Central heating high resistance low performance


Postby forreq » Fri Dec 19, 2008 10:17 am

Our house has a poor performing central heating system.
There is enough heat input from the boiler (30kw).
But it's an old house with four individual circuits including the HW.
The system has a 6m pump feeding the 4 motorised valves.
Trouble is when 2 or more zones are calling some of the more remote rads don't get any feed.
Can I fit another domestic pump to another part of the sytem or does it need a light/commercial pump in?

Any ideas?
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Postby htg engineer » Sat Dec 20, 2008 8:53 pm

Firstly is this a new problem or has it always been a problem. What's the water/system like, free of sludge etc ?

How many radiators do you have ?

If you give more info on the size of the system, someone may be able to offer advice on the type/ number of pumps.

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Postby forreq » Sun Dec 21, 2008 10:45 am

Thanks Htg,

Lot of rads - 44, it's an old vicarage and appears to have been installed mid/late '80s.

The system appears free of sludge, its been cleaned and drained a couple of times recently, at the lowest point in the cellar.

The current system has two pumps in series (normal domestic - peglar terrier) feeding four motorised valves. Which serve the HW and the three floors.

The problem has been there as long as we've been here (6 months).

Craig
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Postby htg engineer » Sun Dec 21, 2008 2:30 pm

You need someone to come out to see the installation. You could go for a larger industrial sized pump or a second pump - but it's a really old boiler/system the extra pressure the system will be under could cause more problems than it'll solve.

The best way for initial installation would have been to have one pump per floor/zone. That way each pump will only feed 14 radiators, and if one pump packs up - the rest of the system will still work.

Although this might prove expensive as it's alot more electrical work and pipework as you don't want pumps pumping against each other.

You would also need to leave one zone open as a fail-safe so if the boiler stat failed all zones wouldn't shut down together. This way excess heat can escape via the radiators.

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