Problems Venting System

[terryplumb]

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

Sounds like it's air locked,what boiler is it ,where are you venting it from ?

 

[Tommohawk2]

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.

I dont have power meter of that sort. But we do have usage meter which is pretty accurate. I just did quick test and looks like only using 13W. But not reliable as too many other things on and off. But still not sure how to make sense of the curves. Surely if pump is in CC mode itll use the same power whatever?

 

[Johntheo5]

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

That's a very common system, you may have a blockage where the cold feed is teed into the pipe.

I dont have power meter of that sort. But we do have usage meter which is pretty accurate. I just did quick test and looks like only using 13W. But not reliable as too many other things on and off. But still not sure how to make sense of the curves. Surely if pump is in CC mode itll use the same power whatever?

No, the pump power required depends on the pump head and flowrate which depend on the system resistance, number of rads etc, it could be drawing 45watts with pump head of 5.0M at a flowrate of 1.1m3/hr. (18.3LPM).

You might change to CP1 (constant pressure) and check the watts again

 

[steven lee]

You are right to be suspicious of that auto vent. If it is piped to a low point it will not clear air sitting at the pump, so check the cap on it is actually loose and not screwed shut. With the pump off, bleed the highest radiators and crack the pump centre screw briefly to let any trapped air out, then refill slowly and let it settle before switching the pump back on. If the feed and expansion tank is full but water is still not reaching the pump, that cold feed tee is worth checking for a blockage, as others have said.

 

[Tommohawk2]

That's a very common system, you may have a blockage where the cold feed is teed into the pipe.


No, the pump power required depends on the pump head and flowrate which depend on the system resistance, number of rads etc, it could be drawing 45watts with pump head of 5.0M at a flowrate of 1.1m3/hr. (18.3LPM).

You might change to CP1 (constant pressure) and check the watts again

I dont think feed is blocked - based on fact that FE tank drained readily and I cleaned it well before refill. But its possible.
I get that power may depend on setting, number of rads etc. But for a given setting eg CC2 you might expect power used to be same whatever the pump id doing? Maybe not. I cant make sense of the curves I'm afraid - the lower set show power on one axis and flow on the other - but what are the various plots for? Theres 7 plot lines and i cant see what each is for.

 

[Tommohawk2]

Update. I part drained again and backfilled via drain cock. FE tank filled so looks like feed is clear although it did seem slow. Can't hear gurgling now so look like airlock has cleared.
But still won't pump round. I did what I probably should have done before which is check with magnet. Feed to pump seems ok but other side Def has some Fe. 3 port valve also a little. All of which fits with heat getting to pump but not beyond.
I've got heating bloke coming tomorrow.. hopefully he can replace pipe/pump as required.