Boiler replacement is not easy

[antgel]

Hi all,

Having decided on a Glow-worm 30cxi combi, I have hit further problems. It's to replace my Potterton Netaheat and associated tanks.

Problem 1: I don't know where the gas pipe goes into this boiler. Can anybody advise? There are four pipes for heating and water, coming from the floor, but nothing else. Could they be coming through the wall / fixing jig at the back?

I need to know the diameter, to make sure that it's suitable for the Glow-worm. I'm assuming that I can't just tell the diameter by looking at the model of boiler.

Problem 2: The heating send / return pipes are 22mm. Glow-worm tell me that they need to be upgraded to 28mm. Is there any basis for this claim? If so, does this mean running new pipe throughout the flat? I'm not sure where these 22mm pipes go to at the moment - the radiator pipes are 15mm. It's an open system with header tank.

Hope that someone can help me unravel this.

Antony

[Ed Sirett]

With all due respect if you can't identify what pipe is what and what the basic components in a boiler are then you are, IMHO, well advised to gain experience on a less challenging project.

DIY gas fitting is permitted _if you are competent_ and in my book that means you should really be able to identify which pipe is the gas supply to _any_ domestic boiler.

22mm flow and return are likely to be OK unless the manufacturer state explicitly otherwise in the fitting instructions.

See the gas fitting FAQ about gas pipe sizing which _might_ have to be upgraded.

__ Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at

Gas fitting FAQ CH FAQ

[antgel]

Thanks for the reply Ed. I'm not going to fit the thing myself, don't worry. I just want to have a look at (and measure!) the pipe before I purchase the new boiler for my (CORGI) man to fit. If the pipe does need upgrading then that might have an influence on my new boiler decision.

So if you can help me here I'd be grateful. I just had a look (admittedly the light's not great in there, and I can still only see the four pipes).

Antony

[Ed Sirett]

This boiler would only need to have gas, flow and return. However there are four holes for water in the back of the heat exchanger one of which should be installed as the main vent and therefore should not go downwards. Therefore there is probably another pipe that goes up?

[antgel]

When you say flow and return, do you mean one flow and return for both CH and HW, plus gas, totalling five pipes, or one flow and return for CH and HW, plus gas, totalling three?

The only pipes going above the boiler go up to the CH header tank.

Antony

[Dave Plowman (News)]

If the hot water primary is gravity circulation, it is usual practice to feed it separately off the boiler, so four water pipes. If it is a fully pumped system with a diverter valve, only two pipes.

[Ed Sirett]

The boiler will have a gas supply pipe and have 2-4 connections to the heating circuit.

It might be that there is only the flow and return (2 pipes) Or you might have flow and return and a dedicated vent Exactly what pipes and connections you have will depend on the controls and features of the heating system.

A common arrangement is just two pipes flow/and return the flow pipe is also the vent pipe to the header tank.

One of which is the vent pipe.

See the main FAQ for background info on heating ystem in general which may help you to work out what each of the pipes are.