Help Gas Hotwater Boiler

[wallywobbles]

Could anyone help please? We are in the process of getting quotes for a rebuild of a c14th house. We are in France, but I don't think that changes anything in technical terms.

The last guy that came made it all seem rather complicated, and I think that he might be trying to run rings around us. I just want to replicate the system that I have in the house we are selling, which has 3 bathrooms and outside shower.

So I want a gas hot water boiler - so we have instant hot water. We will have 4 shower rooms (4 teenagers), and one bathroom for us oldies. I don't think I want any kind of hot tank, as space is at a bit of a premium. And the heating system is going to be separate and rather more complicated, but I'll post separately for that. It would also need to do the kitchen hot water. We think we will need a 15l storage tank for hot water for the kitchen because of the distances.

What kind of capacity do I need and what makes do you recommend. I saw that The Fernox TF1 filters were recommended back in 2012, and as we are planning to use well water (if that's ok?) that's seems like a good idea.

And that Worcester Bosch and Vaillant boilers were recommended by Piglet John, all 3 are available here. Saunier Duval are used here a lot - we have had 2 in the past.

We have a lot of lime scale, so we might have to put in a water softener too.

Really all advise welcome please.

[PigletJohn]

If the water is coming from a well, I am pretty sure you will need a cold-water storage tank, and some kind of hot water cylinder. If you want to run showers I can't see how you could do it without pumps to put up the pressure.

How tall is your house, and what floors will the showers be on?

Are you sufficiently fluent in french to discuss the technical design?

Have you looked at the design and installation in other similar local homes?

[wallywobbles]

Hi Piglet John

Thanks very much for the help.

French not a problem - DP French and I've been here for 20 years (all my adult life).

Technical not an issue as DP is a mechanic/engineer, but not done anything to do with gas.

Ceiling height downstairs in 2.5m. Upstairs is largely in the roof space with dormer window, with 90cm wall before the roof which is at a 70° angle. Insulation will be 20cm of rock wool. Ceiling height will be around 2.5m again.

4 showers will be upstairs bathroom downstairs. (Adding plans)

I use the pump system in my current house, up to 4 bars of pressure. We have no cold water tank in the current house apart from the header tank for the heater. I've seen a similar system to what I think you are describing with a large tank (maybe 1000l) but it has a hell of a lot of stuff coming off it - 4 houses and massive gardens.

[PigletJohn]

Is your current house supplied from a well? I used to live in one and the well pump filled a storage tank, and it had a hot water cylinder heated electrically and/or by the multifuel stove. The pressure and flow from the well were low. I don't know how to run showers straight off a well pump. It needs dependable flow and pressure. I have never seen a combi run off a well and don't know how, or if, it could be done.

[wallywobbles]

The pump system in our current house runs direct without any tanks for the cold supply. It has a kind of trigger system that you set at your required pressure, and when the pressure falls below this point the pump kicks in. So if you are running the tap the pump will automatically kick in after a few seconds. I guess the pump has a small tank (50l or so) itself. I've included a pic which is similar to ours.

I guess my main question is really how powerful would the boiler need to be I've looked at the worcester bosch ones, but I'm not really sure which one would suit. Do I need to be looking at KW or flow or what? So for 4 showers and 1 bath.

[PigletJohn]

Does that pump run off a well?

[wallywobbles]

Yes

[PigletJohn]

I still don't know how to use a combi with a well.

A typical combi has in the region of 30-35kW power, which is enough to supply one good shower, or two reasonable showers at the same time, or to fill a bath rather slowly. It could deliver about 12-14 litres of hot water per minute at 35C rise (so the hot water will be cooler, or less of it, in winter when the incoming supply may be very cold). Because the delivery of hot water is limited, a combi is not very suitable where two or more baths or showers are likely to be used at the same time. A bath uses about 100 litres, a shower might be 25-50 depending how big the spray head is and how long you take.

You might also look at Viessmann systems if you have a local installer.