Unvented Hot Water System

[Racheal1256]

Ah, I am silly aren’t I!! I will try this again now and let you know in the morning

Good morning,
So, the hot water was on from 6-7am, just tried hot water and it’s probably a little warmer but still not hot as it should be.
I did notice that the secondary return pipe where it enters the cylinder was hot to touch when brass valve under the pump was turned off but when I turn it back to open it instantly goes cold. No idea if this means anything.

Thank you.

 

[ShaunCorbs]

Right now turn turning the lever valve off at the top of the cylinder eg the pipe leaving the centre top of the cylinder and the pump one keep that off aswell please

 

[Racheal1256]

Right now turn turning the lever valve off at the top of the cylinder eg the pipe leaving the centre top of the cylinder and the pump one keep that off aswell please

No water runs out of the hot taps when I do this

 

[ShaunCorbs]

Correct but does the cylinder heat up / you have hotter water, if you do have hotter water that means water is flowing out of your cylinder all the time maybe

Also the red valve on the left wall just higher than the immersion is this open?

 

[Racheal1256]

Correct but does the cylinder heat up / you have hotter water, if you do have hotter water that means water is flowing out of your cylinder all the time maybe

Also the red valve on the left wall just higher than the immersion is this open?

So am I to turn of the lever on the top of the cylinder, turn the boiler on, wait a while, turn the lever back to open and test the water temp from the tap?
Red valve to the left is open.
Thank you for your patience

 

[ShaunCorbs]

Yes your testing if the cylinder will heat up at all when you re open the top lever valve after an hour and it gets instantly hot around 6” above the cylinder/ as high as you can feel there’s a problem

 

[Racheal1256]

Yes your testing if the cylinder will heat up at all when you re open the top lever valve after an hour and it gets instantly hot around 6” above the cylinder/ as high as you can feel there’s a problem

Yes your testing if the cylinder will heat up at all when you re open the top lever valve after an hour and it gets instantly hot around 6” above the cylinder/ as high as you can feel there’s a problem

Ok, all turned to off and boiler set to constant. Pipes that are currently hot I’ve detailed on the attached picture. I will give it an hour and the open to lever, feel pipes again and run hot tap.

Red-hot
Orange - warm
Blue - cold

 

[Racheal1256]

Ok, all turned to off and boiler set to constant. Pipes that are currently hot I’ve detailed on the attached picture. I will give it an hour and the open to lever, feel pipes again and run hot tap.

Red-hot
Orange - warm
Blue - cold

Yes your testing if the cylinder will heat up at all when you re open the top lever valve after an hour and it gets instantly hot around 6” above the cylinder/ as high as you can feel there’s a problem

So, after an hour I turn the lever back on. Hot water draw off pipe got warmer (not red hot) to touched after a few minutes. No hot water taps have been turned on at this point.
The coil 1 pipe at the very bottom of the cylinder is now also very hot to touch and the cold feed pipe at the bottom is tepid, whereas before it was stone cold.

 

[ShaunCorbs]

Now try running hot water

 

[Racheal1256]

Now try running hot water

The water does feel hotter.

 

[ShaunCorbs]

Right ok shut that red valve again and turn the hot water on eg heat up and leave it until it finishes eg fully heats up the cylinder you can tell this by moving the stat it’s on 60 ish now if it doesn’t click lower than this it’s fully heated

 

[Racheal1256]

Right ok shut that red valve again and turn the hot water on eg heat up and leave it until it finishes eg fully heats up the cylinder you can tell this by moving the stat it’s on 60 ish now if it doesn’t click lower than this it’s fully heated

Ok, done that. The stat clicked when I turned it down at about the 45 marker, turned back to 60.
Will the ignition/flame light go off on the boiler when it’s fully hot?

 

[Racheal1256]

Ok, done that. The stat clicked when I turned it down at about the 45 marker, turned back to 60.
Will the ignition/flame light go off on the boiler when it’s fully hot?

Red lever on top of cylinder is turned off, boiler is on constant for HW but no boiler flame light has come on?

 

[Racheal1256]

Red lever on top of cylinder is turned off, boiler is on constant for HW but no boiler flame light has come on?

