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How can I cure my gravity circulation problem?

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John.g said:
Sorry Neville, but I just can't locate that link just now but it certainly stated a minimum velocity which I think was 0.5 mps so common sense would indicate that corrugated piping isn't compatible with large bore piping and low flow rates which are common to gravity flow systems, IMO.
Its strange that Telford can't/won't provide "evidence" of a cylinder similar to yours with a corrugated coil running on gravity circulation.
Click to expand...

I have not asked Telford for this evidence. Mainly because some while ago I had unhelpful email exchanges with a senior member of the company so wish to be very sure of my grounds before I go back to him.

From information supplied here I am hopeful that I will be able to get it working but it may first need mains reverse flushing to remove air locks.
 
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John.g said:
Spoke to Joule (Dublin) rep briefly and the technical Dept. informed him that they use 1 ins smooth bore coils in their gravity systems.
Click to expand...

Thanks for the useful information. Nice looking cylinders at joule.ie/knowledge-centre but they don't appear to do vented although this may not alter the gravity circulation criteria. Unvented is probably less likely to suck in air during normal use.
 
One of our people fitted a Replacement Telford Indirect Vented cylinder (type G 9E) today in a three storey property in Oxford. This was a pumped system. However, looking at the literature and the instructions et al that came with the cylinder (delivered to us direct by Telford) - it is fitted with a 28mm inside diameter coil. From the chart ( which sets out the full standard vented Telford range (models 0 to 14 plus 9E)) in the instructions, There are only two models in the standard Telford range the 0 and 1 (96litre and 72 litre respectively) that are fitted with a 22mm inside diameter coil. It is stated in the notes that these cylinders are for pumped primary’s only.

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils
 
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"All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils"
Does it state/implicate corrugations or not?.
 
John.g said:
All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils"
Does it state/implicate corrugations or not?.
Click to expand...

No, copy appended below
 

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Neville Hillyer said:
I am trying to compile a full list of possible reasons for the replacement cylinder not getting any heat. Here is my list so far:
[...]
Click to expand...
7. Bathoom radiator loop providing a low impedance path in parallel with the cylinder coil.

Did you change the lockshield setting on that radiator at some point? If so, you might have left it too open.

Personally, I'd have fitted a circulating pump about a year ago. It doesn't take much to stop gravity circulation working and diagnosing the cause is often a waste of time because the remedy is mostly likely to be 'fit a circulating pump...' anyway.
 
Brambles said:
One of our people fitted a Replacement Telford Indirect Vented cylinder (type G 9E) today in a three storey property in Oxford. This was a pumped system. However, looking at the literature and the instructions et al that came with the cylinder (delivered to us direct by Telford) - it is fitted with a 28mm inside diameter coil. From the chart ( which sets out the full standard vented Telford range (models 0 to 14 plus 9E)) in the instructions, There are only two models in the standard Telford range the 0 and 1 (96litre and 72 litre respectively) that are fitted with a 22mm inside diameter coil. It is stated in the notes that these cylinders are for pumped primary’s only.

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils
Click to expand...

I am afraid I could not read your attachment. I have looked for the equivalent page on Telford's site and found the attached. It appears that the table is for copper and not stainless. I could see no mention of "internal diameter". I suspect 22mm and 28mm refer to the compression fitting sizes and not the pipe diameter. If you do have a readable page specifying an internal diameter of 28mm I would be interested to see it.

My problem relates to the cylinder supplied to me but nevertheless it would be interesting to see if there has been a move to larger pipe sizes.

I suspect that corrugated is the cheaper solution for stainless as a very thin wall will withstand quite high pressures and it is easily made into a coil. A plain copper coil is an established technology and may still be relatively inexpensive.
[automerge]1590231834[/automerge]
Chuck said:
7. Bathoom radiator loop providing a low impedance path in parallel with the cylinder coil.

