Air in CH system and hot water returning to FE tank via the cold feed

[Tiggy1955]

Agreed, speed setting 1 should be fine in normal circumstances but by selecting PP control it will reduce the head from say 3M to ~ 1.5/1.7M and IF the F&E tank "movement" dies down or ceases then at least it will tell you something.

How do I change the PP setting? The pump only has the 3 setting selected via a button.

 

[Tiggy1955]

This doesn't sound like pump-over at all. And if the system is correctly designed, then the speed of the pump is immaterial.

I take it when you turn the boiler off and the system cools and you bleed the radiators, the F&E level is not dropping back down? You'd need to isolate the float valve aka ballcock to check as otherwise it will refill the F&E automatically.

I'm going to come up with the hypothesis that you have a hot water cylinder and that the coil in it is leaking. This would explain the water rising, though not sure where the air issue fits in. Do you have a cylinder or do you have a combi-boiler?

I thought I would post this photo of the piping as it might help to explain the problem in more detail? This piping is directly above the boiler.

 

[Tiggy1955]

So if your ballcock were not refilling the F&E, and no overflowing took place, you think the volume of water in the system would stay the same? There isn't any being added, by, say, a leak from the coil in your hot water cylinder?

How could I check that please?

 

[John.g]

How do I change the PP setting? The pump only has the 3 setting selected via a button.

It has 3 fixed speed settings and 3 PP settings, you press and hold the button for 5 secs to change from FP to PP (page 7 of attachment).
"When you press the button for five seconds, the pump
will change from fixed-speed operation to proportional pressure
control"

 

[Ric2013]

How could I check that please?

If you were to isolate the ballcock and let the system cool, bleed the air out and add back the water you have scooped out, then you should have the same level you started with.

Looking at your photo, I am wondering where your vent is? I am assuming there isn't one? If so, then the system isn't pumping over.

Assuming your pump is somewhere on the boiler flow then anything between the cold feed and the pump inlet is running at a vacuum when the pump is on and there could be a minor weep which is admitting air to the system. Could be a radiator valve, the pump inlet gate valve stem, the pump inlet washer, or one of the joints in or near the boiler.

Alternatively, if there was a blockage, then there must be some degree of scale or rust in the system. Could be the boiler is kettling and creating steam, but I wouldn't imagine that steam could continue to survive as such for very long in the sort of quantity you are experiencing.

You seem to enjoy problem solving, so hopefully this will give you some ideas, but I am beginning to think you may need a professional to attend and have a good look at the system and how it is all arranged.

 

[sammathias]

If the coil has failed in the cylinder the small feed and EXPANSION tank would constantly be overflowing due to the hot water cistern being higher/bigger. It's normal for the water to rise slighlts in the f+e. After all where else is the expanded water going to go????

 

[Tiggy1955]

If you were to isolate the ballcock and let the system cool, bleed the air out and add back the water you have scooped out, then you should have the same level you started with.

Looking at your photo, I am wondering where your vent is? I am assuming there isn't one? If so, then the system isn't pumping over.

Assuming your pump is somewhere on the boiler flow then anything between the cold feed and the pump inlet is running at a vacuum when the pump is on and there could be a minor weep which is admitting air to the system. Could be a radiator valve, the pump inlet gate valve stem, the pump inlet washer, or one of the joints in or near the boiler.

Alternatively, if there was a blockage, then there must be some degree of scale or rust in the system. Could be the boiler is kettling and creating steam, but I wouldn't imagine that steam could continue to survive as such for very long in the sort of quantity you are experiencing.

You seem to enjoy problem solving, so hopefully this will give you some ideas, but I am beginning to think you may need a professional to attend and have a good look at the system and how it is all arranged.

Hi Ric2013 - Thanks for all the info so far. To answer some of your points:

The vent (and by that I assume you mean the pipe that dangles over the FE tank?) is T’d into the boiler flow and is plastered into the wall about 20” to the right of the cold feed shown in the photo.


The pump is in the airing cupboard and I assume is attached to the boiler flow (pretty sure it is - the pipes come up through the floor boards). Above the pump is the 3 way motorised valve - which appears to be functioning correctly when you switch between CH and HW.


As for enjoying solving problems - yes I do - but this one is driving me nuts!!!

Thanks again.

 

[Ric2013]

Ah, so your arrangement is something like this then?

If so, the pump is pulling on the vent and could be pulling in air if it runs too fast. Unfortunately, in PP mode, the pump will start fast even when it then slows down. What you have there is probably a residual of an old legacy system much more than 20 years old that worked very well with the old boilers that had negligable resistance to flow, not so well with a modern boiler. Possibly has never been fully modernised. The pump may well have been on the return once upon a time.

You can try setting down the pump as other have suggested, but my feeling is that this kind of setup is prone to this sort of problem and you might want to look at getting the system reconfigured.

One important question: Did it used to work okay and when did this change?

View attachment 36394

 

[John.g]

Ah, so your arrangement is something like this then?View attachment 36395

If so, the pump is pulling on the vent and could be pulling in air if it runs too fast. Unfortunately, in PP mode, the pump will start fast even when it then slows down. What you have there is probably a residual of an old legacy system much more than 20 years old that worked very well with the old boilers that had negligable resistance to flow, not so well with a modern boiler. Possibly has never been fully modernised. The pump may well have been on the return once upon a time.

You can try setting down the pump as other have suggested, but my feeling is that this kind of setup is prone to this sort of problem and you might want to look at getting the system reconfigured.

