Different boiler temps required for hot water vs radiators.

[siricosm]

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.

Heat exchange is a 2-way street. If the cylinder temp drops below 55C, say 54C and wants heat, and the rads are running with a boiler temp of 40C, then heat will be taken from the cylinder.

I do not believe there is something wrong with my boiler setup. I probably just have way more radiator capacity than the house needs.

 

[siricosm]

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.

I said I want to simply extend my existing system by adding a cylinder.

 

[siricosm]

W plan EVEN

What is difference between W-plan and Y-plan? If it W-plan uses a 2-way valve (with no middle position), is it possible to get hardware for that?

 

[siricosm]

Your primary and Heating circuits need to be balanced.

I only have a heating circuit. What do you mean by primary circuit.

 

[siricosm]

It's marginally possible, but much more likely to be a sign of an underlying fault on the system.

From what I understand, when you set the boiler temperature, this will be the max temp before the flame is turned off. At our place, when the rads reach 40C the house is 21C and the thermostat stops calling for heat.

 

[stevetheplumber]

is this a wind up? just get someone in to price what you want then leave it to them to it although i doubt you will

 

[Worcester]

siricosm, you've been given good solid advise by some of the most experienced heating engineers in the Uk and yet you are still questioning their advice with spurious assumptions on your part.

If you really want to understand what they are saying (S-Plan, heating controls, building regs, Unvented/G3), then buy some of the heating books recommended to others (trawl the posts) and teach yourself.

The answer you will come to is:
a) There is something not quite right with my boiler / system (short cycling etc therefore highly inefficient)
b) I need an S-Plan system with bypass
c) I need a qualified G3 heating engineer to design and install it all including balancing

 

[stevetheplumber]

if your boiler gets to 40 and the room stat is satisfied the heating valve will shut and the boiler will continue heating the cylinder until that to is satisfied when both valves close the boiler cuts of if your heating has cooled and opens that valve again the hot water valve stays shut there by not allowing and water to flow and cool the cylinder

 

[stevetheplumber]

most of the boys on here can do this sort of system in their sleep without any calcs just by experience

 

[siricosm]

siricosm, you've been given good solid advise by some of the most experienced heating engineers in the Uk and yet you are still questioning their advice with spurious assumptions on your part.

I am not here for advice, I am here for understanding. I just want to know what my options are, before I decide how to proceed. As I mentioned in a previous post, I am not installing anything in my house until I fully understand how it works, and what alternatives are available. Your post seems to be suggesting I should just "leave it to the professionals". Unfortunately, I have had too many experiences with "professionals". If you can actually answer the original question in my first post, then please do so.

 

[Dotty]

I think that'll do. As the above posts have stated, have faith in your installer. You don't need to have an informed discussion with him. You just need to tell him what you want, and you need to let him get on with it.

Anything else would make you the type of customer we would try to avoid.

Job 38.11.