Issue with solid fuel stove connected to Systemlink

froshtyv

Hi,

Quick question,

I had an issue with the P&T valve on my cylinder blowing when the solid fuel stove has been lit.
If i am right, the stove should gravity feed to the coil in the cylinder and the pipe stat should then bring on the solid fuel pump which is feeding into one side of the system link and at the same time bring on a dump pump either GF rads or FF rads or both.
But at the moment the pressure / temperature is building in the cylinder until the P&T valve is activated.

Should this happen at all? I thought that the overflow tank in the attic would act as expansion for the solid fuel? For instance if there was a power cut when the solid fuel had been lit no pump could be brought on to act as a dump thus the hot water would expand up the pipes into the overflow?


Any suggestions or tips on the issue would be great thanks.

kerryplumber

froshtyv wrote: »

Hi,

Quick question,

I had an issue with the P&T valve on my cylinder blowing when the solid fuel stove has been lit.
If i am right, the stove should gravity feed to the coil in the cylinder and the pipe stat should then bring on the solid fuel pump which is feeding into one side of the system link and at the same time bring on a dump pump either GF rads or FF rads or both.
But at the moment the pressure / temperature is building in the cylinder until the P&T valve is activated.

Should this happen at all? I thought that the overflow tank in the attic would act as expansion for the solid fuel? For instance if there was a power cut when the solid fuel had been lit no pump could be brought on to act as a dump thus the hot water would expand up the pipes into the overflow?


Any suggestions or tips on the issue would be great thanks.

If the p&t valve is blowing off, I am assuming that u have a solid fuel stove plumbed into a pressurised cylinder???

roy rodgers

kerryplumber wrote: »

If the p&t valve is blowing off, I am assuming that u have a solid fuel stove plumbed into a pressurised cylinder???

Which should be a no no...

Dtp1979

+1

kerryplumber

A definite no no!!!!!! But it does sound like that's the case here.

Dtp1979

kerryplumber wrote: »

A definite no no!!!!!! But it does sound like that's the case here.

It must be. Never seen a t and p valve on an open vented cylinder

Dardania

Dtp1979 wrote: »

It must be. Never seen a t and p valve on an open vented cylinder

Not necessarily. There could be a valve between the cylinder and the overflow tank, which is closed, leading to the p and t blowing...

Dtp1979

Dardania wrote: »

Not necessarily. There could be a valve between the cylinder and the overflow tank, which is closed, leading to the p and t blowing...

Yes but there is no reason to have a t&p valve on an open vented cylinder.

Dtp1979

Dtp1979 wrote: »

Yes but there is no reason to have a t&p valve on an open vented cylinder.

But that doesn't stop some installers from fitting them and I find there fitted often enough.

The installation should be checked by a decent plumber and I'd advise not using the stove until the installation has been checked for safety.

Dtp1979

gary71 wrote: »

But that doesn't stop some installers from fitting them and I find there fitted often enough.

The installation should be checked by a decent plumber and I'd advise not using the stove until the installation has been checked for safety.

Me personally, I've never seen them fitted to an open vented cylinder. There's no harm in fitting one, but also no reason to either

my3cents

Where does the water go when one of these valves opens?

roy rodgers

If a t+p valve is fitted on a open vented system it shouldn't open as the excess heat and pressure should go up the expansion pipe I'd imagine

Dtp1979

Dtp1979 wrote: »

Me personally, I've never seen them fitted to an open vented cylinder. There's no harm in fitting one, but also no reason to either

I got caught out after I told a installer he had to pipe the T&P outlet in a safe manor, he told me he didn't as it was a open vented system and I should get my facts right before I say anythiny, so now I never assum



I think the reason there fitted is due to some unvented cylinders coming with the valve made in already and the installer chooses not to remove it when he pipes it as open.

my3cents

my3cents wrote: »

Where does the water go when one of these valves opens?

I can't see it ever opening on a open system fitted by a qualified plumber(who wouldn't fit one anyway:D).

But for those with unvented cylinders they should have the cylinder serviced every year and one of the checks is to see what happens when the safety valves lift.

As someone who inspects unvented cylinders after problems arise I can tell you that 99% of the unvented installations I see risk or have at times caused 10's of 1000s of Euro worth of water damage.

This is due mainly to the T&P valve pipework(if fitted) not being able to handle the volume of water or the very high temperture of the water, in these cases home owners can have a difficult time claiming on their home insurance as the damage was caused by somebody pretending to be a plumber.

