Filling loop help required - schematic attached

[Dr_Doolittle]

I'm having trouble locating the filling loop on my system. There is no braided pipe with taps to be found anywhere!
Here's a pic of my boiler:

http://i187.photobucket.com/albums/x228/Dr_Doolittle/DSC00454.jpg

Now, i traced all the pipes and this is what i found: (excuse the rough drawing, but i hope you get the idea)

http://i187.photobucket.com/albums/x228/Dr_Doolittle/Pipescopy.jpg

it seems like the cold water tank is feeding into the system? the valve/tap is not fully or open or fully closed.

Can anyone make sense of this? thanks

 

[JonB]

Is it not filling of the cold header tank.

 

[ChrisR]

Standard Irish system?

 

[JohnD]

does the loft tank have a ball-valve (like in a WC cistern) to keep it topped up?

It seems to have the characteristics of an ordinary vented system (except that it has a pressure vessel, don't know why
and too many valves
and no room thermostat or electrically-operated 3-port valve (replacing "B" and "C") to turn off the heating circulation when the rooms are warm, or cylinder stat to turn off the supply to the cylinder once it's hot. Must be wasteful of energy.

It looks to me like the pressure vessel was added later, perhaps to try to tackle some kind of problem.

I hope the cold water tank shown is a small F&E, not the one that supplies the bath taps

 

[chrishutt]

If the feed from the cold water tank had a non return valve on it then the whole thing makes sense. The feed tank could then even be potable water since it would not take expansion (hence expansion vessel). Of course it might not comply with UK regs but we're talking Ireland here.

 

[Moss5]

http://www.idealboilers.com/mexico_he_details.html
Go to the above link and download the Mexico HE manual.pdf
Page 11, Figure 6 shows your system.
Page 12 describes filling.
If you have mains water pressure of 3bar (or greater), use a garden hose and filling loop (attached to valve'D') to fill your system. The cold water tank need not have been fitted if you have the required mains pressure to pre-pressurise.

Since the tank has been fitted, a check-valve in the tank outlet does exist to prevent system pressure escaping to the tank.

The 'not sure' item on your sketch should be the 3bar safety valve. In the event of over-pressure, water will discharge on to the floor via the open-ended pipe.

 

[chrishutt]

Well found Moss5, but it appears from the OP's diagram and picture that the safety valve might be on the return rather than the flow, given that the AAV is on the other pipe and the cylinder connections shown in the diagram. Worth checking, or doesn't it matter that much?

 

[Dr_Doolittle]

hi guys - thanks for all your replies. sorry for only replying now - i've been busy all day.

To answer some questions:
The cold water tank shown is the main cold water tank for the house.
There appears to be no non return valve.
The boiler is a replacement for the one which was installed originally with the system.
Valve c is used to turn off the rads in the summer, to allow the boiler heat the hot water tank only.
All rads have trv's
I dont remember there being a pressure vessel before the new boiler was installed.

moss5, is valve d used for both draining and filling the system?

 

[doitall]

Personally I think the whole thing looks a mess and should be ripped out.

 

[Moss5]

7. Mains Connection
There must be no direct connection to the mains water
supply or to the water storage tank supplying domestic
water, even through a non-return valve, without the
approval of the local water authority.

The above is from page 12 of the manual.
If the pressurized system has corrosion inhibitor added, there is a risk of leakage past the check-valve and contamination of your cold water tank. Do you know what the tank is supplying?
It may be feeding the hot water tank only.

Closing valve 'A' would be a quick-fix solution, but cutting and blanking the connection should be done very soon. Also, the suspect contents of the cold tank should be flushed, by running a tap fed by the tank.

The tank should have only been 3 litres max and is described as 'make-up' in the manual.

You did not confirm that you have mains at sufficient pressure? The only reason for using a 'make-up' tank is that you don't have sufficient mains pressure.

To answer your question: -
Yes - valve 'D' will drain to that level (you may have to open an air-vent at high level), but a drain at lower level would be required for complete draining. Any leak in a pressurized system will act like a drain.

 

[Dr_Doolittle]

hi Moss5 - thanks for taking time to reply with helpful answers and comments.

I just had another look at the system.
Valve A is just under 1 turn from closed, and there is a non return valve after it - sorry didn't spot that before
So i presume this keeps the system topped up? I know it should be closed & disconnected and/or fed from a small header tank instead.
Not sure how good the mains pressure is, but it seems fine.

The cold water tank supplies the calorifier, bathroom cold tap, toilet & and the power shower's cold feed.

I was planning to replace a rad in my bathroom, so i guess i'll use valve A to top up the system, and then close it and disconnect?

 

[chrishutt]

Valve A is just under 1 turn from closed, and there is a non return valve after it - sorry didn't spot that before
So i presume this keeps the system topped up?

Yes, but you should keep valve A fully shut at all times, except when you need to restore the pressure. Practically all filling loops are left connected so your system is no more risky (in terms of contaminating potable water) than most and arguably less so since the feed is via a cistern and not directly off the mains.