FI62612C - ANORDINATION FOR TEMPERATURBEGRAENSING IN CHANNELS - Google Patents

Description

I'rSw'l Γβΐ ^ ADVERTISEMENT, 0 s>, 0 TO&A [B · * (11> UTLÄGGN I NGSSKRIFT 6/6 1 2 C Patent granted 10 01 1033 (^ Ffctent meaöelat (51) Kr.lk.Vc.3 H 05 B 1/02, F 24 H 9/20 FINLAND-FINLAND (21) ρ · * · "* ·" · βι »η | η« 77311 ^ (22) H ^ lwmtepilvt - Antekiilngadag 20.10.77 (FI) (23) AlkupUvft — GIMgh «i4« c 20.10.77 (41) Become Public - Graters off * ntll | 30.0 ^ .78

Patent and Register Management (44) Date of Issue and Registration - 30.0Q.82

Patent- och registerstyrelsan 'Ansökan utlijd och utl.skrlftan publlcared (32) (33) (31) found privilege — Rafird prlerltat 29.10.76 21.0¾. 77 Sweden -Sverige (SE) 76120 ^ -3, 770I1581-3 (71) Backer Elektro-Värme AB, 280 10 Sösdala, Sweden-Sweden (SE) (72) Algot Danielsson, Hässleholm, Kjell Elofsson, Hässleholm, Sweden-Sweden (SE) (7¾) Berggren Oy Ab (8¾) Device for limiting the temperature of a duct heater grain - Anordning för temperaturbegränsning vid kanalvärmare

The present invention relates to a device for limiting the temperature of duct heaters.

Duct heaters, which are used to ventilate the air to workrooms and the like before entering the rooms by means of a fan from outside, usually comprise a battery consisting of thermocouples and metal lamellae arranged transversely to the thermocouples in a heat-transferring manner so that the air absorbs heat from the lamellae directly from the heating elements themselves) as they flow between them. Normally, duct heaters have a temperature limiter (thermostat), the automatic reset of which is connected to the circuit of the contactor coil of the heating elements and which determines the normalized heat transfer in the testing of the duct heaters. According to the regulations, they must also have a temperature limiter without automatic reset, in which case this limiter acts as a protection device in case of catastrophe, ie overheating protection that prevents the lamella temperature from exceeding a certain value, as could happen if, for example, the fan stops due to a motor fault or air duct blockage in addition, the temperature limiter equipped with automatic reset would be short-circuited and thus inoperable.

With known overheating protectors, which operate depending on the temperature of the heating elements and / or lamellae, it can be difficult to control a large battery with several groups and several heating elements, so that the temperature at no point in any lamellae exceeds the permissible value. Therefore, an attempt has been made to find another solution to the problem of securing the heating batteries of duct heaters against overheating in the event of a disaster.

The basic idea of the present invention is to provide the temperature limitation required in catastrophic cases in duct heaters with thermocouple and lamella batteries of any size by means of an overheating protection located in a single location of each battery. Accordingly, the invention relates to a device for limiting the temperature in duct heaters adapted to conduct a fan-fed air flow to a workroom or the like, comprising a battery for heating the air flow, consisting of electric heating elements and preferably also metal lamellaes arranged transversely therewith. for overheating protection with thermal element contactor coil with temperature limiter connected in series without automatic reset. This device is mainly characterized in that an auxiliary heating element with a low heat capacity compared to the battery heating elements is connected in series with the temperature limiter without automatic reset and in parallel with the contactor coil of the heating elements and is arranged in the duct heater so that the air flow is not in contact lamellae, where they exist, and that it is adapted to a temperature limiter without automatic reset so that it closely follows the temperature of the auxiliary heating element to trip when this temperature reaches a certain maximum value before the heating elements of the battery overheat.

The device according to the invention having the above-mentioned general features can be implemented in various embodiments, the specific features of which are set out in the subclaims.