K.Flyer

depends on how it is plumbed,
have u looked at the schematics on the sytem-link site to make sure its done correctly.

You are also mixing ideas here: expansion and overflow are different concepts.
Yes the flow from the stove should have free access to the overflow pipe which should go straight up to the cold water header tank and the return should be tee'd with a cold water feed from the same tank, again free.
I have replied before on this, as have others so go look.

Which coil on the tank is the stove, top, middle or bottom

To avoid confusion.
It is the Open Vent / Expansion pipe that goes from the heating system up to and overhangs the feed and expansion tank, not the overflow pipe.

Dtp1979

K.Flyer wrote: »

To avoid confusion.
It is the Open Vent / Expansion pipe that goes from the heating system up to and overhangs the feed and expansion tank, not the overflow pipe.

Yes. The overflow pipe goes from the tank directly outside. The pipe that goes up over the small tank and points back into it is the vent. The pipe that comes from the bottom of the small tank is the expansion.

K.Flyer

Dtp1979 wrote: »

Yes. The overflow pipe goes from the tank directly outside. The pipe that goes up over the small tank and points back into it is the vent. The pipe that comes from the bottom of the small tank is the feed and expansion.

Wearb

All very sharp today lads. Nice to see you hitting the ground running after all the "socialising".

froshtyv

Thanks for all the replies.

The cylinder is 100% pressurised. There is an unvented kit fitted for the CWS.
The P&T valve has lifted and due to there being no waste pipe fitted, the water started coming down through the ceiling.

I knew myself something is a miss if the P&T has gone off. I would have a good knowledge of plumbing systems but solid fuel setups wouldn't be my strong front.

I always struggle to comprehend how you can have an open vented solid fuel stove connected straight into a sealed system via a system link with out using a buffer tank, heat exchanger etc.

Ive seen a few mechanical schematics with an "injector T" used, but again i dont fully understand this setup.

So from what i gather from the post above, the whole system should be an open vented system in order for it to operate correctly?

May thanks

Dtp1979

froshtyv wrote: »

Thanks for all the replies.

The cylinder is 100% pressurised. There is an unvented kit fitted for the CWS.
The P&T valve has lifted and due to there being no waste pipe fitted, the water started coming down through the ceiling.

I knew myself something is a miss if the P&T has gone off. I would have a good knowledge of plumbing systems but solid fuel setups wouldn't be my strong front.

I always struggle to comprehend how you can have an open vented solid fuel stove connected straight into a sealed system via a system link with out using a buffer tank, heat exchanger etc.

Ive seen a few mechanical schematics with an "injector T" used, but again i dont fully understand this setup.

So from what i gather from the post above, the whole system should be an open vented system in order for it to operate correctly?

May thanks

What you have is a potential bomb.
It will work but it is extremely unsafe. Yes, both should be open vented.

froshtyv

froshtyv wrote: »

Thanks for all the replies.

The cylinder is 100% pressurised. There is an unvented kit fitted for the CWS.
The P&T valve has lifted and due to there being no waste pipe fitted, the water started coming down through the ceiling.

I knew myself something is a miss if the P&T has gone off. I would have a good knowledge of plumbing systems but solid fuel setups wouldn't be my strong front.

I always struggle to comprehend how you can have an open vented solid fuel stove connected straight into a sealed system via a system link with out using a buffer tank, heat exchanger etc.

Ive seen a few mechanical schematics with an "injector T" used, but again i dont fully understand this setup.

So from what i gather from the post above, the whole system should be an open vented system in order for it to operate correctly?

May thanks

You cannot have a uncontrollable heat source heating a unvented cylinder.

Most coils in unvented cylinders are not suitable for gravity circuits which would be one of the traditional ways of connecting a stove.

Don't use the stove till you've confirmed the safety of the installation.

The fact your safety valve isn't piped is a indication of shoddy workmanship as the discharge pipework is of fundamental importance when fitting a unvented cylinder.

Also if your cylinder is fitted in the loft has the extra weight of the stored hot water been taken in to account and has it been fitted on marine ply platform to prevent the cylinder from potentially falling through the loft.

froshtyv

Thanks for the replies.

Sounds like i am going to get another plumber to fix the situation.

I thought that when the stove was lit, it would gravity feed into the coil in the cylinder, then when the pipe stat was activated it would turn on the stove pump and an associated rads pump to act as a dump circuit.

