Low pressure in boiler, but no filling loop?

Hi chaps

Our boiler has low pressure, it heats an invented water cylinder upstairs. There’s no filling loop on the boiler that I can see, there’s three taps – CW return, flow and gas.

Upstairs there’s a filling loop attached to the cylinder tank.

Do you add pressure with the filling loop upstairs?!

The manual is bobbins, and the telephone support told me to call an engineer to show me how it works and they didn’t know.

Cheers

Ricks

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Under the Boiler:

The unvented cylinder:

Looks to be the same as mine – the filling loop is on the cylinder. It’s the braided looped cable with the two black knobs. Yours has the energy efficiency graph just behind it

Looking through the instructions this is what’s required:

Indirect units

Fill the indirect (primary) circuit following the boiler
manufacturer’s commissioning instructions.

Ensure the filling loop hose is connected at both ends
and is tight.

Open the isolaing valves at either end of the filling
loop and allow to fill from the mains inlet supply.

To ensure the cylinder primary heat exchanger is
filled, both of the 2 port motorised valve (supplied)
should be manually opened by moving the lever on
the motor housing to the MANUAL setting. When
the primary circuit is full return the lever to the
AUTOMATIC position.

Air can be vented from the primary heating coil by
unscrewing the small dust cap on the auto air vent
by half a turn.

The primary system should be pressurised to the
minimum pressure required by the boiler (usually 1
bar), the pressure guage fitted should be used to
ensure the correct system pressure is set.

When full and pressurised, the filling loop isolating
valves should be closed and the levers on the
motorised valves returned to the Auto position.

So…. can I just top up the pressure with the hose taps, or do I need to switch the port valves into Manual mode?

Well, I read that as saying ‘how to initially fill the system’, whereas you’re just topping it up. So I’d just use the hose taps to top-up the pressure.

Just checked mine and it was a bit low so topped it up!

Awesome 🙂 Cheers Ric!

Why put the filling loop where I can’t see the pressure gauge?!

Why put the filling loop where I can’t see the pressure gauge?!

Because whoever installed it is a cheapskate and didn’t follow the instructions which will tell you to add a pressure gauge within sight of the filling loop.

Also, the filling loop should be disconnected when not in use.

Flaperon – Member
Also, the filling loop should be disconnected when not in use.

They seem to get away with it by using a braided hose and a tap (or two, mine and looks like this one has a tap at both ends). Makes it a temporary connection then I guess for regulation purposes.

Filling up, I don’t know about this boiler, but I have a simple combi and when it needs a top up I just fill until the pressure gauge reaches the red marker minimum point. I was told this is what you do.

in 12 years working for myself i ve seen two pressurised systems run off a vented tank in the loft and i have had to refit a modern combi that had no system to fill it what so ever.. the householder had been told to use a house pipe into a radiator if needed..

Flaperon – Member
Also, the filling loop should be disconnected when not in use.

They seem to get away with it by using a braided hose and a tap (or two, mine and looks like this one has a tap at both ends). Makes it a temporary connection then I guess for regulation purposes.

Our last two boilers have had the two tap loop on.

Isn’t the reason for disconnecting something to do with not allowing inhibitor to “backwash” (non technically speaking) into the mains side on one hand and preventing an accidental over fill from hugh mains pressure on the other if the filing valve were faulty or something.

Used correctly aren’t the two taps supposed to be able to prevent these two things?

IANA Gas Safe Engineer!