Circulation pump

[Elandrel]

Last night I switched to fixed speed control mode (speed 3) to try and get closer to the target 1 m³/h I think I need. The system had been running on proportional control (speed 3) for 3 or so hours before. The flowrate increased to 0.9 m³/h, but within an hour or so I experienced a pump trip. I restarted and switched back to proportional control mode. The pump tripped again. I noticed "Lo" on the display for flowrate just prior to that trip. I don't know what caused the previous trip(s).

What might have caused a low flow status? The Evosta 3 has a fault code for dry running which I didn’t seem to get. Why would the flowrate be low? The system seems to be running ok again in proportional mode (speed 3). I’m concerned about the trip and would like to know if it could be a faulty pump or whether it is more likely something about my system.

I’ve also included a summary of the system details when I was running in fixed speed (speed 3).

Proportional control speed 3 (just before trip)
8.6W
2.3m head
Lo m³/h

Fixed speed (speed 3) (short running time, system may not have settled down)
34 W
5.2m head
0.9 m³/h

 

[Johntheo5]

I’ve got instantaneous system data for proportional control speed mode 2 and mode 3 from the Evosta 3 faceplate.

Mode 2:
Power: 8.1 W
Head: 1.8 m
Flowrate: 0.3 m³/h

Mode 3:
Power: 22 W
Head: 3.8 m
Flowrate: 0.7 m³/h

Any thoughts on the data? I reckon I need 1 m³/h to deliver the 24 kW rated boiler heat input with a 1 m/s flow velocity. So at 0.7 m³/h I'm a little low. I could try the fixed speed mode 3 but I don't want the additional noise / load. I think the next step is to try and clean the system with an additive like X400?

I’ve also spotted brown silt in my F&E tank. I fully cleaned it before the pump change. I must have gotten carry over from the vent? I need to do more start-up testing to see if it just happened when I first started the pump and perhaps whatever blockage / restriction has now cleared.

Is the next step to run the system with X400? What is the best approach? E.g. how long should I run it in the system for (days? Weeks?)? Is a once per day purge from the magnetic filter enough, followed by the system drain down at the end of the run?

I have quite a few “U” sections where quite a few downstairs radiators are plumbed from above. I’d need to drain those individually which would be quite a bit of effort. Do I have to do a full drain down of the system after running with X400?

Can't comment on the chemical treatment but would suggest running the pump in CP Mode setting 3 at 4.5M, then circulating say 3 or 4 rads only in batches and compare/post pump data readings, also, if HW cylinder installed, just circulate through this as this is possibly the least restrictive, it should give a fair idea of the restriction in the boiler HEX (heat exchanger).

 

[Johntheo5]

Last night I switched to fixed speed control mode (speed 3) to try and get closer to the target 1 m³/h I think I need. The system had been running on proportional control (speed 3) for 3 or so hours before. The flowrate increased to 0.9 m³/h, but within an hour or so I experienced a pump trip. I restarted and switched back to proportional control mode. The pump tripped again. I noticed "Lo" on the display for flowrate just prior to that trip. I don't know what caused the previous trip(s).

What might have caused a low flow status? The Evosta 3 has a fault code for dry running which I didn’t seem to get. Why would the flowrate be low? The system seems to be running ok again in proportional mode (speed 3). I’m concerned about the trip and would like to know if it could be a faulty pump or whether it is more likely something about my system.

I’ve also included a summary of the system details when I was running in fixed speed (speed 3).

Proportional control speed 3 (just before trip)
8.6W
2.3m head
Lo m³/h

Fixed speed (speed 3) (short running time, system may not have settled down)
34 W
5.2m head
0.9 m³/h

Just saw this post, so try settings as I suggested or even CP2, the pump impeller may require a clean out now with a tie wrap even though just installed.

 

[Elandrel]

System appears to be running ok again.

Central heating (but not hot water)
Proportional control mode speed 3
22 W
3.8m head
0.7 m³/h

I've run the heating just to heat the water in the hot water tank. The heating to the radiators was off. The pump provided the following data.
Proportional control mode speed 3
32 W
4.5 m head
1.1 m³/h

Would that system resistance at that flowrate be expected just for running through a hot water tank?

Next step is to chemical clean with X400.

If access to the pump was easier I would take it out and check the impeller is not clogged up. But access to the pump is constrained and I have ball valve pump isolations, which I'm concerned will just start leaking from the spindles if I use them. So unless you think there is clearly something wrong from the data above, then I'll go ahead with the clean and can check the pump when I do the full drain down in a month or so.

 

[Johntheo5]

PP mode increases the head with reducing resistance so there is more resistance when on CH, just run on CP2 mode briefly with both to see how it works.
As long as not running on full speed mode CC3, you should be OK, IMO, to check the impeller in a month or so.