There is not waste pipe on the P&T valve, safety valve on the system link or on the inlet control valve for the CWS.

The cylinder is a Joule cylinder, im not sure of the model, but im hoping that the coil being used by the solid fuel at present is 1"

Dtp1979

froshtyv wrote: »

Thanks for the replies.

Sounds like i am going to get another plumber to fix the situation.

I thought that when the stove was lit, it would gravity feed into the coil in the cylinder, then when the pipe stat was activated it would turn on the stove pump and an associated rads pump to act as a dump circuit.

There is not waste pipe on the P&T valve, safety valve on the system link or on the inlet control valve for the CWS.

The cylinder is a Joule cylinder, im not sure of the model, but im hoping that the coil being used by the solid fuel at present is 1"

No matter what, you'll have to un pressurise your cylinder.
Water at 2 bar boils at 144'C. A pressurised cylinder sits at 3 bar when cold. Let's say the oil heating had that cylinder at 60'C. You come home, light a big fire, the cylinder temp rises to 102. The P and T valve is blanked by some fool(which I've often seen). The cylinder is prob 5 bar now but the water isn't near its boiling point to bring it to steam.
Then you open a tap, bringing the cylinder back to atmospheric pressure, therefore lowering its boiling point. If you boil 1 litre of water, you get 1600L of steam.
So you've a 300L cylinder of water, with 480,000L of steam (1600x300) trying to escape from it.
Bang

selfbuildpaddy

Hi all. I have a question regarding my oil heating/ stove set up and was wondering if anyone else encountered the same issue.

I have a 4 zone system link with (1. Hot water 2. Downstairs rads 3. Upstairs rads 4. Attic rads). When running on the oil boiler all zones heat perfectly through the system link. My stove is located on the ground floor of my house. Once this begins to heat up it heats a buffer cylinder which is located in my attic via gravity loop. Once the stove setpoint is reached on my stove stat located beside my stove, the stove pump which is located beside my system link, also in the attic starts. This will then turn off my oil boiler and start four output pumps of my system link.

The issue I am having is the hot water from the stove is just circulating around my stove, buffer and system link but will not divert out to the 4 zones. There is a non return valve on my oil boiler circuit which means that it is not circulating from the stove through the oil boiler circuit.

Any help would be greatly appreciated, Thanks.

John T Carroll

Dtp1979 wrote: »

No matter what, you'll have to un pressurise your cylinder.
Water at 2 bar boils at 144'C. A pressurised cylinder sits at 3 bar when cold. Let's say the oil heating had that cylinder at 60'C. You come home, light a big fire, the cylinder temp rises to 102. The P and T valve is blanked by some fool(which I've often seen). The cylinder is prob 5 bar now but the water isn't near its boiling point to bring it to steam.
Then you open a tap, bringing the cylinder back to atmospheric pressure, therefore lowering its boiling point. If you boil 1 litre of water, you get 1600L of steam.
So you've a 300L cylinder of water, with 480,000L of steam (1600x300) trying to escape from it.
Bang

My understanding of thermodynamics doesnt tie up with the above.
If you have a 300 Litre of water at 5 Bar and 102C and you depressurise it by opening a tap or whatever you will flash off about 1 litre of steam at 100C and you will be left with 299 litres of water sitting in the cylinder at 0 Bar pressure and 100C. That 1 litre of steam will try to occupy a space of 1.67 M3 of space or 1670 litres, if you take a room of average volume of say 25 M3 then while highly dangerous its not of catastrophic consequences and the cylinder will certainly not blow up.
Now, if the solid fuel stove(uncontrolled heating) had heated that 300 Litres of water to its boiling (saturation) point of almost 159C at 5 Bar then in the event of the opening of a tap, 34 litres of steam will (eventually) flash off at 0 Bar and 100C and you will be left with 266 Litres of water sitting in the cylinder at 0 bar pressure and 100C. Now that 34 Litres of steam will occupy over 57 M3 of space, enough to fill a very large room with a steam/water mix at 100C which can certainly cause fatal injuries due to the huge volume it now occupies. Obviously if one opens a tap, one will quickly close it again but if there is a rupture of the cylinder then that can certainly be catastrophic, thats what makes a solid fuel stove/pressurised cylinder potentially so dangerous.
edit: steam is always measured in Kgs but I left it at Litres so as not to cause too much confusion as its the water that flashes into steam.

