Top-up bottle

[Rob Foster]

Yes, agreed, I was quite upset. Calmed down now.

Ok so we are all back on track
Now, Imwill,look at this again when I get gnome
Rob Foster aka centralheatking

 

[Mark K]

Ok so we are all back on track
Now, Imwill,look at this again when I get gnome
Rob Foster aka centralheatking

Hi Rob,

This explains a little better. Excuse my technical drawing, a bit rusty these days.

Cheers,

Mark

 

[Gasmk1]

why not fit one of these in plave of the tank and set at 1/2 bar you can get them with a guage easy to do

Emmeti UK - 00200514 - 1/2" MBSP x FBSP - Automatic Filling Valve - 00200514

 

[SimonG]

Personally I would go filling loop and do away with tank and just pressurise to half a bar.

 

[Mark K]

why not fit one of these in plave of the tank and set at 1/2 bar you can get them with a guage easy to do

Emmeti UK - 00200514 - 1/2" MBSP x FBSP - Automatic Filling Valve - 00200514

Never seen one of those, every day is a school day. Thank you.

 

[Mark K]

Personally I would go filling loop and do away with tank and just pressurise to half a bar.

I may well do exactly that, and in the fullness of time will change the HW cylinder as we are in a hard water area and that would be an ideal time to do away with both header tanks and go mains pressure HW too.

Initially I want to see what the standing pressure is at the vessel when filled as a vented system and note that as a benchmark. I suspect it may be about 0.6 bar because of the height of the tank.

Then I will know what pressure at low level would definitely fill the system.

Am I thinking correctly there? As you fill an empty system the pressure increases first with the water column and then once full against the expansion vessel and interior of the system, until it reaches mains pressure assuming it doesn't burst?

Or did you mean put the filling loop in the loft and pressurise there to half a bar?

 

[SimonG]

Filling loop somewhere easy accessible. If I fit an external boiler I will fit a gauge and a filling loop inside.

 

[chris watkins]

Perfectly sensible idea to use an existing Feed cistern to continue to automatically top up a now sealed system with the same low pressure it always had on it.
It is often shown in MI's as an option, you will note a check valve is required on the cold feed to create the seal (as you stated you have capped the old vent pipe). It is surprising that some engineers have never seen the diagrams in the boiler instructions!!
Where is the expansion vessel located ? Its gas charge will need to be adjusted to equal the static water head above it, as 1M = 0.1bar you can work it out before you refill the system with water.
One thing to remember is that the point of connection of the vessel will now be the neutral point of the system so ideally it should be located on the suction side of the pump so that as much of the system is under positive pressure as possible.
Just for your info the 418 is a regular or heat only not a system boiler that would be a 618.

 

[chris watkins]

Only other problem you are going to have is rads getting hot in the summer as you have broken the last tee rule ie. return from cylinder must be the last connection before it goes back to the boiler.

 

[Mark K]

Perfectly sensible idea to use an existing Feed cistern to continue to automatically top up a now sealed system with the same low pressure it always had on it.
It is often shown in MI's as an option, you will note a check valve is required on the cold feed to create the seal (as you stated you have capped the old vent pipe). It is surprising that some engineers have never seen the diagrams in the boiler instructions!!
Where is the expansion vessel located ? Its gas charge will need to be adjusted to equal the static water head above it, as 1M = 0.1bar you can work it out before you refill the system with water.
One thing to remember is that the point of connection of the vessel will now be the neutral point of the system so ideally it should be located on the suction side of the pump so that as much of the system is under positive pressure as possible.
Just for your info the 418 is a regular or heat only not a system boiler that would be a 618.

It's a heat only boiler, you are quite right. The expansion vessel is on the boiler return about 400mm before, the pump is directly on the flow, to keep it as far from the first bend as possible, so only 400mm of pipe and the boiler are between the suction side of the pump and the vessel.

The MI for that boiler actually lists the mains filling loop as an option to the top up bottle.

I reckon the header tank is 6m above the boiler, hence my estimate of 0.6bar at the gauge on the expansion vessel.

I had picked up on the need for a check valve.

It is still running as a vented system right now, I will connect in the vessel, blow off valve, cap the vent and install the nrv on the feed all at the same time. Until I was certain I understood what and why I was doing, I put up with a bit of pump over.

Thank you for your advice.

 

[Mark K]

Only other problem you are going to have is rads getting hot in the summer as you have broken the last tee rule ie. return from cylinder must be the last connection before it goes back to the boiler.

Agreed, I will have to live with that, or turn individual rads off.

Do you think that will be different with the new pump location, as it hasn't been up to now?

 

[chris watkins]

If Rads are fitted with TRV's they might be stopping it.
It is not an exact science anyway.

 

[Mark K]

If Rads are fitted with TRV's they might be stopping it.
It is not an exact science anyway.

Thanks,

To be honest, it was installed in 1994 and the HW was put in first, so it may well not be exactly as I have shown.

TRYs are fitted too.