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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> central heating mystery - Glow worm and megaflow https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1289471992 Message started by desperate on Nov 11^th, 2010, 10:39am

Title: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 11^th, 2010, 10:39am

I need someone with a very clever mind to solve this one for me. Our CH was off all summer. When we came to switch in on for the winter the boiler wouldn't fire up and it was because the primary system had de-pressurised.
We have a glow worm boiler in the basement floor of our house. On the top floor we have a Megaflow tank which I understand uses the primary CH heating loop to heat the hot water of the secondary system through a coil in the tank. There is also a small red expnasion vessel.
For some reason we keep losing pressure in the expansion vessel rapidly and have seen intermittent (sometimes large) volumes of cold water coming down the external overflow pipe at the side of the house.
With the heating on last night the pressure reading on the expansion vessel was falling from 1.4 to 0.8 bar every 15 minutes. It fell to zero overnight with the system OFF. There can be nothing coming down the tundish when that happens.
So far we have paid out over £750 and have acquired:
new pump
new pressure guage and pressure release valve on the expansion vessel
three new temp/pressure release valves on tank etc
14 new radiator valves (some were a little leaky)
new auto bleed valve
a system full of automicro sealant.

There are no evident damp patches/puddles but we are still losing pressure rapidly. What the hell do I do now????? Skint and losing faith in plumbers. Also have two very cold children!!!!

Title: Re: central heating mystery - Glow worm and megaflow
Post by CWatters on Nov 11^th, 2010, 10:51am

Has the expansion vessel itself been checked? If you set the system pressure at 1.4 bar with the system cold what happens to the pressure when you turn the system on? Does it climb high enough to open the PRV?

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 11^th, 2010, 1:17pm

The vessel itself hasn't been checked as such (although the air side was "repressurised" with a bicyle pump). The maximum pressure we can obtain at all is 1.4bar. It never rises at all when the system is on. It loses pressure whether the system is on or off.

Title: Re: central heating mystery - Glow worm and megaflow
Post by CWatters on Nov 11^th, 2010, 2:07pm

Doesn't sound like a faulty esp vessel. Perhaps have a look at this thread..

http://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1288880579

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 11^th, 2010, 5:57pm

Thanks. I guess that is pointing me towards a pretty significant leak which I suppose the sealant stuff has little hope of solving. This is a fairly new house (~6 years old) and all the pipes are hidden. There are no clues at the moment. I'd have no idea where to start looking. We can't afford a massive wild goose chase either.

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 12^th, 2010, 12:43am

Ok so it sounds like you're being taken to the cleaners, where are you for starters, I would guess London.

For some reason we keep losing pressure in the expansion vessel rapidly and have seen intermittent (sometimes large) volumes of cold water coming down the external overflow pipe at the side of the house.

That is all you need to consider.

If you depress the valve on the vessel you'll get a jet of water, that tells you the vessel is duff and needs a new one.

For the record the water that is going down the pipe is system water and not from the vessel, the vessel is only there to take the expansion water by compressing the air that is missing.

The other cause, but I assume it worked ok at some time, is the expansion vessel is undersized, but unlikely in this case.

Title: Re: central heating mystery - Glow worm and megaflow
Post by CWatters on Nov 12^th, 2010, 9:03am

Quote:

have seen intermittent (sometimes large) volumes of cold water coming down the external overflow pipe at the side of the house.

I really must learn to read posts more carefully. Scratch my last reply.

If that's still occuring and you are sure that's the water is coming from the PRV then either the pressure must be increasing and causing the PRV to open or the PRV is faulty.

Could still be an expansion vessel problem causing the pressure to rise as thescruff says.

Quote:

The maximum pressure we can obtain at all is 1.4bar

Is that because the water main pressure is 1.4 bar or do you get water coming out of the PRV if you try to use the filler to raise the pressure beyond 1.4 bar?

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 12^th, 2010, 2:24pm

There's several issue CW that need answers.

