Munchkin Heat Exchanger Maintenance

Transcription

1 Munchkin Heat Exchanger Maintenance By: Mike Granahan *Refer to the appropriate boiler manual for your specific model number. Adjustment procedures will vary. Boiler shown below is an HTP Munchkin 80M REV 1 w/ Dungs Gas Valve. Unit has been in use for 3 yrs without being serviced. Customers perform the tasks described in this document at their own risk. Standard Air & Lite does not assume liability for damage to equipment or personnel by providing these instructions. Munchkin Heat Exch. Maint Page 1 of 15 v1/13/13 by M. Granahan

2 1. Turn off power supply to unit & close gas supply. Apply lockout tag on circuit breaker if required. Remove 4 allen screws from gas valve block. Unplug wiring harness from gas valve. Munchkin Heat Exch. Maint Page 2 of 15 v1/13/13 by M. Granahan

3 2. Remove line voltage plug & low voltage plug from inducer motor. Munchkin Heat Exch. Maint Page 3 of 15 v1/13/13 by M. Granahan

4 3. Unplug high voltage spark cable & flame sensor wires. Route away from burner plate. Munchkin Heat Exch. Maint Page 4 of 15 v1/13/13 by M. Granahan

5 4. Remove securing fasteners from control board backing plate & lift assembly & wiring harness away from the burner gun assembly. Use caution not to break wires. Then remove all (6) 10MM nuts on the front of the burner plate. Gently hold the gas valve block in a downward position while gently pulling the entire assembly away from the heat exchanger. Munchkin Heat Exch. Maint Page 5 of 15 v1/13/13 by M. Granahan

6 5. Set burner gun aside paying careful attention not to damage the refractory or electrodes. Observe any damage or a water line present on the rear target wall. As observed above, this would be a normal example not in need of replacement. Munchkin Heat Exch. Maint Page 6 of 15 v1/13/13 by M. Granahan

7 6. Avoid removing the rear target wall during cleaning. Also avoid getting it wet with cleaners or plain water. Rather cover it with a lid or piece of plastic cut from scrap. The diameter will be the same for all models of Munchkin / Contender / Elite. Munchkin Heat Exch. Maint Page 7 of 15 v1/13/13 by M. Granahan

8 7. Use a chemical recommended by HTP (CLR or RYDLYME), source locally a set of plastic bristle brushes. Avoid using steel, brass, stainless, or copper brushes. This will score the stainless tubes and accelerate the corrosion process of the heat exchanger. Munchkin Heat Exch. Maint Page 8 of 15 v1/13/13 by M. Granahan

9 8. Hold your cover in place to protect the target wall. Apply the cleaning solution full strength using a spray bottle and brush the deposits loose. For severely dirty heat exchangers, a credit card inserted thru each coil space will free the deposits and allow proper draining. Flush with plenty of water after using the cleaning chemicals. The water / cleaning solution will simply flow out the condensate drain. Verify the water flow is adequate thru the complete condensate system, including external piping. If it is insufficient, allow a longer soak period of the chemical at full strength, or disassemble the condensate trap / piping for a more thorough cleaning. Munchkin Heat Exch. Maint Page 9 of 15 v1/13/13 by M. Granahan

10 9. When finished cleaning, the heat exchanger coils should be free of deposits. Observed above shows some general stains which are considered normal and do not require further cleaning. Avoid using additional chemicals used for brightening metals. Munchkin Heat Exch. Maint Page 10 of 15 v1/13/13 by M. Granahan

11 10. Inspect the flame sensor, igniter, burner flange, and the refractory. Do not attempt to clean a knit wrapped burner as picture above. If burner is plugged or knit wrapping is damaged / delaminating, replace as needed. Munchkin Heat Exch. Maint Page 11 of 15 v1/13/13 by M. Granahan

12 11. Clean the flame sensor & igniter probe with a piece of scotch brite. Avoid using emery cloth or sand paper. Replace if damaged. Munchkin Heat Exch. Maint Page 12 of 15 v1/13/13 by M. Granahan

13 12. Inspect the swirl plate for erosion, or on REV1 Honeywell valve equipped units, inspect the venturi plastic for decomposition, flaking, or erosion. Replace as needed. These parts are model specific. Assembly is in reverse order. MAKE SURE TO REMOVE YOUR PLASTIC TARGET WALL COVER BEFORE INSTALLING BURNER GUN! Snug the (6) 10MM nuts in a cross directional pattern & torque to value specified by HTP. After completing reassembly, open gas supply & check for leaks on the gas valve block and field installed shutoff valve (ball valve). After you have verified there are none, remove lockout tags (if used), turn power supply back on. Munchkin Heat Exch. Maint Page 13 of 15 v1/13/13 by M. Granahan

14 13. Perform a combustion analysis to verify proper operation. Refer to your combustion analyzer documentation for specific procedures. Initiate a call for heat and enter the test mode by pressing S2/+ and S3 buttons together for 1 second. When Ser is shown on the display, press S2/+ until maximum inducer RPM is heard and shown on the display. To avoid fouling your analyzer, insert combustion probe ONLY AFTER the combustion has stabilized NEVER DURING LITE OFF!!!!!!!! As shown above 76ppm CO and 8.4% CO2 is within acceptable parameters. No adjustment is needed. 12. Press S1/ until minimum inducer RPM is heard and shown on the display. Observe combustion reading after meter has stabilized. As shown above 52ppm CO and 8.7% CO2. CO is showing slightly above spec but was falling slowly. CO2 is within 8.5 ~ 9.5 so in this case adjustment is not needed. CO continued to fall but boiler was approaching its maximum temp. Boiler will exit after 10 min, or if Munchkin Heat Exch. Maint Page 14 of 15 v1/13/13 by M. Granahan

15 it reaches max temp. To exit manually, press and hold S1/ and S2/+ together for 1 sec. In observing the heat exchanger cleanliness after a 3yr usage we decided to not make any adjustments. After performing a combustion analysis, make sure to install proper plugs in the sampling hole(s) prior to leaving jobsite! Munchkin Heat Exch. Maint Page 15 of 15 v1/13/13 by M. Granahan