How long to replace a Vented Cylinder with an Unvented one

[Worcester]

We are always looking to improve our efficiency (and hence money in our pocket )

Just wondered how long most people would estimate for a replacement of an vented cylinder with shower pump to an unvented balanced supply system?

x man hours / days?

Assuming straightforward, i.e mains supply nearby (well it must be to the header tank at least ) no upgrades to DHW heating controls (use existing timers) primarys in OK location for new cylinder, and straightforward access to cylinder location, i.e. average, typical cylinder replacement. Plastic cold water cylinder (aka tank) also to be emptied and removed in pieces from loft (hatch is always too small )

Thx

 

[chris watkins]

Remember that the Approved Documents, are only one way of complying with the Building Regs - the nature of our work means that we end up regularly talking with and challenging Building Control officers - We had to teach them most of the 2010 changes re Competent Persons

The ONLY requirement of G3 is that "any discharges from safety devices is safely converyed to where it is visible but will not cause danger to persons in or about the building"

The Approved Document G gives some examples of how this can be done, if you follow those it is unlikely that you will be challenged by the BC officer, however, as it clearly states in the opening paragraphs ADG "include examples of what, in ordinary circumstances, may be reasonable provision for compliance with the relevant requirement(s) ..." it goes on to say that "following guidance does not guarantee compliance" and further says "that there may be other ways of achieving compliance" AND that "There is therefore no obligation to adopt any particular solution contained in this Approved Document if you would prefer to meet the particular requirement in some other way."

So in summary , there are no MUSTS to any particular way of managing any discharge, high or low... as I said, depends upon the particular installation's circumstances and your relationship with your BC officers

The important bit is what comes in the paragraph after you finished quoting above, it is as follows "However, persons intending to carry out building work should always check with their BCB, either the local authority or an Approved Inspector, that their proposals comply with Building Regulations."
So to summarize, if you follow the AD guidance then there is a presumption that what you have done will comply (very importance if you are self certifying). If you do not follow the guidance & choose to do it another way then you need to check with building control that all is OK!!! (not much point in a self cert then). High level discharge which is turned back against the wall is not given as an example of acceptable discharge arrangement under 3.62 & therefore would strongly suggest that if you are thinking of terminating like this that you consult your local BCB first.

When the new Part G come out in 2010 we were issued with the following information / guidance on this, to pass on to engineers. As there was now the provision to terminate the safety valve discharge to a plastic stack it was very unlikely that high level discharging against a wall would be allowed. I still have this somewhere but for the life of me can't find if I stumble across it I will post it.

 

[Nostrum]

Well Croppie , spanner in the works!

 

[Worcester]

Whether you self certify or not - and we self certify for loads of different sections of the B Regs because of the wide scope of work we do, we find that having developed a good relationship with our local BC department has been well worth while, often we make just a courtesy call - then they feel empowered to advise, which gives us a chance to discuss, and no problems later on.

 

[Worcester]

Well you guys'll love this one... Had a discussion with Building Control today initially about D2 sizing and my calcs based on BS6700, at which point they said that I clearly knew more than they did, and that they were happy with what ever I wanted to do, discussion then got onto renewables, and I have now been asked to go and give the whole of the local BC department (3 District Councils) a talk on Renewables, our design and installation processes, and what to look out for

Their response email said "If we have any queries on renewables we now know who to call" - That's what I call a good relationship with the BC department :sunny:

 

[Ermintrude]

Under your thumb ! Probably want loads of free work from u now !

 

[chris watkins]

Well you guys'll love this one... Had a discussion with Building Control today initially about D2 sizing and my calcs based on BS6700, at which point they said that I clearly knew more than they did, and that they were happy with what ever I wanted to do, discussion then got onto renewables, and I have now been asked to go and give the whole of the local BC department (3 District Councils) a talk on Renewables, our design and installation processes, and what to look out for

Their response email said "If we have any queries on renewables we now know who to call" - That's what I call a good relationship with the BC department :sunny:

I tried the same thing with my local BC at Christmas offered to go along FOC in-between then & new year, bearing in mind how little they seem to know about un-vented in our area.
Did not even get a reply, I suppose it is just easier to keep doing nothing !!! signing things off even if they are wrong, cos at the end of the day they are protected from any legal action themselves.
What water velocity do you use Mr Worcester never tried it using 6700 (or should I now say BS en 806-3)

 

[spanner]

How much Did you weigh in with the pipe removal.. :29::13::29::clap:

 

[spanner]

Sorry you lot but I'm having an early night tonight been up since 4 am ok brb

 

[Worcester]

I didn't offer, they asked and I accepted, and it's renewables I get to talk about

Worked it back from available head (300+5mm/m over 9m) = 345mm with a pipe bore of 20mm gives a velocity of 0.7m/s and flow of 0.22 l/s - or 13.2 l/min the pressure and temperature release valve have to pass a minimum of 8.33 l/min so 13.2 l/min so OK, (that's therefore what the BS/PartG is based on)
If you look at the head loss of the pipe at those flows, you'll see that it also equates to 345mm/9000mm = 0.038m/m or 0.376kPa/m which ties up with the head losses in the pipes at those flow rates - so 'squares the circle'

Then simply showed that the actual hydraulic gradient was better than that so it would easily cope with the flow, so to answer your question in simple terms. 0.7m/s

In effect what this allows you to do is to discount any vertical drops in the pipe from the pipe lengths mentioned in the regs, so long as you maintain the fall and 300mm minimum..

Hope that makes sense