Boiler light came on, I was just impatient!
See below video of me turning the temp switch.
Does this mean water temperature inside cylinder is only 45 degrees ish

 

[ShaunCorbs]

Yes it’s upto around 45 dc correct

 

[Racheal1256]

How long roughly should this take to heat up? The boiler has been on most of the day so far and the temp control is still clicking at about 45.
Both pipes labelled coil 1 are very hot and even the cold feed is rather warm now.

 

[Last Plumber]

How long roughly should this take to heat up? The boiler has been on most of the day so far and the temp control is still clicking at about 45.
Both pipes labelled coil 1 are very hot and even the cold feed is rather warm now.

What temperature is the boiler set to?

 

[Racheal1256]

What temperature is the boiler set to?

Boiler is on 60, cylinder is also on 60

 

[Last Plumber]

Boiler is on 60, cylinder is also on 60

Something isn't right obviously but I don't think it is going to be cured on a forum. I think you need to get someone in to it.
A cylinder that size with that coil rating should get from 10C to 60C in an hour.
If you didn't use it then it would stay hot a relatively long time.

Granted, you will lose heat on a secondary circuit but not to the extent you described.

 

[ShaunCorbs]

If it’s just hot water on and a 25kw boiler an hour if 15kw boiler 2-3 hours

 

[Racheal1256]

Something isn't right obviously but I don't think it is going to be cured on a forum. I think you need to get someone in to it.
A cylinder that size with that coil rating should get from 10C to 60C in an hour.
If you didn't use it then it would stay hot a relatively long time.

Granted, you will lose heat on a secondary circuit but not to the extent you described.

Thank you for all your help. I’m still waiting for proof of competency from the developer/builder and they are the same people who I’ve reported the problem to and I’m awaiting a response! I can’t get my own plumber out, as the developer will no longer be responsible. Hence me reaching out on here.
You’ve been a great help and very patient with me. Thank you again.
I’ll let you know what the problem was once we finally get to the bottom of it.

 

[Racheal1256]

If it’s just hot water on and a 25kw boiler an hour if 15kw boiler 2-3 hours

If it’s just hot water on and a 25kw boiler an hour if 15kw boiler 2-3 hours

Yes, only got hot water on and it is a 25kw boiler.
The plumbers have changed the temperature control on the cylinder last month too!

Thank you for all your help. I’m still waiting for proof of competency from the developer/builder and they are the same people who I’ve reported the problem to and I’m awaiting a response! I can’t get my own plumber out, as the developer will no longer be responsible. Hence me reaching out on here.
You’ve been a great help and very patient with me. Thank you again.
I’ll let you know what the problem was once we finally get to the bottom of it.

 

[Last Plumber]

Yes, only got hot water on and it is a 25kw boiler.
The plumbers have changed the temperature control on the cylinder last month too!

Thank you for all your help. I’m still waiting for proof of competency from the developer/builder and they are the same people who I’ve reported the problem to and I’m awaiting a response! I can’t get my own plumber out, as the developer will no longer be responsible. Hence me reaching out on here.
You’ve been a great help and very patient with me. Thank you again.
I’ll let you know what the problem was once we finally get to the bottom of it.

One last thing.
On the left is a gate valve (red wheel). Is that on the return from the coil? Is it open?

 

[Racheal1256]

One last thing.
On the left is a gate valve (red wheel). Is that on the return from the coil? Is it open?

Yes it is

 

[Racheal1256]

One last thing.
On the left is a gate valve (red wheel). Is that on the return from the coil? Is it open?

Apologies, yes it’s open and on the return coil pipe

 

[Last Plumber]

Apologies, yes it’s open and on the return coil pipe

Turn boiler up a bit. It won't alter this so you'll notice but it will be better for the boiler. 65 C.

It sounded at first like there was a cross flow (cold to hot). That will have a rapid chilling effect on a cylinder but you seem to have ruled that out.

The stat works and from what I can tell, looks to be reading close enough and the valve can be heard to close when you turn the stat down, which tells me it opened.

The gate valve is open so there should be enough flow through the coil to heat the cylinder in one hour.

If the boiler is running at 60-65, then it should heat up OK.