I can do for sums on the above for anyone who's interested

Dtp1979

John T Carroll wrote: »

My understanding of thermodynamics doesnt tie up with the above.
If you have a 300 Litre of water at 5 Bar and 102C and you depressurise it by opening a tap or whatever you will flash off about 1 litre of steam at 100C and you will be left with 299 litres of water sitting in the cylinder at 0 Bar pressure and 100C. That 1 litre of steam will try to occupy a space of 1.67 M3 of space or 1670 litres, if you take a room of average volume of say 25 M3 then while highly dangerous its not of catastrophic consequences and the cylinder will certainly not blow up.
Now, if the solid fuel stove(uncontrolled heating) had heated that 300 Litres of water to its boiling (saturation) point of almost 159C at 5 Bar then in the event of the opening of a tap, 34 litres of steam will (eventually) flash off at 0 Bar and 100C and you will be left with 266 Litres of water sitting in the cylinder at 0 bar pressure and 100C. Now that 34 Litres of steam will occupy over 57 M3 of space, enough to fill a very large room with a steam/water mix at 100C which can certainly cause fatal injuries due to the huge volume it now occupies. Obviously if one opens a tap, one will quickly close it again but if there is a rupture of the cylinder then that can certainly be catastrophic, thats what makes a solid fuel stove/pressurised cylinder potentially so dangerous.

I can do for sums on the above for anyone who's interested

Interesting point John. You are obviously very well versed on maths and equations. I'm certainly not. But you say 0 bar a few times. The water in the cylinder will never be at 0 bar as its being pumped? Unvented Cylinders have exploded as a result of being heated by uncontrolled heat sources. Can you explain how?

John T Carroll

Dtp1979 wrote: »

Interesting point John. You are obviously very well versed on maths and equations. I'm certainly not. But you say 0 bar a few times. The water in the cylinder will never be at 0 bar as its being pumped? Unvented Cylinders have exploded as a result of being heated by uncontrolled heat sources. Can you explain how?

In general, I would say that its a combination of pressure/temperature or may simply be that the expansion allowance isnt sufficient and as water is essentially incompressible then something has to give when the temperature continue to rise. I would like to read some case studies as I havnt come across any despite working (physically) with all sorts of Boilers, Pressure Vessels and Flash Vessels for well over 45 years.

Re the water in the vessel never being at 0 Bar, I used that because thats the example that you used....but it makes no difference really, for example if the pressure in the cylinder was maintained at 5 Bar and was still at 159C and an opening came in the cylinder then as the water is lowered to atmospheric pressure as it exits it will flash off over 11% as steam (the same) and the remainder will be water at 100C, but outside the cylinder, ie you will have 0.89 kgs of water at 100C and 0.11 kgs steam at 100C.

Dtp1979

John T Carroll wrote: »

In general, I would say that its a combination of pressure/temperature or may simply be that the expansion allowance isnt sufficient and as water is essentially incompressible then something has to give when the temperature continue to rise. I would like to read some case studies as I havnt come across any despite working (physically) with all sorts of Boilers, Pressure Vessels and Flash Vessels for well over 45 years.

Re the water in the vessel never being at 0 Bar, I used that because thats the example that you used....but it makes no difference really, for example if the pressure in the cylinder was maintained at 5 Bar and was still at 159C and an opening came in the cylinder then as the water is lowered to atmospheric pressure as it exits it will flash off over 11% as steam (the same) and the remainder will be water at 100C, but outside the cylinder, ie you will have 0.89 kgs of water at 100C and 0.11 kgs steam at 100C.

But how would the 300l @ 159 drop back down to 100?

John T Carroll

Dtp1979 wrote: »

But how would the 300l @ 159 drop back down to 100?

That would only happen if there was a rupture of the cylinder (which is the catastrophic case) where all the contents would very quickly fall to atmospheric pressure, but if there wasnt a rupture and one had a controlled opening or a small hole in the cylinder then you will still get a mixture of 0.89 kgs of water and 0.11 kgs of steam for each kg of water but it will be at a much lower rate and will give people time to get out of the way, what kills people is the sudden release of pressure where all the "flashing" can take place almost instantly, and it will if say the top of the cylinder/vessel ruptures, you can only imagine the consequences if a room full of steam is released instantly. There can be very severe damage as well caused by bits of the vessel material being blown everywhere due to the expansion capabilities of steam even at very low pressures down to 5 PSI (0.35 Bar)

I think maybe I should explain the "flashing" with a few numbers. If you have 1 kg of water at 5 bar and 159C then that will contain 671 units (KJ) of heat, if you have 1 kg of water at 0 Bar and 100C then that will only contain 419 units of heat. Now water can only exist at 100C at atmospheric pressure so the kg of water MUST lose (671-419) units of heat, ie 252 units. But where does it disappear to??, it generates some steam, at atmospheric pressure it requires 2257 units of heat to convert 1 Kg of water into 1 kg of steam but as there is only 252 units available or 11.16%, (252/2257)*100, you end up with 0.11 kgs of steam and the rest, 0.89 kgs, as water.
You know all my secrets now, I must go for some refreshments before they close.