6261 2

The invention will be explained in more detail below with reference to the accompanying drawings. Figure 1 shows a switch diagram of a duct heater provided with a first embodiment of the device according to the invention. Figure 2 shows a switch diagram of a duct heater provided with a second embodiment of the device according to the invention. Fig. 3 shows a switch diagram of an electronic thermostat used in the device according to Fig. 2. Figure 4 shows a switch diagram of a duct heater provided with a third embodiment of the device according to the invention. Fig. 5 shows a longitudinal section of a truncated part of the sensor, in which a resistance coil is wound around the sensor and is intended for use in the temperature limiter and thermostat unit of the device according to Fig. 4. Fig. 6 shows a switch diagram of a duct heater provided with a fourth embodiment of the device according to the invention. Fig. 7 shows a longitudinal section of a part of the sensor and the resistance coil of the temperature limiter and thermostat unit of the device according to Fig. 6. In Figures 1, 2, 4 and 6, the same reference numerals are used throughout for the same parts.

The device according to the invention is primarily intended for use in duct heaters consisting of a plurality of horizontally and spaced superimposed, parallel tubular heating elements and a plurality of vertically, i.e. directly spaced, metal-to-tubular heating elements directly connected to the tube heating elements. During operation, a fan-driven air stream flows through the battery made of tubular heating elements and metal lamellae, which then heats up before entering the study room or the like. Duct heaters adapted as described herein, with an automatic reset temperature limiter adapted to the heat transfer connection with the battery to determine the normalized heat transfer from the battery, are generally known. They are not explained in more detail below, nor are they shown in the drawings.

However, as already stated in the introduction to this description, duct heaters must have a temperature limiter without automatic reset, in which case the limiter is set to operate in the event of a catastrophe with a maximum permissible value. In contrast to the prior art, the device according to the invention provides that a single 4 6261 2 temperature limiter acting as an overheating protection without automatic reset operates depending on the temperature rise of the auxiliary heating element, the auxiliary heating element being arranged in the duct heater. However, the auxiliary thermocouple is not in heat transfer communication with the metal lamellae of the battery at the locations where these lamellae are present. In addition, since the auxiliary heating element has a low heat capacity compared to the heating elements of the battery, it reaches a certain maximum temperature before the latter. This ensures that the thermal power is switched off before the heating elements of the battery overheat, and in particular in such a way that an unacceptably high temperature cannot occur even at a point of the lamellae which is relatively far from the overheating protection. In addition, this device has the advantage that after the fan motor and the battery are switched off at the same time - the temperature of the latter lamellae still rises due to the already stored heat, as will be explained below - the limiter temperature no longer rises, so that this temperature limiter (with manual reset) standardized heat transfer and no temperature limiter with automatic reset is therefore required.

Only those components that are necessary for understanding the effect of the overheating protection are included in the circuit diagram of Figure 1. The circuit which passes through the phases R and 0 of the three-phase network and is connected in parallel with the fan motor contactor coil 1 and thus connected in series with the motor contactor holding contact 1a is connected in series without automatic reset (but with manual reset) and heating elements 3 contactor coil and thermostat 5 with closing function. An auxiliary heating element 6 is connected in parallel with the contactor coil 4 and the thermostat 5, which has a low heat capacity compared to the heating elements 3 and which, unlike these, is not in thermal contact with the metal lamellas of the duct heater. The temperature limiter 2 and the thermostat 5 are each placed in good heat transfer contact with the auxiliary heating element 6, suitably so as to form a temperature limiter unit with it. As an example of the structure of this unit, the auxiliary heating element 6 may be a tubular heating element and the temperature limiter (overheating protection) 2 may comprise a sensing element placed next to or inside the helically wound resistor wire of the element, adapted to act on the outside of the tubular element. The thermostat 5 can be adapted accordingly. Thus, when the element 6 heats up quickly due to its low heat capacity when the fan-motor contactor is connected, the temperature limiter 2 and the thermostat 5 can follow the temperature rise of the element with little omission. When the predetermined temperature is reached, the thermostat 5 closes and thus allows current to be supplied to the contactor coil 4 (provided that the room thermostat 7 is closed) so that the contactor switches on and off the duct heater thermocouples 3. If no malfunction, eg fan motor stop, then operates in such a way that the heating elements transfer heat to the air flowing through partly directly, partly indirectly via metal lamellae under the control of a room thermostat 7.

