Air intake on open vent Y Plan CH system

[PClem]

Problem with air heard in some radiators when pump starts up and then in Bermuda back boiler when pump stops (water settling noise).

Y Plan open vent system with 7 radiators controlled by TRVs and another radiator in hall which acts as a bypass (wall thermostat is located here).

System consists of:
Baxi Bermuda 45/4 Electronic Back Boiler (2001 version)
HW Cylinder
Grundfos UPS2 Pump
7 x Danfoss RAS-C2 trvs
Honeywell V4073A 3 way valve

15mm copper piping to rads
Aladdin autovent on bathroom towel rad
Thumbscrew air vent on HW cylinder high point
Cold feed from F&E tank is on Return to boiler
Vent 22mm is on Flow before pump

System has worked fine for years but recently developed this fault.

All rads get hot, boiler temp set at halfway point. If temp increased this has resulted in intermittent hot water venting into F&E tank.

Pump set to PP1 pulsing mode
Have tried in PP2 mode and standard 1 mode without success.

Checked F&E tank when pump switched on and off but no air activity detected. Water level remains constant.

Recently drained system down and refilled. Had airlock which was cleared by applying mains pressure hose to vent pipe on expansion tank until air came up feed to tank.
System then ran fine for 3 days before air problem returned.

Would appreciate any pointers or areas to check from those with experience of a similar fault.

Thanks in advance
Pete

 

[Chuck]

All rads get hot, boiler temp set at halfway point. If temp increased this has resulted in intermittent hot water venting into F&E tank.

Assuming the temperature is not getting to extreme levels due to a boiler fault, this is almost certainly the primary symptom and the air ingress is a side-effect.

Could be the three-port valve not opening fully but more likely, as it's an open vented system, there is likely sludge blocking the pipework in the vicinity of the pump and F/E junctions. Use the search box on the top right to find loads of similar reports/discsussions of what to do about it.

 

[John.g]

Assuming the temperature is not getting to extreme levels due to a boiler fault, this is almost certainly the primary symptom and the air ingress is a side-effect.

Could be the three-port valve not opening fully but more likely, as it's an open vented system, there is likely sludge blocking the pipework in the vicinity of the pump and F/E junctions. Use the search box on the top right to find loads of similar reports/discsussions of what to do about it.

Three port valve fairly suspect alright, could try it on CH only & check rads only heating,,, HW only.. check cyl coil heating & rads not heating,,,, CH+HW & check both heating.

Did you retrofit the UPS2 recently? and if so did the problem commence with this?
If UPS2 installed recently what pump/model did it replace?.

Link worth reading....Search Results for Query: john.t | Plumbing Advice | Gas Engineers Forum | Plumbing Jobs - DIY and Professional

 

[PClem]

Thanks for the input Chuck and John.

Have replaced the Honeywell 3 port valve and confirmed that is functioning correctly.

UPS2 pump head replaced an UPS 15-50.
Sorry but not sure if this was when air intake problem started, as the replacement of this pump head led to other control problems and this caused me a lot of confusion over a period of time. After posting on your brother electricians forum was advised about the excessive current drawn by the UPS2. Issue was fixed by fitting suppressor cable and replacing relevant damaged control parts. I can confirm the control system now works correctly.

Do you think the UPS2 could be the cause?

Failing this, looks like I will have to replace F/E junctions in the pipework to eliminate possible sludge blockage. I have tried Sentinel X400 but problem remains.

Thanks again.

 

[Chuck]

Failing this, looks like I will have to replace F/E junctions in the pipework to eliminate possible sludge blockage. I have tried Sentinel X400 but problem remains.

Before you get your hacksaw out, sludge is mainly magnetite, which is magnetic enough that you can detect it by feeling it pull on a magnet touching the outside of the pipe.

If the problem has started since you modified the pump, you might have it set too high.

 

[John.g]

Thanks for the input Chuck and John.

Have replaced the Honeywell 3 port valve and confirmed that is functioning correctly.

UPS2 pump head replaced an UPS 15-50.
Sorry but not sure if this was when air intake problem started, as the replacement of this pump head led to other control problems and this caused me a lot of confusion over a period of time. After posting on your brother electricians forum was advised about the excessive current drawn by the UPS2. Issue was fixed by fitting suppressor cable and replacing relevant damaged control parts. I can confirm the control system now works correctly.

Do you think the UPS2 could be the cause?

Failing this, looks like I will have to replace F/E junctions in the pipework to eliminate possible sludge blockage. I have tried Sentinel X400 but problem remains.

Thanks again.

The UPS2 running in PP mode should not cause the problem.

IF the old UPS 15-50 had been running on speed 1 and you ran the UPS 2 on speed 1 then it could cause a problem as the UPS 2 is considerably more powerful but as you are presently running in PP1 mode then there should be no problem as in this mode the pump head(s) and flow rate(s) are even below the UPS 15-50 on speed 1 heads & flowrates.
If the UPS 15-50 had been running on speed 2 then there should be no problem running the UPS2 on fixed speed 1 (or any of the PP settings)

 

[John.g]

The UPS2 running in PP mode should not cause the problem.

IF the old UPS 15-50 had been running on speed 1 and you ran the UPS 2 on speed 1 then it could cause a problem as the UPS 2 is considerably more powerful but as you are presently running in PP1 mode then there should be no problem as in this mode the pump head(s) and flow rate(s) are even below the UPS 15-50 on speed 1 heads & flowrates.
If the UPS 15-50 had been running on speed 2 then there should be no problem running the UPS2 on fixed speed 1 (or any of the PP settings)

I have included a copy of the equivalent UPS2 PP1 flowrates & heads which would apply based the flowrates & heads on the UPS 15-50, for example if the system was running at 13.3 [email protected] then on PP1 this becomes [email protected], if you had/have a very high system resistance due to sludge or whatever then [email protected] = [email protected] and so on.
Another point is the boiler, I see it is range rated to its midpoint of ~ 11.7 kw, I don't know if these back boilers modulate (I think not) and probably just cycle on/off based on the temperature setting?? you say you get pump over if the temperature setting is too high so is there possibly some fault with the boiler temperature sensor?'
Also you say "Y Plan open vent system with 7 radiators controlled by TRVs and another radiator in hall which acts as a bypass (wall thermostat is located here)." this implies that the wall stat controls this one rad so if the wall stat is satisfied or turned down to minimum then there is no permanent by pass.