unvented cylinder or shower pump?

[Neber]

I want more pressure for 2 showers and the kitchen sink. I was thinking of replacing the gravity fed cylinder with an unvented cylinder to get mains pressure but because of awkward discharge positioning and the £700 cost (fitting myself, including building control checks) I have been thinking it would be much easier to fit a shower pump by the current cylinder and just pump all hot and cold gravity fed taps/showers.

Is it OK to pump the entire hot and cold system (only gravity fed side obviously) or should you only do part of the system, alternatively is it better just to go the whole hog and fit unvented?

Any advice gratefully received

Thanks

Ben

 

[lagunaglen]

If you need to pump the cold then i doubt you will have an adequate supply for an unvented cylinder,you need to test the flow rate and pressure against manufacturers reccomendations first to ensure your not wasting your money. Plus you must have a relevant qualification to fit an unvented system, you cant fit it then have it checked retrospectively hoping any faults will be picked up, its not a diy job.

 

[Neber]

Thanks for the quick reply Lagunaglen
It has been 4-4.5 Bar for the last couple of weeks and >50litres/minute so should be plenty, I just want to pump the gravity fed cold not mains pressure.
I had to re fit/configure the current cylinder, and all of its controls mostly due to the terrible job the plumber had done on it, I’ve also done a lot of other plumbing in other houses, so feel comfortable doing this, an unvented system looks much simpler to fit than vented the only tricky bit is the discharge.
If you are saying I am not allowed to fit it then you may be right I am not absolutely certain about the rules there. I have spoken to building control and they said all I would have to do is pay £50 do some plans and then someone would come and check/sign off, similar to electrics if you are not a qualified electrician If anyone thinks building control have misguided me there then please let me know.
Otherwise back to my original questions Is it OK to pump the entire hot and cold system (only gravity fed side obviously) or should you only do part of the system, alternatively is it better just to go the whole hog and fit unvented?

 

[Deleted member 105431]

Definately go unvented but you cannot fit yourself legally. if an incorrectly installed cylinder explodes your house (and the neighbours) will be reduced to rubble! You have been warned. . . .

 

[Neber]

Thanks dangermouse46 are you 100% sure that the building control guy was wrong? I was quite looking forward to a new challenge...............
Perfect example of how dangerous pressure vessels can be whilst writing this my wife has just tried to hard boil an egg in the microwave, what a nob nearly blinded herself.

 

[lagunaglen]

If you fit an unvented then you can have a balanced cold which is what you generally take to showers so you have equal hot and cold pressures.But you would know all this if you were qualified , as it stands you would be best getting in someone to advise you further.
As you cant boil an egg between you then boiling a real big egg could be dangerous.

 

[Neber]

I understand the concept of an unvented system very well, as you will see from my first post (I put the bit in brackets just in case someone else misunderstood)

"Is it OK to pump the entire hot and cold system (only gravity fed side obviously)"
i.e. get the same from a pump (the whole system) as you do from unvented.

My wifes cooking skills do not reflect on my ability to do plumbing.

 

[powell30]

Hi Neber,

yes unfortunately you can't fit one and then notify buildings control to 'sign it off'. You need a G3 ticket this means you have completed an exam and are 'competent' to install. These installers have two options then, either belong to an organisation which allows 'self certification' or they get buildings control to certify the install. As these all come in complete packs they are fairly easy to install but you have to comply with all regs and notify (it will cause you hassle with hips packs etc if you don't get a registered installer). Yes it is ok to pump hot and cold gravity side only but you will need to rework piping to all showers plus you need to look at cold water storage levels.....will the CWS feed the cylinder too? Best fit another seperate CWS and ensure these are large enough to supply the water demands.

Oh, and Unvented's don't really explode in the sense described........but they will flash steam when they rupture......and thats just as deadly

 

[Neber]

Hi Powell30
The more I research the more it looks like you cannot get someone to sign off the work but I have just spoken to someone else in building control explained my doubts he conferred with his colleagues (including the Principal Building Control Surveyor) and agreed that I can do it??? And has sent all the application forms etc. and said all that matters is at the end they will check the work and give me a certificate of conformity.

Assuming they are wrong and I do decide to use a pump then I have a very large CWS (used for Power shower previously) but can add another if needs be.
Currently the tank has two feeds, one to the cylinder and one to the cold which conveniently runs down beside the tank so I plan to just stick a pump in the airing cupboard and pump the separate cold and then the hot out of the cylinder before they branch off anywhere. All Bath shower taps/mixers are currently fed only by both gravity cold and gravity hot not mains so should not need to reconfigure any pipes for the sake of balancing/back flow etc. The kitchen mixer will need isolators on but balancing is not so important.
The question is, if I were to pump the whole system are there any issues I have not thought of and is there a certain flange I should use i.e. Surrey Essex etc that are presumably meant for just part of the output of the cylinder.
Also do you have a rough cost for fitting an unvented cylinder if I did get someone with a ticket to do it.

Many Thanks

Ben

 

[The Baker]

A similar performance to an unvented cylinder can be obtained from a heat store, this is an open vented arrangement, which does not require that you prove competency.

Which ever cylinder you decide to go for choose one with a long warrantee.

http://www.albionwaterheaters.com/Mainsflow.htm

Tim

 

[Deleted member 105431]

have u seen an unvented cylinder explode powell30? I have on a video test rig in america and believe me they go pop! Anyone who has dealt with boilermates and other thermal stores will know they're not very efficent as they run at high temperatures and so the boiler heating them is rarely in "condensing mode" (less than 55 deg return). They are very prone to scaling up and the blending valves don't last very long in my experience, also as they are open vented corrosion is a big issue. Best avoided. . . .

 

[The Baker]

have u seen an unvented cylinder explode powell30? I have on a video test rig in america and believe me they go pop! Anyone who has dealt with boilermates and other thermal stores will know they're not very efficent as they run at high temperatures and so the boiler heating them is rarely in "condensing mode" (less than 55 deg return). They are very prone to scaling up and the blending valves don't last very long in my experience, also as they are open vented corrosion is a big issue. Best avoided. . . .

I have fitted some heat stores in the Preston Lancs area with no problems, other than particals passing through the strainer which then start to clog the blender, but I clean that out at the annual boiler service.

I accept that Dangermouse46 has different results with the heat stores that he comes across. Could that be because of the differing hardness of the incoming mains in different areas of the country?

I agree about the fact that the boiler will not unnecessarily be condensing whilst raising the heat store beyond lets say 50 Degree,s (assuming 10 degrees minimun difference between cylinder content's and coil temperature) but we are only talking about a small loss of efficiency when compared with overall gas use.

Tim

PS, and a DIY installed heat store could be less of a health hazard that a DIY Unvented

 

[simond]

My suggestion to the OP would be to sign up with a local accreditation centre and take a one day G3 course, and fit his own cylinder, since he has plumbing skills.

Alternatively, he could go on a manufacturer one day course eg: Vaillant uniSTOR. Then you would be familiar with the actual product you are fitting rather than a generic item.

Actually registering with BC is far less important (in my opinion) than doing the installation properly by having the correct ticket and training.

BC don't make the installation safe, they are civil servants extracting a living from taxation of others. If it is your own work in your own house a BC certificate is probably not of great interest until you sell up.