The temp/pressure relief valve is on the Megaflow, and nothing to do with the primary water. ::)

How little is the red expansion vessel, 14 rads would need 14 plus Ltrs as an average.

1.4bar pressure on the top floor, could be too much if the boiler is in the basement, depending how many floors we're talking.

Has the pressure relief valve in the boiler been checked.

Quote:

a system full of automicro sealant.

That is a very bad idea as it can block the waterways in modern boilers.

Need answers, and more information about the system and property.

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 12^th, 2010, 2:27pm

Nothing to do with the problem, but why the heck wasn't the megaflow installed in the basement with the boiler. ::)

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 13^th, 2010, 2:03pm

Thanks to everyone for the comments.

The sysetm was installed when the house was brand new and every other house in the development has exactly the same seutp and components. It has worked a dream for the last 5+ years and as far as I know, no-one else has had this problem. I must, I suppose, asusme the expansion vessel is approprite for the 14 rads and four floor house....

The max pressure we can get is 1.4 bar which I think is because that is the most we can get out of the mains on the toe floor. When you open the fill loop it reaches 1.4 bar but no more. At 1.4 bar the pressure releif isnt being opened.

We haven't had anything significant coming out of the outside overflow pipe in the last couple of days. We watched a complete drop from 1.4 bar to zero in under an hour a couple of nights ago. We had a tissue in the tundish too which was bone dry.

Things are worse than ever now. the last time we filled it up (less than 24 hours after the last plmumbe bled the sytem of all air etc) and switched it on, there was clearly a lot of air in the system. You could hear it in the pipes and the boiler and it was hissing out of the auto release valve. The pump was clearly struggling andd the needle on the exp vessel prssue guage was bouncing around. we have had to switch it all off again. Sixth plumber visit due this pm. I can only asusme now wemust have a significant hidden leak. How else would all that air get in in under 24 hours?

We are in Cambridge. Taken for a ride....almost certainly and feeling cold, cross and stupid! >:( :-[ :'(

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 13^th, 2010, 2:13pm

Just checked...its a 15 litre vessel which has a max working pressure of 4 bar so that seems Ok.

The pressure/temp relief valve on the hot water tank was changed but I think I have been taken for a ride there as (now I am beginning to understand this) it would appear it has nothing to do with the problem at all!

The boiler doesn't seem to have a TPR. It has cold water in, hot water in, gas in only. There is no evidence of any relief or overflow from the boiler itself (expcet a gas flu to the outside). The boile does sitch off when the pressure reading ont he expansion vessel drops (which I assume it suposed to do for saftey)

Incidentally, the origianl plumbers (whose business card sticker was on my boiler) insisted I pay before they left the property and has since given me a false address for their business. Ironically I am quite an intelligent, educated person. Feel like a total idiot right now! :-[

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 13^th, 2010, 5:39pm

As I said 1.4bar on the top floor is too much, by the time you get to the boiler in the basement it will be nearly on the maximum 3 bar.

What model Glowworm is it.

It's quite easy to find the guy on the gassafe register if you type his number in the box.

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 13^th, 2010, 6:40pm

It's a glow worm MICRON.
I'm told that we have a cold water regulator between the mains and the boiler itself to take the pressure down accordingly. The filling loop to the expansion vessel however is however directly mains fed so, in theory should be able to reach more than 1.4bar.

We had a british gas guy here today who has conlcuded

1)the last thing to change is the expansion vessel on the basis that:
a)all the leaky radiators going at the same time idicate overpressure
b)the intermittent leaks ot the outside would also indicate over pressure, at least at times
c)the fact that the pressure in the expansion vessel is impossible to drive beyond 1.4 bar may suggest that it is is falsely reporting the pressure and that we believing it to be lower than it is
d)the "dodgy" first plumbers changed the guage/valve to the vessel but may not have done it correctly (especialy since they changed two parts that have no bearing on the problem and also changed the pump which also looks like it was unnecessary)
He has ordered the parts and is coming back on Monday

If that fails

2)we are searching for a hidden and substantial leak (odd cos we have NO evidence at all of damp pataches, soggy floor etc) Terrified of the cost implications there as we have already been drained financially on thsi problem

I'm a bit baffled. I still don't understand how a faulty vessel would cause so much air to get it? :-?

