Buffer tank set-up

[Guest Alphonsox]

Pictured below is my buffer tank as acquired from Ebay a year or so ago. This is a 90ltr RM Cylinders Stelflow stainless unvented cylinder. It will be connected as follows :-

- To/from an ASHP to provide water heating

- To/from an underfloor heating manifold

- To/From a Dimplex SmartRad wet radiator

It will also be electrically heated using an immersion heater to around 30C for situations when the ASHP is non-functional.

I bought the tank "as is" with no additional parts (Pressure valves, expansion tank etc.). The system will be self contained filled with water/inhibitor at a pressure of a couple of bar.

 

Does such a system need to be considered as a full scale UVC install complete with pressure relief valves, tundish, part-G etc ? (The cylinder does not have a pressure relief valve fiting). I would guess the inclusion of a heating element would make this desirable if not compulsory.

 

I am assuming that a sensible connection strategy would be to use the bottom "cold feed" input as the fill point, the top connection for the expansion tank, with the to/from feeds connected to the mid-point connections. Does this make sense or should I be taking all hot water feeds from the very top ?

 

Does having separate thermostat and heater elements give any advantage ? or should I just use a single combined unit ?

 

All thoughts more than welcome.

 

 

 

[Nickfromwales]

If you have a cold mains fed filling loop, then it has the potential to be left open by mistake / misadventure and then it is subject to that max static pressure. 

As I have never fitted an ashp, I don't know if these are dumb units which rely on a pressurisation kit to be retro fitted elsewhere accordingly, ( fill loop, pressure gauge, PRV and EV ). If the ashp is a dumb unit then you'll need to fit these additional components just to cover the known criteria ( water expands when it's gets heated / ev's fail and then cylinders pop if there's no PRV and so on ). Even without the G3 requirement ( which is iirc any volume of stored + pressurised ( sealed / unvented ) heated water of 15litres or more ) you'd need these components to comply with the basic physics and safety side. As per my last, I firmly believe your going to need G3 as your at or above 15 litres   

The filling loop left open / partially closed issue can be easily removed as your not supposed to leave the loop connected after filling up. The flexi hose on the filling loop has 'wing nut' like nuts at each end and rubber seals so it can be fitted and removed by hand ( tool free ) so it's not supposed to be there anyway. Discipline is your friend there.  

A failed immersion stat is the only thing here that's going to cause this cylinder to overheat and breach the working value of expansion of the EV so, as most have an operational stat + a manually resettable overheat stat that is a rare occurrence. Regardless of how slim the chance of both of those failing is, you must still, under G3, allow for that eventuality. That's why the regs exist. 

Example of the kits ( ready to go off the shelf )

Before I advise on the connections, does the cylinder have any coils or is it all one unified body of water. ?

 

Edited October 20, 2016 by Nickfromwales

[Guest Alphonsox]

Thanks for the reply Nick - No coils at all, one body of water with a cold-in on the bottom right, hot out at the top and 8 flow/return ports. The thermostat points are sealed pockets. The immersion boss seems to be a standard 2 1/4".

[Nickfromwales]

Hot and cold in/ out ? I'm a bit stuck with that, is that a coil? Otherwise how is it defined? Each tapping should be installer definable. 

 

[Guest Alphonsox]

4 minutes ago, Nickfromwales said:

Hot and cold in/ out ? I'm a bit stuck with that, is that a coil? Otherwise how is it defined? Each tapping should be installer definable. 

 

 

I'm just quoting from the attached labels - there is no difference apart from threads on the tappings. There is definitely no coil.

 

 

[Nickfromwales]

So if you blow into that does air come out of all the tappings? 

Stick your hand over the cold tapping and blow into the hot. If there's back pressure you know there is a coil.

i genuinely don't know why they'd define those two tappings other than  if they are a coil in / out.  

?

[Guest Alphonsox]

There is no back pressure - Just to be certain I shone a torch through the immersion boss and peered into each of the tappings. Light was visible from each so it is just one body of water and definitely no coils. The labels must just be there to add FUD.

[Trw144]

Some of the buffers I sell have stratification devices inside (a steel column with lots of holes in it) - so even though it is the same body of water, there are dedicated points for flow and returns that should be used