Air consistently entering F&E system? Circulation error, Help needed

[Jay1986]

Hi all,

hoping to get some help on an issue that has stumped me so far, builder mate has also had a look and not come to a conclusion. I’m new to plumbing issues and struggling to get my head round everything.

- Potterton Suprima HE 50 located on ground floor
- Hot water tank in airing cupboard directly above
- seperate F&E pipes leading up a tank in the attic
- 8 rad CH system, piping a mix of 22/15

System has had a few old rads and piping removed, optimised by using 21s instead of two 11s in two rooms, piping routed under floor boards, nothing major. Ran the system like this after the changes for a day and it worked fine, filled/bleed rads with no issues. I knew the pipes were dirty so then had a magnaclean filter fitted on the boiler return, plumber unfortunately balsed this up and leaked water into the PCB/cabling above it. I dried off all the electrics and he replaced the pcb. Boiler then ran for a short time before throwing up a circulation error code, plumber said the pump is not strong enough to push water through the system with the debris etc. the error shuts the boiler down for two mins and then it fires up again.

We agreed I’d run the MC3 for a week or so to see if it shifts the pump problem, I cleaned the filter multiple times over the next ten days and sure enough there is lots of debris on it. The circulation shutdown error happens consistently during this period, although if I run 4 rads only it seems to cope.

Pump was then changed as the problem kept happening, Grundfos UPS3. Pump running on slowest speed. Upon filling the system and running it with the new pump there seemed to be a ridiculous amount of air. Pump also sounds like it’s working against air/resistance which gets worse/louder on a higher speed. I also consistently had to bleed the HW vent and the few rads which were on. I wondered if air was entering via the vent.

System was drained today to fit an auto vent for the hot water, filled back up and bled, issue still happening. Builder mate thinks maybe heat exchanger is blocked up.

When I just put HW on the circuit is small an doesn’t seem to trip - boiler/HW/expansion towel rad, but there is still a ridiculous amount of air in it. The pump is audibly drawing water and maybe air, the auto vent is consistently venting, I can also consistently vent a small amount of air from the top of the towel rad, when I Ioosen the top magnaclean vent whilst everything is running it also releases air bubbles, almost consistently in sync with how the pump sounds when pushing. I’ve been in the attic and as the pump pulls the water level drops but then goes back up, the vent is also sucking, tried with a cup of water.

Could there be a blockage so pump sucks air via the vent which is then getting into the system? Is the boiler tripping because of the air or a blockage? I’ve check the thermistor readings and they are within tolerance and consistent with each other to 25%.

Anyone have any ideas????

Pic of the airing cupboard layout should hopefully be attached to this post. I believe the vent is directly below the pump and the feed goes into the HW return.

Thanks!

 

[kidgreen61]

Assuming your system is piped correctly, have a look (test with a magnet) to see if the pipe is blocked where the cold feed from header tank joins the pipework. If magnet sticks, there's your problem.

 

[Exedon]

Looking at the pictures expansion is connected just before pump but is that the cold feed connected into cylinder return?
If so that's wrong.
I take it you have checked the expansion tank to make sure expansion pipe is not pumping over?

 

[Jay1986]

Thanks the replies.

I’ll give the magnet a go tomorrow, although the system fills fine when I’ve refilled it.

Exedon I think you’re right, and through this forum I’ve learned thats not right, but what puzzles me is the system was working like that for years prior. Expansion tank is not over pumping, levels seem right, few cm above the feed, few below the drain and vent.

 

[Exedon]

Your probably going to have to cut into pipework at some stage.
While I realise you could move cold feed I would just convert to sealed system run it say 1/2 a bar job done .

 

[Jay1986]

Do you mean to reroute the feed so the piping hen runs vent - feed - pump? My builder mate could reroute it but he’s away till early Jan now. The plumber who fitted the filter spoke about a sealed system but cost would be around £2k which isn’t feasible right now.

