What sort of boiler?

[JohnnyF]

Hi,

We've bought a terraced house that spans 3 floors and it needs everything gutting including new central heating / boiler.

We've had 4 plumbers round but they each seem to recommend different systems so I was hoping someone here could give some independant advice.

In our current house we have a Worcester combi but as soon as someone puts a tap on the flow to the shower cuts down drastically and the water temperature goes colder. This is in a one bathroom house so we are unsure as to whether a combi is suitable in the new house.

The new house will have one main bathroom and two shower rooms so we don't want to risk the flow to one shower being impacted by someone using another shower simultaneously.

The new house has 4.7bar mains pressure and a 13 / 15 litre flow. We would like to be able to run more than one shower simulataneosuly, and have appliances on as well that doesn't impact the flow. The living area spans 3 floors and it is a 5/6 bed house.

What we have had recommended is:
1. A large combi.
2. An unvented tank (another plumber said we've been told our flow isn't adequate)
3. Put a header tank on the second floor that will feed the first two floors and a seperate combi that will feed the shower/basin and heating on the 2nd floor.

Basically what I would like to know is what system would plumbers recommend for a large house where you do not want the flow of water to be impacted by other users.

Hope you can help

Cheers

John

 

[JohnD]

I like option 3 except I don't see the need for two boilers. Combi or unvented supply will need a good flow, and a good pressure. Your plumbers will be familiar with local conditions, but sooner or later they (or you) will have to test it. You can start by filling a bucket upstairs and timing litres/min, this will give a rough guide.

You can get a very good flow from an unvented system, with a nice big tank, and a nice big cylinder (cylinder recovery time from cold to hot is about 20 mins). If the tank is big, then it doesn't matter much if the mains supply is weak, since it will provide a buffer of stored water (mine is rather bigger than a bath, and supplies one bathroom and one shower room).

With good flow, no one tap or shower can take enough water to starve the others (it is important though to have separate pipes to each shower room/bathroom or they will compete).

I understand you to mean that the second floor is the top of the house, like a loft conversion, so you can't put a tank above it? It is possible to use a single boiler to supply heat to a hot water cylinder, and also an instant combi supply to your upstairs shower. You will need reasonable mains pressure and flow to the top of the house, though. This arrangement is not very common. you could also consider an electric shower on the top storey, though the amount of hot water delivered will be far inferior to the stored-water showers.

 

[Agile]

I am sure the plumber meant that it would be a vented cylinder heated by the combi which would also supply one HW outlets on the top floor. He is the only one who seems able to understand the situation.

You did not say how many people will live there. Your requirements are over the top if its only two! If its 4 or more then you will need a cylinder of about 300 li if they are all going to use the facility at the same time.

Tony

 

[Nixt]

The new house has 4.7bar mains pressure and a 13 / 15 litre flow.

If the above is correct there could well be a restriction somewhere. Check flow rate at an unrestricted outlet such as a garden tap. Even at 3bar I've had 20lpm through a 15m pipe with a 7lb lead supply.