Unvented Cylinder Vs Tradiotnal Vented - Did I Do This All Wrong?

[opps]

Never actually seen how one is made but it may be the same process of how other cylinders are made whereby a blank is pressed out of steel so it only has one open end, the coil etc is then installed and then base is welded on, therefore that's the weak point?

Good point, the top seems to be part of the extruded metal.

 

[Millwright]

Hahah ... yeah right ... apologise .... as if ... get the context right.

Jeesh ... grammer lessons on a DIY forum, whatever next.

Unfortunately the statement was that "it wouldn't happen" it doesn't matter follows it. By using the contraction 'wouldn't' meaning 'would not' it means that - a certain thing will not happen - i.e. there is 0/none/nada % chance that it will happen regardless of what text follows it, hence why that was the only quoted part of the comment, the rest of it doesn't matter. That there is 0% chance though is quite simply not the case. There is a chance, however small/unlikely, that the safety devices on an unvented could fail at the same time either be innocent or malicious interference and there is a run away heat source. Not being very specific on a DIY forum can be fraught with risk as there are people that will believe anything and act incorrectly on the back of it.

Edit posts ???? I don't think so , I didn't change any wording, I only quoted the section relative to the comment, happens all the time in here.

Anyways ..... Apologies @JackK for the digression


If you have an adequate min dynamic mains pressure and flow (As per @Johntheo5 suggests) and a suitable location to allow a 22mm mains supply to be run to it then an easy path/access to run the D2 safety discharge pipework to a suitable internal drain or external space, then yes and unvented could be considered.

You did edit, you removed the rest of what I said, rather than quote the whole thing.....you lied.

 

[Madrab]

Am I a million miles away because I could lay it all out so the engineer can just install and do the building control notic

You're not a million miles away but there are a few standards that need to be observed and the qualified engineer will need to specify those. Material for the D2 pipe would be one, the overflow may not be the correct material to be used as a discharge pipe. Test will need to be perfomed on the HW and CW circuits to ensure what was under gravity pressure can take being under mains pressure(3 bar)

Mains pressure and flow is key though. First place would be to get the mains checked by the water transporter (flow and pressure). Then run a dynamic test yourself with at least 2 full flow outlets open at the same time.

 

[LeeJC]

I found this, which would explain why the weakest point is going to be the bottom plate brazed/welded on.
But............ I had a look at a promotional video for Macdonalds water storage and it looks like the process they use welds/brazes side/top and bottom.
Just noticed now that this is the type with the expansion vessel in the body of the tank, so manufacture process is likely to be different.
I still don't know why/how they got it to fail at the bottom, there is likely to be a reason if not by design then by physics, I don't know what it is though.

 

[JackK]

You're not a million miles away but there are a few standards that need to be observed and the qualified engineer will need to specify those. Material for the D2 pipe would be one, the overflow may not be the correct material to be used as a discharge pipe. Test will need to be perfomed on the HW and CW circuits to ensure what was under gravity pressure can take being under mains pressure(3 bar)

Mains pressure and flow is key though. First place would be to get the mains checked by the water transporter (flow and pressure). Then run a dynamic test yourself with at least 2 full flow outlets open at the same time.

Thanks - You have been truly remarkable and helpful

One further piece of information is : I have a one pipe steel barrel heating system from a gas boiler (Ideal Mexico 2)

I cannot pressurise the steep barrel pipes but I can pressurise the cold / hot domestic water taps and plumbing

Can an unvented cylinder run off a normal flow / return to heat? I would imagine yes... My flow and return is only pumped up but gravity down from return so not fully pumped This was one of the reason why I stuck to a vented system

Am I crazy to try a unvented in these circusmtances

 

[wundaboy]

Post #15??

It doesn't state in any detail what aspect of their system they're unhappy with!!

 

[Johntheo5]

Post #1 suggests a unvented system may give more pressure which presumably means more flow, the present performance can easily be checked as suggested in post #60 so relatively easy to see what mains dynamic conditions required to give the same or better performance. The pump is definitely noisy but someone suggested a slab of concrete might cure this.

 

[Madrab]

Can an unvented cylinder run off a normal flow / return to heat? I would imagine yes... My flow and return is only pumped up but gravity down from return so not fully pumped This was one of the reason why I stuck to a vented system

An UV HW cylinder can be heated by the same heat source that can heat an open vented HW cylinder. If the pump currently pumps the primary HW system and the CH circuit, i.e. they are on the same flow and return pipework but are separated by either 2x2 port valves or 1x3 port valve, then it would be classed as a fully pumped system.

Only when there are larger pipes coming from the other side of the boiler, separate to the CH pipework and only heats the HW primary circuit would it be classed as gravity HW.

Gravity HW with pumped CH ............................................................. Fully pumped Y plan ( 3 port valve - would be an S Plan with 2x2 port valves)
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