Junkers Euromaxx ZWC28-1MF2K PCB · 8748300455

It is the control board of the boiler: it manages the ignition, modulation, and safety features. It is suspected when the boiler does not ignite, does not respond to the panel, restarts by itself, or displays fault codes that do not match the fault.

Type of part: Junkers
Status: Refurbished
internal SKU: PLC253
Warranty: 1 year

VAT included Stock · 2 units

Compatibility

Compatible Junkers boilers

Junkers. A proven compatibility: Junkers Euromaxx ZWC28-1MF2K.

Proven compatibility

Boiler model	Family	Verification
Junkers Euromaxx ZWC28-1MF2K	Junkers	Contrasted

Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.

Guide

How to check if it is the part for your boiler

The part reference, model, and equipment revision must be verified against the manufacturer's documentation.

Look at the PCB: it should have 8 748 300 printed and 465 written by hand. In our technical sheet, the complete code is 8748300455.
Compare the models 1274-BF, 0251PY004, and HTII-3, the relay RT314024, and the protective screen T3.15A.
Do not rely solely on the prefix 8 748 300 or HTII-3: the official lists mention other PCBs (454, 506; the 533, in an unassigned column 2892 not securely assigned to the ZWC28-1MF2K) and a different HTII-3 is from the -6 series. Compare the complete code.
Check on the rating plate that your boiler is a Junkers ZWC28-1MF2K.
If they match, call us at 911 17 77 77 with your boiler model and we will confirm if we have it.

Diagnosis and fault codes

Symptoms that require diagnosis in the junkers

Common symptoms and faults

01
Fault code F0: internal error of the PCB.
Cause: The official technical manual from Bosch 6720607122 indicates to replace the PCB. Have a technician confirm it before changing it.
02
Fault code F7: false ionization signal
Cause: The same manual lists ionization, the PCB, and moisture on the board as causes.
03
The boiler does not ignite, restarts or turns off by itself, or shows erratic faults.
Cause: Symptoms associated with the PCB of this boiler. Check the power supply and fuses first.
04
The display shows F0 and the boiler locks out.
Cause: Internal fault of the PCB. The boiler remains locked until the reset is pressed.
Note the fault code and reset the boiler. Have a technician confirm the fault and replace the PCB.
05
The display shows F7 and the boiler locks out.
Cause: False ionization signal. Possible causes are ionization, the PCB, or moisture on the board.
Check the ionization and if there is moisture on the PCB before replacing it. Have a technician confirm it.

Junkers fault codes that require diagnosis

Code	Fault	Technical checks
F0	Internal fault of the PCB. Boiler lockout until reset.	Replace the PCB. Have a technician confirm it before changing it.
F7	False ionization signal. Boiler lockout until reset.	Possible causes: ionization, PCB or moisture on the board. Check the ionization and moisture before replacing the board. Have a technician confirm it.

These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.

Technical data

Technical sheet: Junkers

Uniclima internal SKU: PLC253
Brand: Junkers
Type of part: Junkers
Units in stock: 2 units
Status: Refurbished
Warranty: 1 year
Shipping: Delivery time shown at checkout
Return: 14 days

Part data and available documentation

Contrast the label codes, PCB, and revision with the installed part; they are not necessarily equivalent references.

Protection screen printing: T3.15A
Inventory — Subcomponent relay: RT314024
Inventory — Subcomponent fuse: F2.5A
Inventory — Subcomponent condenser: 470nM
Inventory — Application indicated in inventory: ZWC28-1MF2K
Inventory — Marked code: 1274-BF; 0251PY004; HTII-3; BB BA BG
Printed PCB silkscreen: 8 748300
Handwritten suffix on PCB: 465
Stock code: 8748300455
Identification — Printed PCB silkscreen: 8 748300
Identification — Handwritten suffix on PCB: 465
Identification — Code on bag: 8748300455
Identification — Marked code: 1274-BF; 0251PY004
Identification — Marked code: HTII-3; BB BA BG
Technical sheet: Protection screen printing: T3.15A
Inventory data — Subcomponent relay: RT314024
Inventory data — Subcomponent fuse: F2.5A
Inventory data — Subcomponent condenser: 470nM
Inventory data — Application indicated in inventory: ZWC28-1MF2K
Inventory data — Marked code: 1274-BF; 0251PY004; HTII-3; BB BA BG
Additional markings: CI NEC JAPAN: D1274 BF / 0251Y00. Relay: RT314024. Fuses: F2.5A and T3.15A. Capacitor marked 470nM (literal reading). Other codes: 1274-BF; 0251PY004; HTII-3; BB BA BG. PCB base 8 748 300 and handwritten suffix 465. Bag code: 8748300455.
Pending applications to verify: ZWC28-1MF2K — compatibility noted; pending confirmation by variant.

