Hot water temp is 40 Degrees - Ideal Mexico 2 Boiler

[DP]

Flow pipe needs to be redone in 28mm without a loop yes?

System needs accessed for proper configuration. Is the flow and return to cylinder pumped or gravity fed? If gravity fed, then cylinder possibly not suitable as most cylinders are high recovery with large indirect coils (some even have bunched microbore pipes for larger surface area)

Footnote. On your radiator, you have two valves. One is control valve and other a lockshield. If you were to close the lockshield and then crack it open a quarter turn, top of the radiator will still be hot as will the inlet pipe but heat radiated will be below par. This appears to be the root cause

 

[JackK]

My system is "complicated"

It’s a one pipe system using two inch steel pipework for the radiators and main flow and return - Work was done to get a copper thread for the hot water cylinder flow but the rest of system is in steel pipe work - Not ideal but does work

Flow is pumped but return is not - I think that’s normal as you only have one pump in most systems

My radiators are cast iron and old - I don’t think the lockshields can be changed so easily

There is one two port valve on the system to control hot water being taken from the main flow pipe - This means that central heating needs to be on for hot water to work

 

[Mister Banks]

My system is "complicated"

It’s a one pipe system using two inch steel pipework for the radiators and main flow and return - Work was done to get a copper thread for the hot water cylinder flow but the rest of system is in steel pipe work - Not ideal but does work

Flow is pumped but return is not - I think that’s normal as you only have one pump in most systems

My radiators are cast iron and old - I don’t think the lockshields can be changed so easily

There is one two port valve on the system to control hot water being taken from the main flow pipe - This means that central heating needs to be on for hot water to work

From your description the system is pumped, not gravity.

 

[MNW67]

This means that central heating needs to be on for hot water to work

So in warmer weather, do you use an immersion for the hot water?

 

[JackK]

So in warmer weather, do you use an immersion for the hot water?

Yes if I am honest - Or turn off the TRVs

 

[MNW67]

Yes if I am honest - Or turn off the TRVs

So, with the previous cylinder, what setting was the boiler at, to get the water nice and hot.

 

[JackK]

So, with the previous cylinder, what setting was the boiler at, to get the water nice and hot.

Mid way - But the flow pipe was 2 inch pipework (not 22mm) and went into the top of a copper cylinder

 

[DP]

Mid way - But the flow pipe was 2 inch pipework (not 22mm) and went into the top of a copper cylinder

Therein lies the problem
There is nothing complicated about the system
In essence, sure other pros will correct me on this if I am wrong, heated water flows into a large bore pipe and return to base of the boiler exchanger. To set up circulation, a pump is used that moves the water in the ring and through the boiler.

The radiators are plumbed with 3/4" or similar size pipes with flow entering (usually ) at the top and opposite bottom is where the primary water leaves the radiator to join the circulating stream of water. Flow in the radiator will be a mix of gravity and use of swept tee (if the installer had swept tees

While the loop is pumped, the primaries going to the cylinder are not. I would remove the zone valve and fit a pump there. I am quite confident there is no restriction or whatever- it is the 22mm and 15mm as well as the high resistance coil, not forgetting the flow pipe rising then dropping down to the cylinder that is stopping the circulation due to high circuit resistance.

I would fit a pump to that loop, switching carried out by the cylinder thermostat. It would not hurt to look at smart radiator thermostats to keep gas usage in check enabling a solid uneconomical boiler that does not require expensive re[airs to be put to good use. Will enable summer/ winter setting on the programmer.

If possible to take cylinder pipes to the boiler, two motorised valves would allow better control than what you have just now.

 

[JackK]

Therein lies the problem
There is nothing complicated about the system
In essence, sure other pros will correct me on this if I am wrong, heated water flows into a large bore pipe and return to base of the boiler exchanger. To set up circulation, a pump is used that moves the water in the ring and through the boiler.

The radiators are plumbed with 3/4" or similar size pipes with flow entering (usually ) at the top and opposite bottom is where the primary water leaves the radiator to join the circulating stream of water. Flow in the radiator will be a mix of gravity and use of swept tee (if the installer had swept tees

While the loop is pumped, the primaries going to the cylinder are not. I would remove the zone valve and fit a pump there. I am quite confident there is no restriction or whatever- it is the 22mm and 15mm as well as the high resistance coil, not forgetting the flow pipe rising then dropping down to the cylinder that is stopping the circulation due to high circuit resistance.

