Hot water temp is 40 Degrees - Ideal Mexico 2 Boiler

[JackK]

I think your system is quite unusual and it might be difficult to know what to search for.

The following bit is nothing to do with it being a one-pipe system. It is just an explanation of "gravity" and "fully pumped" systems

In the old days, two separate flow pipes would come out of the boiler. One flow pipe was pumped through all the radiators, before eventually returning to the boiler, in the central heating return pipe. The other flow pipe went up to heat the cylinder, but it wasn't pumped. The hot water would rise up to the cylinder by convection and then, when it had cooled after passing through the cylinder, it would fall back down to the boiler in the hot water return pipe. So, this setup was called a "gravity" system. And there were four pipes in total at the boiler, two flows and two returns.

Then in the 1980s, I think, we moved to a different set up. Only one flow pipe would come out of the boiler. It would pass through a pump and then would immediately be split by a zone valve (or valves) into two circuits. One circuit would be pumped to the radiators as before. The other circuit would be pumped through the cylinder. So that system is called "fully pumped" because both heating and hot water circuits are pumped. There is just one flow and one return pipe at the boiler.

Your system is different. Only one flow pipe comes out of the boiler and then, halfway around the main circuit, it tees off on a loop which passes through the cylinder before rejoining the main circuit. The cylinder effectively seems to being treated as if it was another radiator. I have no idea how common your type of system used to be. I know you are wondering why the water is not being "pumped" through the cylinder and that is tricky I think to understand and explain. I think the answer is that the cylinder loop is rejoining the exact same pipe very close to where it left it. So, there is no pressure difference between where it tees off and where it rejoins so there is nothing to force the water through the cylinder.

A very solid explanation - Thank you - The boiler has one flow pipe but two returns - The hot water cylinder has a dedicated return pipe straight to the boiler - I am 100% sure of that

There is one shared flow pipe and one return for hot water and one return for radiators

Does that change anything about bending pipe or additional pump suggestion?

 

[JackK]

In my small brain (and I know nothing) I have fully pumped system by virtue of pump and big bore pipework - I know this is not straightforward but I feel likely to get to th ebottom o fthis on this forum rather than with engineers who will suggest repipeing house : (

I really appreciate your help

 

[MNW67]

The boiler has one flow pipe but two returns - The hot water cylinder has a dedicated return pipe straight to the boiler - I am 100% sure of that

There is one shared flow pipe and one return for hot water and one return for radiators

Does that change anything about bending pipe or additional pump suggestion?

TBH, I can't think through the implications if that were the case. But clearly my attempt at analysis was wrong

 

[JackK]

Thanks - I thinkI am so close to finally understanding my system - Would be really great to get a handle on it

I think its pumped up the flow and then gravity drops to downstairs radiators because I can see in the loft the pipework being run at an angle to help wanter flow

It has caught many engineers out and myself as well

 

[JackK]

@DP - If you can share any thoughts I would be really grateful - You seemed highly experienced and I hope the further picture of the cylinder would help

What are my options at this stage?

1) Is a pump after the two port valve the only thing?
2) Rebending wont work - Is that certain and not worth 150 punt?
3) I anyway want to change the boiler - Would a new heat only boiler with a 8metre pump make things better?

Currently running on immersion heatingthe cylinder

 

[Notch7]

It's a diy job

has to be

No pro plumber would ever use Ptfe tape on compression threads

 

[DP]

@DP - If you can share any thoughts I would be really grateful - You seemed highly experienced and I hope the further picture of the cylinder would help

What are my options at this stage?

1) Is a pump after the two port valve the only thing?
2) Rebending wont work - Is that certain and not worth 150 punt?
3) I anyway want to change the boiler - Would a new heat only boiler with a 8metre pump make things better?

Currently running on immersion heatingthe cylinder

Fit pump in place of the motorised valve
Do not see how changing the boiler and 8m head pump is going to make any difference to present setup
Circulation in large bore single pipe is pumped but radiators and cylinder rely on gravity/ convection currents.

