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Dead legs and central heating circulators (Read 19251 times)

runninwata

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Dead legs and central heating circulators
Oct 1^st, 2008, 7:06pm

Here goes!! Have installed a Grant vortex 36/46 condensing oil boiler, supplying a 4 bed house with 11 rads with a 15/60 grundfos pump, unfortunately 4 radiators which were added at an earlier date when the house was extended are not heating.

The radiators all heat when i crack open the valve without one of the radiators in place and drag the water through to them which leads me to believe the circulator isnt fit to cope with the job,

I have tried balancing the system and shutting down the rest of the house and only bringing these rads into service but all to no avail.

My question would be is there any light commercial circulators available that would be stronger than this grundfos 15/60 pump but would still fit into the 130mm port to port dimension or will i have to go for a commercial flanged pump and re jig all the pipework

any help and advise greatfully received

Steve

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thescruff Global Moderator Trade Member Author Offline Who said plumbing was easy. Posts: 6037 Total Thanks: 147 For This Post: 0 Gender: Trade: Plumber	Re: Dead legs and central heating circulators Reply #1 - Oct 2^nd, 2008, 1:40am I would think if the 15/60 don't shift enough water then you have a system problem.
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runninwata

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Re: Dead legs and central heating circulators
Reply #2 - Oct 2^nd, 2008, 7:52am

System problem? maybe but the system was heating ok before the boiler swap and pump swap, the old boiler was pumped using a 15/50. Shocked

I am goin to check pump resistance again as i cant understand that it all worked fine previously, only other thing i was thinking about was a blockage somewhere but that seems unlikely as when i crack open valves without rad the others in this leg heat evenly and ok confused I am!!

Is it possible to get a F Shocked

cked pump straight out of the box?

regards

steve

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CWatters

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Re: Dead legs and central heating circulators
Reply #3 - Oct 2^nd, 2008, 8:45am

Re the balancing.. If shutting down the rest of the system totally didn't cause at least one of the four to heat up then something is wrong with those four. Air lock? sludge? Incorrect plumbing? The pump should be able to push water around.

Not wired in series are they? Perhaps just the one you removed is blocked?

« Last Edit: Oct 2^nd, 2008, 8:53am by CWatters »

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runninwata

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Re: Dead legs and central heating circulators
Reply #4 - Oct 2^nd, 2008, 12:54pm

No, I have removed each of the four rads and cracked the valves at each of the points and the others have begun to heat up as soon as rad re instated the rads then cool, system was flushed prior to instal and has been drained and re filled twice since, initially thought airlock but have had aav installed in leg to these rads ,magnaclean installed also and is remaining pretty clean since installation just minor debris!!

I am going to double check everything is off and isolated other than these rads and will update later

cheers for the advice

steve

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runninwata

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Re: Dead legs and central heating circulators
Reply #5 - Oct 4^th, 2008, 12:49pm

Hi, checked pump resistance was ok, double checked isolation of all other rads, allowed problem rads to call for heat, lifted landing floor (much to the annoyance of swmbo Roll Eyes

) to access flow and return that supplies this side of the house flow gets hot but nothing on return side,
cracked open valve without rad on and rads begin to heat, I am goin mental!! contrary to what my trade is I AINT A PLUMBER! Cry

The installer unfortunately is out of the country on hols at the moment and can not be contacted either!!

Anybody any other ideas, if it is a bockage could this just be flushed by breaking a joint underneath and flushing each of the flows and returns at each of the four rads?

Help

Steve

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bill577 GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #6 - Oct 4^th, 2008, 9:22pm it sounds like you have a block on the return, but before you hack into the pipework, check the pump is installed the right way round, believe me it does happen
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runninwata GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #7 - Oct 5^th, 2008, 7:06am cheers lol i will check this out this morning!! its gettin really cold here now and mrs isnt happy about the fact that we spent approx 4kon boiler and unvented and half the house is colder than it was with the old boiler!! thanks steve
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greg GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #8 - Oct 5^th, 2008, 1:13pm Do any of the radiators heat up or is it just these 4?
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runninwata GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #9 - Oct 5^th, 2008, 7:27pm Hi Greg, rest of house heats up great, only these four no heat at all, they were installed as part of an extension. regards steve
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greg GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #10 - Oct 5^th, 2008, 7:37pm What happens if you shut of the valves to all of the radiators in the house except 1 of the 4?
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runninwata

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Re: Dead legs and central heating circulators
Reply #11 - Oct 5^th, 2008, 7:50pm

Hi greg, tried shutting down all the system except these four then all these four in turn still none of them even start to heat, there is a slight warmth at the valve on the first rad in the extension but seemingly no circulation, i have had this rad off and flushed through water was clean nothing amiss,

regards

steve

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greg GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #12 - Oct 5^th, 2008, 8:11pm I take it that it is a 2 pipe system and that the flow and returns are connected correctly? How high are the rads above the pump?
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runninwata GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #13 - Oct 5^th, 2008, 8:14pm It is indeed a two pipe system and the rads would be on the same level or thereabouts as the pump regards steve
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runninwata GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #14 - Oct 5^th, 2008, 8:16pm flow and return connected correctly, was all operational before boiler swap and adding of 2 extra rads 700 x 300 and 700 x 600 k2s all bi directional valves regards steve
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greg

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Re: Dead legs and central heating circulators
Reply #15 - Oct 5^th, 2008, 8:22pm

A 15/60 should be OK. Are the tails to the rads getting hot? You say you have had the floor up, can you trace the pipes back to where they connect to the rest of the system that is heating OK? If you are getting no circulation it will most likely be an airlock, blockage or piping error ie flow and return are connected together

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runninwata

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Re: Dead legs and central heating circulators
Reply #16 - Oct 5^th, 2008, 8:36pm

yes had the floor up to install two aavs (initially thought airlock) on the leg just as it enters a wall to drop vertically to serve this leg with 4 rads on it,

No only one of the tails is getting hot, (the first rad in the line) the rad doesnt get hot and the other 4 rads are stone cold along with Mrs! lol

Have just managed to speak with installer, he says he thinks the pump could be struggling! I am now doubtful and believe blockage, it worked previously with the old boiler and a 15/ 50 pump, would it do any harm upgrading the pump to a commercial type or is that money wasted.

is powerflush best way to remove blockage or could i do it by removing rads, draining system , connecting hose and mains cold water then opening valves in turn on problem rads with all other rads isolated to flush out blockage?

your help is greatly appreciated

steve

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