Unvented HW Cylinder: what are the essentials?

[miljee]

I am looking to put in an indirect HW cylinder in the loft. We have had a couple of quotes and we realise we haven't a clue about what is essential to the installation and what isn't. Quotes have ranged from £1800 to £3000.

• Does the plumber have to have an unvented licence? Am I right in thinking that the installation rules regarding these cylinders are being relaxed to encourage an increase in their uptake in the UK?
  
  Does the discharge pipe have to be 28mm or is this dependent on its length?
  
  What is an "RM wiring box with additional 2-port zone valve" which is apparently a requirement?
  
  What does changing an open vented to a sealed heating system mean?
  

Sorry for these numpty questions but I am a plumbing virgin and not sure if I'm being taken for a ride!

 

[Andygasman2010]

Your plumber does need a specific unvented qualification. Check this first as a dodgy installation can be dangerous. There are loads of specific regs covering unvented cylinders, too many to list on here but a qualified plumber should know them. To answer the ones you refere to :-

- The disscharge pipe is dependant on it's length, amongst a few other things.
- It has to have a spring-closed zone valve wired up to the cylinder overheat stat.
- Open vented to sealed heating system means to remove the header tank in the loft and pressurise the system.

One thing to be sure of is wether or not your incoming mains supply is sufficiant enough. To get the best out of it it must have a 22mm cold main feed, preferably balanced.

It can get a bit complex if you're inexperienced so make sure your plumber knows what he's talking about

 

[The Baker]

Andygasman2010 is giving you sound advice but looking at it from a slightly different angle, may I take it that you are thinking "unvented cylinder" because you want good hot flow at the taps.

And that you currently have plenty of flow at the cold taps.

If thats the case, why not do what I did for a customer who was told by a National Company that she could not get a water heater that would give her the amount of hot water that she wanted.

By the way the large National Company didnt get the job, some old geezer who showed the Lady a Rinnai broachure did get the job.

Please have a look at the Rinnai web site, in particular the bit about the 26i infinity, its absolutly brill, and probably not much more to purchase than an unvented cylinder, and wont have to standing losses a cylinder has.

Tim

PS I know a reputable installer in the Southampton area if you need one.

http://www.rinnaiuk.com/2_Products/2_Gas_Water_Heaters/1_Internal/2_26i/1_26i.html

 

[tamz]

The most important thing you need to know is that they know what they are doing. They need a G3 unvented ticket not because they are hard to do but there are certain rules that need/must be adhered to. Most qualified plumbers /heating eng. now have this qualification but a lot do not.

Without seeing what you already have but from what you say you require, i would guess around £2k would be a ball park. Not getting ripped off at that.

 

[Agile]

There are only two essentials, adequate dynamic flow and an qualified installer.

The second should check the first but many dont which is worrying.

Tony

 

[Nige F]

No one expects the Spanish Inquisition

 

[miljee]

Thanks, all.

Thankfully the one thing we DO have is very adequate mains pressure!

What does 'balanced' mean in relation to a 22mm cold main feed?

One plumber did tell us we needed to look at getting the 'sytem balanced' so that we had equal pressure on the hot and the cold side. Wot? Though the concept makes sense, is that a valve thing that goes in between the mains and the cylinder?

 

[Agile]

Thanks, all.

Thankfully the one thing we DO have is very adequate mains pressure!

I told you that you need adequate dynamic flow.

You replied that you have good mains pressure.

Obviously you are asking all these questions but not taking the time to understand what we are telling you.

You should spend a little time researching the subject. You can do that by reading so many past postings about unventeds on this forum.

Or just take the advice of a good qualified installer as most people do.

Tony

 

[miljee]

I stand corrected.

 

[miljee]

No, actually, I will go further.
As I made clear in my post, I know nothing about plumbing, let alone unvented cylinders.

I have asked many, many questions. I have received many, many answers; many, many of which directly contradict what I've already been told, which is why I came on here as generally the replies are very helpful and non-patronising.

How do I know that my installer is 'good'? And as for 'qualified', at least someone has pointed me towards G3 unvented tickets, for example! And how will I know if my installer HAS checked 'adequate dynamic flow' seeing as 'many don't'?

