Joining two unvented cylinders.

[Long]

Hi I'm a selfbuilder looking for advice on joiing two unvented cylinders in series one above the other together.

What I am after is to gain an extra input coil. Do you think this is possible?

I have an existing twince coils 300 litres Megaflow in the loft and a single coil Keston Spa 200. The idea is that Keston will be fitted directly at the bottom of the existing one and the hot water out let from it feeding the in let of the cylinder above.

Your advice on this is much appreciated.

 

[justlead1]

Hi. What are you proposing to connect to the coil?

 

[Puddle]

Would recommend you get someone in who is qualified to work on unvented cylinders and can design a system correctly and safely for you

imho

 

[bptheplumber]

This cannot be done because the thermostatic controls of the upper cylinder will not turn off the lower cylinder which will then cause the upper cylinder to over heat, linking the controls so that one cylinder controls the other is in breach of the building regulations. Sorry.

 

[Long]

Hi. What are you proposing to connect to the coil?

Hi JustLead1, I am planning to connect a wood stove to it, the feed will be pump fed with thermalstat control etc. The stove has a separate safety gravity fed ciruit with heat sinks built in and another for the pump to take the heat to the cylinder as well.
I know this idea has been discussed on other threads, namely one raised by Lennox in March 2009, but that was inconclusive.

 

[Gray0689]

You can't connect a wood burning stove to an unvented cylinder

 

[ecowarm]

You can't connect two unvented cylinders in series as you want. It is possible two connect two identical cylinders side by side and follow the manufacturers instructions (correctly qualified installer) Why don't you install a thermal store instead?

Eco

 

[Rtrak]

I agree with everyone about the two cylinders. On the other hand I regularly connect wood burning stoves to unvented cylinders, OK not legal in the UK but I work in Portugal and it's common here, in France & Spain. Safety is always the first priority and it's relatively simple to achieve a reliable, safe and efficient system for DHW & CH providing the correct components and control systems are used.

 

[Gray0689]

I agree with everyone about the two cylinders. On the other hand I regularly connect wood burning stoves to unvented cylinders, OK not legal in the UK but I work in Portugal and it's common here, in France & Spain. Safety is always the first priority and it's relatively simple to achieve a reliable, safe and efficient system for DHW & CH providing the correct components and control systems are used.

How and what do you use for safety?????

 

[fuzzy]

the reason they cannot be fitted is you cannot simply turn off a wood burning stove, but i suppose you could divert the water to a heat leak by using motorised valves?

 

[Gray0689]

the reason they cannot be fitted is you cannot simply turn off a wood burning stove, but i suppose you could divert the water to a heat leak by using motorised valves?

And what happens if mot valve goes faulty or someone lockes it on manual ??

 

[Rtrak]

I really didn't want to Hijack this thread and am not suggesting for a moment that these types of systems are ideal, but there are circumstances where they have their place.

The system is powered via a UPS that gives more or less an hours power in the case of a cut, if this happens it switches automatically and sounds an audio alarm in the house, (mine also activates an auto dialler to my mobile phone). The supply to the system is permanently live. A dedicated mechanical over temperature dump valve actauted by a sonde in the stove's flow pipe is installed. A 3 Bar OP dump valve is also installed. The system is pressurised to 1.25 bar using a PRV with NRT on the stove return pipe this is left open. A pressure vessel sized to the system is also installed. A large combined temperature / pressure gauge is installed at the back of the stove where it can easily be seen. My system uses the Gledhill stainless Lite Solar cylinder and a Hunter Herald 14 with the optional thermostat. I like these cylinders as even in the winter, the solar makes a contribution. (I use a 20 tube evacuated tube panel and controller from Navitron in the UK) I also liked the inbuilt safety features but realise the warranty was invalid as soon as it was hooked up!

The pump operates automatically when the water in the stove reaches 40 deg C The power is also activated to the cylinder 'stat with integral resettable over limit. The cylinder 'stat controls two Honeywell valves, one normally open (CH), the other normally closed (DHW) we find this safer and more reliable than a 3 port. The system is tested to ensure all controls work correctly, normal operating water temperature is 50-70 deg C.

In the event of an over temperature dump, the system is purged with cold water until stable.

I'm not saying these systems are infallible, I raced back home from a local bar when I got a mobile call from the UPS only to find it was a momentary power outage, these are common here. Personally I never leave the system operating at full belt with the house unoccupied and I've always got one eye on the gauge and the other on the telly. These systems (and variations) have been installed here for a long time by the local heating engineers / electricians, obviously the systems have to be correctly sized and balanced and an understanding of the system's operation is vital for the homeowner although many have no idea how they work. One old guy opens the OP valve to draw hot water to wash his car! Some of the systems the Portuguese install for themselves would terrify many of us from the UK!

Again, not suggesting anyone goes with this type of system in the UK, as I said it 'can' be done.

 

[fuzzy]

And what happens if mot valve goes faulty or someone lockes it on manual ??

then they have messed with a safety device, same on any system. an unvented needs a two port as a safety feature anyway, same could be said for that
2 ports fail to off

 

[Gray0689]

I really didn't want to Hijack this thread and am not suggesting for a moment that these types of systems are ideal, but there are circumstances where they have their place.

The system is powered via a UPS that gives more or less an hours power in the case of a cut, if this happens it switches automatically and sounds an audio alarm in the house, (mine also activates an auto dialler to my mobile phone). The supply to the system is permanently live. A dedicated mechanical over temperature dump valve actauted by a sonde in the stove's flow pipe is installed. A 3 Bar OP dump valve is also installed. The system is pressurised to 1.25 bar using a PRV with NRT on the stove return pipe this is left open. A pressure vessel sized to the system is also installed. A large combined temperature / pressure gauge is installed at the back of the stove where it can easily be seen. My system uses the Gledhill stainless Lite Solar cylinder and a Hunter Herald 14 with the optional thermostat. I like these cylinders as even in the winter, the solar makes a contribution. (I use a 20 tube evacuated tube panel and controller from Navitron in the UK) I also liked the inbuilt safety features but realise the warranty was invalid as soon as it was hooked up!

The pump operates automatically when the water in the stove reaches 40 deg C The power is also activated to the cylinder 'stat with integral resettable over limit. The cylinder 'stat controls two Honeywell valves, one normally open (CH), the other normally closed (DHW) we find this safer and more reliable than a 3 port. The system is tested to ensure all controls work correctly, normal operating water temperature is 50-70 deg C.

In the event of an over temperature dump, the system is purged with cold water until stable.

I'm not saying these systems are infallible, I raced back home from a local bar when I got a mobile call from the UPS only to find it was a momentary power outage, these are common here. Personally I never leave the system operating at full belt with the house unoccupied and I've always got one eye on the gauge and the other on the telly. These systems (and variations) have been installed here for a long time by the local heating engineers / electricians, obviously the systems have to be correctly sized and balanced and an understanding of the system's operation is vital for the homeowner although many have no idea how they work. One old guy opens the OP valve to draw hot water to wash his car! Some of the systems the Portuguese install for themselves would terrify many of us from the UK!

Again, not suggesting anyone goes with this type of system in the UK, as I said it 'can' be done.

Sounds like a bomb waiting to go off andvwould never be aloud in uk regs
An uncotrolled heat sourse is not to be conected to an unvented cylinder in uk end of story

 

[Reg Man]

Do not even consider connecting an unvented vessel directly to a wood burner. This is very dangerous. There is a method of indirect connection, but it requires seperation via an open vented thermal store from the wood burner. Seek expert advice, before designing your system. Speak with HETAS for best way forward.