boiler "cycling" and tripping out after rad removal and new pump

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blocky71

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Morning all
I've had a bit of a disastrous wkend and am hoping I can get some much needed advice before I call in an engineer.
I have a 3 story town house with a couple of rads on ground floor that don't get very warm . Heating is a sealed system, British gas 300+ boiler, 14 rads, 11 small,1 medium, 2 large.
I bled and balanced system, still colder rads on ground floor. They get hot at the top but cool at the bottom.
Possibly sludge I thought so removed and cleaned ground floor rads.
That's where my problems started, after I'd refilled sytem and put boiler on it tripped out with an " f22 dry" message. I soon found that the pump (circulatingpumps cp63) wasn't spinning. Once I'd manually spun it it took over and everything was ok. The next issue was every time the boiler turned off then back on the pump failed to start and needed manually starting. I tested the resistance of the impellor ( finger test) and it was fairly week. This and the cold downstairs rads led me to buying a new pump ( grundfos alpha2).
I swapped pumps and now boiler is cycling and tripping out with "f25 diff" message. This relates to either an airlock or too high or low differential on the flow and return to the boiler according to the hand book. I re bled system and have tried pump on each setting, no joy . Any suggestions welcomed. Cheers Chris
 
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I would say that either you have put the pump the incorrect way round or you still have an airlock in the pipe work. Bleeding the radiators doesn't solve this, check for any air vents on the pipe work in the airing cupboard etc. It's a case o persisting with it, add a little more pressure than usual and keep cycling the pump on and off to move the air in the pipes. Turn the stat down on the boiler to reduce the chance of lockout until the air is cleared
 
Cheers for your time rampage. I'd persist for ages but the other half isn't quite as patient after 2 days with very little hot water and heating!. Pump is right way up, electrical plug should face down and does. I found a couple of bleed points on flow and return pipes above boiler and vented them but virtually no air came out. I cant see any other bleed points apart from rads. I had turned temp back up to 60 on the boiler to try and warm the rads and hot water. It was still tripping out when it was set on 38 (min) though...
 
What would be a safe pressure to take the system up to in trying to force the air out?. It's always sat at around 1 bar, I did take it up to 1.3bar.
 
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I don't think your new pump has an air bleed point.

Turn off all the rads on the TRV except one and run for 2 min.

Then open another and close the first. Proceed like this through all the rads and if you are lucky you might solve the problem.

Tony Glazier
 
It sounds as if you completely drained your system.

If so that was a lot more work and a very foolish thing to do.

You should always just isolate the component part being worked on, one at a time and replace it and repressurise before removing another.

Tony
 
He says its an Alpha 2.

I hope it was a late manufacture new one!
 
Thanks for your time guys, the pump instructions say to " ensure " electrical connection plug faces downwards. It can only be fitted one way for this to be the case, if I did fit it the other way all the pump settings and led's would be upside down too. I will look for a flow arrow just to rule it out but am certain its correct. I think it is the newer model alpha2 as its a little different to the pics on the web. There's a lot of conflict on pumps, I got this one as the reviews and forums all make out grundfos make the best pumps?. You're correct agile, it is a self bleeding pump and has 7 settings. £140, trust me I could of bought far cheaper!, I was led to believe this was a tried and tested company. I only drained the whole system after the boiler kept tripping. When i cleaned rads originally I did one at a time and refilled each rad before next was emptied as you said Tony. I'd been cycling and resetting the boiler as much as I could over 24hrs before I took the plunge and drained the system. I only did that on the advice given here in the FAQs. I'll try your suggestion of working my way round the rads Tony. When you say run system for 2 mins then what ? Leave system on while I tackle the rads or turn off?. What about that upping the pressure suggestion too?, good or bad idea? . Thanks for your replies, I know some of you are rolling your eyes......
 
Check the arrow on the old pump if you're not sure which way is correct.

If the arrow direction on the new one is now wrong turn the whole thing around then remove the four allen bolts to separate the pump head and turn it to be the right way up.

I'm guessing you have a Vaillant boiler and, judging from the price you paid, the pump is an Alpha2L 15-60. Turns out the one in my system has to be run at constant Speed 3 to keep our Vaillant Boiler happy.
 
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Sounds very much like you've got your pump the wrong way round to me - the location of the plug is no guide to the direction in which it is pumping. You needed to pay attention to which way the arrow was pointing on the body of the old pump, and ensure that the new pump's arrow points in the same direction
 
I'm on till 6 at work so will double check on the pump thing when I get in, if that is what's happened I'll be both highly embarrassed and elated if its just a case of turning it/ the head round. I never saw a direction arrow on the new pump when I was fitting and am pretty sure all the instructions just referred to the plug pointing downwards. Thanks again, I'll be back with results.
 
Tripping out at 38 I would still go with my first post of pump wrong way. I hope it is this as it's an easy fix to the problem for you.
 
Well you guys are legends and I'm extremely upset that it turns out I am indeed a plank. Just got the " love of my life" to take some pics and you were all right with your diagnosis of the pump wrong way round. I dunno what to say except thanks. I'm so f#*#ing annoyed at my incompetence! . Will refit and report back. Nice one !
 
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