Direct or indirect

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Direct or indirect that is the question following on to my first post i got no feedback. new cylinder fitted, could it be possible the wrong one was fitted. what is the difference?which part of the system h/w, c/h,or boiler is drained by outside drain tap. Ideal classic boiler.hot water keeps going cold which is gravity feed no valves or other devices are apparent.
 
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may sound daft but how can i tell now its fitted the old cylinder has gone as well how do i know which one it should be thanks
 
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Well if the boiler heats the cyl it's indirect. If not you need elec to heat it.

Gravity heating from the boilr is desperately slow.

The drain tap -? drains whatever it's connected to!
 
Could you answer the following to help us identify the type of cylinder you have and that which is required and this will help to figure out whats going on.

How many tanks do you have?
Is one of them a lot smaller than the other/s?
Are the flow or return pipes going to the cylinder 'falling' down toward the cylinder connections at any point?
Is there anything else you think you should mention ? eg. does the tank always seem to be filling up

It is possible that you have whats known as a 'primatic' or single feed and vent type of indirect cylinder.

I should point out that all cylinders fitted since 2002 should have blue insulation. If it is green or yellow then additional lagging should be provided. All pipes connecting to the cylinder should be lagged for at least 1 metre from the cylinder.

The CH water is what comes out of the outside drain point. This is connected to the boiler but it depends on pipe layout whether the boiler will drain from this point . If not it should have its own drain off valve.
If the most of the cylinder drains from this point. [tap it to see if it is hollow] then you will almost certainly have a primatic cylinder.

Incorrectly fitted cylinders usually produce the symptom of dirty brown tap water. Primatic cylinders produce dirty brown tap water periodically cos its a design weakness and must be drained and refilled to cure the problem.

Many a time I have seen a cylinder replaced based purely on its size and not on its type so what you are suspecting is not something I would rule out without proof

Yours however seems as though it has an airlock or other blockage in the flow and or return to the boiler from what you have told us so far
 
what a day!!! have taken cylinder out today, flooded airing cupboard[wife not happy] it is indirect with a coil in it.flushed out coil just to make sure, refitted cyl just the same, tried to bleed cylinder by undoing unions on coil water is now heating up in reverse flow to before ie hot water is now going into cyl at bottom of coil is this correct or does it matter which way flow goes? time will prob tell anyway. thank you everybody will keep looking in, can be quite addictive this.
 
two tanks in loft 1 lge 1small cylinder is vented. the fill pipe from small tank goes to lower coil pipe. vent from top coil pipe, been in house 6 yrs been ok up to fitting this cyl, could plummer have mixed up pipework? just a thought!! old pipes etc in garage maybe able to reconstruct to see , which way round should it flow?just been reading other posts 28mm pipes. the old cyl had 28s new one 22s he had to chop of pieces and reduce 2 22s could this affect gravity feed?
 
Strictly speaking it should be 28 but 22 should still work ok.
On a gravity system like yours its considered important to have the flow ['hot water from the boiler'] going in to the top.
On a pumped system it doesn't matter but flow on top is the convention.
On unvented cylinders the trend is toward what you have referred to as 'reverse flow'
 
The flow ought to go to the pipe which has the vent coming off it, otherwise any "steam" would have to go through the coil!
 
thank you to all who helped all working ok now. in the end i put hose pipe to drain cock from boiler outside and to tap blew it through to tank in loft got the info from other posts,alls be well since.thanks again its been an experience, glad i found this forum.
 

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