Central Heating - or not!!

[Steve]

Hi,

Having more problems with CH/HW and wonder if there's any advice (it really would be appreciated as I'm rapidly losing hair!)

Two weeks ago I filled my central heating system with Salamander FastCleanse cleaning agent. Yesterday, I drained the system and flushed it for an hour or so from the header tank, and that's when the problems started. I now cannot get the upstairs rads to refill. I also noticed this morning, that the hot water is only warm.

Now, my system is a Baxi Bermuda where the boiler is behind the fireplace, and the hot water needs to be on in order for the C/H to be on. The downstairs rads are steaming hot (I assume because there is no circulation to upstairs)

Anyone any ideas why my upstairs rads won't fill up? I thought they would fill from directly from the header. Does this indicate a blockage? If so, how do I find/clear it? Also, why would I be out of H/W?

Any advice would be greatly welcomed. Thanks for reading Steve.

[Dave Plowman (News)]

Almost certainly an airlock. Common way round is to connect a mains water pressure hose to the drain point and force water into the system that way. Have someone keep an eye on the header tank and make sure it doesn't overflow.

[.]

if it ain't broke, don't fix it ?

seriously, it sounds like you've dislodged some chunks of sludge wheich have blocked either a flow pipe or a return. you could try a proper powerflush to clear any blockage but you may ahve to resort to dropping various rads off.

[Steve]

Thanks for the replies guys, I wondered if it was a blockage. The reason I did it was because the flow was week upstairs, so I gave the treatment a go before forking out 300 quid on a power flush.

Incidentally, how has this stopped the H/W working? There are no hot pipes into the H/W tank at all...

Many thanks again for the assistance. Steve

[Wingedcat]

Have you bled the upstairs rads? If not, do so.

Is the header tank at the correct level?

Is the pump working? If yes then try turning off all downstairs rads, what happens to the upstairs rads now, do they get warm? If not systematically turn off all rads upstairs except one.

Once you overcome these problems you will probably get a huge gurgling noise resonating around the system and the problem will sort itself out.

I doubt it will be a piece of smeg which has gunged up the system, more likely an airlock.

[Wingedcat]

The treatment won't have done any harm but I suspect the reason why the flow is weak upstairs is because the system requires balancing (see FAQ for details).

Don't fork out on a powerflush, there is no way the upstairs radiators will be blocked and the downstairs not, so this is surely not the root of the problem. You would be getting triagular cold patches in all radiators most likely, if this were the case.

You must have SOME pipes into the HW tank surely! How would water get in/out for a start! Odds are there'll be a bleed valve of some sort at the high point, this will allow air out of the HW loop. Try forcing the air round first by turning off the rads, (followed by repeated bleeding of air from rads). This will at least confirm the airlock theory.

Luke

[Set Square]

I presume that you mean that there *are* pipes but they are not hot - rather than the pipes not existing?

I imagine that you've got 4 water pipes connected to the boiler. Two will be

28mm and will connect to the indirect coil in the hot water cylinder. When everything is working properly, water will circulate by gravity (convection) through these pipes and heat the hot water. The other 2 pipes (22mm) will go to the radiators - and will probably split into an upstairs and downstairs circuit after the pump. The fill and expansion tank is probably connected to the gravity circulation pipes in the airing cupboard.

Filling such a system can be a bit tricky - because the water has to take a tortuous route to get everywhere - particularly to the upstairs radiators.

As others have said, you've almost certainly got airlocks both in the gravity circuit and in the upstairs heating circuit. Filling from the bottom by *gently* introducing mains water in through the drain c*ck will often cure this.

If, when you've done this, you're still having problems with the upstairs radiators, bleed quite a lot of water (couple of litres at a time) out of each rad - first with one valve open and the other closed, and then vice versa - to ensure that you bleed *both* supply pipes.

[Steve]

Hi Luke, must have made a typo, what I meant to say was that none of the pipes going into the tank are warm, they are all cold.

Sorry for the confusion. Thanks for the reply Steve

[Wingedcat]

No my fault for not reading it properly!

Set Square's a good man so between the two of us I am sure you will get it sorted. Airlock for sure.

Luke

[Steve]

Thanks for the reply. I did as Luke suggested and switched off the rads downstairs. I got a bit of gurgling in the pipes, then all upstairs rads seemed to bleed (water eventually came out of the bleed hole, but the rads aren't as hot as I expected.) Anyway, there are still no hot pipes near the hot water tank. Should I therefore try the bottom fill method? I'm just concerned that now the rads are full, and C/H header tank is full, I'll end up just pushing water out of the overflow.

Forgive my ignorance, I just want my hot water back :(

Thanks again for taking the time to help DIY newbies like myself, I for one appreciate it a great deal, and would be lost without these groups!

Steve.

[Wingedcat]

Do you definitely have no bleed tap anywhere near the HW cylinder? It might well look a bit like this:

it looks like it will be at a high point and connected to the HW coil in the cylinder as opposed to the cold in/hot out connections. On one like this you undo the top and air comes out.