 

[Harry Bloomfield]

Fit pump in place of the motorised valve

Pretty much what I suggested, in post 66. Just power the pump, from the 'demand signal', which at present opens that valve. A pumped flow, would also help overcome an airlock in the pipe, above the bend.

Do not see how changing the boiler and 8m head pump is going to make any difference to present setup
Circulation in large bore single pipe is pumped but radiators and cylinder rely on gravity/ convection currents.

Quite, without an additional valve in the flow to the radiators, changing the pump will add little or nothing to solve the problem.

 

[JackK]

Thank you dp and harry.

@DP did you suggest removing the two port valve in its entirety ? Isn’t that necessary to shut off when water is at temperature ? Or as harry suggested after the two port valve ?

 

[DP]

Thank you dp and harry.

@DP did you suggest removing the two port valve in its entirety ? Isn’t that necessary to shut off when water is at temperature ? Or as harry suggested after the two port valve ?

To Labour the point, there is no circulation as the plumbing exists and that valve is manually open, what purpose is it serving at present- is it controlling cylinder temperature? Is the issue not lack of hot water temperature?

 

[Harry Bloomfield]

Thank you dp and harry.

@DP did you suggest removing the two port valve in its entirety ? Isn’t that necessary to shut off when water is at temperature ? Or as harry suggested after the two port valve ?

No, was suggesting to replace the 2-port with a pump, or at least putting that idea in the pot. My assumption being that there would not be much flow through the pump, unless it was powered...

Question for the more experienced guys on here - is my last point correct, or not?

 

[JackK]

In

To Labour the point, there is no circulation as the plumbing exists and that valve is manually open, what purpose is it serving at present- is it controlling cylinder temperature? Is the issue not lack of hot water temperature?

Thank you - I am just looking forward when the flow will go through the cylinder - The two port valve should switch on when temperature is achieved and avoid boiling water in the cylinder

That is the reason it is there surely ?

 

[Harry Bloomfield]

The two port valve should switch on when temperature is achieved and avoid boiling water in the cylinder

T'other way round...

The two port valve, has nothing to do with preventing the water boiling, the water in the heating system, should never get to boiling!

What it should do, is when the time control says time for hot water, and the cylinder stat says there is need for heat, it opens the 2 port, and tells the boiler to fire. Once the cylinder stat achieves temperature, or the time runs out, the 2 port closes, and the boiler shuts down (unless there is demand for central heating).

 

[cdbe]

If were you I would pick up a used pump from eBay and give it a try, I can see what the experts are saying, why would your hot water want to force it's way into that tiny 22mm pipe and tight little coil when it can just bumble round those 2" pipes till the cows come home?

I would fit it separately from the valve, (just keep the length of copper you cut out and you can reinstate it with a couple of 22mm compression fittings if it doesn't work), and you won't have disturbed the valve (which I guess you'll need to control the pump if it works). You'll need a pair of 22mm pump valves.

I'm assuming you're capable of a bit of basic plumbing and safely powering up the pump for testing purposes.

I'm not a heating engineer so if I'm talking nonsense just ignore me!

 

[DP]

You can take the horse to water, you know what I mean. Helping the op is like pulling teeth. Unless you can understand the basics, better to leave the task to someone else.

Jack, do you understand that the water in the large pipe is propelled by the system pump. The flow through the radiators has nothing to do with said pump- flow through the radiators is by convection currents in 3/4” pipe and also point of connection. Eg a radiator- Water flowing in the large pipe, tee on it to feed the radiator. The other end connects to top of the radiator. Hot water rises in the pipe and enters top of the radiator displacing the cold water that exits from the lower end and joins the stream of pumped water in the large pipe.
Use this explanation and reason why you have poor flow in the cylinder.

Same for the cylinder Until it was replaced and it was decided to go agains physics of hot water rising- you are now asking for hot water to sink through pipework ( like ONLY cold water can) that is also restricted diameter. I cannot understand whose idea it was to instal a motorised valve ( at that a 22mm while standard is 28mm on 28mm pipes for gravity circulation that your cylinder connection is) on pipework that is normally angled UPWARDS all the way to the cylinder and returns similarly for return.

Either you follow advice and do what has been suggested or close the thread