Heating system design

Will I need two expansion vessels in a closed system design if the boiler doesn't have an internal one?
One for the heating and flow to direct hot water tank one for supply to tank
To explain further see schematics here http://www.eco-hometec.co.uk/Schematics%20&%20Forms/ECOSCH8.pdf where two expansion vessels are shown
Also do I need to fill the hot water and heating sides seperately or will they be connected together somewhere?
mant thanks
Nick
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Nick
More info. What boiler? What cylinder? Vented with a cold storage tanks or unvented (pressurised)?
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Eco Hometec EC31 HS Condensing Boiler Eco Hometec Duo tank Unvented mains pressure Cylinder Schematic of my proposed system will be available asap
Nick
IMM wrote:

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one unvented circuit is the boiler flow and return circuit, and the other is the unvented hot water cylinder. Note that if you do not have unvented hot water (you have a cold header tank in the loft) then you do not require the second expansion vessel. IIRC, the Eco hometec has an internal expansion vessel, albeit a small one, which may meet your needs for the heating circuit.
Andy Hall has one of these in a system, so he may be able to add more.
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That will depend on how the circuit is implemented and the boiler chosen. It isn't clear from the schematic what the two different flow and return lines from the boiler are. Are they isolated circuits? Are they just two outlets from a diverter valve on the same circuit? (i.e. similar to a Worcester-Bosch system boiler with the optional internal diverter valve).
You may need one anyway, as the water content of such a system might be so high that a boiler internal expansion vessel wouldn't be big enough to contain the pressure rise.
Christian.
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Here is a schematic of what I propose. Please let me hace any suggestions.
http://www.saucefx.com/nick/heating/heating_system.jpg
many thanks Nick
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water in the cylinder when it is heated and so needs to have an unrestricted connection to the cylinder; you've currently got a non return valve between them.
Be aware that UK water regs prohibit amateur installation of unvented DHW systems and that building regs approval is required.
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My understanding that it is an "or", not an "and".
i.e.
Be aware that UK building regs prohibit amateur installation of unvented DHW systems unless building regs approval is obtained.
Christian.
P.S. it is only above a certain storage capacity that this applies. (For some reason 13 litres rings a bell, but I could be well out). This enables unvented mains pressure water systems not using storage to be fitted without approval (unless also required by Part L).
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fred

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After investigating further, I've found it is in Approved Document G3. It does seem more strictly defined than other such "competent person" situations, but I think there is still a loophole. I am not a lawyer, though, so if intending to do this, you should check with your local building control before doing anything to ensure that they agree.
"3.8 The unit or package should be installed by a competent person i.e. one holding a current Registered Operative identity card..."
It goes on to list various bodies. Although this indeed might suggest that it is not permitted, I doubt that legally speaking the use of "i.e." could be said to exclude other competent people. (Again, I'm not a lawyer, so maybe it can so exclude alternatives). One thing is not in doubt though. You certainly need to be in one of those bodies to be able to self certificate the work. You would, therefore, need to get approval from the building control department, which could be costly and involve an inspection.
Christian.
P.S. It is 15 litres for the exemption, not 13 litres.
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Do a Google. Andy posted the regs here not long ago.

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So, an amature can do, but has to go to building control. How much des this cost.

10 actually - from memory.

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Regarding fitting, we are doing other work on the house as well so the building regs people are already involved.
The inspector's opinion was that it was fine for me to do the work providing it met the regulations.
The only thing he specifically asked about was the temperature/pressure relief valve.
I'd be very grateful if people could comment on my system design which as mentioned earlier is available here:-
http://www.saucefx.com/nick/heating/heating_system.jpg
or
http://www.saucefx.com/nick/heating/heating_system.gif
many thanks
Nick
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The temperature/pressure relief valve will be supplied with the cylinder as a package. The installation instructions that come with the package will describe the pressure relief measures which must be followed to the letter. There may be restrictions and requirements about where the pressure relief line must run to. There will be a separate safety zone valve on the indirect coil, which MUST NOT also be used for functional switching/temperature control. The immersion heater must have two thermostats, one of which must be manually resetting requiring user intervention.
You must also ensure that the system is designed to work without relying on expanding water backwards into the water supply, like some US systems. UK systems typically have pressure reducing valves or check valves that prevent such expansion.
If you are doing this yourself and haven't yet bought the system, consider a heat bank instead. I've just fitted one myself and it definitely works. Installation couldn't be simpler. Connect the flow/return lines, mains water in, hot water out. Connect to mains electricity. Fill it up with water. That's it. No safety valves. No overflows. No vents. No additional tanks. Nothing. Costed the same as an equivalent Megaflo.
The main possible problem is that the boiler might limit the flow temperature to below the 80-85C you need to reheat it. This will depend on the internal electronics of the boiler. If the boiler can select different flow temperatures for heating the cylinder or running the underfloor/radiator circuit, then it could be ideal.
Christian.
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On Tue, 11 Nov 2003 17:42:19 -0000, "Christian McArdle"

On the MAN Micromat, actually you have a lot of control via the programming.
You can buy a water cylinder temperature sensor for it quite cheaply from Eco Hometec for optimum control. This is normally intended to monitor the temperature of the cylinder water and the boiler firmware allows that to be set at up to 70 degrees.
Alternatively, for a heatbank, where 80 degrees for the bulk water may be desirable, a conventional cylinder thermostat could be used and the boiler can be programmed to use that instead.
The flow temperature can be set separately for HW (or heatbank) service vs. the CH and boiler has electrical outputs to operate pumps or motorised valves as appropriate. In addition, the boiler power level is increased in the case of the EC31 up to 36kW vs. 28-31kW for CH.
.andy
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