Comprehensive Guide and FAQs on Condensing Boilers: Everything You Need to Know

Do you want to replace your traditional open-chamber boiler or your low-efficiency sealed-chamber boiler with a new condensing boiler model? It’s important to know that the work can be laborious, let’s see step by step

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What are the prices of a condensing boiler?

Prices vary based on the quality of the product. At trade shows, you can see various models with very attractive prices. Some focus on aesthetics, while others on new heat exchange patents. If the price is too low, you might get a product with poor materials or one that performs poorly with very hard water or is unsuitable for large families. The quality of the internal components of the boiler is crucial. In the past, copper and brass were often used, while today many groups and collectors are made of plastic, so it is not worth skimping too much if you want peace of mind.

The best condensing boilers definitely have a boiler in sizes of 8, 20, and 40 liters, which over time have proven their ability to withstand very hard water and large families. The best condensing boiler has several modulations; for example, a Radiant condensing boiler has about 8 modulations that allow it to work at very low power and make the most of the boiler’s condensation.

Changing the traditional boiler, whether it is a sealed or open-chamber boiler, with a new condensing boiler pays off very quickly over time.

Does the flue need to be lined?

New condensing boilers require the flue to be lined. Compared to low-efficiency boilers, the flue gas temperature is significantly lower, causing a lot of water vapor to stagnate. The condensing boiler has plastic pipes because they need to resist the condensation of the flue gases rather than the heat. The condensate will return to the boiler to be discharged, so it is important that the new pipe that goes inside the flue is well secured to avoid siphons and considering that the piping will lengthen with heat during the winter.

Because of the need for lining, your flue cannot be branched unless the other appliances are also condensing. In condominiums, it is common to find branched flues, which often cause draft problems for type B open-chamber appliances currently present. It’s not uncommon to decide to change the appliance, perhaps following a recommendation from the technician due to stricter inspections on appliances, especially in the Emilia Romagna region.

Still on the subject of branched flues, for reasons of construction convenience, some of these flues are made of refractory material and square, in cement to be precise. This is why we have very low drafts in open-chamber boilers; the flue heats up very little, and there is no draft that carries the combustion products to the chimney. What’s worse is that these flues are square and very small, making it impossible to convert them with lining even if the condominium agreed to change all the boilers together.

More and more often, we see installations of insulated external flues, just look around in cities to notice that some condominiums have installed these shiny external pipes for some years now. It is a reflection of the need to change the appliance and the problems related to branched flues. Usually, these insulated external flues are decided in condominium meetings and offer the opportunity even to those who do not yet want to change the boiler to have a ready-made arrangement. So, investing in this solution is very wise; the condensing future has already begun, also considering the savings that can be achieved with these appliances.

Another solution is the external discharge, also known as wall discharge, which consists of exiting with the piping outside the perimeter wall. The wall discharge is regulated by the municipality, and it should be noted that new appliances produce a lot of steam. In fact, combustion produces two parts of water vapor, which at the temperatures of a condensing boiler (from 30 to 55 degrees) generates a lot of steam, especially in winter. It is not uncommon for a neighbor to complain, and the situation in a condominium can be very delicate. To avoid having to transform the system after a few months, perhaps with a dispute in progress, it is always good to clarify the type of flue gas evacuation with the plumber in charge of the installation. It is not uncommon to find budget installations where wall discharge was chosen, creating discord with the neighbor.

Do condensing boilers have a drain?

Under the new boiler, we will therefore have a new pipe, the drain, like washing machines. The regulation requires that the condensate drain goes directly into the sewer without the possibility of collection by the user, so no condensate drain in a tank. The condensate pipe must have a minimum slope unless we are forced to adopt communicating vessels. However, these can cause obstruction problems in the long run due to boiler oxides or can test the seal, so it is better to use pipes without joints and, if possible, respect the slope.

Regarding the condensate from the condensing boiler, we have a certain degree of acidity. This acidity of the condensate is due to the high heat generated in the combustion chamber and contact with the boiler metals. This is why the regulation absolutely forbids its use and requires direct drainage without the possibility of interception. So, absolutely no reuse, neither for watering plants nor for putting in steam irons. In fact, we should also worry about neutralizing its acidity through an accessory called a neutralizer. The neutralizer is especially useful if the discharge is done in a gutter; if we do not use it, the condominium gutter will fall apart within a few years.

Adopting the magnetic filter

Important, important, important, your system with radiators continuously creates dust; materials oxidize, creating sludge, especially in cast iron radiators. Although these can be washed, in the future, you will always find yourself fighting with this dirt that will form on its own. Modern boilers, to achieve such high efficiencies, have narrow passages, also called bottlenecks, and scales from the system can clog them. During installation, it is important to also install a filter to protect the boiler and avoid warranty problems. In fact, manufacturers are increasingly paying attention to this detail when there are breakdowns.

Today, magnetic filters are very common; for example, RBM has perfected one called MG in versions MG1 and MG2. The MG2 is a really nice magnetic filter, with an integrated tap that isolates the filter during maintenance operations. With the boiler off, it is therefore possible to clean the magnetic filter without having to remove all the water from the system. Once the ring is unscrewed, the magnetic insert is removed, and the white plastic component can be cleaned. The fine metal mesh cylinder should also be cleaned from larger scales.

Another factor to consider is the capacity of the magnetic filter; some cheap products have very small containers. If the system releases a lot of dust, this forces the technician to visit the boiler more often, wasting a lot of time.

The magnetic filter is a must; during our tests on a dirty system, it was completely clogged in one day, considering that the system was with fan coil units.