If, for example, the fan stops or the air duct becomes blocked, the duct heater temperature will of course start to rise. If the duct heater is now equipped with a temperature limiter with automatic reset in a known manner, and if this temperature limiter is operational, it takes care that the power to the heating elements 3 is switched off. However, if such a temperature limiter did not exist or if it had been short-circuited and thus become inoperable, which corresponds to a catastrophic case, the temperature will rise continuously. In this case, the temperature limiter 2 without automatic reset starts to operate due to the temperature rise of the auxiliary heating element 6 and limits the temperature rise of the duct heater to the maximum permissible value, e.g. 150 ° C. The temperature limiter 2 is adjusted to turn off the contactor coil 4 of the heating elements 3 (simultaneously switching off the auxiliary heating element) early before the temperature of the lamellae has reached this value, since after cutting off the temperature In the event of a possible fault in the auxiliary heating element 6 or its connection lines or contacts, in which case there is no temperature rise, the thermostat 5 is not closed and therefore no current is supplied to the contactor coil 4. Therefore, the heating elements 3 of the duct heater cannot be connected at all. This ensures that no overheating of the heating elements or metal lamellas can occur, regardless of the fact that the overheating protection (temperature limiter) 2 cannot then start to operate.

6261 2 6

The circuit diagram of Fig. 2 is basically similar to that shown in Fig. 1, since the temperature limiter 2 and thermostat 5 of Fig. 1 correspond to two electronic thermostats 8 and 9, each having its own thermistor 10 and 11, respectively, arranged in heat transfer contact with the auxiliary heating element 6. The auxiliary heating element 6 and these thermistors 10 and 11 suitably together form a temperature limiter unit with connections to the duct heater power supply network and thermostats 8 and 9. These electronic thermostats 8 and 9, represented by the block symbols in Fig. 2, are known and similar in structure, as shown in detail in the switch diagram of Figure 3. The thermistor 10 connected to the inlet 12 of the thermostat 8 is assumed to have a positive temperature coefficient, while the thermistor 11 connected to the inlet 13 of the thermostat 9 is assumed to have a negative temperature coefficient. Before starting the duct heater, the resistance of the thermistor 10 is low, which means that the thermostat 8, the output 14 of which is connected in series with the contactor holding contact 1a and the contactor coil 1, is conductive through this output. The connection of the contactor can therefore take place, in which case, in addition to starting the fan, power is applied to the auxiliary heating element 6 with a low heat capacity and it heats up quickly. When the auxiliary heating element has reached a predetermined temperature corresponding to the normal operating state of the duct heater, the resistance of the thermistor 10 has increased, but not more than that the thermistor is still conductive through its output 14. At this temperature there is a thermistor 11, the resistance of which was initially so high that the thermostat 9 was not conductive through its output, on the other hand, received a lower resistance, as a result of which this thermostat becomes conductive through its output 15. As a result, the circuit to the contactor coil 4 is closed and the heating elements 3 of the duct heater are switched on, whereby a normalized heat transfer is obtained.

In the event of a catastrophe, so that the temperature of the auxiliary heating element 6 rises to the maximum allowable value, the resistance of the thermistor 10 becomes so high that the thermostat 8 becomes non-conductive through the output 14, interrupting the holding circuit of the fan motor contactor. When the holding contact 1a is therefore disconnected, not only is this contactor switched off, but also the power to the heating elements 3 and the auxiliary heating element 7 6 2 61 2 6 of the duct heater is switched off. As a difference from the connection according to Fig. 1, the hold contact 1a thus also acts as a cut-off contact for the overheating protection. This has the advantage that the connection of the duct heater after disconnection due to high temperature can take place in the same way as in normal start-up, without the need to retrieve the duct heater. If a fault occurs in the auxiliary heating element 6 or in the associated control and connection elements, the duct heater heating elements 3 cannot be connected as in the connection of the figure, because the thermistor 11 controlling the electronic thermostat 9 does not reduce its resistance so that the thermostat can become conductive through its output 15.

The connection of the electronic thermostats is suitably selected so that a fault in one of the wires leading to the thermostats makes it impossible to connect the heating elements 3. Such a connection can be obtained if thermistors with a positive and a negative temperature coefficient, respectively, are selected as the thermistors 10 and 11, as shown here.

The switch diagram of Figure 4 is approximately similar to that shown in Figure 1. It should be noted, however, that the closing and disconnecting contacts of Fig. 1 for switching the duct heater on and off and the holding contact of the fan motor contactor are omitted, while the circuit breaker 16 for connecting and disconnecting the duct heater is connected from phase R to the temperature limiter 2. As a result, the switching step of the duct heater start-up and the disconnection step when the temperature limiter starts to operate differ from the corresponding steps of the duct heater of Fig. 1, as will be explained later.

