Cylinder Venting

[sparkatan]

Hi, does anyone know of a solution to this problem?

Vented cylinder with immersion heater, mains cold water fed, supplying domestic hot water to taps.
The system (one of 60 flats) currently has the vent to a soil pipe running through four floors of the building. We have had problems with thermostat failure causing the water to overheat and consequently discharge steam into the plastic soil pipe, causing pipe failure.

My question is, is there an alternative method of venting i.e. a desuperheater so that steam cannot enter the soil pipe?
A safety stat is an option but the insurers will not accept just that and are insisting on some other venting method.

 

[justlead1]

Hi (The system you describe is likly to be Un-vented) Although i think reg's have been changed to accept this method of discharge. The results often mimic that which you describe. However the options are few and can be costly, also requiring agreement and cost of others in the block. Good Luck

 

[sparkatan]

Do you mean it has a pressure relief device fitted?

 

[GQuigley67]

that is an unvented cylinder you describe and is discharging from the pressure relief valve due to a fault which you must get repaired.

 

[sparkatan]

Yes, I know there is a fault! The question is, is there an alternative venting method. The insurers will not reinsure until the venting method has been altered.

 

[diamondgas]

Sparkatan, The only other alternative is to run the vent outside to a drain! Long ladders needed by the sounds of it!

However if it is unvented you need to be qualified to work on that type of issue.. Good way of getting out of a tricky situation ...lol

 

[GQuigley67]

so what seems to be the problem ? this method is acceptable as long as the pipework is copper for long enough and connecting to a soil pipe i dont see the problem.

 

[sparkatan]

Is there a minimum copper tubing vent length requirement between cylinder and soil pipe?

 

[justlead1]

Hi, As said the pressure / temp relief valve have opened, producing super heated steam, which has deformed the plastic pipework. Installing a metal stack to cater for this may well be impossible. Owing to the acceptance of others who live in the flats. You may well have to go back to the insurance company telling them it will be installed/altered to meet regulation and or ask them for a specification that will comply.
My opinion being that some of the regulation changes we see are driven by manufacturers/suppliers rather than basic physics. I feel you are experiencing the outcome of bad judgment. Good Luck

 

[mikegas]

Hi, does anyone know of a solution to this problem?

Vented cylinder with immersion heater, mains cold water fed, supplying domestic hot water to taps.
The system (one of 60 flats) currently has the vent to a soil pipe running through four floors of the building. We have had problems with thermostat failure causing the water to overheat and consequently discharge steam into the plastic soil pipe, causing pipe failure.

My question is, is there an alternative method of venting i.e. a desuperheater so that steam cannot enter the soil pipe?
A safety stat is an option but the insurers will not accept just that and are insisting on some other venting method.

In some circumstances you can just elbow it back to the outside wall but you would need clearance from building control

 

[diamondgas]

In some circumstances you can just elbow it back to the outside wall but you would need clearance from building control

Hi Mikegas ... You can't do that with unvented PRV it must run to a drain because of the potential high temps from UV cylinders!

Sparkatan, you shouldn't get superheated steam into the stack at there should be a tundish/air break before it enters the stack. Now that makes me wonder how the pipework has been configured. I'm thinking of foul smells and the need for a trap! They would have to be metal!

A picture would help

 

[GQuigley67]

it should have a tundish and discharge into a hep vO trap

 

[mikegas]

Hi Mikegas ... You can't do that with unvented PRV it must run to a drain because of the potential high temps from UV cylinders!

Sparkatan, you shouldn't get superheated steam into the stack at there should be a tundish/air break before it enters the stack. Now that makes me wonder how the pipework has been configured. I'm thinking of foul smells and the need for a trap! They would have to be metal!

A picture would help

Im sure you can providing it cant discharge over anybody and you get approval from building control

 

[stani]

Mike, Diamond is right it and its because it is a combined pressure and temperature relief not just pressure relief

 

[mikegas]

just checked my bpec book and it says,
it may be acceptable to discharge at high level if the discharge outlet is terminated in such a way as to direct the flow of water against the external surface of the wall

 

[mikegas]

also the gap between the wall and pipe must be greater than the diameter of D2 pipework

 

[stani]

spot on, just got my BAXi paperwork for my renewal on monday it does indeed say 'High level discharge' is this a new addition to the original G3? which we would only have to do the once and it would last forever.

 

[mikegas]

It might be a recent addition i only did my unvented 4-5 month ago

 

[stani]

this has got to be one of the questions they ask I will definitely shine now.

 

[diamondgas]

just checked my bpec book and it says,
it may be acceptable to discharge at high level if the discharge outlet is terminated in such a way as to direct the flow of water against the external surface of the wall

I stand corrected mikegas *s* .... I never did renew my unvented so things have changed somewhat! Maybe I should invest in renewal

 

[stani]

same with me the only reason I checked was another thread a few weeks ago, it got me to look and bingo, ran out nearly 18months ago, got a renewal on monday with Baxi at warrington, cheapest around and you actually sit in on the full course, but just do a re-assessment test.

 

[justlead1]

Hi, i think its worth mentioning that if dangerous temp and discharge occurs the force of the steam generated is capable of purging the water content of the trap. As the tundish is inline and speed of steam can be high. However to reach this state of affairs other faults are present in the system. A complete check of the unvented cylinder and components would be the way forward.

 

[diamondgas]

Hi all ... picked this up from a previous thread ... may answer your question regarding connecting to a stack

http://www.nhbc.co.uk/NHBCPublicati...ical/StandardsExtra/filedownload,34921,en.pdf

I definitely need to get myself booked in for re-assesment/update training.

 

[tackleburger]

I've been to loads that are elbowed to walls in fact one new build area near me the pipe sticks straight out like a copper drain off I was at one with a knacked expansion vessel dripping onto the path round the side. Running to a drain is okay if the house has a few gully traps kicking around but if not I discharge to ground level and cover. Have elbowed back to the wall when pipework is unsightly and it is safe to do so.