Did you change the lockshield setting on that radiator at some point? If so, you might have left it too open.

Personally, I'd have fitted a circulating pump about a year ago. It doesn't take much to stop gravity circulation working and diagnosing the cause is often a waste of time because the remedy is mostly likely to be 'fit a circulating pump...' anyway.
Click to expand...

The coil gets zero heat with all settings of bathroom radiator valves including completely closed.

Gravity circulation has never been a problem for me with older central heating systems. It had worked, without any difficulty, in this property for about 50 years until I changed the traditional Hercal copper cylinder to a Telford stainless cylinder.
 

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Have the horizontal runs been checked after the new install? Is it possible the horizontal run could have been disturbed and pushed down under the floor causing a drop in the pipework rather than a steady rise. As I think other's have said the distance the gravity circs are run Horizontally seems quite large - however if it's worked for 50 years before must be OK
(And Bathroom rad works)

I had a very similar issue with my in Laws log burner and heat sink rad that was fitted by a previous installer. The rad would always work however the coil in the cylinder wouldn't - I concluded before ripping the thing out was that the circs to the cylinder didn't have great enough horizontal gains as the pipework was clear.

I've replaced old gravity cylinders with cylinders that are meant to be fully pumped before now (Due to what was needed and future upgrades coming) and never had any issues with them circulating on gravity systems.

What was the issue with the old cylinder? Did it leak or was a leak developed on the coil and CH & HW water was mixing?
 
EvilDrPorkChop said:
Have the horizontal runs been checked after the new install? Is it possible the horizontal run could have been disturbed and pushed down under the floor causing a drop in the pipework rather than a steady rise. As I think other's have said the distance the gravity circs are run Horizontally seems quite large - however if it's worked for 50 years before must be OK
(And Bathroom rad works)

I had a very similar issue with my in Laws log burner and heat sink rad that was fitted by a previous installer. The rad would always work however the coil in the cylinder wouldn't - I concluded before ripping the thing out was that the circs to the cylinder didn't have great enough horizontal gains as the pipework was clear.

I've replaced old gravity cylinders with cylinders that are meant to be fully pumped before now (Due to what was needed and future upgrades coming) and never had any issues with them circulating on gravity systems.

What was the issue with the old cylinder? Did it leak or was a leak developed on the coil and CH & HW water was mixing?
Click to expand...

From the calculations in this thread it appears very unlikely that there is insufficient pressure around the circuit to promote gravity circulation. However removal of air locks is another matter. I am not aware of the pipes under the floor having moved very much but there could be less slope than before. The only practical way to examine this is to remove a portion of kitchen ceiling which I am reluctant to do unless all else fails.

Earlier cylinders only lasted about ten years but this last one was over 20 years old. They were all Hercal but the latest one had a sacrificial anode. The early ones leaked between primary and secondary but the last one developed a small hole at a weak point near the blanked immersion heater opening. This had been patched several times. Initially by Araldite and more recently by solder.
 
Neville,

All the information is in the Telford 2019 technical product catalogue 40. If you cannot source a copy PM me and I will email you a PDF copy. I don’t think that I can post a PDF on this site (But may wrong on that).
 
Brambles said:
One of our people fitted a Replacement Telford Indirect Vented cylinder (type G 9E) today in a three storey property in Oxford. This was a pumped system. However, looking at the literature and the instructions et al that came with the cylinder (delivered to us direct by Telford) - it is fitted with a 28mm inside diameter coil. From the chart ( which sets out the full standard vented Telford range (models 0 to 14 plus 9E)) in the instructions, There are only two models in the standard Telford range the 0 and 1 (96litre and 72 litre respectively) that are fitted with a 22mm inside diameter coil. It is stated in the notes that these cylinders are for pumped primary’s only.

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils
Click to expand...

Thanks for the PDF. Whilst you may be correct about the internal diameter I am unable to find any reference to 'internal diameter'. In the attached enlarged chart I can only see a column called 'Size of Primary Heater' which I am inclined to think are compression fitting sizes.
 