John T Carroll

Dtp1979 wrote: »

Unvented Cylinders have exploded as a result of being heated by uncontrolled heat sources. Can you explain how?

Thats still a very good question and the answer I gave re the solid fuel stove raising the temperature to 158C or whatever could only happen if the solid fuel system was itself a unvented system with a 3 bar safety valve in which case the temperature in the hot water storage tank could theoretically rise to 142C, still very dangerous from a Flash Steam point of view. If the solid fuel stove is fitted properly with an vented system then the maximum temperature reached may be 105C to 110C depending on the static head before it starts venting into the combined F&E Tank. In my opinion this temperature can be reached whether there is a vented or non vented hot water storage tank fitted so I really cant say why the unvented cylinder is more at risk under these circumstances, if the solid fuel coil was holed for whatever reason then pressurised water from the hot water storage tank would flow into the solid fuel system and could possibly overflow from the C&F Tank if the C&F Tanks own overflow pipe was too small.

Dtp1979

You mentioned earlier about the culinder rupturing that would cause and explosion. How big of a rupture are you talking about? If the p&t valve failed or stuck, and only opened at say 110 degrees, would this cause a bang?

John T Carroll

Dtp1979 wrote: »

You mentioned earlier about the culinder rupturing that would cause and explosion. How big of a rupture are you talking about? If the p&t valve failed or stuck, and only opened at say 110 degrees, would this cause a bang?

No, because 110C is equivalent to only 0.5 Bar, the cylinder will only rupture if its design pressure is exceeded (normally by a factor of at least 1.5). I don't know what the design pressure of unvented SS cylinders is? but its probably > 6 Bar??. Re the cylinder rupturing, it could be of any size, obviously the smaller the better as it gives a sortof controlled release of the contents but boiler shells have sometimes opened up all along a welded seam and released all the boiler contents in seconds.

Dtp1979

John T Carroll wrote: »

No, because 110C is equivalent to only 0.5 Bar, the cylinder will only rupture if its design pressure is exceeded (normally by a factor of at least 1.5). I don't know what the design pressure of unvented SS cylinders is? but its probably > 6 Bar??. Re the cylinder rupturing, it could be of any size, obviously the smaller the better as it gives a sortof controlled release of the contents but boiler shells have sometimes opened up all along a welded seam and released all the boiler contents in seconds.

Would you personally pipe a stove into an unvented cylinder?

John T Carroll

Dtp1979 wrote: »

Would you personally pipe a stove into an unvented cylinder?

If its against regulations, I think I dont have to tell you my answer, do you know if it is?

In th FAS attachment below, page 39, "Interlinking of Solid Fuel to Automatic Boiler" its gives a nice schematic of the system, unfortunately it just shows the hot water cylinder as a "box", they do specifically state....."1 ins Unristricted Gravity Flow and Return on Solid Fuel" but strangley enough no specific mention of the hot water cylinder which is a bit baffling seeing that this publication is "Trade of Plumbing".

Dtp1979

John T Carroll wrote: »

If its against regulations, I think I dont have to tell you my answer, do you know if it is?

In th FAS attachment below, page 39, "Interlinking of Solid Fuel to Automatic Boiler" its gives a nice schematic of the system, unfortunately it just shows the hot water cylinder as a "box", they do specifically state....."1 ins Unristricted Gravity Flow and Return on Solid Fuel" but strangley enough no specific mention of the hot water cylinder which is a bit baffling seeing that this publication is "Trade of Plumbing".

Honestly im not sure if it is against regulations. I'm sure I read it somewhere that it is though.
Aside from regulations, with your extensive knowledge of the subject, would you do it in your house?

Dtp1979

Just had s look, and yes, it's against regulations.

