Hi everyone. First post, but one name I recognise...

I have had the great {srcsm} experience of having our Edinburgh tenement
living room back boiler replaced by a condensing boiler off the kitchen.
They seemed (at first glance) to manage the gas and pumbing fine. It
took the three visits to sort out the electrics, and ended up with me
telling them what wires to put where...

Next problem is:

The system is a two independent valve system, and a pump in the boiler.
The boiler is permanent mains, so the pump doesn't cut out until a while
after the boiler presumably for cooling reasons? I guess that is
standard. Inevitably a bypass is needed as both valves (or even all the
radiators) can be off. They seem to have put the bypass as close to the
boiler as possible, which I can't say flls me with joy as there is
hardly a lot of room for circulation.

Anyhow the issue is that is appears that even when the (say) central
heating valve is open, I am getting some flow through the bypass which
has what I presume is, from Ed's decription, a gate valve. the result is
that the return to the boiler is hotter than it should be.

My questions are

1) Is this right? I am presuming I should get no flow through the bypass
if one or other valve is open and the radiators are on?
2) What is a gate valve precisely, and how does it work?
3) Is there some way I can solve this problem?
4) Is there anything the fitters should have done/do.

Gate valves seem to be something every google hit wants to sell me, and
none wants to tell me about

Thanks!

Amos

On Wed, 08 Dec 2004 22:12:15 +0000, Amos wrote:

Hi everyone. First post, but one name I recognise...

I have had the great {srcsm} experience of having our Edinburgh tenement
living room back boiler replaced by a condensing boiler off the kitchen.
They seemed (at first glance) to manage the gas and pumbing fine. It
took the three visits to sort out the electrics, and ended up with me
telling them what wires to put where...

Next problem is:

The system is a two independent valve system, and a pump in the boiler.
The boiler is permanent mains, so the pump doesn't cut out until a while
after the boiler presumably for cooling reasons? I guess that is
standard. Inevitably a bypass is needed as both valves (or even all the
radiators) can be off. They seem to have put the bypass as close to the
boiler as possible, which I can't say flls me with joy as there is
hardly a lot of room for circulation.

Anyhow the issue is that is appears that even when the (say) central
heating valve is open, I am getting some flow through the bypass which
has what I presume is, from Ed's decription, a gate valve. the result is
that the return to the boiler is hotter than it should be.

My questions are

1) Is this right? I am presuming I should get no flow through the bypass
if one or other valve is open and the radiators are on?
2) What is a gate valve precisely, and how does it work?
3) Is there some way I can solve this problem?
4) Is there anything the fitters should have done/do.

Gate valves seem to be something every google hit wants to sell me, and
none wants to tell me about

A gate valve is a simple metal plate that slides into and out of the pipe.

They are not very good at completely sealing the flow.
They offer little resistance to the flow when fully open.
The don't corrode when half open like some 1/4 turn valves, which is what
it likely is set to hear.

They have been surpassed by 1/4 turn stop valves for use in plumbing.

1) Maybe, depends on the boiler instructions.
A smart bypass would off little or no flow until needed.
2) See above
3) It may take some experimenting to get the best setting for the bypass.
Or it may require replacing with a smart bypass valve.
4) Depends on the boiler instructions - which may specify a minimum length
for the bypass circuit.











--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

In an earlier contribution to this discussion,
Amos wrote:


My questions are

1) Is this right? I am presuming I should get no flow through the
bypass if one or other valve is open and the radiators are on?
2) What is a gate valve precisely, and how does it work?
3) Is there some way I can solve this problem?
4) Is there anything the fitters should have done/do.

Gate valves seem to be something every google hit wants to sell me,
and none wants to tell me about

A gate valve is just a manually adjustable tap, which offers less flow
resistance than an ordinary tap when fully open.

In order to act as a by-pass, the gate valve would need to be partially
open - so there *will* be some flow through it even when the CH and/or HW
circuits are open.

It's far better to use an automatic by-pass valve (referred to by Ed as
'smart') which is spring-loaded and only opens when the flow has nowhere
else to go.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

In article ,
Set Square wrote:
Gate valves seem to be something every google hit wants to sell me,
and none wants to tell me about

A gate valve is just a manually adjustable tap, which offers less flow
resistance than an ordinary tap when fully open.

A tap screws a 'flat' washer of some sort up against a 'flat' seat - and
assuming both of these are in reasonable condition will shut off fully. A
gate valve relies on an accurate match between the gate and body - which
wear or debris soon spoils, so rarely work as a stop cock properly after
some service.

--
*I didn't drive my husband crazy -- I flew him there -- it was faster

Dave Plowman London SW
To e-mail, change noise into sound.

Set Square wrote:

In an earlier contribution to this discussion,
Amos wrote:
snip

A gate valve is just a manually adjustable tap, which offers less flow
resistance than an ordinary tap when fully open.

In order to act as a by-pass, the gate valve would need to be partially
open - so there *will* be some flow through it even when the CH and/or HW
circuits are open.

It's far better to use an automatic by-pass valve (referred to by Ed as
'smart') which is spring-loaded and only opens when the flow has nowhere
else to go.

Thanks everyone. It is possible it might not be a gate valve then. I
guess it may be an automatic by-pass valve, but I know little about
recognising these things (give me wires or bits of wood anyday!). I
probably better work it out.

In the meantime , the said valve is adjustable at the top. Ignoring
the obvious damage I could do to the boiler by cutting of the bypass, is
there likely to be any damage I could do to the valve by messing about
with this. Are spring loaded valves generally adjustable as to how much
pressure differential is needed to open them?

Thanks again for your help.

Amos

Amos wrote:

Thanks everyone. It is possible it might not be a gate valve then. I
guess it may be an automatic by-pass valve, but I know little about
recognising these things (give me wires or bits of wood anyday!). I
probably better work it out.

Some piccies might help:

Gate valve:

http://www.screwfix.com/app/sfd/cat/...18334&ts=60752

Bypass valve:-

http://www.screwfix.com/app/sfd/cat/...60907&id=98894

In the meantime , the said valve is adjustable at the top. Ignoring
the obvious damage I could do to the boiler by cutting of the bypass, is
there likely to be any damage I could do to the valve by messing about
with this.

Unlikely to do much mischief to the valve unless you take a large
spanner to it!

Are spring loaded valves generally adjustable as to how much
pressure differential is needed to open them?

Often, yes.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In an earlier contribution to this discussion,
Amos wrote:


Thanks everyone. It is possible it might not be a gate valve then. I
guess it may be an automatic by-pass valve, but I know little about
recognising these things (give me wires or bits of wood anyday!). I
probably better work it out.

A gate valves looks like
http://www.screwfix.com/app/sfd/sea/...pi=1&cn=1&cd=1

and an automatic by-pass valve should look something like
http://www.screwfix.com/app/sfd/sea/...pi=1&cn=1&cd=1

In the meantime , the said valve is adjustable at the top. Ignoring
the obvious damage I could do to the boiler by cutting of the bypass,
is there likely to be any damage I could do to the valve by messing
about with this. Are spring loaded valves generally adjustable as to
how much pressure differential is needed to open them?

Yes, they are adjustable. I don't know whether there's a recognised
methodology for adjusting them, or whether it's just suck-it-and-see.

I've never owned one, but others may well come in with some advice.
--
Cheers,
Set Square
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