The temperature limiter 2 schematically shown in Fig. 4 comprises a housing 17 surrounding a normally closed circuit breaker member 18 and a sensor 19 for switching this member at a predetermined temperature, e.g. at about 150 ° C, consisting of a liquid-filled metal capillary tube connected to the housing 17. For manually resetting the circuit breaker member 18 to the closing state, the temperature limiters are provided with a pressure pin 20 or the like. Such a temperature limiter acting as an overheating protection is known per se and is commercially available. The thermostat resembles a temperature limiter 2 in terms of structure, as it comprises a housing 21 surrounding a circuit breaker member 22 and a sensor 23 acting on this circuit breaker member, consisting of a liquid-filled metal capillary tube connected to the housing 21. However, since the thermostat 5 will have a closing function, the circuit breaker 22 is normally switched off, and the sensor 23 closes it when the temperature has risen to a predetermined value, which can be selected to be e.g. about 75 ° C, and switches it off again when cooling is occurred at a slightly lower temperature, e.g. about 55 ° C.

The auxiliary heating element 6 is in heat transfer contact with both sensors 19 and 23. For this purpose, it is assembled from two resistor coils 24 and 25 connected in series, each of which is wound on its own sensor. Figure 5 shows the method of winding resistance coils used in practice. Immediately on top of the sensor (capillary tube) 26 is a shrink tubing 27 made of a suitable insulating material. Such materials are commercially available, e.g. under the trade names Teflon or Kynar. The shrink tubing is heated so that it is tightly confined to the sensor. A pre-wound resistance coil 28 is threaded over the shrink tubing 27, and one end thereof is soldered to the free end of the sensor outside the end of the shrink tubing. A connection cable is soldered to one end of the coil, which runs to the circuit breaker member in the housing of the temperature limiter 2 and the thermostat 5, as shown in the circuit diagram of Fig. 4. The second shrink tubing 29 is threaded onto the resistance coil 28 (and over a portion of the connection cable (not shown)) and shrinked thereto by heating. In the structure of the sensors and the auxiliary heating element described herein, the series of resistance coils 24 and 25 forming this heating element are connected in series by a wire 30 soldered to the sensors close to their point of attachment to the housings 17 and 21.

The switch diagram of Fig. 6 is completely similar to the switch diagram of Fig. 4, but the temperature limiter and thermostat unit, which has the structure shown in Fig. 7 and described below, is shown more schematically in connection with this structure.

Fig. 7 shows a longitudinal section of a long steatite body 31 of suitably circular cross-section, acting as a jacket and support for the resistance coils 6261 2 of the temperature limiter 2 and the thermostat 5 and the auxiliary heating element. It has four longitudinal channels symmetrically arranged in a symmetrical manner. The resistance coils 32 are arranged in two opposite channels, i.e. in a diametrically plane channel. These are connected to each other at one end and have terminals 33 at the other end for series connection to the auxiliary heating element circuit. The sensors 34 and 35 of the temperature limiter 2 and the thermostat 5 are arranged in the third and fourth channels, which are located perpendicular to the diametrical plane opposite the first. The steatite body 31 is attached to a holder 36 made of insulating material at its end, where the terminals 33 of the resistance coils 32 are located. and 35 come out for connection to housings 37 and 38 surrounding circuit breakers 39 and 40 (see Figure 6). In Fig. 7, the steatite body is shown surrounded by the jacket tube 41 up to the holder 36. It terminates in an insulating plug 42 at the free end of the jacket tube, but the latter may be omitted (whereby the channels of the steatite body may each be closed by its own end plug).

Referring to the circuit diagram of Fig. 4, the start-up phase of the duct heater and the shutdown phase under the influence of its temperature limiter (overheating protection) will be explained below. The same steps take place in the duct heater according to the switch formula of Fig. 6, so they do not need to be explained separately.

