Draining central heating question

Nuggy96

Hi all,

I recently put some sentinel x400 into my central heating to breakdown the sludge in my system. I now need to get rid of what's in the system and refill my boiler I've got a question though. When I refill the boiler with the filling loop, I can't see the pressure without turning the boiler on as the pressure gauge is on a digital screen, so is it safe to turn the boiler on with no water in the system or should I just add some in with the filling loop for a period of time before turning the boiler back on?

Steps:
Turn boiler off
Attach hose to drain valve and open drain valve
Open all bleed valves
Close drain valve
Close bleed valves
The next bit is the struggle do I turn boiler back on so I can see pressure before using filling loop, or fill first and guess?

Thanks in advance

Mr.Generous

Yes you can turn it on, the boiler won't run with low pressure on the heating loop including for just hot water.

FreeBear

Nuggy96 said: Steps:
Turn boiler off
Attach hose to drain valve and open drain valve
Open the filling loop and let water run through the system until it comes out clear from the drain hose.

Turn off the filling loop.

Open bleed screws and let any remaining water drain out.
Close drain valve
Close bleed valves

Once the drain valve & bleed screws has been closed, add corrosion inhibitor - I take a plug out of the top of one radiator and use a funnel with a flexible spout to get the inhibitor in (my funnel has a 1/2" BSP fitting to screw in to the radiator). Replace the plug... Once dosed, open up the filling loop and go round each radiator to let the air out. Shut off the filling loop, and fire up the boiler.

Over the next few days/weeks, go round each radiator and bleed any air out. Keep an eye on the boiler pressure, and top up via the filling loop if required.

Note - You may have multiple drain down points - On my system, I have three. One on every drop. It is as well to connect a hose to each one in turn and flush water through.

ThisIsWeird

Make and model of boiler, Nuggy? 
Turn the boiler output controls to off, any timer/programmer controls ditto, then it should be ok to power it up to view the pressure.
The filling loop is usually (should be) connected to the CH return pipe to the boiler, so if you fancy trying FreeBear's 'flush' method, you may need to ensure the draincock is on the 'flow', or else your flush could bypass most of your rads. A flush like this will also rely on having a decent flow getting through each rad, but some lockshields could be barely open a crack, so unless you are prepared to mess about with these as well, your draindown method might be best.
If you don't already have one fitted, consider adding a magnetic filter since your system will be drained down.

Lorian

Also things are a bit different flushing it out if you have a manifold and microbore pipes.

Albermarle

ThisIsWeird said:

Make and model of boiler, Nuggy? 
Turn the boiler output controls to off, any timer/programmer controls ditto, then it should be ok to power it up to view the pressure.
The filling loop is usually (should be) connected to the CH return pipe to the boiler, so if you fancy trying FreeBear's 'flush' method, you may need to ensure the draincock is on the 'flow', or else your flush could bypass most of your rads. A flush like this will also rely on having a decent flow getting through each rad, but some lockshields could be barely open a crack, so unless you are prepared to mess about with these as well, your draindown method might be best.
If you don't already have one fitted, consider adding a magnetic filter since your system will be drained down.

I do not have one of these, and as far as I can remember, nothing has been added to the system ( inhibitor etc ) for at least 7 years. Heating/boiler ( serviced every 18 months or so) all run without problems.
I wonder how necessary all these items are, or whether I have just been lucky.

FreeBear

ThisIsWeird said: The filling loop is usually (should be) connected to the CH return pipe to the boiler, so if you fancy trying FreeBear's 'flush' method, you may need to ensure the draincock is on the 'flow', or else your flush could bypass most of your rads.

(quickly checks my boiler) Oooo... Filling loop is indeed on the return side. Also have a drain point on the flow side as fitted by the manufacturer. Not sure if turning the isolation valve off on the flow side will still allow the system to be drained down from that point...

