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Plumbing query


Gardengirl
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Hi Jo,

In the abscence of Le plombier who will no doubt post a deatiled version later.

An isolating valve is usually a ball valve which completely shuts off a supply some are full flow ball valves and some are not, the smaller flow ones are used as service valves near taps etc.

Gate valves use a gate that rises and falls according to the setting you give it, they do not usually totally shut off, they drip a lot [:D] but also allow a high flow rate.

Personally I think that the gate valve is a thing of the past.

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All already explained, Jo.

Gate valves (In plumbing parlance) are used primarily to adjust flow: an isolating valve, as it says on the tin, isolates - as in isolating a piece of equipment - e.g. a Loo - in order to service the equipment; such as change the ballcockle (I've used my self-invented word "Cockle" 'cos the word Nazi will probably object to two rude words!).

In older style conventional central heating systems, part of the process of commissioning, should be to adjust the radiator temperatures so that once the whole system is up to designed heat - i.e. boiler jacket and core; pipework, rads -  then the rads are all at the same temperature.

If there is no restriction on flow, then the first rads in any circuit are hotter than the subsequent rads: and the end rad can be almost cold: since the circulating water loses heat each time it rises to impart heat to a rad in the circuit.

The way this is done, is by using a surface thermometer on each rad and closing down the gate vales on the first rads in the circuit: and opening up later rads, incrementally,  until surface temps are roughly the same.

Technically, it is called "Balancing the system".

Modern closed circuit systems tend to be designed with far smaller circuits (The system is "Zoned"), and flow detectors with associated temperature detectors and motorised or solenoid valves which keep cutting in  and out to achieve balance. The water flow is also much faster owing to greater pump capacity.

Few "Plumbers" understand the relationship between Pressure and Flow: pressure will be equal throughout any system: flow is dependant on the diameter of a pipe; basically.

Thus a gate valve which can progressively "Lower an obstruction or "Gate",  to the smooth passage of fluid", is very much like a dam or a sluice gate: and then this will thus reduce flow. However, the pressure will remain the same. (Basically since fluids conform to the First Law of Hydraulics; viz, fluids are basically incompressible. Becoming even more technical and pragmatic, fluids are compressible a tad, 'cos they tend to contain a smidgeon of gas such as air. But it is always the gas which compresses: never the fluid).

Me fingertips hurt now and I'm off to bed!

 

[:D]

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Thankyou so much to you lovely people; my husband is very pleased to have that knowledge.

Our system is an old one; he is changing the boiler and putting it in a different place. Ordering on the internet, he saw these 2 different parts described as doing the same job - confusing!

In case anyone is concerned about the safety aspect, our usual plumber will be coming in to join up the gas to the system and test it all when he returns from holiday in September.

Thanks again,

regards, Jo

PS Hope the fingertips have fully recovered!
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I would take you to task on that one Gluestick

Isolating valves and gate valves, whether ball and gate purely shut off flow, they are totally useless for balancing

For balancing you need a regulating valve which allows a gradual reduction of flow over the whole range of the valve

Gate valves only have an effect on flow rate over the final quarter turn (or less) before total closure

Motorised valves only regulate flow if they are the correct type, the common ones installed merely open and close

Radiators valves are designed for individual flow regulation but they are not gate pattern

Whilst pressure is not affected by pipe diameter the flow rate and pressure drop across the system are and therefore correct sizing of pripework is essential. Where pipes are correctly sized a system is effectivly self balancing

Le Plombier
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"Where pipes are correctly sized a system is effectivly self balancing"

Dead right M Le Plombier. Is it just my age or what? I seem to remember in days of yore that central heating systems were DESIGNED i.e. careful consideration was taken of heat loss room by room, radiator output, flow through the system and the whole shebang. Now it seems to be done by rule of thumb or some vague approximate methodology based on standard Wates boxes ... oooh I am grumpy tonight .... I'll get back in me box
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[quote user="Le Plombier"]I would take you to task on that one Gluestick Isolating valves and gate valves, whether ball and gate purely shut off flow, they are totally useless for balancing For balancing you need a regulating valve which allows a gradual reduction of flow over the whole range of the valve Gate valves only have an effect on flow rate over the final quarter turn (or less) before total closure Motorised valves only regulate flow if they are the correct type, the common ones installed merely open and close Radiators valves are designed for individual flow regulation but they are not gate pattern Whilst pressure is not affected by pipe diameter the flow rate and pressure drop across the system are and therefore correct sizing of pripework is essential. Where pipes are correctly sized a system is effectivly self balancing Le Plombier[/quote]

Apols for taking so long to respond LP: I have been away.

Yes indeed: very poor choice of terminology by myself: as always, thinking in engineering terms rather than basic plumbing.

