Plenty of Hot water - new pump - but slow, slow heat to radiators

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Nellymac

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Hi all - hope you can help

We've an old CH system, which was installed before we moved in 16 years ago...and to be honest not well serviced, but has never let us down. BAXI boiler and expansion tank in loft, that feed a pump and HW tank in an airing cupboard below. The boiler, or surrounding pipes, have been a bit clonking when it first fires up, and on one occasion I saw steam or air spluttering up out of higher expansion tank. But we have plenty of hot water in the tank and pipes. 

We extended the house around 12 years ago and now have 11 radiators.

The main issue at preset is that more and more across this winter season, many of the rads would not get hot. I did all I could to balance them. But unless i closed all but the further ones...I could not get heat to them at all. Back up stairs the pump would be whirring away...and the pipes either side of it red hot, and likewise both the A & B feeds after the 3-port valve.

I wasn't convinced the old analogue room thermostat was effectively clicking on/off...so replaced that with a Honeywell digital one. Didnt make much difference, but at least I have accurate readings now

The Groundfos 15-50 pump was a bit rumbly at times, and only smoothed out when I turned it up to speed 3 (it had previously always lived on 2). Then only 3 would work at all, and I could just hear and feel it purring, but turned back to 2 or 1 ...and nothing. So i assumed the old pump was on its last legs and couldn't cope pushing all over the house.

I installed a brand new UPS2 15-50/60, which purrs on all speeds - and has an 'intelligent' setting too. 

But cranking up the new thermo to really high - and with the pump on its top speed...slowly, slowly, painfully slowly ...over an hour or two heat gets to the rads.

Some red hot - some still only tepid...so I continue to try and balance, but notching up and down the lock-shield valves (we have no TRVs) ....but so easily can one quarter turn seemingly send another once hot rad, cold....and the wait for a warm house is sooo slow. 

I wondered about the 3-port valve. But the A & B pipes either side are red hot, and when powered off the little auto lever does offer motor resistance and spring back....which I was told was the first obvious check that its working ok. 

Is it all fighting against some sort of blockage somewhere ? ....when I've taken rads off for decorating, we get dirty water of course....but not sludge or filth you would associate with enough build up to block...but the systems not been flushed in our time tbh. 

So, what can you suggest.... I may have an old boiler (and cant really afford to replace that at present)...but stacks of hot water in the boiler and 3-port pipes...and a brand new UPS motor next to it whirring away (which I'm worried is overworking to the extent that killed the last one).....which takes an hour or so to just (just) get 20'c+ heat to the thermostat in the hall, and leaving radiators very varied around the house, despite efforts to balance them.   

What can be making it so slow.....any ideas please

thanks

Neil 

 
Yes it could be blockages or trapped air in the pipework, I work with a plumber who is ace at fixing these types of problems, there is a skill to it, where we mere mortals spend ages chasing our tails....

 
"but the systems not been flushed in our time tbh."


Have you ever put in new inhibitor fluid or sludge remover after removing / reconnecting radiators when decorating?  http://www.screwfix.com/c/heating-plumbing/central-heating-treatments/cat831046#category=cat831046&page_size=100   I'd start with drain system down. then refill with a suitable cleaning fluid, run it for a few days opening / closing rad valves to force it around whole system.  Don't forget to open up both rad valves including the lock shield ones to let ensure you haven't got a plug of sludge backing up behind a rad valve.  Then re-drain to let any loosened muck out. Refill again with suitable dose of inhibitor fluid. go back round re-balance all rads.

Doc H 

 
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I can't help but wonder,   would it not be better to ask on a forum that has plumbers?

 
There are serious flow issues with this that have been ongoing since before you extended it.  Steam coming from the expansion tank is a sure sign of the flow rate being WAY too low for the boiler and the water kettling in the boiler.

I think some serious stripping down and flushing through of pipework is needed to solve this.

I can't help but wonder,   would it not be better to ask on a forum that has plumbers?
If you can find one then go aherad. Every time I have tried I get "Diyer shouldn't be touching it call a plumber" so I don't bother any more.

 
Sorry I do not agree, I am on a couple of other forums, and they have "plumbing "sections" and most replies are given by plumbers / heating engineers and the only time a DIY'er has been told don't touch it, is  if its to do with gas.

As for which forum, that has to be up to the OP, as not every forum is for every person.

Click here

 
I wondered about the 3-port valve. But the A & B pipes either side are red hot...


Does the pipe feeding the circulating water to the coil in the HW cylinder ever get cooler? If not, perhaps the valve port to the HW side never closes, so there's never enough pressure to push the water round the radiators with an adequate flow rate. Maybe the cylinder stat is faulty, thus holding the valve open to the HW side?

 
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Dont know HandySparks...good call. I'll turn the HW off for a while and check ?

 
Thanks all

Attempting to flush and add a cleaner for a few days as Doc suggested

 
Come back and let us know how you get on.

Doc H.

 
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