Condenser Boiler V Back Boiler

jinkybhoy

We are going to update our heating system.

We just have a oil boiler at the moment.

If we get a back boiler - there's going to be a lot of building work to be done for where we want it.

What I want know is - If cost was the same for both - What is the best one to go for?

Thanks

Jinky

Ddad

Replacing your existing boiler with a condensing oil boiler and an upgrade to some of your heating controls will cost between 2 and 3k depending on the type of boiler (heatpac, boiler room, model, size etc) and any ancillary works you want to carry out. By a back boiler I'm assuming you mean a stove with a back boiler; as aback boiler alone on an open fireplace is very ineffecient. The cost of this varies greatly depending on the size and quality of stove you'd like/need to install to heat the space in the room and the heat load of the house(i.e how much heat output do you need to provide from the backboiler). In adition there are many variables on plumbing the boiler in to your system; this is best assesed by a professional.

Im adding a 30kw boiler stove to my house at the moment and it'll cost €2700 for the stove, hearth, flue and installation. This excludes the plumbing cost.

I'm taking this approach as we have ready access to fuel and we light the fire every day in the colder months and there is always someone in the house to tend it. I like clearing and tending the fire, if I didn't we wouldn't be getting the stove as there's fetching and carrying to be done.

You might also consider the less costly option of a space heating stove which could make a significant input into the heating of your home without the need to pull and drag at your plumbing.

By the way you are eligible for a grant for the upgrade of your boiler but not the stove backboiler option. Check www.seai.ie for grant info.

DoneDL

If the oil boiler is in reasonable condition I would be tempted to go for a stove that is connected to the heating system and update the heating controls for which a grant is available.

jinkybhoy

Hi

We don't really have space to put a stove in - the only option we have really is for an inset back boiler in the kitchen - involves a lot of building work etc.

To put the condenser boiler in is fairly straightforward - all existing pipes are ok - so just boiler needs to be changed - minimal fuss really.

Just want to know is it worth all the extra hassle and work to get a back boiler put in - will it save me more money on heating costs.

DoneDL

jinkybhoy, it does depend largely on factors like usage and access to fuel. If you have got good storage facilities then you can get deliveries of logs at a reasonable price. If the heating is on a lot then I would choose the stove option. Whether you connect it to the heating system will depend on the layout of the property to determine if it is viable and sensible to do so. But before you take the plunge make sure your insulation is up to standard.

jinkybhoy

DoneDL

Thanks for replies.

The heating would be on constantly from november to february. It heats 20 radiators.
We have a fire in the sitting room that would also be on constantly but just heats that room. It would be very awkward to connect that as a back boiler.

I'm kinda confused about these condenser boilers - even if they only saved me 25% on heating costs, I would get it for this year and then see about getting a stove for next year and run the two of them together - IE in summer just use boiler if needed - winter, use boiler to get house heated and stove for rest of day and night.

What do you think?

DoneDL

20 radiators is a large heating load for any solid fuel stove and I dont think a 25% saving is possible just by changing the boiler, most especially an oil boiler. Consider updating the heating controls, zoning the system and upgrading your insulation. Whether you choose the condensing boiler or stove these updates should take priority. There are insert stove that can be installed eg stovax which may lessen the building work required.

heinbloed

The heating would be on constantly from november to february. It heats 20 radiators.

So the thermal demand has to be calculated. It's the rooms which have to be heated, they loose the energy via ventilation and surfaces.
The number of radiators doesn't matter, the thermal energy demand is not caused by them but by the thermal losses via the fabric and holes in it.
It reduces the thermal energy demand if chimneys are closed for good.
If there is space for thermal storage the inclusion of a cheap ST system could reduce the bills.
If there is no space for a thermal storage a combi-condensing boiler might be the straight forward solution.

To determine the necessary 'size' of it - the minimum thermal out put and maximum thermal output - the thermal demand of the structure has to be calculated.

Otherwise there is only guess work.

If going for a condensing boiler ( "condensors" are producing destilled water for industrial purpose and are not designed to heat a space !) choose one with a wide range of output. Standard types start at about 2 kW and go to about 25 kW. The lower the min. output the less cycling will be there, the more economic it will supply the thermal energy.

For example:

HANSA Öl- und Gasbrenner GmbH

There are many more out there, as long as the min. output covers the minimum demand and the max. output covers the max. demand you have made the right choice.

Note that a condensing boiler will not save on bought-in energy (by condensing the flue gases) if the return temperature from the heating system is too high. It depends on the return temperature of the heating system if the investment in a condensing boiler makes sense.
Not on good will or legislations or sales men talk. The laws of physics determine if a condensing boiler is economic and installed legal, safe.

If the return temperature does not allow for the condensation to happen in the boiler then the incoming air can be used to cool down the outgoing flue gases, reducing thermal losses.
See the device at the bottom of the linked page.

A condensing boiler must be run in a condensing modus. If not it is illegal, against the manufacturer's recommendation, unsafe. And not worth the extra investment.
A cheaper standard boiler with a flue-gas/fresh air condensation (the device at the bottom of the linked page) would be the better choice.

So the first step is to calculate the thermal demand of the structure, then meassure the return temperature of the existing central heating system.
With these numbers an independant heating engineer will be able to point you to the right boiler.
Most plumbers wouldn't bother. They want to sell what generates them profit.