Central Heating Flush

[jazzyb88]

Hello again,

I'm looking to flush out my central heating system sometime this week, but was wondering whether it was safe to leave the pilot light on in the boiler? - set to the 'off' position. I flushed the hot water cylinder with the immersion off (fuse removed) and pumps off, but with the pilot light on.

I don't think that has caused any problems but would that also be the case when it comes to flushing the F&E tank and rads?

Perhaps i am being overly cautious...

 

[ChrisR]

Turn it off. If the boiler is empty for a while it could overheat.

 

[D_Hailsham]

Turn it off. If the boiler is empty for a while it could overheat.

Good advice!
My boiler has a pilot light. Only the hot water is on, just morning and evening, but the pump overrun runs frequently during the day just to get rid of the heat generated by the pilot light.

 

[jazzyb88]

Okay, thanks for the advice. Do you think it was okay when the hot water cylinder was flushed?

I seem to think that wouldn't affect it because as i understand it; there is a coil that runs through the hot water tank and the water within that coil is fed by the F&E tank. So emptying the hot water tank should have no bearing on that.

 

[D_Hailsham]

You are correct about the coil inside the cylinder. As long as you did not have hot water circulating though the coil when you flushed the cylinder, you should be ok.

 

[jazzyb88]

Yes the system was off for two days before draining and the hot water cylinder had lukewarm water...if that!

Thanks for the help Great forum!

 

[jazzyb88]

Well i completed the flush earlier today, but now it seems i may have a new problem! Just wanted to confirm a few more things with you guys before i might run into any serious problems...

I bled the entire system, then partially filled and added some cleaner into the F&E tank; then allowed it to fill fully. I then bled the rads starting from downstairs and then upstairs until all air was removed - so far so good. Now here comes the silly part: i was anxious to get the cleaner running through the system so ran the pump with the boiler off. Big mistake! As soon as i turned the pump on, i heard churning which seems to suggest it may already be dead. I quickly turned the power off and then sought to drain air from the drain cock.

I ran the pump again and heard a few odd noises but now it seems to have gone quiet again - maybe it's okay after all? Although there is a buzzing sound...

I then thought i'd run the boiler but as soon as it starts it makes a loud 'roar' as it lights up and i can hear air circulating through the intake pipe. When i come upstairs, i can also hear air coming through the pump and so i switched it off immediately as i was worried it might damage the pump further - if not already! Anyway, i drained the drain cock again and there were a few bubbles of air and then it started to drip, at which point i shut it off.

Am i correct in thinking there is air trapped in the boiler? Which is the best way to correct this, if so? A bleed valve on the boiler itself/connect a hose to the drain cock above the pump in the airing cupboard and run just the pump/run the boiler and pump and hope for the best? Or is this a job for the plumber?

Once again, i really do appreciate the excellent help i have received on these forums so far! I am also trying to read up a little more while i'm at it.

 

[Fluffster]

You still have air in the system. Bleed the pump through the screw in the front.
Hopefully you may have a vent on the boiler make sure the plastic cap is a few turns loose.
If it is still full of air you can backfill the system with mains pressure through a hose via either a drain cock or even the cold feed from the f/e.

What make model is the boiler/

Pete

ps is your a boiler a potterton netaheat by any chance?

 

[mickyg]

If your satisfied you have filled the system as best you can, just run the pump without the boiler and with the mid-pos valve in the flushing position. it will make a bit of a racket while it clears the air, but it shouldn't do any damage. leave it for a while and occasionally bleed the front of the pump and the make shift air release(drain cock) you have.
On an observatory note, your cold feed and open vent appear(at least it looks like it from here) to be badly configured thanks to a previous(poor) conversion from gravity. This will hamper your attempts at keeping air and sludge out of your system and I would recommend having this rectified.

 

[jazzyb88]

You still have air in the system. Bleed the pump through the screw in the front.
Hopefully you may have a vent on the boiler make sure the plastic cap is a few turns loose.
If it is still full of air you can backfill the system with mains pressure through a hose via either a drain cock or even the cold feed from the f/e.

What make model is the boiler/

Pete

ps is your a boiler a potterton netaheat by any chance?

Hi,

Thanks for the help. Do i just take the cap off the front and then bleed from the screw underneath? The pump is a Myson Compact CP-53

I checked the boiler all over earlier and there doesn't appear to be a bleed valve, so i'll have to use the make-shift one from the drain cock. Boiler is a Glow-worm 55-60 i believe. Programmer is a Potterton though.

If your satisfied you have filled the system as best you can, just run the pump without the boiler and with the mid-pos valve in the flushing position.

Will i manually have to do this? I can see the markings: Water, Mid Position and Heating underneath but if i move the lever, the valve just goes back to where it was before.

it will make a bit of a racket while it clears the air, but it shouldn't do any damage. leave it for a while and occasionally bleed the front of the pump and the make shift air release(drain cock) you have.

You are spot on. I have been running around bleeding all upstairs rads and turning the pump off occasionally to bleed from the drain cock. I did manage to get quite a bit of air out at first, but now two of the four downstairs radiators are stone cold which, i read, could be: an air lock/sludge/dead pump. I'll keep trying to bleed from the drain cock as there is still some air coming from there. I have shut off the upstairs rads and the two downstairs ones that were working in an effort to force the other two cold ones to come on, but nothing yet...

On an observatory note, your cold feed and open vent appear(at least it looks like it from here) to be badly configured thanks to a previous(poor) conversion from gravity. This will hamper your attempts at keeping air and sludge out of your system and I would recommend having this rectified.

For your reference... pipe on far right is central heating feed (15mm), then a expansion into F&E tank (22mm), cold feed from tank (22mm), hot feed from cylinder + expansion into cold tank (22mm) and finally - not pictured - mains water feed going into the loft (15mm).

I'm not sure whether this confirms what you were thinking before though? Is the problem quite serious? I didn't appear to have much sludge, only rust deposit in the F&E tank...maybe i shouldn't have bothered with cleanser and just cleaned the tank and added inhibitor?

 

[Bambergaspipe]

Hello again,

I'm looking to flush out my central heating system sometime this week, but was wondering whether it was safe to leave the pilot light on in the boiler? - set to the 'off' position. I flushed the hot water cylinder with the immersion off (fuse removed) and pumps off, but with the pilot light on.

I don't think that has caused any problems but would that also be the case when it comes to flushing the F&E tank and rads?

Perhaps i am being overly cautious...

How you gonna flush it???

 

[Softus]

I'm looking to flush out my central heating system sometime this week

Why? What are the symptoms that cause you to think that flushing is the cure?

but was wondering whether it was safe to leave the pilot light on in the boiler? - set to the 'off' position.

No. Turn off the boiler completely.

I flushed the hot water cylinder

Why?

What are the symptoms that cause you to think that flushing your cylinder is the cure?

 

[D_Hailsham]

Well i completed the flush earlier today, but now it seems i may have a new problem!

That was written two days ago! You really should try to keep up, Softus!

 

[Softus]

Well i completed the flush earlier today, but now it seems i may have a new problem!

That was written two days ago!

And yet, in all that time, you've failed to ask the right questions.

 

[jazzyb88]

I'm looking to flush out my central heating system sometime this week

Why? What are the symptoms that cause you to think that flushing is the cure?

I was getting cold spots in some of my rads downstairs.

I flushed the hot water cylinder

Why?

What are the symptoms that cause you to think that flushing your cylinder is the cure?

The cold water tank had a lot of sediment at the bottom, so i felt it wouldn't really hurt to drain and fill the hot water cylinder while i was at it? I got a bit of sediment out of it towards the end of the drain.