Problems Venting System

[Johntheo5]

Maybe forget for the moment opening the drain valve to check the cold feed, breaking the pump inlet will check that anyway and the piping up to there.

 

[Tommohawk2]

You mean break the pump inlet without draining?? Also I've got x400 I'm trying to get in there so will probably need to drain a bit. What's best way to ensure x400 gets into system rather than sits in FE tank?
Also today on firing up system hot water has definitely got round a bit further and faster that yesterday.. but still most rads cold and HW not getting heat through coil

 

[Johntheo5]

Yes, obviously shut pump valves first, I'm talking about breaking the pump flange which is downstream of the valve.

 

[Tommohawk2]

So isolate pump both sides, undo joint on outlet just enough to be sure water in there? Sorry if sounding dim!

 

[Johntheo5]

Yes, isolate valves, then break the joint on pump outlet, open the pump inlet valve to get a nice little flow, shut the pump inlet valve, repeat with the pump outlet valve, when finished test, tighten up the outlet pump flange joint, reopen both valves fully.

Have you tried the pump on CC1 and taken the watts or on any other settings??.

You could shut the ballcock mains supply and keep draining until the water is at the bottom of the cistern, this should get the chemicals into the system, reopen ball cock supply.

 

[Tommohawk2]

Just done watts - they fluctuate slightly but only by about 1w:
with CH and HW on
CC1 5w, CC2 6w, CC3 7w
PP1 3w, PP2 3w, PP3 4w
CP1 2w CP2 4w, CP3 5w
with CH only the figures are the same, with HW only the figures are about 2w lower in CC, and about 1w higher in CP mode

 

[Johntheo5]

All useless, do the above, read the last paragraph re ball cock sullpy in case you missed it while posting.

 

[Tommohawk2]

when you say useless, you mean not correct? so low reading imply airlock rather than blockage?

Alos just realised I dont have large enough spanner for pump nuts - only a DIY guy!

 

[Johntheo5]

Looks like airlock as all those power readings (W) are all way too low even if the pump is dead heading..........to be sure run on CC2, confirm that the power is 6W then shut the pump outlet valve fully for say 3 or 4 seconds, check power again and reopen outlet valve fully. If those pump isolating valves are wheel type gate, ensure that there is ~ 3 to 4 full turns between fully shut and fully open.

 

[Tommohawk2]

ok with outlet closed briefly, power goes to 24w and can hear flow restriction in valve

 

[Johntheo5]

That's very interesting, pump curves shows a deadheaded ~ 20W (on CC2) with a shut outlet so looks very much like the flow into the pump is severely restricted or non existent.
So, boiler off, shut both pump isol valves, break the pump INLET flange, reopen pump inlet valve and check flow at the parted flange.

Are you sure that the isn't a isolating valve somewhere on the 15mm feed???

 

[Tommohawk2]

OK all pretty hot at moment so will need to wait a while before doing anything. I dont recall doing or seeing any isolation on feed, and tank drained OK on last drain down so feed should be clear. That said, in effort to clear airlock I backfilled and there was very little flow up into tank which is why I thought feed T on pump inlet side might be blocked. That also fits your comments on watts flow at pump - maybe some kind of intermittent blockage.

 

[Johntheo5]

You will probably be at this for some time so to stop the boiler cycling etc you could remove the pump cable from the terminal box after carefully noting the terminal numbers, connect a plug to the pump cable end, and just plug in to a extension lead any time you require the pump to run, the mid position 3 way valve will ensure that there the water can flow in one or other of the rads or HW coil.

 

[Tommohawk2]

Ok some progress. I've drained down just enough to clear the section of speedfit which includes vent and inlet. I then removed the speedfit section completely. The 15mm feed was fairly clear, but the 22mm straight section was quite blocked... maybe 5mm diameter. To my mind this could account for restricted flow and difficulty backfilling. I've cleared that section and will now reassemble.. but will be a while before reporting back. Massive thanks for help so far, and fingers crossed!

 

[Tommohawk2]