ThisIsWeird

Albermarle said:

ThisIsWeird said:

Make and model of boiler, Nuggy? 
Turn the boiler output controls to off, any timer/programmer controls ditto, then it should be ok to power it up to view the pressure.
The filling loop is usually (should be) connected to the CH return pipe to the boiler, so if you fancy trying FreeBear's 'flush' method, you may need to ensure the draincock is on the 'flow', or else your flush could bypass most of your rads. A flush like this will also rely on having a decent flow getting through each rad, but some lockshields could be barely open a crack, so unless you are prepared to mess about with these as well, your draindown method might be best.
If you don't already have one fitted, consider adding a magnetic filter since your system will be drained down.

I do not have one of these, and as far as I can remember, nothing has been added to the system ( inhibitor etc ) for at least 7 years. Heating/boiler ( serviced every 18 months or so) all run without problems.
I wonder how necessary all these items are, or whether I have just been lucky.

Yeah, you got 'lucky' written all over you, pal.

The Mag Filter is a good-to-have, but inhibitor, pretty much essential.

If Nuggy has concerns about sludge in their system, then fitting one will continue to capture most of whatever remains as it flies around, after they've done the 'flush'.

Albermarle

ThisIsWeird said:

Albermarle said:

ThisIsWeird said:

Make and model of boiler, Nuggy? 
Turn the boiler output controls to off, any timer/programmer controls ditto, then it should be ok to power it up to view the pressure.
The filling loop is usually (should be) connected to the CH return pipe to the boiler, so if you fancy trying FreeBear's 'flush' method, you may need to ensure the draincock is on the 'flow', or else your flush could bypass most of your rads. A flush like this will also rely on having a decent flow getting through each rad, but some lockshields could be barely open a crack, so unless you are prepared to mess about with these as well, your draindown method might be best.
If you don't already have one fitted, consider adding a magnetic filter since your system will be drained down.

I do not have one of these, and as far as I can remember, nothing has been added to the system ( inhibitor etc ) for at least 7 years. Heating/boiler ( serviced every 18 months or so) all run without problems.
I wonder how necessary all these items are, or whether I have just been lucky.

Yeah, you got 'lucky' written all over you, pal.

The Mag Filter is a good-to-have, but inhibitor, pretty much essential.

If Nuggy has concerns about sludge in their system, then fitting one will continue to capture most of whatever remains as it flies around, after they've done the 'flush'.

I am going to Screwfix on Monday !

FreeBear

Albermarle said:

ThisIsWeird said:

Albermarle said:

ThisIsWeird said:

Make and model of boiler, Nuggy? 
Turn the boiler output controls to off, any timer/programmer controls ditto, then it should be ok to power it up to view the pressure.
The filling loop is usually (should be) connected to the CH return pipe to the boiler, so if you fancy trying FreeBear's 'flush' method, you may need to ensure the draincock is on the 'flow', or else your flush could bypass most of your rads. A flush like this will also rely on having a decent flow getting through each rad, but some lockshields could be barely open a crack, so unless you are prepared to mess about with these as well, your draindown method might be best.
If you don't already have one fitted, consider adding a magnetic filter since your system will be drained down.

I do not have one of these, and as far as I can remember, nothing has been added to the system ( inhibitor etc ) for at least 7 years. Heating/boiler ( serviced every 18 months or so) all run without problems.
I wonder how necessary all these items are, or whether I have just been lucky.

Yeah, you got 'lucky' written all over you, pal.

The Mag Filter is a good-to-have, but inhibitor, pretty much essential.

If Nuggy has concerns about sludge in their system, then fitting one will continue to capture most of whatever remains as it flies around, after they've done the 'flush'.

I am going to Screwfix on Monday !

Screwfix and Toolstation are both open until 16:00 on a Sunday.

This little device looks to be useful for dosing a sealed heating system ->

Worth shopping around as the price does vary wildly (from £8 up to £30).

jj_home_80

Never turn the boiler on with no water in the system—it could damage the pump or heat exchanger. Start refilling with the filling loop first, even if you have to guess initially. Once there's some water in, briefly turn the boiler on just to check the pressure, then turn it off again if needed to adjust. Aim for around 1.2 bar when cold before fully restarting.