Cutting Barrel Steel Pipework For new cylinder

[JackK]

If the HW is gravity now, it will still be gravity until you alter things and convert to fully pumped. But fully pumped won't be a problem with increased pressure, if that's what you're concerned about. Though looking at it again - are you sure it is currently gravity HW? Doesn't the pipe that the HW tees off feed the rads? If it were gravity I'd expect dedicated pipes from the boiler to the coil. Not that it makes any difference to your plans.

I trust you'll weigh it in for scrap! Don't leave it outside or it will disappear.

The old cylinder is in the car and ready to go to scrap on Tuesday - I expect to get £100 for it which is nice

I have one flow pipe coming in which then tees off at the airing cupboard for hot water with a 2 port control valve - The return from the hot water cylinder is dedicated. If hot water is met the flow goes around the radiator bypassing the hot water tee and return.

I do not know if that makes it a gravity hot water system

 

[fixitflav]

I do not know if that makes it a gravity hot water system

It sounds to me like it's fully pumped.

What controls do you have currently? Is there a motorised valve in the rad pipework? Do you have a roomstat?

 

[JackK]

It sounds to me like it's fully pumped.

What controls do you have currently? Is there a motorised valve in the rad pipework? Do you have a roomstat?

Hi I tried to put a video here : https://drive.google.com/file/d/1bLFSi1fMST4SFZmH7pRq8k5tEYzlsMod/view

I am pretty sure the green pump that you can see is on the hot water return - I suspect there is another pump for central heating under the floorboards but i cannot be sure.

I have only one two port valve for hot water only - There is no way to turn on hot water without radiators getting hot (I have TRVs) in some places but the whole pipework gets hot. There is no motorised valve for the radiators

 

[jeff the gasman]

It’s leaking from the backnut!
Drain the cylinder and apply a grommet of PTFE between that and the cylinder.
Re tighten and relax!
Job done

 

[JackK]

It’s leaking from the backnut!
Drain the cylinder and apply a grommet of PTFE between that and the cylinder.
Re tighten and relax!
Job done

The cylinder is out and has been removed ! So a bit too late !

 

[JackK]

The new cylinder went in today - Here is a picture

I have not connected the thermostat yet to the cylinder and also switched the two port valve to always be in manual mode meaning it should demand the boiler flow first.

I notice two things which are puzzling but remember the pipework went from 1 inch steel pipe to 22mm flow to fit in the cylinder. I have left the heat only boiler to be always on

1) The water coming out of the cylinder is approx 50 degree - And not red hot - I would have thought that with the two port valve in manual the flow will heat up the cylinder so it becomes red hot (more like 80C). When the shower is switched on and it is at the maxmium hot setting it is warm but not red hot. The same from the tap

2) The radiators are getting hot even though the hot water cylinder is not been heated

I put this down to the volume of water from the flow being high and then restricted to 22mm so carrying on into the radiators (remember this is a one pipe system)

 

[jeff the gasman]

Well for a starter you have a massive airlock!

 

[Hugh Jaleak]

No need for PTFE on Compression fittings, the Olive makes the seal. Swear of jointing compound is all you need.
As above, the big loop you got from the MV going up, over and back down to the Primary Flow connection is likely to be full of air. Advise you reconfigure, flow needs to drop back down from the MV to Primary flow tapping, any air will then go straight up the Vent pipe and out.

 

[JackK]

The vent pipe is much much higher

I could not get the flow to come down the side because of the tight space

The flow pipe is red hot all the way through to the cylinder

Any other suggestions

 

[jeff the gasman]

Where’s your manual vent ?

 

[jeff the gasman]

I don’t think you are reading the situation properly!
How does the air get released from the cylinder flow?
Yo probably have a flow rate of 1 L/min. If you’re lucky!
Especially on a single pipe system! If that’s what you said it was.

 

[JackK]

I don’t think you are reading the situation properly!
How does the air get released from the cylinder flow?
Yo probably have a flow rate of 1 L/min. If you’re lucky!
Especially on a single pipe system! If that’s what you said it was.

Thanks - So firstly there is a vent pipe from the hot water draw off much higher into the loft. I am sure you know that

The air that is in the flow gets released through the F&E tank - When i filled up the system I saw a lot of air getting removed when the system was getting filled and I bled the radiators. Kind of like a gurgling sound.

There also was not a manual air valve in the last cylinder which I took out

Are you suggesting i need a bottle vent and if so would it sit at the highhest point of the flow from boiler which is in the loft or somewhere else.

 

[jeff the gasman]

It’s obvious you are not a plumber or a heating engineer now!
Yes is the answer! On the highest point on that dead loop!

 

[JackK]

It’s obvious you are not a plumber or a heating engineer now!
Yes is the answer! On the highest point on that dead loop!

I am a DIY man trying to do it myself because of funds and because I enjoy it - If there was air in the system would that not get pushed all the way up the one pipe flow and therefore the air vent needed in the loft rather than the hot water cylinder? Please educate me so I do not make a mistake

 

[fixitflav]

1) The water coming out of the cylinder is approx 50 degree - And not red hot - I would have thought that with the two port valve in manual the flow will heat up the cylinder so it becomes red hot (more like 80C). When the shower is switched on and it is at the maxmium hot setting it is warm but not red hot. The same from the tap

Do you mean the cylinder primary return is at 50°C? That's what I would have assumed, but then you refer to the shower, which is obviously on the secondary. You wouldn't want the 2ndary to be anywhere near 80°C, if that's what you mean.
Does it behave different from the old cylinder?

2) The radiators are getting hot even though the hot water cylinder is not been heated

Have you tried throttling the rad pipe, at any valve as it's a 1-pipe system? To force the water through the coil. As somebody said, an air vent (manual) in the horizontal pipe would have been a good idea, but pushing all the water through the coil should push the air round the system and out via the vent (can't remember where that is).