Properly designed Gate Valves should indeed regulate flow quite delicately since they progressively reduce the orifice: which is why they are used to adjust liquid and slurry flow in industrial processes.

Also agree about correct pipe sizes in "A properly designed system": I haven't seen many such animals! Usually, simple 22 m.m. for the secondaries reducing to 15 m.m. at or near each rad.

I did earlier mention Zoning: again, I've rarely seen this in practice even with quite large houses: anymore than I've seen pressure bypass valves on fully pumped systems with TRVs.

Trouble is right now, that with the increasing complexity of detectors and controllers, really effective new systems need design by properly qualified heating engineers: and most installers are plumbers with a Corgi cert, which means squat.

Looking at a neighbour's new boiler install just yesterday: total abortion!

Perhaps worst of all, whilst the DHW worked OK, the heating when he tested it didn't! How could the installer leave without firstly bothering to test that the heating actually worked?

Beats me!

 

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Reading this thread endorses what I have been thinking for a while, lots of people with the best of intentions reply to things they have only a little knowledge on. Why can't there be designated people who do have expertise in disciplines to give advise. I'm not trying to stop anyone posting but there are certain things said on here that can be downright dangerous i.e. people advising on gas regulator adjustment and settings, elecrical repairs, installing woodburners etc etc.

The reason for this post is not to put anyone down but to highlight what I feel is a situation that at best can lead to confusion and at worst is dangerous.

Charlie.............   

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This is the problem with forums

Who does have knowledge of what they are talking about, especially with the use of our old friend Google

From my position I run a plumbing and heating company in France, I am gas qualified in France, I am an associate member of the Chartered Institution of Building Services Engineers and I am a Registered Incorporated Engineer with the Engineers Registration Board

I do try to offer advice from time to time but, I suspect, like my fellow practising professionals in France, I am far too busy to commit to a heavy involvement to a forum

A quick look while I deal with my email at night is the only time I have

Le plombier

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The other problem is that there frequently a number of different alternative solutions to problems that are equally safe and viable within the French system. Sometimes there aren't (for example always listen to Le Plombier on gas matters) but there can be different methods that comply with NF etc and can be used.
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This was the reason for my earlier post, if LP posts a reply you don't need to read the forum for long to realise he's the man when it comes to plumbing matters, it must be quite frustrating LP when there is also a lot of dross[:D]

teapot, if you need your oil refinery maintaining anytime, or a safety presentation, or oil spill response I'm your man!!!!!!![6][6][:D]

Heat exchangers and controlled bolting systems a speciality, a bit of laser alignment on the side.

Regards.

Charlie.  

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I would admit that my comment and opinion is influenced by the fact that anything I do is subject to guarantee and the dreaded decennal insurance

There are plenty of solutions but I tend to stick to the ones I can guarantee as if I was doing the installation myself

Le Plombier
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Boy!

This place becomes more like the WI each month!

Bitchy?

Shame the smart derrieres aren't so quick in coming forward to respond in a timely basis to the OP's question with their erudition and expertise.

It is always the newbies who carp.

They are so quick to join the fray in criticising other posters and their responses.

How many enjoy the personal integrity to revert - vacations included - and hold their hands up and say" Apologies:: confusion and bad terminology"?

Nope! Not as much fun as bitching.

It's no wonder I don't bother to come here much anymore and post.

I'm sure LP you are an acknowledged expert: shame in my UK town of circa 250,000 there was only one!

The rest were, as I earlier stated, plumbers in charge of a Corgi certificate

Seems to be the same in la belle France too: from my and so many others experience as a consumer. OOne day French heating installers might actually, for example, measure the thermal load of rooms and heat loss and thereafter specify the optimum sized radiators.

I'm not holding my breath, mind...........................

Still, CF members can sleep easy: their problems and confusions concerning such esoteric conundrums as oil refinery maintenance, safety presentation, (???[8-)] whatever that means in the real World), or oil spills are now solved.

Whilst diagnosing Heat exchangers and "controlled bolting systems" plus a bit of bit of laser alignment on the side.

An eclectic mixture of engineering disciplines which beggar belief.............

 

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Hey Gluey,

Some of us do the heat load calcs and design our system using proper thermal numbers (including radiator factor- something often ignored), pipe flow rates, pipe sizing etc. Mind you, I am not a plumber or a heating engineer. I do however have a vested financial interest in achieving a system that is efficient, its my money thats paying the capex and opex. 

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Having originally asked the question, the answers to which have ranged far and wide, can I say that all of us untechnical people are very grateful for answers. I won't claim understanding of all or even most - but the fact that good people give up their time to help us is very much appreciated.

Jo
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