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Ask The Trades › DIY Forum › Plumbing Questions › Dead legs and central heating circulators

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Dead legs and central heating circulators (Read 19325 times)

greg

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Re: Dead legs and central heating circulators
Reply #17 - Oct 5^th, 2008, 8:51pm

Are you able to do a drawing of the pipework layout? Its difficult to see it in the minds eye.

If you go to next pump up from the 15/60 then you are into the magna range if i remember correctly and you will be looking at a couple of hundred quid and im still not convinced the pump is the issue, ive used 15/60's on 3 story houses with 14 rads with no problems what so ever.

Is it a sealed system or open vent? Does the pipework have any rises / drops in it before these rads? Can you definitively trace the flow and returns that they haven't been crossed over anywhere? Are there any valves in the pipework?

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runninwata

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Re: Dead legs and central heating circulators
Reply #18 - Oct 5^th, 2008, 9:12pm

It is an open vent system,

Pipework drawing difficult as can only just do two finger typing on the pc lol

Pipework has not been altered other than installing motorised valve as went for unvented cylinder and previous boiler was on single channel timeclock!

boiler is housed externally in insulated purpose built room Pipe work rises from boiler onto first floor then along landing to first floor rads (4x)drops down walls in three positions at either side of house to serve ground floor rads (8x)

first floor 4 x rads all heating

ground floor 4 x rads heating
4 x rads stone cold they are on the leg that i can feel the flow is red hot as it enters the wall (return is cold)

only valve other than the motorised valves that was added to system was an auto bypass valve.

the flow and returns were never altered boiler was swapped rads added back to back with existing rads to eliminate cold spots on landing etc

i aint really worried about the cost! just as long as it works and we are not cold lol

Old boiler was a 15/ 19 worcester which was never upgraded as the house was extended twice Mrs was freezing last winter I am expecting divorce if she cold this winter!!

regards

steve
regards

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greg

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Re: Dead legs and central heating circulators
Reply #19 - Oct 5^th, 2008, 9:31pm

The rads are filling Ok with water, both directions?

If the system worked before and there have been no pipework alterations then it deff sounds like either an airlock or blockage.

The fact that turning off all the other rads has no effect from what i can understand from your posts shows that its not the pump, it is pumping the right direction?

Are you able to drain the system and cut into the flow and return serving these 4 rads and connect hose to see if you can get flow through?

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runninwata

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Re: Dead legs and central heating circulators
Reply #20 - Oct 5^th, 2008, 9:38pm

Rads all fill ok from both directions, when one of the cold rads removed and valves cracked open rest of cold rads warm up ok,

pump is pumping in right direction.

would i be right in saying that to cut into the leg serving these rads i need to cut a tee into both flow and return with iso valves then open up when filled and calling for heat to see if heated water flows? I aint a Plumber by the way!! lol

steve

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greg

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Re: Dead legs and central heating circulators
Reply #21 - Oct 5^th, 2008, 10:09pm

Quote :- when one of the cold rads removed and valves cracked open rest of cold rads warm up ok,

bit confused by this

if you drain the system down completely, cut into flow and return serving these 4 rads, attach one end of hose pipe to the flow pipe, other end to outside tap. Connect another hose pipe to the return pipe and run to outside. Make sure the hose pipe connections to pipes are good, you don't want water going everywhere Wink

The 4 radiators still conncected, valves fully open, remove TRV heads if needs be. Turn on tap. In theory water coming out of the return pipe should be equal in terms of volume / pressure as what it goes in. Whilst water is running through, bang the radiators across thier surface with rubber mallet. How clean is the water coming out? If all seems to be flowing OK rejoin the flow and return pipes.

When is the original plumber back off hols - bit naughty that he left the system like this

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runninwata

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Re: Dead legs and central heating circulators
Reply #22 - Oct 5^th, 2008, 10:20pm

Quote :- when one of the cold rads removed and valves cracked open rest of cold rads warm up ok,

bit confused by this

confused you need not be Grin

lol

when heating on, remove one rad on circuit, open valves into bucket seperately and slowly in turn, lol rest of rads at this side of house get red hot! (Like i said I am not a plumber) ( cheers lec!)
all rads have been of and flushed through independently and water clean,

Plumber back sometime next week, he is a friend and wasnt aware when he left that the system wasnt peforming as it should unfortunately he balamed the pump when i called him earlier.

regards steve

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CWatters Super Member Offline "Daddy fick it" says James Posts: 5150 Total Thanks: 58 For This Post: 0 Gender:	Re: Dead legs and central heating circulators Reply #23 - Oct 5^th, 2008, 10:52pm Is it possible flow and return got swapped and the TRVs are unhappy about this? Perhaps removing a rad and opening a valve is chaging the pressue enough for them to open?
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qwertyman

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Re: Dead legs and central heating circulators
Reply #24 - Oct 6^th, 2008, 9:38pm

Do the Radiators have TRV`s on them?....If there is hot water to the valve but not entering the radiator it could be that the thermostats are stuck in the off position.To check this - unscrew the TRV cap and you should see the top of a pin sticking through.Lightly tap the top of it until it "pops" up into an open position.Water will now pass into Rad.

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runninwata GDPR opt-out Total Thanks: 58 For This Post: 0	Re: Dead legs and central heating circulators Reply #25 - Oct 7^th, 2008, 9:33pm 100% sure flow and return not reversed, TRVs not faulty, nHave spoken with tech rep for grundfos and confirms pumps is satisfactory for what i am requiring. so.. Have organised powerflush unit for the weekend with the installing plumber, will post further details after flush. 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 #26 - Oct 8^th, 2008, 10:28pm OK m8 hope you get it sorted, let us know
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runninwata

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Re: Dead legs and central heating circulators
Reply #27 - Oct 12^th, 2008, 1:49pm

Just an update, powerflushed system twice for a total period of about 4 1/2 hours or longer! No improvement! so..... Much to the annoyance of Mrs, lifted carpets created hatches and lifted flooring to discover the following,

Extension which was built approx six years ago had been completely piped in Non Barrier hep pipe, The flow off the tee from the last rad that was getting partially hot was completely choked approx 2.0m length solid of sludge particles etc! powerflush didnt even get near it, Cut into system removed this leg of pipework and established circulation again by connecting hose and opening each rad in turn until good flow received in each.

However have set a date to get the extension completely re piped so as there is no doubt.

Cheers everybody for your input it was greatly appreciated

Just goin to re lay floor before i get a divorce

Cheers

steve

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CWatters Super Member Offline "Daddy fick it" says James Posts: 5150 Total Thanks: 58 For This Post: 0 Gender:	Re: Dead legs and central heating circulators Reply #28 - Oct 16^th, 2008, 8:23pm Glad to hear it's sorted. Don't forget the corrosion inhibitor once the system is finished.
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