- Messages
- 7,272
C plan EVEN
Discuss Different boiler temps required for hot water vs radiators. in the Plumbing Jobs | The Job-board area at PlumbersForums.net
- Status
An S plan is a much better solution, it's more logical, simpler and more reliable generally.
Heat is never taken from the cylinder to heat rads, I'm not sure where you have gained that assumption.
The cylinder will require a min flow temp of around 70, return of 60ish to ensure the bottom of the cylinder can reach 55.
The radiator circuit is another matter. If you're saying you can run them at 40 comfortably then great, however when you add a cylinder you'll need to have the boiler temp set to satisfy the cylinder. Short of turning the boiler stay up and down like a yo yo, you could blend the radiator circuit down with a mixing valve if required. If not then just run them at a higher temp. With your current boiler, there's not a huge saving to be made running a lower temp.
Unvented cylinders need to be able to be shut off from the heat source in the event of overheating, a 3 port valve doesn't achieve this, a zone valve does.
Heat is never taken from the cylinder to heat rads, I'm not sure where you have gained that assumption.
The cylinder will require a min flow temp of around 70, return of 60ish to ensure the bottom of the cylinder can reach 55.
The radiator circuit is another matter. If you're saying you can run them at 40 comfortably then great, however when you add a cylinder you'll need to have the boiler temp set to satisfy the cylinder. Short of turning the boiler stay up and down like a yo yo, you could blend the radiator circuit down with a mixing valve if required. If not then just run them at a higher temp. With your current boiler, there's not a huge saving to be made running a lower temp.
Unvented cylinders need to be able to be shut off from the heat source in the event of overheating, a 3 port valve doesn't achieve this, a zone valve does.
Last edited:
- Messages
- 185
When both heating and hot water zones are open, I don't see how heat will not move from the cylinder to the rads. I am not sure if this is a problem since eventually the house will heat, the rad zone will close and the boiler can then heat the water. However, I would prefer the priority be the other way round.
I have my boiler set at 70C. It rarely goes over 40C. This will need to change if a cylinder is installed.
I have my boiler set at 70C. It rarely goes over 40C. This will need to change if a cylinder is installed.
D
Dotty
Look up balancing.
- Messages
- 5,073
We do not understand this statement please explain what you mean?
Because the zone valve to the cylinder will only be open when the cylinder is below set point eg 55 degrees. When the flow temp is greater than 55, heat will only be transferred into the cooler medium, ie the water in the tank.
The laws of physics prevent it doing any different.
When the cylinder is satisfied eg > 55 degrees, the zone valve will close, preventing circulation, although this is still preventing it from being heated further as opposed to any heat being removed.
If your boiler stat is 70 yet you can only get a flow temp up to 40, something is wrong.
The laws of physics prevent it doing any different.
When the cylinder is satisfied eg > 55 degrees, the zone valve will close, preventing circulation, although this is still preventing it from being heated further as opposed to any heat being removed.
If your boiler stat is 70 yet you can only get a flow temp up to 40, something is wrong.
- Messages
- 185
My current setup seems reasonably well balanced, no hot or cold spots in the house. All the rads have thermostatically controlled regulators. What do I need to know about balancing that can help me in this?
- Messages
- 5,073
You will be having work carried out that means your new heating system & controls will need to be compliant with Building Regulations AD Part L1b.
The C-plan system will not meet these & it will not be suitable when you have to install a new boiler.
- Messages
- 7,272
W plan EVEN 
- Messages
- 185
I set the boiler temp to 70C. Before it gets much over 40C, the main house thermostat stops calling for heat. I guess my house has more radiator capacity than it needs, but I guess low return temps will be good when I eventually have to convert to a condensing boiler.
- Messages
- 1,005
It sounds as if there is possibly a problem with your boiler if it doesn't get up to 70°.
S Plan meets you're needs don't over complicate it . if you go for and Unvented ("mains pressure") hot water cyclinder your installer will also need to be 'G3' certified.
If you want to reduce the flow round the radiators to a lower temperature, then use a weather compensated blending valve.
You'll also need an auto bypass as the boiler with have a pump overrun so it doesn't overheat when both valves are shut.
C Plan only normally used on gravity feed - download the Honeywell wiring guide you'll see the options.
S Plan meets you're needs don't over complicate it . if you go for and Unvented ("mains pressure") hot water cyclinder your installer will also need to be 'G3' certified.
If you want to reduce the flow round the radiators to a lower temperature, then use a weather compensated blending valve.
You'll also need an auto bypass as the boiler with have a pump overrun so it doesn't overheat when both valves are shut.
C Plan only normally used on gravity feed - download the Honeywell wiring guide you'll see the options.
D
Dotty
Your primary and Heating circuits need to be balanced.
It's marginally possible, but much more likely to be a sign of an underlying fault on the system.
- Status
Reply to Different boiler temps required for hot water vs radiators. in the Plumbing Jobs | The Job-board area at PlumbersForums.net
Similar plumbing topics