In the meantime I got an address for the dodgy plumber from Companies House and am about to send a registered letter asking for a refund.......

Thanks for everyone's support

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 13^th, 2010, 6:51pm

One other thing I think is now perhaps worth mentioning, back in February we had some building work done. The outside overflow pipe, which was at basement level, was relocated to the side of the house at ground level. The builders and ALL the plumbers and handymen involved in this so far, all agree that this can have NOTHING to do with it. I only mention it now cos it is bugging me.
Why do the overflow pipes get sited at the lowest point in the house if it isn't that important? We now have a series of 3 radiators in the basement that are BELOW the level of the overflow pipe. I have no concept of how the the two are related (if at all). I hope everyone is right and there is no way this is part of our problem. We did run the heating successfully for several weeks after the building was completed and at the moment the overflow has a hosepipe connection to basement level so in practice is now back the way it was (this was done to make it easier to check on the outflow rather than have to go out around the side of the house all the time). My mind in conjuring up all sort of complex syphoning phenomena...

There was no extra plumbing involved in the extension (its electric underfloor)

I'm sure everyone else is right but it's just a niggle. :-/

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 14^th, 2010, 12:01am

wrote on Nov 13^th, 2010, 6:40pm:

Ok I'll repeat.

The vessel is on the top floor and the gauge is reading 1.4bar.

lets assume it 10m from the ground floor radiators to the vessel, that make the pressure in the radiators on that floor 2.4bar and even more in the boiler. when the water heats up that will be over 3bar.

Going on the boiler model I assume it's quite an old system.

What the BG man says about the pressure is correct to a point, but it will be interesting to know what parts he's ordering, before he fits them.

Several times the BG man has mentioned over pressure. ::)

Over pressure is all related to the vessel that he's dis-counting ::) Yet it's the simplest thing in the building to check.

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 14^th, 2010, 12:59pm

Thanks for the input. I have just re-read what I last wrote and I paologise that iImight not have made it clear. The BG man is coming to change the expansion vessel and all it's knobs and whistles on monday (I said it was the last thing to check as pretty much everything else has lready been done!) Sorry for the confusion.

I take your point about the pressure in the basement floor being higher than the top floor. What I don't understand though is why that relates to our sudden, new problem of rapid pressure loss. Especially given that this sytem (new when house was built just 6 years ago) has been running without a problem for the last 6 years, In addition, every other house (over 40 of them) in this development has exactly the same system and layout. I wish to God I understood it as I find my ignorance really frustrating. Thanks for the help

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 14^th, 2010, 3:23pm

wrote on Nov 14^th, 2010, 12:59pm:

On the red vessel is a car tyre valve, maybe under a black plate which unscrews, if you depress it quickly, you either get a jet of water or air, if water it is duff and needs a new vessel. it is that simple.

If you have several radiators with leaks, the pressure on the top floor will drop rapidly.

Forgot about the air problem before, assuming the vessel is duff and it certainly sounds like it, and as above, takes about 10 secs to check, then the numpty's pumping air in is going straight into the system.

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 14^th, 2010, 3:34pm

I think I have already mentioned that all the leaking rads have been fixed so that can no longer be the issue. The "bicycle" valve still hisses with air.

I'm dubious that the vessel is the issue. If it isn't, does that take us back to a significant hidden leak? If so, it is well concealed. No idea what we do at that point. :-?

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 14^th, 2010, 4:09pm

If there's air in the vessel then there's no point changing it, but the pre-charge pressure should be checked, and set at no more than 1bar, you need to take the pressure off the system to check.

What to do next.

