve and find it breaks in a few years. But if the original was Honeywell , its not been touched since it was fitted and is only 7 years old!!

3. If it is short circuiting - either because it is broken or set too low, then cranking it up a couple of 0.1 bars should then let the boiler shunt water further and faster around the circuit?

Any feedback from a knowledgeable person would really be appreciated. WFH now and study always freezing!!

 

[BlueLoo]

I think my one is Kaput. We added a radiator a bit far out and it never warmed up. But I also noticed that the boiler would go on and off regularly even when the radiator return pipe was still cold. But the flow from the ABP was always hot and the boiler sensing the hot water coming in would then shut off even thought the demand was still there for heat.

I tried to adjust the valve and had no idea how to make it change - same issue as described above - but I wasn't smart enough to see that it did change slowly after several turns. I went to city plumbing and they showed me another and we figured out how it worked and theirs was the same as mine. So back home I tried to shut it off but it just turns and turns. I turned at least 20-30 turns in either direction and never a hard stop so I think it is just rotating inside and is non functional so have to replace it. But I have 2 questions:
1. It is located only 2-3 feet from the boiler. There are branches off to the bathroom radiators immediately after so it is the furtherst point from the boiler before a split. I know it needs to be before any branching but is this far enough?

2. Honeywell have one - I think the original is Honeywell - but its GBP50-60. There are similar looking ones - one is Corgi and others in Toolstation or Screwfix for a lot less. They are a paid to fit as no shutoff valves so will drain the boiler in the process. Should I go for the Honeywell or are the cheaper - identical looking ones really the same. Don't want to save on the valve and find it breaks in a few years. But if the original was Honeywell , its not been touched since it was fitted and is only 7 years old!!

3. If it is short circuiting - either because it is broken or set too low, then cranking it up a couple of 0.1 bars should then let the boiler shunt water further and faster around the circuit?

Any feedback from a knowledgeable person would really be appreciated. WFH now and study always freezing!!

There are some recent posts about abvs.

In short, they are grossly misunderstood with regards to their operation by almost everyone, especially so where modern, variable speed pumps are installed.

This is your 1st action.
What pump do you have and where is it.
If your pump is in a system boiler, you might not need an ABV.
Same if your boiler is a combi.

If you have a std boiler with an external pump, then a boiler bypass is required to suit the plumbing and system setup.

For old pumps (constant speed), ABVs are fine.
For new pumps (Variable speed) ABS don't work. Unless you replumb the bypass accordingly (manual bypass and flow meter) you will have to set the pump to work in Constant Speed mode. Not a huge problem but you will be giving up the energy benefits of the modern pumps. A manual bypass isn't hard to do if you are DIY minded.

 

[jmac88]

Boiler is Combi but I called Worcester Bosch and they confirmed that I should have an ABV with TVRs (its a 20 year old boiler 35CDi) and the ABV should be on a minimum circulatory loop of 2m, ie 1m from boiler giving a 2m round trip. SO its is situated correctly and is recommended.
But...
Its clearly not working. as I can turn it forever in either direction. Like 30+ turns. I have taken off the cover and dial as they make ti hard to test but it should have a hard stop at some point. From seeing one at the local plumbing store, it turned around 12 times before a hard stop - looked an identical type.

Based on your helpful comments. The pump they said is equivalent to an older Grundfoss with around 6M header but I have no idea if it is variable speed or constant speed. Inherited boiler with house and I personally would never never have a combi. Much prefer the individual components too. Separate pump etc.
Just opened up the boiler. It has 2 pumps - Bosch (actually Grunfos) Type UPS 15-60/1A. Now I understand the Grunfos Coding - UPS is 1 single speed. UPS3 is 3 speed
But still water seems to be circulating via the ABV and I can't adjust it as it just turns

 

[jmac88]

I also have no idea if the ABV is a Honeywell one or a cheaper version that looks identical. There are no markings on it to say Honeywell. Thus is If i replace ti, should I replace with the expensive Honeywell - which the original may have been and has broken or was always faulty - or save GBP40 and get one from Tool-station for GBP20 which looks identical. I hate to use inferior parts when the expense and hassle is in fitting and not the part. But if the Honeywell one was duff, why spend the extra? Any views on that?

 

[BlueLoo]

Odd.

The iom for the combi does not require a bypass.

Are you sure it's the model type you say?

Do you have a photo?

 

[jmac88]

I called up Worcester Bosch Tech Support and they said it does need a bypass valve

I have added TVR to all rads & Honeywell Evohome smart heating. Evohome will control demand for heat if all TVRs shut off but they advised for general cooling and if a valve closes and boiler demand for heat is not shut off - lets say a Evohome system glitch
I don't actually know if the system ever really worked properly. The new UFH is fine as it has a pump and clearly draws hot water in as required. But the other rads on the system at the far end - via a 22mm branch are not heating. ie. 3 branches - One 22mm from boiler which splits to UFH manifold and to the otehr rads on GF. Then nearer the boiler a feed on 15mm to 1st floor and attic room - 2 circuits as well as a split to bathroom.

Just enabled all three 1st floor rads and boiler kicked in for around 2 mins then cuto out. Demand for heat still there as EvoHome shows its on but hot water has circulated the bypass valve and come back to the boiler piping hot sot he boiler has shut off heat again.

Definitely need to replace the valve as it is definitely faulty. But would prefer to have a shutoff valve in there as well as perhaps I don't need the auto one and can then shut off the auto bypass or just use a manual one and close it off mostly.

If the working auto ones go up to 0.6bar then is that enough to force the water around the entire system or even on the max setting will it still not be enough.

 

[BlueLoo]

I called up Worcester Bosch Tech Support and they said it does need a bypass valve

I have added TVR to all rads & Honeywell Evohome smart heating. Evohome will control demand for heat if all TVRs shut off but they advised for general cooling and if a valve closes and boiler demand for heat is not shut off - lets say a Evohome system glitch
I don't actually know if the system ever really worked properly. The new UFH is fine as it has a pump and clearly draws hot water in as required. But the other rads on the system at the far end - via a 22mm branch are not heating. ie. 3 branches - One 22mm from boiler which splits to UFH manifold and to the otehr rads on GF. Then nearer the boiler a feed on 15mm to 1st floor and attic room - 2 circuits as well as a split to bathroom.

Just enabled all three 1st floor rads and boiler kicked in for around 2 mins then cuto out. Demand for heat still there as EvoHome shows its on but hot water has circulated the bypass valve and come back to the boiler piping hot sot he boiler has shut off heat again.

Definitely need to replace the valve as it is definitely faulty. But would prefer to have a shutoff valve in there as well as perhaps I don't need the auto one and can then shut off the auto bypass or just use a manual one and close it off mostly.

If the working auto ones go up to 0.6bar then is that enough to force the water around the entire system or even on the max setting will it still not be enough.

You can replace the abv and add a manual valve as well. You can add a device like a tacotherm commissioning device as well if you know the minimum boiler through rate. (Recommended by grundfoss iirc)

TacoSetter Inline: Taconova

www.taconova.com

 

[jmac88]

i replaced the ABV with a similar one, quick swap and when I saw the inside of the old one the part that moves on the screw had come off and was completely loose and hence it was always open. When replaced, all the rads came on fine when I cranked up the setting to around 4 from 2. Top is 6.5