If the flow from the boiler is being shared with something else, such as under floor heating, radiator circuits etc. Then they can in some cases rob the coil of heat. They would have to be open though and obviously will be warm/hot. You say they are off when trying to heat the cylinder? I suppose we can rule that out too?

If the flow rate through the coil is restricted in some way, you won't get the heat loss from coil to secondary (tap) water in the cylinder. That is unlikely on a new cylinder install. The honeywell valve looks to be the right way round and pipes are 22mm.

No water running through tundish (back right black thing with opening in)?

Thinking out loud as well as clutching at straws. The frustrating thing is that I know it's something that would be diagnosed on site and probably fairly easily too.

 

[Last Plumber]

When you said that the secondary return went cold?
It will do for a short time if it has been off or closed. Once the water has circulated though (minute or so), it should get warmer. Normally you would expect it to be coming back around 50 C if the outgoing was 60 C. In your case I would expect it to be around body temp?

 

[Racheal1256]

Turn boiler up a bit. It won't alter this so you'll notice but it will be better for the boiler. 65 C.

It sounded at first like there was a cross flow (cold to hot). That will have a rapid chilling effect on a cylinder but you seem to have ruled that out.

The stat works and from what I can tell, looks to be reading close enough and the valve can be heard to close when you turn the stat down, which tells me it opened.

The gate valve is open so there should be enough flow through the coil to heat the cylinder in one hour.

If the boiler is running at 60-65, then it should heat up OK.

If the flow from the boiler is being shared with something else, such as under floor heating, radiator circuits etc. Then they can in some cases rob the coil of heat. They would have to be open though and obviously will be warm/hot. You say they are off when trying to heat the cylinder? I suppose we can rule that out too?

If the flow rate through the coil is restricted in some way, you won't get the heat loss from coil to secondary (tap) water in the cylinder. That is unlikely on a new cylinder install. The honeywell valve looks to be the right way round and pipes are 22mm.

No water running through tundish (back right black thing with opening in)?

Thinking out loud as well as clutching at straws. The frustrating thing is that I know it's something that would be diagnosed on site and probably fairly easily too.

So I do have UFH both upstairs and down, no radiators. Today I have turned the thermostat down on all floor, they are mostly off anyway.
My original problem (in summer heatwave) was when I turned the floors off, the house was being warmed up as the via the HW as HW would travel to both upstairs and downstairs manifolds before being told no HW was required for floors just taps! Eventually the builder agreed to get additional valves installed and now the pipes at the manifold do not get hot when HW is needed and solved my problem…so I thought.
How exactly can I test if something is robbing the heat supply?

Currently the water coming out my taps is hotter than normal but that’s down to the boiler being on constantly all day.
I’ve now set this back to timed (2hours morning and evening) and over the next couple of days it will slowly loose heat until day 2/3 when it isn’t even hot enough for my 3 year olds bath!

Tundish is dry.

 

[Racheal1256]

When you said that the secondary return went cold?
It will do for a short time if it has been off or closed. Once the water has circulated though (minute or so), it should get warmer. Normally you would expect it to be coming back around 50 C if the outgoing was 60 C. In your case I would expect it to be around body temp?

Didn’t see this question, sorry.
I’m lost as to where in the thread the secondary went cold happened!
I still have the brass valve below the secondary pump turned off, should I turn this back open and see what happens? The timer switch for this is also off at the wall

 

[Last Plumber]

I’m lost as to where in the thread the secondary went cold happened!

Post 36.
You said it was hot when the valve was closed but went cold when you opened it.
That pipe should be cooler than the outlet? not cold though?

 

[Racheal1256]

Post 36.
You said it was hot when the valve was closed but went cold when you opened it.
That pipe should be cooler than the outlet? not cold though?

I’ve turned so many things on and off I can’t remember!
I’ve just opened this

Post 36.
You said it was hot when the valve was closed but went cold when you opened it.
That pipe should be cooler than the outlet? not cold though?

yes that was cold, it’s warm now though. Could that be because the boiler has been on all day?

 

[Last Plumber]

I’ve turned so many things on and off I can’t remember!
I’ve just opened this

yes that was cold, it’s warm now though. Could that be because the boiler has been on all day?

No it won't be why the boiler is on all day.
I think you need a Plumber who is experienced with hot water systems or a heating engineer.