Check there's not a pressure relief valve on the boiler or connecting pipework

After that you need to isolate the boiler and do a hydrolic test on the system with a test bucket, that will tell you whether you have a leak but not where.

Have you run a finger around every surface pipe and fitting with the system cold. valves, nuts etc.

Connected to the expansion vessel is a pressure relief valve, find the end of the pipe, I assume it's outside, and tie a plastic bag or balloon over the end, that way you'll know if it's letting water out.

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 14^th, 2010, 9:01pm

Thanks, balloon in situ.

There is no evidence of a PRV for the boiler at all.

Have looked and looked for any sign of a drip from any pipe but there is just nothing.

I'll pass on advice to the BG guy tomorrow and see where we end up

Cheers [smiley=wave.gif]

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 15^th, 2010, 5:21pm

OK ,so seriously furstrated. I had to go to work and leave the BG man to it. He has replaced the expansion vessel and place a couple of new isolation valves in the system. He left the sytem at 1.2 bar with everything switched off. Predictably, when I got home from work, it is back to zero!! Nothing at all in the balloon attached to the outside pipe. AAAAGGGGGHHHH
I've left him a message but I'm lead to believe he needs to discuss with his manager. I guess the only option is a leak. Just bothered that it must be big and yet there is no sign of it. :'(

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 16^th, 2010, 12:56am

What is the make of the floors, assuming the pipes are under the floor somewhere.

If you have a leak, are you covered by the house insurance.

I know you said you looked for a drip/leak, but have you run your fingers around the fittings

Title: Re: central heating mystery - Glow worm and megaflow
Post by Lectrician on Nov 16^th, 2010, 7:14pm

If the ground floor is a suspended timber floor you will not ever notice a leak below it. If it is a leak under the first floor, the water could have chance to evaporate without causing damage if your house is warm.

One of my neighbours had a drain valve for the central heating which was punched out through the wall (rather than having to use a hose pipe to drain). This began to leak and went unnoticed for ages until they had problems with the ball valve in the header tank (obviously you don't have one of those, but could have a hidden drain valve?).

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 17^th, 2010, 11:54am

The floors are either solid wood or laminate or stone on the ground and basement floors, all laid directly onto concrete so I think we should have seen something ???

Here's another crazy theory, tell me if it's bonkers.....

IMORTANT OBSERVATIONS
Twice now (with the central heating and hot water off at the timer control panel but with the immersion heater on), having run a bath or a shower, we have noticed that 20 mins or so later the pump is going like the clappers and clearly struggling. It has had to be switched off at the wall socket.

We have mainly observed loss of pressure from the primary side but there have been intermittent releases from the overflow pipe over that past few weeks

The hot water tank, pump and connecting pipes are on the top floor (4 storey) in a cupboard that is raised above floor level by about 1metre. As such all these elements are ABOVE the level of the top floor radiators expect perhaps the uppermost portion of the vertical radiator/towel rail in the bathroom. I have heard a lot of bubbling and gurgling coming from that towel rail.

CRAZY THEORY...

could the primary loop/coil inside the MegaFlo/Heatre Sadia tank have ruptured leaving a route for the central heating water in the primary system to discharge into the hot***er? This would at least explain why there is no evidence anywhere of water loss.

I know we would perhaps expect some sediment or dirty water coming out of the taps, but as the tank etc are ABOVE the level or the radiator, could it be possible that we are just losing the clean fesh water from the top that we are adding to the system each time we top it up?

It's just a thought but we are running out of feasible options. :-?

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 17^th, 2010, 3:48pm

Bonkers ;D

The megaflow is a mains pressure unvented cylinder, therefore the pressure in the cylinder will/should always be higher than the heating system, but even if it was equal or even slightly less it would never be zero.

Can you tell us what controls you have, there should be a 2port valve on the cylinder, which is wired through the thermal cut-out. Do you then have an additional 2 port for the heating or a 3 port diverter or mid position valve.