Before purchasing

F0 and F7 are listed in the official manual table 6720607122, which the official Bosch sheet links to the ZWC28-1MF2K23S2892. Check the code in your boiler's manual.
Not compatible or excluded at source: Junkers ZWSE-4 — A distributor assigns another PCB: 8748300506
Not compatible or excluded: Junkers ZWN18-6AE21 and ZWR24-6KE31 (series -6) — they use the PCB HTII-3 GZT3: 87483005540
Do not confuse: 8 748 300 454 — PCB from the official Bosch list 6720611196 (ed. 02.10), which covers ZWC24/28-1MF2K — Another code: differs in the last digit. Do not consider them the same.
Do not confuse: 8 748 300 506 — Official list plate 6720611196 (ed. 05.08) and 6720611197 — Another plate code from the same family.
Do not confuse: 8 748 300 533 — PCB from the official Bosch list 6720611196 (ed. 05.08), in a column marked 2892 not assigned to the ZWC28-1MF2K — Another PCB code from the same family.
Do not confuse: 8 748 300 449 — PCB from the J 1455 list of the ZWC24/28-1MFK — Another model (MFK) and another code
Do not confuse: 87483005540 — HTII-3 GZT3 PCB from the ZSN/ZWN/ZWR/ZSR -6 series (German) — It also carries the HTII-3 brand, but it is from a different series and has a different code.
without additional external confirmation read quote 8748300455. The official lists of the family provide other PCBs (454 and 506); the 533 appears in a column marked 2892 of the list 6720611196 (ed. 05.08) that we cannot confidently assign to the ZWC28-1MF2K. Always compare the printed code.
Part, codes, and boiler confirmed. Without additional external confirmation, read quote 8748300455 (external level 0); the official lists provide other PCBs (454 and 506) and a 533 in a column marked 2892 from list 6720611196 (ed. 05.08) that we cannot confidently assign to the ZWC28-1MF2K.

Frequently Asked Questions

Frequently asked questions: junkers

How do I identify the Junkers 8748300455 PCB?

Look at the PCB: it is printed with 8 748 300 and handwritten 465. In our technical sheet, it is listed as 8748300455 and has the markings 1274-BF, 0251PY004, and HTII-3, the relay RT314024, and the silkscreen T3.15A. Compare those codes with those on your board.

Is it compatible with my Junkers ZWC28-1MF2K?

Yes: Confirmed: for the ZWC28-1MF2K. Without additional external confirmation, reference 8748300455 is read, so the confirmation is from the workshop. The official Bosch sheet for the ZWC28-1MF2K23S2892 (art. 7 716 704 133) sets its production between 01.09.2002 and 31.07.2007 and links to the spare parts list 6720611196.

Is it the same as 8 748 300 454, 506 or 533?

Do not take it for granted. The official Bosch spare parts lists for the Euromaxx ZWC 24/28 mention the PCB as 8 748 300 454 (list 6720611196, ed. 02.10) and 8 748 300 506 (6720611196 ed. 05.08 and 6720611197). The list 6720611196 ed. 05.08 also provides 8 748 300 533, in a column marked 2892 that we cannot confidently assign to the ZWC28-1MF2K. The 8748300455 does not appear in them. Compare the printed code or send us a photo from Contact.

What do the codes on the PCB mean?

The printed circuit boards from the official Bosch lists for this family carry codes 8 748 300 xxx: the silkscreen 8 748 300 is not enough, the complete code must be compared. 1274-BF, 0251PY004, and HTII-3 are markings on the board that explain without additional confirmation. HTII-3 also appears on the board 87483005540 (HTII-3 GZT3) from series -6, so it does not identify it by itself.

Is it compatible with other Euromaxx models like the ZWC24-1 or the ZWC28/32?

It is only confirmed for the ZWC28-1MF2K. Also listed are ZWC24/28-1MFA, ZWC24/28-1MFK, and ZWC28/32-1MFA for its PCB, but without providing a code, so we cannot assert that it is the same part.

What do faults F0 and F7 indicate in this boiler?

The official technical manual of Bosch 6720607122 (Euromaxx / Aquastar ZWC 28 AE and KE), linked in the official sheet of the ZWC28-1MF2K23S2892, indicates F0 as an internal fault of the PCB (replace the board) and F7 as a false ionization signal (ionization, board or moisture on the board). Have a technician confirm it.

Who should install it?

To confirm: A qualified technician. The official Bosch lists indicate that spare parts can only be installed by an authorized installer, and the PCB is located behind the front panel, in the control box, with electrical risk.

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Junkers Euromaxx ZWC28-1MF2K PCB · 8748300455