If you walked into MY work place and I announced I was going to perform a gradient echo sequence on you, versus a spin echo sequence, I wouldn't be taking the p*ss if I heard you tell your mate you'd had an woopty doo echo as I'd recognise you know nothing about MRI scanning, and nor would I expect you to. Similarly I don't know about 'adequate dynamic flow' versus 'good mains pressure' as I am not a plumber.

I will look at your other posts re unvented cylinders in my continuing quest for education.

 

[gigz]

Thanks, all.

What does 'balanced' mean in relation to a 22mm cold main feed?

On the cold water controls there is a connection for balanced cold water, its used so the hot and cold have the same pressures (mixer showers/mixer taps etc)

 

[Biguns]

No, actually, I will go further.
As I made clear in my post, I know nothing about plumbing, let alone unvented cylinders.

I have asked many, many questions. I have received many, many answers; many, many of which directly contradict what I've already been told, which is why I came on here as generally the replies are very helpful and non-patronising.

How do I know that my installer is 'good'? And as for 'qualified', at least someone has pointed me towards G3 unvented tickets, for example! And how will I know if my installer HAS checked 'adequate dynamic flow' seeing as 'many don't'?

If you walked into MY work place and I announced I was going to perform a gradient echo sequence on you, versus a spin echo sequence, I wouldn't be taking the p*ss if I heard you tell your mate you'd had an woopty doo echo as I'd recognise you know nothing about MRI scanning, and nor would I expect you to. Similarly I don't know about 'adequate dynamic flow' versus 'good mains pressure' as I am not a plumber.

I will look at your other posts re unvented cylinders in my continuing quest for education.

miljee, don't let Agile's superiority complex get to you. no one else does

 

[Andygasman2010]

No, actually, I will go further.
As I made clear in my post, I know nothing about plumbing, let alone unvented cylinders.

I have asked many, many questions. I have received many, many answers; many, many of which directly contradict what I've already been told, which is why I came on here as generally the replies are very helpful and non-patronising.

How do I know that my installer is 'good'? And as for 'qualified', at least someone has pointed me towards G3 unvented tickets, for example! And how will I know if my installer HAS checked 'adequate dynamic flow' seeing as 'many don't'?

If you walked into MY work place and I announced I was going to perform a gradient echo sequence on you, versus a spin echo sequence, I wouldn't be taking the p*ss if I heard you tell your mate you'd had an woopty doo echo as I'd recognise you know nothing about MRI scanning, and nor would I expect you to. Similarly I don't know about 'adequate dynamic flow' versus 'good mains pressure' as I am not a plumber.

I will look at your other posts re unvented cylinders in my continuing quest for education.

Sorry for agile and his patronising ways, to be honest i don't know why he comes in here as he seems to HATE everyone that has a question that he feels is above him.

balanced incoming mains just means to have all the water draw-offs after the pressure reducing valve. Actually "flow" and "pressure" are two different things, difficult to explain really but these are things a qualified installer should know, mention a few of these things to him and if he doesn't know what you're on about you know he's crap

 

[spacecat]

Andygasman2010 is giving you sound advice but looking at it from a slightly different angle, may I take it that you are thinking "unvented cylinder" because you want good hot flow at the taps.

And that you currently have plenty of flow at the cold taps.

If thats the case, why not do what I did for a customer who was told by a National Company that she could not get a water heater that would give her the amount of hot water that she wanted.

By the way the large National Company didnt get the job, some old geezer who showed the Lady a Rinnai broachure did get the job.

Please have a look at the Rinnai web site, in particular the bit about the 26i infinity, its absolutly brill, and probably not much more to purchase than an unvented cylinder, and wont have to standing losses a cylinder has.

Tim

PS I know a reputable installer in the Southampton area if you need one.

http://www.rinnaiuk.com/2_Products/2_Gas_Water_Heaters/1_Internal/2_26i/1_26i.html[/QUOTE]

does this feed radiators as well or is it literally just for heating water for a bath/shower/washing up?

 

[Agile]

Most of the Rinnai appliances are gas instant water heaters.

They are unusually in the UK, a Japanese applicance which seem to work well and very reliably and are small in size but high in output.

They do look a little untidy inside though.

With relation to MRI scanners it always surprises me that most hospitals seem to only use them for a few hours a day even though they are expensive to instal amd give some very useful information very quickly and without any discomfort to the patient.

I would have expected they would have been used 24 hours a day!

Tony