Condensing boiler technology Page 53

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14.3 Function

The ZEBA demonstration model shows how the condensing process in condensing boiler systems works and also illustrates different energy balances.

The on top installed catalytic burner is operated with a propane/butane mixture. It is located in the glass combustion chamber where only primary combustion air flows by the inlet nozzles of the burner. In this way, a very calm catalytic combustion is achieved. The heat exchanger located below is slowly being surrounded by the up-heated gases and extracts, at a corresponding reverse running temperature, the humidity from the air in the burner.

Depending on the adjustment of the flow rate, coolant temperature and catalytic burner temperature a corresponding efficiency results. The quantity of the obtained condensate clearly shows if those adjustments were optimal. The gained condensation heat is supplied to the heat exchanger. The condensate resulting at the glass heat exchanger drops into the condensate trap/collector and can be removed through the ball cock/tap. The adjustable fan is removing the produced exhaust gases.

14.4 Preparing measures

Since the model is delivered completely assembled, it can be put into service in a relatively short period of time.

After the model has been installed in a safe location and after it was checked if no parts are missing, the modular pipes should be tied up again since it can happen that they have loosened during the transport.

Afterwards the water circulation has to be connected (over a thermostat), the adjustment of the pressure monitor has to be checked (max. 1 bar) and it has to be examined if the system is tight.

The flow should be adjustable up to the maximum of the flow meter (25 l/H) using the ball cock/tap located in the inlet (pressure-reducing valve adjustment). Possibly, the pipes and the glass combustion chamber have to be adjusted to each other in order to guarantee a steady flow through the heat resistant, soft silicone hoses at the connections of the heat exchanger. Now the feelers/sensors of the digital thermometers can be introduced into the measuring connecting pieces. Those should be moistened first with vaseline or silicone oil in order to preserve the rubber seals. The voltage supply of the fan has to be attached on the back of the module rack and its two plugs have to be plugged in with correct polarity/poling.

After the automatic controller has been connected to the mains (230V/50 Hz), one has to check the rotation direction of the fan by switching it on and by adjusting it for the highest number of revolutions. The air flow coming out of the exhaust gas pipe can be easily checked with the hand. If the air flow should be directed to the inside (towards the heat exchanger), the polarity/poling of the plugs is not correct and has to be changed.

The gas bottle has to be screwed into the fine flow control valve and then has to be hang up vertically and firmly secured on the module rack with the valve pointing upward. The hose connection at the burner may not be loosened. An examination on tightness also has to be performed here after transport. This can be easily done by opening the fine flow regulation valve and by observing the upward turned burner against the light. If a creation of reams/stains at the hose connection is occurring, the connection has to be tied up before the device is started. The burner has to be held upward (in burn direction) for this test since otherwise a creation of reams/stains through gas leakage at the supply air openings of the primary combustion air may take place.
The condensate drainage possesses an adjustable drain valve/tap whose lock nut must be loosened at the beginning and then has to be tied up again after some movements.

14.5 Measuring procedure - experimental/test setup

If all described preparing measures have been carried out, the condensing boiler demonstration model is ready for use.

The automatic fan controller has to be switched on now and has to be adjusted to a medium number of revolutions.

Burner start:

The burner has to be held upward with the catalytic fabric/tissue and then the gas supply has to be opened. The fine flow control valve regulates very precisely. However, pressure changes are normally occurring with a short time delay. The gas can now be ignited. After the catalytic combustion has started - this can be easily recognised by the disappearing flame and the following glow of the fabric/tissue - the burner has to be slowly inserted into the glass combustion chamber and has to be centrically placed there.

Graphic: Burner adjustment

Fine flow control valve
turn back
Optimally Fine flow control valve

The fan now has to be completely back-regulated. A minimum number of revolutions is factory adjusted for safety reasons.

Depending on the adjusted/chosen starting values, the condensation starts after a short period of time and a measuring protocol can be made and different test measurements can be performed.

The following two graphics show experimental/test setups with which one can perform different measurements as a function of the flow. The last graphic shows an example for a measuring protocol/report that has to be filled out by the students.

Graphic: Experimental/test setup

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