Another year, another problem.....

[nfollows1982]

Morning all,

I was here this time last year with central heating problems, which you guys did a great job helping me out.

Unfortunately, I have similar problems again after a pump change and wanted to see if this is something simple I can tackle myself again.

This is what I know about my system:

Conventional boiler (Potterton RS30 – very old unit)

F&E tank in loft
7 radiators (3 upstairs, 4 downstairs)
Downstairs radiators are drop fed
Drained upstairs via drain on kitchen rad (directly below boiler) – other 3 rads downstairs drain independently

The old pump packed up in April. Diagnosed by heating engineer as water leak into electrical components. Pump has been changed to this unit: http://www.screwfix.com/p/flomasta-central-heating-pump-a-rated-230v/77771

When I fitted the new pump, I only drained upstairs, refilling and bleeding the rads upstairs when I’d finished.

The boiler then fired up, confirmed that the pump was working, but initially this struggled to get water past the outlet on the pump to the closest radiator.

I turned the pump on and off a few times which seemed to push the water along and I managed to get the radiator in the same room as the pump hot, but nothing else.

So this weekend I started again, drained the whole system down, refilled and bled bottom upwards, but I’m still having problems.

This is where I’ve got to, and what gets hot and what doesn’t:

Radiator above boiler – in same room as pump – hot
Radiator directly below this – in same room as boiler – hot
Radiator in downstairs bathroom – hot
Radiator in bedroom adjacent to where pump is – luke warm
Radiator in next bedroom – luke warm
Both drop fed rads – living room and dining room – cold (pipework feeding these 2 rads also cold)

I haven’t altered the balance of the rads from last year where they all heated up but could the new pump have some effect on the balancing of the system?

I also feel that the cold level on the F&E is too high – the ballcock turns off the call for water – but it seems to be at a high level. Not sure if this has an effect on how the water flows round the system, but worth mentioning.

The other thing I noticed is that, once the above rads have got hot, and the boiler stat stops kicks in (flame goes down), the hot rads tend to cool down quickly rather than keeping the heat in them.

So with the colder weather on the way and a new baby in the house, I’m under strict instructions to get this working again, any advice or pointers would be greatly appreciated.

Thanks

 

[alan333]

I'm not a heating expert but it sounds like air locks (or a blockage) to me. Try turning off all rads except one, so the water is forced to pump through that particular radiator, then repeat with another etc until you've gone through them all. Personally I'd bleed each one once I had it working too, and I'd do it with the lockshield fully open, just count the number of turns so you can put it back once you've finished if you so wish. Don't bleed with the pump running tho.

 

[JohnD]

you say some radiators are hot. Turn them off. Do the cold ones now heat up?

Do you have thermostatic radiator valves? A photo would be nice.

when you bleed the highest radiator in the house, does water squirt out forcefully and without dying away?

Is the pump surprisingly hot?

Have you used any chemicals in the system?

You can adjust the water level by adjusting the float arm. method depends what sort you have. Photos please.

 

[nfollows1982]

John, to answer your questions:

I turned all the rads off that got hot, still no heat in the drop fed rads - yet to try with 1 rad at a time.

Yes I've got TRV's on all the rads - all fitted new 12 months ago, all checked so I know the pin isn't stuck.

I wouldn't say 'forcefully' but there's water in all upstairs rads, no sign of air coming out the bleed valves.

The pump is as hot as the water flowing through it - similar temp to the working rads - doesn't feel too hot.

No chemicals to flush, only inhibitor when refilling - just the stuff they sell in screwfix.

Photo's will have to wait until I get chance.

Thanks

 

[JohnD]

I wouldn't say 'forcefully' but there's water in all upstairs rads, no sign of air coming out the bleed valves.

Do you mean water doesn't squirt out?

 

[nfollows1982]

Hi John,

Not been able to get online until now.

The water squirts out yes, there's no air in any of the rads, as soon as I open the bleed valve there is water there.

I've not had chance to do anything much tonight, but I did turn the heating back on and the rads that were getting hot this morning didn't tonight until I flicked the pump on and off again.

When I fired up the heating tonight it was only the rad in the same room as the pump that got any heat - it didn't reach downstairs at all. I turned the pump on and off a few times quickly and left it running and then eventually the heat made its way to the kitchen and bathroom rads.

I left it for an hour and then bled again and there's still no still no air, but when I fired the boiler up again, there's nothing getting to downstairs again.

The pump is definitely running and even on the highest setting still doesn't seem to be sending the hot water anywhere.

Could this just be a really big airlock that the pump is unable to shift?

 

[JohnD]

you say you changed the pump. I wonder if it might be the wrong way round. Or the pump valves might be broken or clogged. Photos please.

IMO when you have an open-vented system, it is always worth using a chemical cleaner like X400 when it is going to be drained. It may be badly sludged.

 

[nfollows1982]

John I know 100% that the pump is fitted the right way round, arrow is the same way round as the one it replaced. I didn't close or touch the pump valves, I drained down when I replaced the pump.

When I did work last year I removed all rads and flushed out in the garden. The water draining from the system this time around is clear.

I've followed everything by the book in terms of draining, filling, bleeding etc.

Just feels like there's something that's preventing good circulation.

 

[nfollows1982]

Morning,

I thought I would report back this morning after a weekend of frustration, tell you what I’ve done and what the current result is.

Using the drain point downstairs I let the F&E flow through the upstairs rads to give them a clear out and left it running for about half an hour. I also did the same individually downstairs.

The water coming out is clear but there are tiny little black particles in the water if you collect it in a clear container.

I then went round all the rads when cold to bleed and confirmed that water was coming out straight away from all of them.