 

[Exedon]

2 k to convert a system to sealed? Wow can I have some of that?
18 ltr expansion vessel and kit less than £60 add tube fittings and say a days work.

 

[Jay1986]

Hmm, me thinks he may have been talking bull then. He was talking about needing a different tank in the airing cupboard which would have cost about 800 or so, then mains fed expansion vessel near the boiler. I’ll have to do some research.

 

[Gasguru]

The pipework looks to be a bodge job...with several issues including a safety flaw.
Could you confirm that the 22mm pipe running down on the right and tee'ing in to the pump inlet is the safety vent and the 15mm tee'ing into the cylinder return near the red valve is the feed and expansion pipe. If so the simplest fix is to convert to a combined feed and vent arrangement...the 15mm is capped near the red valve and the 15mm pipe then tee'ed into the 22mm vent pipe just above the ceiling.

 

[Jay1986]

Thanks for the reply, there’s a lot I’m finding in this house which has been completely bodged, has made doing it up a right pita… From what I can see I think what you’ve written is correct, any way of confirming it for sure?

 

[Jay1986]

Would I need to do anything else to the piping apart from joining the 15 to the 22? And when you say ceiling do you mean near the top of the airing cupboard?

 

[Johntheo5]

That piping mod should work OK, mine from new 50 years ago has the feed teed into the vent right at the feed&expansion tank and works perfectly well, I could run one rad with the pump running at a 6M head and still get no pump over or air ingress.

Just to be sure, to be sure, have look at the arrow on the poump body and ensure its pointing upwards, also ensure that the pump is on minimum speed, one solid green light, as shown. This is still a 4.2M head, suggest changing to constant pressure CPI as per LEDs, this is a constant 3M head which just may stop the air ingress and should/may give sufficient head. When/if you do change to CPI, continue to vent afterwards as it may take considerable time to get rid of any entrained air, vent with boiler/pump off.

Any idea of your old pump make/model, and setting?.

 

[Jay1986]

Thanks for the reply and tips John. The pump is the right direction and it has been on speed 1, although I have tried it on the other speeds which was accompanied by increased noise from the system.

I’ll give CP1 a go today along with the magnet test, fingers crossed! Unsure of the old pump but I’ll find out today. At this stage I just need the system working half decently for the next few weeks till I can have the feed teed into the vent.

 

[Johntheo5]

Thanks for the reply and tips John. The pump is the right direction and it has been on speed 1, although I have tried it on the other speeds which was accompanied by increased noise from the system.

I’ll give CP1 a go today along with the magnet test, fingers crossed! Unsure of the old pump but I’ll find out today. At this stage I just need the system working half decently for the next few weeks till I can have the feed teed into the vent.

Thats strange re noise since your present head is 4.2M so the head should have been lower with decreaed noise levels on CP1 (3M) and PP2 (3.7M, max), PP2, even though probably a bit weak at ~ 2.5M at say 0.9ms/hr may be worth another go?.

 

[Gasguru]

Would I need to do anything else to the piping apart from joining the 15 to the 22? And when you say ceiling do you mean near the top of the airing cupboard?

If you pist pics of the Feed & Expansion cistern and associated pipework it would help to clarify where the connection should be.
If the pipework layout is incorrect then it's futile to faff about with pump speeds as you're just masking the real issues.
The pressures around the system are currently favourable to the pump drawing in air. Connecting the feed into the vent enables the 2 pipes to operate at the same pressure (the neutral point) preventing air ingress.
If you take a look in the install manual you will see a diagram of the close coupled feed & vent arrangement. This is better than a combined feed & vent as the air is vented quicker. Again the idea is to keep the pressure at the 2 pipes equal (or very close). These pipes connect just before the pump inlet for safety reasons and to allow the pump to exert its full pressure across the entire system helping to further prevent air ingress.
Currently if the red cylinder balancing valve were to be inadvertently closed the system no longer has the feed pipe connected (when the cylinder 2 port is unenergised) presenting a safety issue.