Hot Water Cylinder with Flow In / Flow out swapped around ?

[Blaze]

I have been studying my current pipe setup - trying to make sense of where my new pipe setup may have to go and two things are puzzling me.

Bit of background, 1963 house, Floor standing Ideal Mexico boiler, gravity fed system, f&e and cold tanks in loft and one pipe radiator system (nice!).

The boiler is downstairs, hot water cylinder in airing cupboard, around 900mm in height with a foam jacket on it. Looks modern but here before we moved in.

There are vertical 5 pipes in the airing cupboard. From left to right, these seem to be:-

1) Hot Feed from Boiler with a vent pipe that continues up to the loft but connects to the bottom of the f&e as well as providing a vent over f&e

2) Pipe that runs from cold water cistern down, presume this feeds bath etc

3) Pipe that runs from cold water cistern to most bottom part of hw cylinder with a draincock before connection

4) Rising Mains that goes up in to loft to feed cold water storage and f&e

5) Hot water from top of tank which has a vent that goes over cold water storage

The Hot Water Cylinder has two pipes going into the side.

The pipe in the middle comes from vertical pipe feed 1) and you can hold this with your hand (warm).

The pipe below this near the bottom is very, very hot and you can only hold the copper pipe for a second.

QUESTIONS
Is this correct, should the hot be in the bottom and cold in the midde ? Doesn't sound right to me.

Also, should the vertical pipe 1) be acting as a vent for f&e and feed ?

Would welcome comments on whether this is OK or not. Cheers.

 

[ChrisR]

Yes, all ok, within normal variations.

 

[Blaze]

Phew, good to hear. Been working well for us, but just seemed weird that flow in from boiler was at bottom rather than top.

Made sense in one way in as much that the heat was at the very bottom and could therefore heat quicker ? but most drawings, diagrams seem to suggest heat comes in the middle.

Thanks for your feedback.

 

[ricarbo]

The convention is that the hot pipe is connected to the upper connection on a hot water cylinder coil. Presumably to assist gravity flow. I've long thought it is a wrong notion if you have a fully pumped system as it makes more sens to me that you put the hottest part of the coil in the coldest part of the cylinder, to get the maximum heat transfer. I'd need to think about it a bit more for an unpumped hot water system.
If it is working well, i.e. reasonable warm up time for the cylinder and heating working ok, why worry about it?

 

[Agile]

On a pumped system it makes little difference which way round it is.

On yours I have to say that it appears that the boiler is connected wrongly as the flow from the boiler should go to the top AND should be the one going to the vent.

Its always possible that the pumped heating circuit is disturbing the gravity circulation so run the system for 30 minutes on HW only and check which pipes are hot.

These systems can get sludged up and that can change the flow pattern.

Tony

 

[Softus]

I found one like this last year, but only when testing the cylinder I'd just fitted

It turned out that it had always been 'wrong', so I had just unwittingly copied the wrongness, but when I quizzed the owner he remembered that the previous plumber, 20 years ago, had asked him if he wanted either fast recovery or abundant hot water; with a family he had opted for the latter.

So I offered to swap over the primaries, but he had been happy with it how it was, so I didn't.

It worked, and continues to work, just fine on gravity, with 28mm / 1" pipework and the boiler almost vertically below - it's just if you use all the hot water you don't get it back quickly.

 

[ChrisR]

it appears that the boiler is connected wrongly as the flow from the boiler should go to the top AND should be the one going to the vent.

Sounds like he has a "combined feed and vent", and it IS on the flow.
CF&V may not be specifically allowed by the boiler manufacturer, but as long as the vent pipe is 22mm all the way they seem to work ok, if slowish to fill. (nb Keston specify 28mm; QI)

Feeding the upper end of the heating coil stabilises temperature stratification in the cylinder, which as has been mentioned, may or may not be desirable. It means you get a smaller amount of hotter water more quickly.
Net heat input to the water IS higher with the flow in at the lower end. On older cylinders with a short coil at the bottom end of the cylinder, the difference is pretty small. How far apart are the boiler connections to the cyl?

 

[bab]

As Tony stated it is the correct way to connect gravity hot water circulation with the flow off the boiler to the top connection on the coil. the primary circs should be 28mm .We were taught that the convection of the hot water once it reachs the flow on the coil contains hot water then weighing less than the cooler return thus causing the thermal syphon to start the slow movement of the water thus heating the cylinder. having the flow into the return can reduce the circulation as the hot water in the flow can be cooled before it reachs the top of the thermal syphon(top of coil) This is a bigger problem if the primary circs travel a horizontal distance with little fall before reahing the coil.Have been to such installations & a cheap answer is to put on a programmer with seperate switchings so u can heat the cylinder 1st before the heating pumps takes priority.

 

[Blaze]

The run from the cylinder to the boiler is around 3 metres. Out the back of the airing cupboard, under the bath then down in to the outside Boiler room, then straight down on to the floor standing Boiler. Middle pipe can be held, bottom pipe very hot.

Here is a picture from the loft:-

This shows Pipe 1 acting as a vent over f&e as well as flow out from f&e.

The airing cupboard:-

Hope pictures help add some more light to the issue.....

 

[bab]

Yes you do have a combined feed & vent & the large pipe at the bottom of coil should be the cooler of the 2. But hey if it aint broke don't fix it.

 

[Agile]

Ignoring the question of which way round the coil can be connected, yours is definately wrong if the vent is connected to the return!

The flow from the boiler should be the one going to the vent! Yours apparently does not.

What wonderful acess you have in your pictures. I would even work on it myself!

I saw one once and the plumber had to make a hole in the wall behind to change the motor valve.

Tony

 

[Blaze]

What wonderful acess you have in your pictures. I would even work on it myself!

Tony

Is this good ?

The airing cupboard is only 550mm depth from front to back, but around 1200mm wide. This is proving challenging when trying to find an unvented cylinder to replace the old. Most are around 560mm upwards. Think I may need to ask the installer to install Boiler and Unvented Cylinder in loft when the time comes!

 

[Agile]

I seem to remember the Ariston used to be 515 mm dia.

Dont remember the Santon.

Tony