Advice on gas boiler size please

Meteor67

Hi,

what would be the correct size for a gas boiler for the following type of house:

4 bed semi, 170sqm, A3 rated (I guess just about), solar system for hot water, Dublin area

Also what would be a reasonable good make and model?

Thanks

JohnnieK

Meteor67 wrote: »

Hi,

what would be the correct size for a gas boiler for the following type of house:

4 bed semi, 170sqm, A3 rated (I guess just about), solar system for hot water, Dublin area

Also what would be a reasonable good make and model?

Thanks

Viessmann and Ariston would be the choice of brands for my self.
a heat loss calculation should be done for each room to ascertain the correct size boiler.

If you went for the Viessmann and if it was possible you could utilise the 4 pipe system and go for the 19kW boiler. It is a hot water priority boiler with an independent circuit for the cylinder.

This allows the boiler to have potentially 19kW for heating and 19kW for hot water.

The hot water circuit can be on high temperature (to heat the cylinder as quick as possible) and a lower temperature for the heating to utilise the condensing technology for longer in the heating cycle and combined with a weather compensator would add an extra saving especially if your house is A3 as stated.

esox28

i would second the vessmann vitodens 19kw system, lovely boiler, super heat exchanger and the 4 pipe connection split is the business where possible to use it.

but its not really possible to size a boiler from the ber a3 cert as this is a total energy demand for the house being 50kwh/m*/yr. your total energy demand being 8500kwh

taking that your overall boiler operating hr /year @200 hr

the vessmann outputs 19kw or 3800kwh plus the boiler can modulate to meet reduced demand to 1300kwh.

you need to calculate the max heat load for the house taking all factors into consideration, u-values (wall,windows,doors,roof) airtightess. then calculate the total heat loss to give you an figure for boiler output.

are you in a new build with a A-3 rating?

Dtp1979

Would it not be measured by the size of the existing rads plus an allowance for pipework?

JohnnieK

Dtp1979 wrote: »

Would it not be measured by the size of the existing rads plus an allowance for pipework?

Either way it's a retro fit so existing radiators will have to be factored in. They would have probably been sized for an 11oC differential so there will be a performance loss to cater for the 20oC differential for new condensing boilers.

In saying that i wonder if there has been insulation upgrades considering the suspected BER is A3 and if this is the case the existing rads might suffice.

Either way a heat loss calculation will need to be done.

SmallBalls

esox28 wrote: »

vessmann vitodens 19kw system

How much for boiler and flue?

esox28

roughly €950 for boiler and €70 flue kit.

Meteor67

Hi,

The cert states 74kWh/sqm/yr

It's a new house and not an upgrade.

Builder plans for a Baxi Megaflo 2 15 Compact GA.

Not sure if I should go ahead with this.

JohnnieK

Meteor67 wrote: »

Hi,

The cert states 74kWh/sqm/yr

It's a new house and not an upgrade.

Builder plans for a Baxi Megaflo 2 15 Compact GA.

Not sure if I should go ahead with this.

If it's a new house you must have an architect. He must of had some sort of an input in the design.

Also if it's a new build the insulation values would be high.

Is the house air tight and if so is there a heat recovery ventilation system going in.

These factors would all need to be factored in.

Who is designing the system for you?

I would still be exploring the viessmann 4 pipe system.