Regarding the fact that your upstairs radiators are still reluctant to get hot, despite bleeding, I reckon it's a question of balancing the radiators.

Regarding the bottom fill method if you do go down this route, you can either keep filling until the tank overflows or drain down and start again. Remember to add inhibitor when the job's done. I'd use this is a last resort though. You might still end up with air in the HW circuit because there is no easy way to force the air around.

Good luck

Luke

[Steve]

Thanks, I'll have a root around the airing cupboard.

I think you're right. I switched all except one upstairs radiator off, and it got hot. Did this with each radiator, and all responded in the same way. I've found the guide in the FAQ so I'll have a go over the weekend.

Typical!! I could live without hot radiators (don't let my missus read this!) Just the hot water I can't!

Thanks again for your assistance, Luke, and all.

Steve.

[Set Square]

Have you got an immersion heater in the tank which could heat the water in the short term until you've sorted the circulation?

Where do the fill and vent pipes from the fill & expansion tank join the other pipework? With gravity systems, it is common for these to be connected to the HW circulation pipes close to the cylinder - in which case the air should escape up the vent pipe. But maybe yours is not like that in which case there should be an air vent at the highest point - or even higher, using a little stack pipe - of the gravity circuit.

[Steve]

Hi Set Square,

The pipes from the fill/expansion tank do indeed join at the cylinder heater. The other side of the cylinder heater also goes up to a vent pipe. Would this not indicate that air *should* get out of the system on its own?

Just a thought...and shoot me if I'm being stupid...could I feed a hose into the vent pipe, and fill the water heater pipework up that way? I'm assuming the water would all join back up at the boiler?

Thanks again, Steve

[Set Square]

I doubt whether that would work - the water would probably flow through the coil in the hot cylinder, and back up the fill pipe. You really need to fill from the bottom, to push the air upwards.

Where do the pipes run between the boiler and airing cupboard - are they more or less straight up and down, or do they cover a significant horizontal distance? If the latter, could there be a dip part-way along the horizontal section which could trap air?

[Ed Sirett]

Steve I haven't bothered to read all the replies - I guess you have an air lock. Open vented systems can be really difficult to refill and get the air out.

Ideally there air places to get the air out:

There may be air bleed points other than just the radiators. If the pump pushes water downwards then it can easily fill with air (the bleed plug at the back may help). Once the water circulates air will easily get sorted into the radiators and things will rapidly improve.

In your case you can't have a blockage between the feed and the circuit as you managed to flush water through earlier.

[The Natural Philosopher]

My system here did that when first installed - on the radioatr siude anyway,

Some upstairs rads fed my a lomng loop of high pipe simply would NOT circulate, although the water pressure filled them with water, the length of pipe going to them retained an air bubble, and it effectively meant the pump would not force the air past it.

The solution was fairly drastic (I should have put bleed points in the loft pipes really)

I shut off every radiator but one of the cold ones, and ran the pump at its fatstest setting. A massive amount of gurgling ensued,and eventually the air tirned up in a rad where it was trapped and could be bled.

I repeated for all the other rads in the 'cold section' and eventually got it all out.

If te HW tank is on a similar loop, then you may be in trouble as these tend to not be bleedable, but if its all the same pump shutting off all rads may dislodege the tank bubble.

Reverse filling via an oiffendingf radtiors bleed nipple or drain pluh (if fitted) is another possibility, but harder to do.

Watch out for overflowing header tanks, if this is such a system, too.

[Steve]

Ok, tried filling from the bottom (incidentally, it's a drain point inline with the pump, is this normal?) Bu couldn't seem to get any water in. I switched all rads off and blocked the outlet of the header tank in the hope water would eventually flow out of the vent pipe of the coil. No such luck. In fact, I'm not sure if any water actually went into the system. Am I better off draining and starting again?

There's a 9-ish foot vertical out of the boiler and up the side of the chimney breast, then about 10 feet horizontal to the tank. I guess it's time to get the floor boards up to check for dips.

Incidentally, something you'd mentioned before about pipe sizes, there are 4 pipes coming out of the boiler, as you said, but they're all 22mm. There doesn't seem to be any 28mm ones. Of these one is untouchably hot (C/H flow?) one is cooler but still quite hot (C/H return?) and the other two or just mildly warm (and are the outermost two pipes of the 4, if this helps anything!)

Thanks again for your advice. Steve.

[Set Square]

Silly question - you did actually *open* the drain c*ck?

It seems to be going that way!

It might be a good idea. Whether you'll be able to do anything about it is another matter! If the pipes run between the joists - rather than across them - and are not supported, they may sag in the middle - and supporting them may help.

That is not good news! Gravity circulation really *needs* 28mm pipes - and is not likely to work very well with anything less. I think that, in your position, I'd be looking seriously either at installing a second pump or at re-arranging the pipework to provide a fully pumped system with a single pump.

[Dave Plowman (News)]

You probably didn't open the drain c*ck enough. The mains pressure water will tend to push the washer onto the seat, while draining pushes it off. Or something.