I would fit a pump to that loop, switching carried out by the cylinder thermostat. It would not hurt to look at smart radiator thermostats to keep gas usage in check enabling a solid uneconomical boiler that does not require expensive re[airs to be put to good use. Will enable summer/ winter setting on the programmer.

If possible to take cylinder pipes to the boiler, two motorised valves would allow better control than what you have just now.

Wow that is a solid answer and very accurate - I can confirm this is kind of true from my limited experience

"heated water flows into a large bore pipe and return to base of the boiler exchanger. To set up circulation, a pump is used that moves the water in the ring and through the boiler.

The radiators are plumbed with 3/4" or similar size pipes with flow entering (usually ) at the top and opposite bottom is where the primary water leaves the radiator to join the circulating stream of water. Flow in the radiator will be a mix of gravity and use of swept tee (if the installer had swept tees"

1) It is difficult to take a new flow pipe from the boiler sadly : ( so I do not think this will work like you prefered
2) If I rebend that pipe and use 28mm pipe and gravity into the cylinder will that help much? The immersion heater to heat a tank of water is not a long term solution sadly
3) If I move that two port valve and add a pump is that really neccessary? The cylinder is on the first floor so (half way up the house) and the water has to continue up the pipework into loft before it comes back down again, so I would have thought there is plenty of flow at the cylinder to overcome the pipe bend obstruction

 

[DP]

If I rebend that pipe and use 28mm pipe and gravity into the cylinder will that help much?

Doubt it

If I move that two port valve and add a pump is that really neccessary

you do not need the valve. Water is not moving in that circuit, how is the valve going to help the problem. Pump is required to shift the water.

 

[JackK]

Doubt it

you do not need the valve. Water is not moving in that circuit, how is the valve going to help the problem. Pump is required to shift the water.

Sorry I think you are mitaken - Water is moving in there but I have a feeling it is slow running because of the pipework restriction! It was working before but witha different copper cylinder true which had bigger coils no doubt.

There is a pump on the boiler return which as you said pumps around the primary pipes - This hot water draw off is the first place the water tees off so I think it is already under pressure

If I replaced the pump at the boiler would that force more water through the flow pipe at a faster speed and therefore into the cylinder?

 

[MNW67]

Sorry I think you are mitaken - Water is moving in there but I have a feeling it is slow running because of the pipework restriction! It was working before but witha different copper cylinder true which had bigger coils no doubt.

There is a pump on the boiler return which as you said pumps around the primary pipes - This hot water draw off is the first place the water tees off so I think it is already under pressure

If I replaced the pump at the boiler would that force more water through the flow pipe at a faster speed and therefore into the cylinder?

These threads seem to be tangentially related:

One Pipe System Central Heating

Just moving into the ground floor apartment of a 7 storey building. The building has a central one pipe heating system. We needed to move one radiator but the problem is that it no longer heats up. The pipe going in is hot but the one leaving the radiator is cold. The radiator, valves etc are...

www.diynot.com

One pipe radiator system

It's simple physics. With a one pipe system, the water is pumped around the one pipe loop, meaning that because the radiator inlet and outlet pipes are connected to the same pipe they receive the same pressure from the pump, as a result, the pump can't force the water through the radiator in the...

www.diynot.com

It seems one pipe systems are tricky beasts which rely a lot on gravity and not adding any new restrictions. One post says adding a further pump will mess up the whole system, but that seems to be in a different scenario. Just mentioning it for the sake of completeness.

 

[DP]

2” pipe connected to previous cylinder, now the return is 15mm stub. High recovery coil in new cylinder- are You taking the p155 when you say
I am mistaken?

Read what you have posted. Clearly you are out of depth here with your thinking.

Crack on, you have superior knowledge that a fault person who does this for a living ( according to you) fails to comprehend.

 

[MNW67]

2” pipe connected to previous cylinder, now the return is 15mm stub. High recovery coil in new cylinder- are You taking the p155 when you say
I am mistaken?

Read what you have posted. Clearly you are out of depth here with your thinking.

Crack on, you have superior knowledge that a fault person who does this for a living ( according to you) fails to comprehend.

I think it's more that this one pipe stuff is so difficult to understand for us lay people and so much to take in. Things that seem logical turn out not to be and that is confusing. It's probably just human nature to ask for confirmation when you are struggling to grasp it. Clearly the original plumber has had difficulty as well.

 

[DP]

Clearly the original plumber has had difficulty as well.

Original plumber must be a diyer looking at the joints, so will be forgiven missing essential elements, same as many who have tried to understand the system without a site visit.