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Author Topic: Central heating layout question (with thermal store)  (Read 3031 times)
julian
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« on: September 20, 2014, 10:46:42 AM »

Feed & expansion -

Is it acceptable to tee the feed / expansion off the central heating circuit itself?
With a boiler system, there are three way valves in place, but in this case, the central heating circuit will come direct from the thermal store (no valves outside of service isolators) so i cant see that it would make any difference at all where the F/E connects, providing there is not suction / pumping to the f/e tank (and how likely is this if it is 9 feet above the tee?


The thermal store will be vented in the usual way - its just the feed that im wondering about, as, if i take it to the tank, im just laying pipe right next to other pipe going to exactly the same place!

Thank you
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Countrypaul
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« Reply #1 on: September 20, 2014, 11:02:58 AM »

I am sure I have misunderstood something as if the CH circuit comes direct from the TS and the TS has a F&E tank, why does the CH circuit also need one?

I will shortly be putting in UFH with a TS with F&E tank above, but have not been considering a F&E for the CH. I am assuming that a ASHP we will be adding will be on a spearate circuit using an indirect coil in the TS will need either a F&E header tank or a pressure vessel is my understanding.

Paul
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julian
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« Reply #2 on: September 20, 2014, 11:12:12 AM »

CH comes direct from the lowest and mid points on the TS.

So, the same fluid will be in both, with no valves, except service valves (which will be open in all but service conditions)


Due to the layout of the place, i can either bring the pipe down, from the header tank in the loft, along and through the floors etc. to the thermal store...

...or i can tee it in to the CH pipe, so as the TS is fed (again, only fed, not vented) through the CH circuit.

I just cant see the point in running two pipes parallel to one another, through all the floor, to the same place.


I guess, however, if the CH curcuit blocked, the pump would try and pump up to the headder, but, even then, the TS would not empty, as the CH pump would never have enough power / head to do anything but the upper floor rads (im thinking worst case scenario, and if the TS could empty)
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desperate
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« Reply #3 on: September 20, 2014, 11:19:33 AM »

You do need the feed and expansion pipework near the heatsource (boiler) or more correctly the feed and vent. To clarify, the feed and expansion pipe is the same 15mm pipe, the vent is a 22mm pipe that goes over the top of the feed and expansion cistern(tank, header etc) So basically you have two pipes one 15mm to provide for feed and expansion, and one 22mm pipe to provide an open vent in case of a meltdown in the boiler. Normally they both need to be tee'd into the pipework close to the boiler, to provide an effective safety vent and also to prevent pumpover through the cistern or air entrapment down through the feed/vent pipe. Placing the feed and vent on the heating circuit somewhere convenient risks not venting the boiler effectively and also pumpover/entrapment.

Sorry to labour this point, but the position of these pipes is very important for the wellbeing of the system, your house, and you.

Desp
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julian
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« Reply #4 on: September 20, 2014, 11:25:12 AM »

I keep saying... : )

The vent (which is the most important one) would be from the store.  Its only the feed / expansion that im on about.

The FE pipe (the 15mm one) is low flow, and its not exactly a saftey thing.
The vent pipe, if the system boils, is high flow / saftey.  Im not talking about moving the 22mm vent pipe.

The TS is situated about 3 feet away from the boiler (rayburn) with 28mm between.
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desperate
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« Reply #5 on: September 20, 2014, 11:45:59 AM »

I'm sorry Julian, I'm not clear in my mind how your system is going to be laid out, it will probably work ok

Desp

To ease my effing conscience Grin

The relative position of the F/E and Vent is important to stop pumpover etc,
The  relative position of the vent/boiler is important to provide safety.

From what you say it sounds as if, if your boiler has a hissy fit it can only vent itself through the T/S, which is not good.

Edited cos I'm a stobborn git Grin
« Last Edit: September 20, 2014, 11:54:09 AM by desperate » Logged

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