John T Carroll

Dtp1979 wrote: »

Honestly im not sure if it is against regulations. I'm sure I read it somewhere that it is though.
Aside from regulations, with your extensive knowledge of the subject, would you do it in your house?

Dtp1979 wrote: »

Just had s look, and yes, it's against regulations.

Thanks for that but I will reply to your query, above.

NO, I wouldnt connect a vented Solid Fuel Stove into a unvented Hot Water Cylinder in anyones house including my own for the following reasons.

I am a great believer in Murphy's Law that if it can happen, it will.

If you consider the unvented cylinder with an expansion vessel, the expansion vessel,s diaphragm can fail and more than likely will over a period of time, the P&T valve may start leaking and some bright spark in the house might just decide to blank it as you said previously so now you have a system with no expansion space and no safety valve. If the solid fuel isnt connected then its more than likely that the cylinder temperature will be around 60C and the expansion volume will be about 4.5 Litres which the pipework and entrained air in the system might take up without raising the cylinder pressure to dangerous levels and even if something did blow on the system, pipework etc then water at 60C will leak /spray around the place. On the other hand, if the solid fuel was connected then the temperature can and probably will rise to 105C/110C on occasions and the system will have to try and accomodate 15 ltrs expansion which quite possibly could raise the cylinder pressure to dangerous levels with the resultant leakage of water/steam at 100C.
On the other hand if the solid fuel is connected to a vented cylinder then dangerously high pressure levels cant build up under any circumstances.

Thats why I wouldnt do it, why take any risk when its avoidable.

gctest50

Dtp1979 wrote: »

Would you personally pipe a stove into an unvented cylinder?

vaguely related,

plugged T&P valve , stat disabled ~ bit like uncontrolled stove heat source

launch velocity 900fpm

they disable the stat (~much the same as uncontrolled stove heat source ) and get the pressure up

the little house is built to building code

John T Carroll

gctest50 wrote: »

vaguely related,

NO, not in any shape or form, to anyone out there who may have a system with a vented solid fuel stove connected to a unvented cylinder, you are not sitting on a time bomb as long as all the protections described above are in place plus the fact that all unvented cylinders now have a expansion relief valve as well.

Dtp1979

John T Carroll wrote: »

NO, not in any shape or form, to anyone out there who may have a system with a vented solid fuel stove connected to a unvented cylinder, you are not sitting on a time bomb as long as all the protections described above are in place plus the fact that all unvented cylinders now have a expansion relief valve as well.

Only a few days ago I came across a brand new installation where there was no p&t valve fitted. In fact, there was nowhere on the cylinder to actually fit it which was strange to me.
Another question,
The above scenario but this time it's a bath tap with 3/4" piping that's opened by a child, the child hears rumbling and panics, runs away and leaves the tap open full. What would happen?

John T Carroll

Dtp1979 wrote: »

Only a few days ago I came across a brand new installation where there was no p&t valve fitted. In fact, there was nowhere on the cylinder to actually fit it which was strange to me.
Another question,
The above scenario but this time it's a bath tap with 3/4" piping that's opened by a child, the child hears rumbling and panics, runs away and leaves the tap open full. What would happen?

Again if one assumes a 300 Litre cylinder, mains fed, reduced to 3.0 Bar pressure and at a temperature of 110C (because no P&T v/v fitted) and also no antiscald valve fitted and someone opens a 3/4 ins bath tap. Again a mixture of water and steam at 100C will exit from the tap, because of the 110C temperature, 1.89% (461.56-419)/2257)*100) of the tap water will flash off as steam. If one assumes a flowrate of say 30 LPM then flash steam at a rate of 0.57 kgs/min (30*1.89%) will flow from the tap, the remainder will be water at 100C, this 0.57 kgs of steam can occupy a space of almost 1.0 M3 so would fill a small bathroom of 5M3 in about 5 or 6 minutes or so after which time the 300 Litres of hot water will be exausted and you will be left with a cylinder full of cold water at 3.0 Bar pressure.

Wearb

I have been following this thread and deliberately kept out of it so as not to drag it in another direction. Thanks John T Carroll for all your informative input on this subject. And dtp for your pertinent questions.

In this area, I often find comparing it to the old style pressure cooker (with the jiggling weight) helpful.

I do know that there is a perception out there that in the instance with the 3/4" bath tap -above- the whole contents of the cylinder would instantly turn to steam with catastrophic consequences. The fact that this doesn't happen (in this instance) is obviously no reason to ignore regulations, the reasons are explained in this thread.