The duct heater is connected by closing the manual circuit breaker 16. In this case, current flows from phase R over the closed circuit breaker 18 of the temperature limiter (overheat protection) 2 via the auxiliary heating element 6, i.e. through each resistor coil 24 and 25 connected in series. When the element 6 has heated the sensor 23 of the thermostat 5 to a certain temperature, e.g. 75 ° C, the thermostat is switched on (the circuit breaker 22 is closed), passing current through both the contactor coil 1 of the fan motor and the contactor coil 4 of the thermocouple battery 3. and the battery is connected simultaneously as a difference from the connection according to Fig. 1, in which the fan motor starts immediately when the duct heater is switched on, regardless of the closing of the thermostat 5, but the thermal

Claims (14)

1. A temperature limiting device for duct heaters, which is arranged for introducing a fan-driven air stream into a work room or the like and which for heating the air stream comprises a battery of electric heating elements (3) and preferably also transversely thereto. heat transfer connection therewith provided with metal enamels and is equipped with a temperature limiter (2) connected to the heating element (3) contactor coil (4) with no automatic return, in series with the overheating protection, characterized in that in series with the temperature limiter (2) without automatic recoil and parallel to the contactor coil (4) of the heating element (3), an auxiliary heating element (6) is provided which has a low heating capacity in relation to the heating elements (3) in the battery and is so arranged in the duct heater that is set for the air stream but is without heat contact with the slats, where the seeds are located, and is so arranged in relation to the temperature limiter (2) without automatic is that it closely follows the temperature of the auxiliary heating element (6) to trigger, when this temperature reaches a set maximum value, before the heating elements (3) in the battery become overheated. 2. Device according to claim 1, characterized in that the auxiliary heating element (6) is placed in contact with the temperature limiter (overheat protection) (2), in order that it can follow the temperature of the auxiliary heating element with a small temperature difference. 3. Device according to claims 1 and 2, characterized in that the auxiliary heating element (6) is a tube heating element and that the overheating protection (2) has a sensing body inserted into the element's insulating material adjacent to or inside the spiral-wound resistance tree, which is arranged to affect the overheating protection. switch heating element located switch means. 4. Apparatus according to claims 1 and 2, characterized in that the auxiliary heating element (6) is connected in parallel with the contactor coil (4) of the heating element (3) and a thermostat (5) with closing function in series with each other, said thermostat ( 5) is positioned in relation to the auxiliary heating element (6), that when connected to the auxiliary heating element it is heated by it and closes upon reaching a predetermined temperature, so that the contactor coil (4) can supply current for connecting the heating element of the duct heater (3). this temperature. 5. Device according to claims 1 and 2, characterized in that the temperature limiter without automatic return is formed by an electronic thermostat (8) of a kind known per se, together with a thermistor arranged in close contact with the auxiliary heating element (6). (10), upon reaching the set maximum temperature of the auxiliary heating element, causes the thermocouples (8) to break the power to the heating element (3) of the duct heater. Device according to claim 5, characterized in that the thermistor (10) is of the kind having a positive temperature coefficient. 15 6261 2 Device according to claims 1, 2 and 4, characterized in that the thermostat with closing function is formed by an electronic thermostat (9) of a kind known per se, together with a temperature sensor in close contact with the auxiliary heating element (6). provided thermistor (11) which, upon reaching the predetermined temperature, causes the thermostat (9) to close the circuit to the contactor coil (4). 8. Device according to claim 7, characterized in that the thermistor (11) is of the kind having a negative coefficient of temperature. Device according to claims 5 ... 8, characterized in that the auxiliary heating element (6) and the thermistors (10 and 11) are connected to a unit with their respective connections to the duct heater's power supply network and to the two electronic thermostats (8 and 9). Apparatus according to claims 1 and 2, characterized in that the temperature limiter (2) comprises a housing (17) which encloses a normally closed switching means (18), and this means at a predetermined temperature breaking sensing body (19) in the form of a fluid-filled capillary tube connected to the housing, and that the auxiliary heating element (6) is constituted by a resistance coil (24) extending along the sensing body (19) in heat transfer contact therewith, the resistance coil being wound outside of a sensing body tightly enclosing 27 of insulating material and itself tightly enclosed by a second crimp hose (29) of insulating material. Device according to claim 10, comprising a thermostat (5) with a closed function, characterized in that this thermostat (5) comprises a housing (21) which encloses a normally broken switching means (22), and this means upon reaching a a predetermined operating temperature closing sensing body (23) in the form of a fluid-filled capillary tube connected to the housing (21), the auxiliary heating element (6) being composed of two series-coupled resistor coils (24 and 25), each wound outside a respective sensing body ( 27) and itself tightly enclosed by a second shrink tubing (29).