One important question: Did it used to work okay and when did this change?

View attachment 36394

My own system has a combined vent and cold feed, ie the cold feed is teed directly into the vent where it passes by the Feed & Expansion tank, I know of a number of systems like Tiggy1995,s above that were modified to this combined system, this obviously isn't allowed in a solid fuel system. However he did say his system worked well as is and the boiler was renewed 9 years ago, I don't think he has had this problem for the past 9 years.

Re the pump speeding up on PP setting, it does, but only for a few seconds to find its steady state condition, its only the press of a button to try it out and it may alleviate if not cure the problem until a permanent solution is found.

 

[Tiggy1955]

Ah, so your arrangement is something like this then?View attachment 36395

If so, the pump is pulling on the vent and could be pulling in air if it runs too fast. Unfortunately, in PP mode, the pump will start fast even when it then slows down. What you have there is probably a residual of an old legacy system much more than 20 years old that worked very well with the old boilers that had negligable resistance to flow, not so well with a modern boiler. Possibly has never been fully modernised. The pump may well have been on the return once upon a time.

You can try setting down the pump as other have suggested, but my feeling is that this kind of setup is prone to this sort of problem and you might want to look at getting the system reconfigured.

One important question: Did it used to work okay and when did this change?

View attachment 36394

Yes that diagram is correct. The system has never been reconfigured. We have lived here since the house was built. The only thing that has changed is the boiler. The original was an Ideal now a Worcester Bosch (I think the builder might have used BG to install the heating system at the time - over 20 years actually).

You are also correct in that this problem has just started in the last few weeks. I have also just realised something else this evening. When the system is set to CH and HW the heating hardly gets hot. On CH only it heats up nicely. I'm at the end of what I think I can do so I'm going to get a heating engineer to have a look at it now. I'm even considering replacing the whole lot with a combo boiler. We live in a bungalow and there are only two of us so a combo should be OK. I'll get advice.

 

[Ric2013]

I think getting someone in may be a good idea. No point fitting a new boiler as a soution until you can be sure what the problem is. Good luck, and please do let us know how you get on - makes it worth our while, you know.

 

[Tiggy1955]

OK guys here is an update on my situation...............

Action taken yesterday:

• I fully drained the system.
• I fitted a brand new diverter mid-position valve. I did this because a) it was old, b) the CH and HW were not working together c) the system was empty so do it now as a preventative measure.
• I have filled the system with Sentinel X400 and that is currently still in the system.

Outcome:

• The system is working very very well - getting a lot hotter that it used to.
• The CH and HW work together now.
• The whole system seems quieter and more efficient.

But:

• The rads still need bleeding within 30 minutes of the CH starting up. One in particular is gurgling and this is the one loosing most of it’s water back to the FE tank.
• The FE tank is still getting water pushed back into it via the flow outlet at the bottom of the tank. I know this because, apart from the rads getting cold at the top, if you watch it for 5 minutes you can actually see the levels rising and you can see murky water entering via the flow outlet. The tank water was perfectly clear yesterday, now it’s rusty red (well at least I guess the X400 is doing it’s job .
• When I bleed the rads the water level in the FE drops back to the correct level.

Planned next steps:

• Leave the X400 in for a couple more days and see if this makes any difference.
• Drain, flush and add some X100 inhibitor.
• Test for another couple of days.
• If I still have the back fill/bleeding problem call a good Heating Engineer for advice.
• Go off and resolve the Brexit Crisis because that looks a lot easier

Thank you all for your help - I’ll keep you posted.

 

[John.g]

OK guys here is an update on my situation....

Action taken yesterday:

• I fully drained the system.
• I fitted a brand new diverter mid-position valve. I did this because a) it was old, b) the CH and HW were not working together c) the system was empty so do it now as a preventative measure.
• I have filled the system with Sentinel X400 and that is currently still in the system.

Outcome:

• The system is working very very well - getting a lot hotter that it used to.
• The CH and HW work together now.
• The whole system seems quieter and more efficient.

But:

• The rads still need bleeding within 30 minutes of the CH starting up. One in particular is gurgling and this is the one loosing most of it’s water back to the FE tank.
• The FE tank is still getting water pushed back into it via the flow outlet at the bottom of the tank. I know this because, apart from the rads getting cold at the top, if you watch it for 5 minutes you can actually see the levels rising and you can see murky water entering via the flow outlet. The tank water was perfectly clear yesterday, now it’s rusty red (well at least I guess the X400 is doing it’s job .
• When I bleed the rads the water level in the FE drops back to the correct level.

Planned next steps:

• Leave the X400 in for a couple more days and see if this makes any difference.
• Drain, flush and add some X100 inhibitor.
• Test for another couple of days.
• If I still have the back fill/bleeding problem call a good Heating Engineer for advice.
• Go off and resolve the Brexit Crisis because that looks a lot easier

Thank you all for your help - I’ll keep you posted.

Thanks for the feed back, did you try the pump on PP control?.

 

[Tiggy1955]

Thanks for the feed back, did you try the pump on PP control?.

Going to do that today. Will let you know - thanks.

 

[Tiggy1955]

Thanks for the feed back, did you try the pump on PP control?.

John G you are a star!!! Set the pump to PP2 and all is sweet! I thank you sir.

Would you mind spending 2 mins explaining to me in laymans terms exactly what the Proportional Pressure setting does? It must be more that just a lower pressure setting - thanks.