Problems Venting System

[Tommohawk2]

Hi all. Have just drained and refilled system and added Sentinel X400 for a clear out. Previously it was working OK but flow seemed slow on distant rads.

But now the system wont circulate hot water. USP3 pump is running, boiler is heating water and outlet is v hot but the hot water isnt getting as far as the pump. The pump should self vent and advice is leave it on max CC pressure for 30 mins minimum... but if theres no water getting to pump it'll be running dry.

Important point to note - the pump is pretty much at the highest point on the system, although the FE tank is about 1 meter higher than the pump.

There is a Flamco auto vent but I'm not convinced this is working, although the vent itsel is high in the loft, the pipework connects it to a low point on the system - which I would have thought wouldnt do much.

Any ideas? I dont want to ruin the pump obviously.

 

[CountryFan]

All relevant valves open? F&E cistern got water in it? Motorised valve(s) working?

 

[Tommohawk2]

Yes all valves open, F and E has filled, 3 port valve working normally. Heat seems to circulate as far as pump, but no further. Feels like either lots air in system or pump no working properly - not sure how old it is.

 

[Exedon]

Select hot water only to make sure primaries are clear back to boiler.
If still no go try pulling power plug out of pump wait until any air/water noise stops plug power back in.
May need repeating several times .
Auto air vents are the work of the devil we replace with manual ones if system drained.

 

[CountryFan]

Any air vents at the cylinder?

 

[Tommohawk2]

Select hot water only to make sure primaries are clear back to boiler.
If still no go try pulling power plug out of pump wait until any air/water noise stops plug power back in.
May need repeating several times .
Auto air vents are the work of the devil we replace with manual ones if system drained.

I've tried all combos but esp HW only as simpler run. The autovent looks iffy - but I released top and water comes out suggesting no air in that pipe.
I tried powering down and back up and get lots gurgling which suggests air in system. Have tried running several times but just doesnt seem to clear. Boiler cuts because feed v hot and return still cold.

Any air vents at the cylinder?

The Flamco flexvent is on the return from the HW loop, on a short vertical run.

 

[Johntheo5]

This Boiler has a Grundfos UPS3 pump?, if so, unfortunately, it doesn't display the power in watts like most A rated pumps now. The pump flowrate (if any) can then easily be derived from the pump curve or if the pump is defective or impeller vanes sludged up. If you have, or obtain a energy monitor like my one then you can read off the power in watts very accurately and from that and the pump curves rule the pump in/out.

 

[Tommohawk2]

This Boiler has a Grundfos UPS3 pump?, if so, unfortunately, it doesn't display the power in watts like most A rated pumps now. The pump flowrate (if any) can then easily be derived from the pump curve or if the pump is defective or impeller vanes sludged up. If you have, or obtain a energy monitor like my one then you can read off the power in watts very accurately and from that and the pump curves rule the pump in/out.

Sorry, I dont follow. Yes its UPS3 pump, and although its powered its difficult to know if its actually pumping. The manual gives the pump curves, but thats only if its working propery. Its on CC setting, so it shouldn't be varying according to demand.

 

[Exedon]

I've tried all combos but esp HW only as simpler run. The autovent looks iffy - but I released top and water comes out suggesting no air in that pipe.
I tried powering down and back up and get lots gurgling which suggests air in system. Have tried running several times but just doesnt seem to clear.



Keep trying lol it will
Gurgle and shift.
Maybe clear pic's of pump & close pipework?

 

[Tommohawk2]

one odd thing. the vent which runs to the FE tank is on the boiler side of the pump ie the feed to the pump. but that means the pump can suck air in through that vent??

Edit: sorry that hasty sketch is misleading. There is feed also after vent so pump should take from there... assuming feed is clear. I did clean tank before refilling.

 

[Johntheo5]

Sorry, I dont follow. Yes its UPS3 pump, and although its powered its difficult to know if its actually pumping. The manual gives the pump curves, but thats only if its working propery. Its on CC setting, so it shouldn't be varying according to demand.

Yes, remove the pump cable cable from the terminal box, get a bit of cable and connect a socket to one end connect the other end to the terminals that you removed the pump cable from. Connect a a 3 pin plug to the end of the (now removed) pump cable, plug the energy monitor into the socket and plug the pump cable plug into the energy monitor. Start the boiler and I would suggest change the UPS3 to CC2, then start the boiler and read off the watts.
If the pump is OK but pumping against a full restriction the power will be 20watts, if its pumping say, 0.5m3/hr (8.3LPM), the power will be 30watts, if its pumping 0.8m3/hr (13.33LPM) the power will be 38watts, etc.

 

[Johntheo5]

one odd thing. the vent which runs to the FE tank is on the boiler side of the pump ie the feed to the pump. but that means the pump can suck air in through that vent??

View attachment 425086

That pipe should be from the boiler flow (hot), the cold feed is then normally teed in after the vent but no more than 150mm from it, try and establish where the cold feed is, are you sure that the cold feed isn't teed in to the vent with a short bit of pipe from the F&E cistern, a combined vent and cold feed, like mine.

 

[terryplumb]

Your boiler may have air trapped in it.

 

[Tommohawk2]

Your boiler may have air trapped in it.

I've vented it, seemed full. But does gurgle like mad on first start.

 

[Tommohawk2]

That pipe should be from the boiler flow (hot), the cold feed is then normally teed in after the vent but no more than 150mm from it, try and establish where the cold feed is, are you sure that the cold feed isn't teed in to the vent with a short bit of pipe from the F&E cistern, a combined vent and cold feed, like mine.

Its not combined. vent first then feed after about 120mm