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“Size of the primary heater” is the Internal diameter of the coil in mm.

The connections on Telford vented cylinders are normally all the same - G1 which has a Nominal Bore of just under 30mm irrespective of the internal coil internal diameter.

in essence, you cannot determine the internal coil diameter from the external connection. Unless of course you have long thin fingers!

The external fittings are shown in the last two columns of the chart that you have posted
 
Brambles said:
“Size of the primary heater” is the Internal diameter of the coil in mm.

The connections on Telford vented cylinders are normally all the same - G1 which has a Nominal Bore of just under 30mm irrespective of the internal coil internal diameter.

in essence, you cannot determine the internal coil diameter from the external connection. Unless of course you have long thin fingers!

The external fittings are shown in the last two columns of the chart that you have posted
Click to expand...

My understanding is that G is the German/ISO designation equivalent to BSPP. These were specified for thick steel gas pipes and so tend to be a size larger than copper. G1 was originally for a pipe with a 1 inch internal diameter.

Whilst I am not saying you are wrong, I continue to have two problems with this chart:

1 - it is for copper cylinders and not stainless
2 - internal coil diameter is not clearly stated.
 
Neville,

I don’t think that there is any further help I can offer. I am sure that Telford will explain how your cylinder has been configured.

With respect to ISO G1 and G1/2 is a very common fitting in the UK.
 
Neville Hillyer said:
My understanding is that G is the German/ISO designation equivalent to BSPP. These were specified for thick steel gas pipes and so tend to be a size larger than copper. G1 was originally for a pipe with a 1 inch internal diameter.

Whilst I am not saying you are wrong, I continue to have two problems with this chart:

1 - it is for copper cylinders and not stainless
2 - internal coil diameter is not clearly stated.
Click to expand...
Neville Hillyer said:
I am a retired Chartered Electrical Engineer and am looking for information about the necessary conditions for gravity primary circulation in a 28mm domestic indirect vented hot water circuit.

Until recently I have fitted Hercal cylinders in my house and they always worked without any difficulty. I have now replaced the old copper Hercal with a stainless Telford cylinder but cannot get any primary circulation.

I have flushed all sections of pipework and tried bringing the boiler up to boiling point but there is still no hot flow down the coil. I can only assume that there is an air lock resulting from a coil which probably does not go consistently down all the way. It may not be helped by the non-smooth very flexible pipe. Perhaps a corrugated surface is not particularly good at promoting downward flow of water combined with chalk and cast iron particles whilst encouraging upward flow of trapped air.

I would be grateful for any advice or pointers to sources of information about this.

Neville
Click to expand...

Hi Neville,

Any update on your problem?.
 
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Neville Hillyer said:
Not yet - too many other things going on.
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A member of my family is having the same problem as you. Gravity fed boiler.28mm sloping pipe from boiler to cylinder. She had no heating too. The boiler had not been on all summer and when she recently tried it, had no hot water or heating. The boiler was installed in 1977. I found that the radiators were full of sludge and that this had caused the heating pump to jam. However, there are still no hot water. The 28mm flow pipe was stone cold. I then flushed the heating water for 5 mins with the drain connection on the base of the Ideal Vulcan boiler where there is a drain cock. Only 5 mins of gravity fushing and the flow pipe immediately got hot. I left because it was getting late and later found that she still had no hot water. I am going round to power flush the system. I think there is a build up of sludge at the base of the flow pipe. Will be carrying the flush out next week. I think a power flush with cleaner will do the trick removing any air lock and sludge ( just the risk of a leak but at least the problem will hopefully be cured ).
 
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Don't think that was/is Neville's problem as the rad adjacent to the cylinder circulates on gravity only and the cylinder just replaced another one with the exception that it has a corrugated coil which was the subject of much discussion in the posts above.
 
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