Latent heat recovery type water heater

Abstract

A latent heat recovery type water heater A being designed such that water flown in a secondary heat exchanger 2 is heated, and the heated water is supplied to a primary heat exchanger 1 and is further heated. A controller 4 compares heat exchange efficiency η of the secondary heat exchanger 2 with a predetermined threshold value Th, and the controller 4 determines whether the primary heat exchanger 1 is in a normal condition or not. The threshold value Th is changed corresponding to temperature of inflow water to the secondary heat exchanger 2. Accordingly, an abnormality such as scale adherence in the primary heat exchanger 1 is accurately detected regardless of the fact that the primary heat exchanger 1 and the secondary heat exchanger 2 are connected by a bypass path or not.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a latent heat recovery type water heater, more particularly to a latent heat recovery type water heater capable of detecting an abnormality such as scale adherence or exhaust clogging.[0003]2. Description of the Related Art[0004]One example of a latent heat recovery type water heater is disclosed in Patent Literature 1.[0005]In the water heater disclosed in Patent Literature 1, sensible heat and latent heat are subsequently recovered from the combustion gas generated by a burner using a primary heat exchanger and a secondary heat exchanger. Water to be heated passes through the secondary heat exchanger and then is supplied to the primary heat exchanger. It is for avoiding such disadvantage that the recovery efficiency of latent heat decreases when the temperature of the inflow water to the secondary heat exchanger rises.[0006]When the above-mentioned water heater is used for a relatively...

AI Technical Summary

Benefits of technology

The invention provides a water heater that can recover latent heat and reduce the disadvantages of existing technologies.

Problems solved by technology

Scale adherence easily appears when water is supplied in the heat transfer tube; however, scale adherence hardly appears in heat transfer tubes of the secondary heat exchanger because of low temperature in the secondary heat exchanger.

Scale adherence may deteriorate the heat exchange efficiency of the primary heat exchanger and furthermore the water heater may have troubles when such adherence phenomenon becomes prominent.

Therefore, detection of the scale adherence in the primary heat exchanger becomes difficult.

Therefore, in the conventional art, it is difficult to improve detection accuracy of scale adherence and there is a room for improvement.

In addition, it is difficult to accurately detect scale adherence in the conventional art when only a part of water having passed through the secondary heat exchanger is supplied to the primary heat exchanger.

However, there is a fear that the primary heat exchanger may have exhaust clogging (fin clogging).

Exhaust clogging is caused when soot in combustion gas adheres to a plurality of fins provided with the heat transfer tube of the primary heat exchanger and accumulates thereon, thereby causing breakdown.

In the conventional art, it is difficult to exactly detect exhaust clogging of the primary heat exchanger at high accuracy like the case of scale adherence.

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