Which pipe are you getting the intermittent release from, if the cylinder then it is a separate problem to the heating, but again pressure related, white vessel or internal air bubble.

You need to proof the leak is in the pipework by isolating the boiler and pressure testing with a test bucket, actually finding the leak will be another story, and could be very disruptive, although you should be able to make a rough drawing of where the pipes run.

As said earlier, your house insurance should cover the leak, or most of it.

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 17^th, 2010, 9:36pm

Can you tell us what controls you have, there should be a 2port valve on the cylinder, which is wired through the thermal cut-out. Do you then have an additional 2 port for the heating or a 3 port diverter or mid position valve.

SORRY, YOU'VE LOST ME, i HAVE NO IDEA WHAT YOU ARE TALKING ABOUT. FRUSTRATED AND STUPID!

Which pipe are you getting the intermittent release from, if the cylinder then it is a separate problem to the heating, but again pressure related, white vessel or internal air bubble.

THE INTERMITTENT RELEASE WAS FROM THE EXTERNAL OVERFLOW PIPE WHICH I UNDERSTAND WOULD COME EITHER FROM THE PRIMARY OR SECONDARY SYSTEMS IT WAS NEVER CLEAR WHICH ONE AS FAR AS I KNOW

You need to proof the leak is in the pipework by isolating the boiler and pressure testing with a test bucket, actually finding the leak will be another story, and could be very disruptive, although you should be able to make a rough drawing of where the pipes run.

BG ARE PLANNING TO TEST FOR A LEAK ON FRIDAY (BY ISOLATING THE BASEMENT FLOOR FROM THE REST OF THE HOUSE IN THE FIRST INSTANCE. I DON'T UNDERSTAND THE TEST BUCKET THING AT ALL. THEY HAVE NEVER EVEN MENTIONED THAT AS AN OPTION

As said earlier, your house insurance should cover the leak, or most of it.[/quote]

YES I THINK IT DOES. I JUST WANT IT FIXED BEFORE WE ALL FREEZE TO DEATH. MANY THANKS FOR YOUR CONTINUED INPUT.

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 17^th, 2010, 11:21pm

Can you post a pic or two of the fittings in the cylinder cupboard.

The secondary should go into a tun dish, or are you saying the red vessel joins in cylinder pipe to outside.

The test bucket is a means of pressure testing the system with water.

Isolating the ground floor is a good idea if they can test the ground floor, as that is the most likely place if you have a leak.

Have you any idea what the pipe material is for the heating.

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 18^th, 2010, 9:57pm

I must be one of the only people in the world to be genuinely delighted to find a large damp patch! Finally the leak has shown itself. It was hiding behind a book case that is fixed to the wall (on the ground floor) and has extended down into the basement floor (hidden behind a tall wooden cabinet and curtain). The wooden floor has also lifted but it was underneath a large heavy sofa. Eureka, I think we've found it! ;D

Title: Re: central heating mystery - Glow worm and megaflow
Post by thescruff on Nov 19^th, 2010, 1:36am

Good news indeed. [smiley=thumbsup.gif]

Title: Re: central heating mystery - Glow worm and megaflow
Post by CWatters on Nov 19^th, 2010, 8:28am

Yup, Good news.

Who nailed the bookcase to the wall?

Title: Re: central heating mystery - Glow worm and megaflow
Post by desperate on Nov 19^th, 2010, 11:20am

It was nailed by a handyman about 3 months ago. With the heating completely off during that subsequent few months it went unnoticed and no-one made the connection........ sure enough the plaster board has just been taken down and the nail goes right through the pipe and out the other side. OOOPS! Just enquiring what insurance he might have (he is a fully VAT registered business perhaps unlike my dodgy first plumbers). At the very least I am hoping he will be providing the remedial services free of charge.

Many thanks to everyone for the input. It has been a great source of "comfort" during this very cold and frustrating couple of weeks. Great site!!! [smiley=wave.gif]