What Boiler System Do I Have

[JackK]

I have an old Ideal Mexico 2 floor standing boiler - It is also a one pipe system.

Gas engineers want to rip it all out and repipe the whole house which I cannot afford

I want to understand what system I have

I have a flow out of the boiler which then has a two port valve for hot water cylinder - There are no other valves

1. Does that mean that in order to have hot water I always have to have the radiators circulating?
2. Is my system with a two port valve called a Y plan or something else - I think its an S plan but with only one two port valve

 

[stem]

Possibly it's a 'C Plan' generally as below, but with the radiators sitting atop a one pipe loop.

If it is a C Plan and, if it's been wired correctly the heating and hot water should work independently. Can't you tell when you use it?

The C Plan has two sets of pipework to the boiler one for the heating and one for the hot water, you only mention one set. If that's the case you may not be able to have the hot water on on it's own.

The only way to be sure is to follow the pipework and see where it all goes, there are all sorts of hybrid systems out there.

 

[JackK]

I think I do have a C Plan - Thank you so much

It an old system and I replaced the boiler programmer when I first moved in

If I call for heating the boiler fires up straight away and heats the flow pipe which is used by the hot water gravity tank, but annoyingly also heats up the radiators as well

If I call for hot water the boiler does not fire up

I think this was wired up wrongly if I am honest - It’s a drayton wall attached programmer

Is the 2 port motorised valve connected to the cylinder thermostat meant to link to the boiler - I cant see a wire from the cylinder to the boiler to be honest

 

[stem]

Here's a wiring diagram of a C Plan. The changeover switch inside the motorised valve (top right) facilitates the isolation of the heating and hot water systems so that they can operate individually, so there won't be a wire from the cylinder thermostat to the boiler other than via the motorised valve.

The problem I think you will have with a new installation is that new boilers due to their energy efficient design and lack of the second set of 28mm inlet and outlet connections won't work with systems having gravity circulated hot water systems. A fully pumped system is required, such as the S or Y Plan.

The 'one pipe' radiator system would probably work, but whether it would enable a new condensing boiler to operate at maximum efficiently or not may be in question. And if the hot water system has to be replumbed then it would make sense to upgrade the radiator pipework at the same time.