This thread will be of great help in increasing understanding of the issues and consequences.

Thanks again.

John T Carroll

Wearb wrote: »

I do know that there is a perception out there that in the instance with the 3/4" bath tap -above- the whole contents of the cylinder would instantly turn to steam with catastrophic consequences. The fact that this doesn't happen (in this instance) is obviously no reason to ignore regulations, the reasons are explained in this thread.

That perception may be out there alright but at least it "errs" towards caution which is certainly no bad thing in itself, the ironical thing re the above scenario is that exactly the same thing would happen with a properly installed system, a vented solid fuel stove paired with a vented hot water cylinder, and while an antiscald valve in both instances would prevent potential scalding I think everyone is aware that antiscald valves just don't work very well with gravity flow systems, especially upstairs.

Wearb

I often thought -with an unvented cylinder- that failed overheat stats on immersion heater was potentially a more immediate source of danger.

John T Carroll

John T Carroll wrote: »

NO, not in any shape or form, to anyone out there who may have a system with a vented solid fuel stove connected to a unvented cylinder, you are not sitting on a time bomb as long as all the protections described above are in place plus the fact that all unvented cylinders now have a expansion relief valve as well.

WOW, strong statement and one I totally disagree with. Tell me why unvented cylinder manufacturers instruct installers that no uncontrollable heat source can be connected to a cylinder?

Would it surprise you that the main reason behind the introduction of UK G3 unvented cylinder safety regs was due to the amount of explosions that destroyed homes because of bad installation practices and homeowners capping pesky dripping safety valves.

My day job is to promote safe unvented cylinder installations and as someone who has seen hundreds of installations I find it frustrating when a post like this appears because it strengthens the hand of those who don't wish to fit unvented cylinders safely.

Go sit a G3 safety course which factors in human nature then lets have a chat about what is and isn't safe.

gctest50

John T Carroll wrote: »

NO, not in any shape or form, to anyone out there who may have a system with a vented solid fuel stove connected to a unvented cylinder, you are not sitting on a time bomb as long as all the protections described above are in place plus the fact that all unvented cylinders now have a expansion relief valve as well.

and thats hy i put in "plugged T&P valve , stat disabled"

gctest50 wrote: »

vaguely related,

plugged T&P valve , stat disabled ~ bit like uncontrolled stove heat source

gctest50

John T Carroll wrote: »

NO, not in any shape or form, to anyone out there who may have a system with a vented solid fuel stove connected to a unvented cylinder, you are not sitting on a time bomb as long as all the protections described above are in place plus the fact that all unvented cylinders now have a expansion relief valve as well.

cos you get this kinda thing for real:

Dtp1979 wrote: »

Only a few days ago I came across a brand new installation where there was no p&t valve fitted.............?

Wearb

Wearb wrote: »

I often thought -with an unvented cylinder- that failed overheat stats on immersion heater was potentially a more immediate source of danger.

3kw vs 25-30 kW coil.

As a manufacturers tech I'v never known it to be a problem but our immersion are limited to 65c.

Instead of talking about explosions let's talk about more common day to day things, TP lifts due to stove being fitted, house gets flooded as TP pipework is not there or unsatisfactory, home owners house is destroyed home owner is scolded, where does that leave the home owner regards compensation, where does that leave the installer who thought he done a great job.

John T Carroll

Wearb wrote: »

I often thought -with an unvented cylinder- that failed overheat stats on immersion heater was potentially a more immediate source of danger.

I remember reading of a fatal accident in the UK (which I think triggered the fitting of Immersion overheat stats) in which a mother moved into rented accommodation with a child, the Immersion stat failed and water/steam started venting into the "plastic" header tank and started recirculating the contents, the tank then failed because of the high temperature and the contents of the tank came through the bedroom ceiling and the child died due to scalding.

John T Carroll

gary71 wrote: »

My day job is to promote safe unvented cylinder installations and as someone who has seen hundreds of installations I find it frustrating when a post like this appears because it strengthens the hand of those who don't wish to fit unvented cylinders safely.

I certainly don't want to appear to encourage this, far from it, I was referring to existing systems which may have a vented solid fuel stove paired with a unvented cylinder with all the safety devices operational. Are you suggesting that if someone had an arrangement like this and had it inspected by a competent person like yourself that it should be decommissioned and a vented cylinder fitted? or to go a step further, are these systems, where fitted, illegal in the UK?