No hot water, rads fine, open vented system

[mysteryman]

If there is a drain off on the boiler, try opening that with the mains water on and the heating switched off. If it runs with any muck, sludge or debris, let it run until it runs clear water. That may help. You could, if you are very careful, cause the boiler to boil momentarily. You must be confident of what you are doing, as there is danger in this.

 

[purpss]

The immersion heater installation was an utter failure. I could not get the port cover off; I shocked it, banged it, swore at it, heated it, wrenched it, nothing.

So I turned my attention to the gravity primary. I drained it down and ran mains pressure through the system from the header. That took care of the hot supply. Then I removed the pipe from the coil inlet (managed to take a photo, see attached), and blasted mains down there as well. Then I filled the system back up, pausing halfway through to add some Sentinel X400.

Less than 6 hours later (with the boiler running continuously), the lower pipe started to get warm. Now it is working better than it ever has, and I am finally getting some peace.

Thank you all for your guidance and advice, I found it invaluable. Let's hope it holds out for the next year or so!

Cheers, Matt.

 

[purpss]

Woops, forgot to upload the picture.

Untitled

• purpss
• 19 Jun 2012
• 1

 

[artieG123]

sorry to add to this old post - but just have a basic question relating to this

(i have a similar problem)

however, as i understand it, the pipe (28mm?) comes from the boiler going thru the cylinder and round in a coil fashion within it to heat the water, then out at the bottom of the cylinder back to the boiler to be heated and repeat the cycle

my question is thus - this pipework seems a 'closed' system with the water just looping round and round inside, from boiler to cylinder to boiler again. How does the water actually get in there in the first place? Apart from a vent pipe leading to the header tank in the loft, which comes from the top of the 28mm pipe going into upper part of cylinder (T joint), i can see no way of how this 'closed loop' got filled with water. And how you can replace any lost water (?) or flush it thru.

i know of course how the cold water gets into the cylinder from a feed from a cold tank in the loft. Its just this loop that i cant get my head around

 

[purpss]

Start at the header tank (the smaller tank, assuming you have two up there) and see what pipes you have exiting from it. There should be one coming out horizontally from the side of the tank near the bottom - that is the supply to the primary system.

There will be another pipe which supplies fresh water to the tank, this will be near the top and have a ballcock attached to it.

There will also be an open-vent - in my system the pipe mentioned above that supplies the primary system tees off almost straight away and goes back up and hangs over the side of the tank. So it's the same pipe that supplies the primary system and acts as the open vent. My understanding is that this is the old way of doing it and not what you would see in a newer system - now they would be separate (someone please correct me if I am wrong).

Cheers,
Matt.

 

[danplumb]

Artie, if you only have one cistern in the loft which is feeding into the bottom of the cylinder, you may have a primatic cylinder which fills the heating from the same cistern, its different to a coil in a standard cylinder, once the heating is full it makes it own airlock to seperate the heating from the water stored in the cylinder, google it to read up fully.

 

[artieG123]

oh blimey

had a look in loft - three tanks in there (i shall ignore the one i have identified as being for the central heating to save confusion)

one main cold water tank - c/w ball valve etc. Pipe in to it of course from the mains water supply, and one pipe leading from the tank to cold taps etc. Then next to it is a seperate tank. There is a big pipe leading from main tank at the bottom into this second tank at the bottom. Looks like the two tank water levels are the same (gravity/air pressure). There is only one pipe from this second tank and that leads into the bottom of the hot water cylinder. Above this tank sits a bent over vent pipe.

dont know if that describes a primatic cylinder or not.

if it helps, the hot pipe from boiler enters the cylinder half way up on the left, while the return pipe to boiler exits down at the bottom on the opposite side.

 

[artieG123]

primatic sounds likely

regarding the air bubble, how can i restore this? Google informs me that i can open and run all the hot taps for a while, then turn them off and let system settle. If this is worth a shout, should i turn the supply to the cylinder off first using the valve (or i guess that as hot water exits from the top cold water simply enters from the bottom to refill it constantly, thereby achieving nothing)?

 

[danplumb]

If you have just identified a cistern in the loft that feeds you're C/H then you don't have a prismatic cylinder. Prismatic cylinders don't require a cistern.

 

[hazetimesfive]

jesus h, do not put tape and lsx on the element thread...

clean the sealing face, use a new washer and put paste on it, nothing else..

 

[artieG123]

called a plumber out yesterday to give his opinion and to quote.

Not too sure he was able to diagnose problem as he couldnt quite tell whether i had a coil or primatic cylinder!!! So am not really the wiser!

He tried to find something called a motorised 2 port valve (?) but said it might be behind the back boiler as he couldnt see it after removing the fire front, nor feel it with his hand. I am not sure about this motorised 2 port valve existing (or it has previously been altered/removed). My boiler fires up and heats both pipes, central heating and hot water, both at the same time. How my timer unit has been wired up is that i cant independently control either. It comes on at the appointed times and heats both pipes up. Not been concerned by this in the 20 years i have lived here. Nor about energy efficiency etc etc. I am also not sure about this valve fault, in that there has been as slow and steady decline in the hotness of the tap water over many months - surely if a electrically operated valve fails then the lack of hot water is instant!

His remedy would be to remove the whole cylinder and replace it with a new coil one and rejig the pipe work to suit. By rejigging, he would split the central heating pipe from the boiler into two - diverting one into the coil. Obviously the boiler return pipe from the cylinder would again branch back into the CH return pipe back to the boiler. Using something called an 'S plan' system it would then allow me to independently control the hot water and central heating.

sound feasible? Or does it sound like a good flush out is all that is required?

i await his quote

 

[AdamPeter78]

I'd stop wasting valuable time. CH System power flush with Sentinel X400. Save time and money. You've proven to have severe magnetite presence, so restriction on flow is there.
Whilst system is drained, fit yourself a magnaclean filter on.
Clean your CH top up tank, make sure there's a lid on it.
Depending on your water hardness, softness, fit a salamander to your cold mains where it enters your property.
Refill CH with inhibitor.

I know this thread is old, but for anyone searching for similar problems, this is the solution tailored to this one.

Regards

Adam