Starting with all rads off, barring the one closest to the pump, I turned the system on and the rad got hot but then the flow into the rad seemed to stop and it didn’t heat up like it used to; at this point I couldn’t get heat to any other rads even when only 1 turned on at a time.

I repeated step one above and have had mixed success but still nothing consistent.

Rad nearest to the pump is hot and stays hot. Moved to the next room and got the same result. The next bedroom across the hall got hot, but similar to the first rad on the first attempt.

I managed to get hot water to the downstairs rads below 2 of the bedrooms, but I couldn’t get the rads themselves to get hot. One of the downstairs rads got warm but soon cooled down again.

I’ve had the pump running for a long time and still no change.

In the end I tried a quick experiment and rebalanced the system, turned it on and rad near pump and next rad are hot but then no heat was reaching the 3rd bedroom or downstairs.

Turning the pump on/off a few times seems to get the flow to come downstairs but not enough that the rads get hot.

I turned the system back on this morning and the boiler sounded like it was filling up – the same noise you get from the rads when refilling the system.

Any ideas what to try next?

 

[alan333]

I mentioned earlier that I'm not a heating expert, but I paid attention when the Scottish Gas guy fixed the circulation problems in my system. Here's what he did (after the powerflush and refilling/bleeding etc)...

Turn off the heating.
Take a "bad" rad and turn off the trv and lockshield.
Drain that rad, and remove one of the valves from it. If there's no drain valve at the rad then undo the valve and catch the water as it comes out anyway. He used a flat tray to catch any water.
Open the valve into the tray to check the flow. The flow should be reasonable - not under any pressure as such, but enough as you would expect from a hosepipe flowing under gravity from your header tank height.
Repeat with the other valve. The flow should be similar from both valves (since they're both effectively siphoning from the header tank).
This showed that one of the pipes wasn't flowing properly (IIRC it was the flow pipes on my rads).
Isolate (or tie up) the header tank float valve, and let some water out the system so that the header tank isn't so full (he just drained some from the "good" valve).
Blast pressurised air up the "bad" pipe (while it is full of water). You'll hear the big bubbles/gurgle going through the pipework and bubbling into the header tank.
Disconnect the air blaster and catch the dirt and bits of sludge as they come back out the pipe.
Check the flow rate and repeat the air blasting if necessary. Remember to keep some water in the header tank, so you might need to untie the float valve occasionally and let more water in.
Once the water is running clean, re-connect the valves and bleed the rad.
Repeat with any other "bad" rads.
Untie the float valve and allow tank to fill again.
Turn heating on and check all rads now heating properly.
Bleed all rads and pump as necessary.

He removed the complete valve from the pipe to do the flushing, ie he had an open 10mm pipe to blast the air up. There was a little water escape as he did all this but it's easily stopped by putting your finger over the end of the pipe.
He used a garden sprayer for the pressurised air, like this...
http://www.amazon.co.uk/Flostream-L...d=1442222264&sr=8-2&keywords=pressure+sprayer
He connected a bit of rubber pipe between the sprayer hose and the flow pipe with jubilee clips.

Hope this helps

 

[Agile]

Morning all,

The old pump packed up in April. Diagnosed by heating engineer as water leak into electrical components. Pump has been changed to this unit: http://www.screwfix.com/p/flomasta-central-heating-pump-a-rated-230v/77771

When I fitted the new pump, I only drained upstairs, refilling and bleeding the rads upstairs when I’d finished.

Thanks

I do hope this heating engineer was paid for his diagnosis???

It would be more usual for him to fit the new pump and attend to any circulation and balancing! Your apparent reluctance to ask him could be because he gave you a quote and you decided to fit a new pump yourself.

Tony

 

[JohnD]

Plain water is not much good at removing sludge and sediment. Add some X400 which will loosen it as long as you can still get movement through that pipe, e.g. by turning off all the other rads.

Once it becomes fully blocked, your chemical will no longer be able to flow past the blockage.

 

[nfollows1982]

Hi all, I'm not any further with this, it's a weekend thing!

However, I managed to get back in the loft this lunchtime and I've taken a picture of the inside of the F&E tank which is attached.

This is the COLD level of the tank which as you can see is basically at the level of the top drain.

You can see at the back and side of the tank is the brown residue and it's at this level where the tank used to fill to - it must be a good 2 inches above this level.

Does this high level of water have an impact on what happens when the boiler kicks in and hot water is trying to circulate around the system?

For info, where the ballcock arm is connected to the back of the tank, this is where the water flows from when the ballcock is pressed down, so I can imagine this is going to be tricky to fix/replace?

 

[JohnD]

it's very likely that the ballcock is dripping a bit. If you go outside and look at the other end of the overflow pipe you can se how much. This will introduce fresh oxygenated water which will accelerate corrosion, and will also wash away your anti-corrosion chemicals.

The Pegler Prestex Part 2 is a very good valve, you can probably fit it to your existing stem by undoing the big brass nut. It has a better depth adjustment for the float, you only need a couple of inches above the lower F&E pipe entry to the tank.

http://www.screwfix.com/p/pegler-prestex-float-valve-part-2/27627
it may be more expensive in a DIY shed. Inferior valves are available. Fitting a new one is easier and quicker than dismantling and refurbing the old one, but if you like, you can clean up the old one at your leisure and fit a new cone and washer, after swapping. Keep the refurbed one ready to swap back next time.

 

[nfollows1982]

John thanks for you quick response. I take it it's just a case of unscrewing the existing valve and replacing it with the Pegler one then? Is this a mains water off job?

I've noticed water trickling down the roof of the rear extension into the gutter, it's been dripping constantly for ages, so I assume now that this is the water from the F&E tank?

Apart from the issues you noted above, will the water level be impacting on the circulation of the water in the system, or are they unrelated?