Flushing/Descaling The Heat Exchangers - andrews MAXXflo EVO CWH 150/302 Installation And Maintenance Manual

6.3 FLUSHING/DESCALING THE HEAT EXCHANGERS

A fl ushing kit (P/N 7800417) is available from Andrews Water Heaters. This kit
enables easier connection directly onto the heat exchanger and speeds up
descaling. Follow the instructions provided in the kit.
CAUTION
Operation of the burner during the de-scaling process is not recommended, as this could result
in damage to the heat exchanger.
Maintenance
Flushing procedure (twin heat exchanger models)
CAUTION
Protect electrical components from water
note: see page 1 for single heat exchanger models.
contact during the procedure.
1. Before commencing, isolate the Mains Cold Water supply, the
E Domestic Hot Water (DHW) FLOW, the Domestic Hot Water SEC-
C
ONDARY RETURN, GAS & POWER to the heater.
2. To gain access to the heat exchangers remove the door and inner
cover. (refer to section 4.2 of the installation and maintenance
manual).
3. Isolate the top heat exchanger (K) and drain off water using hose
drain off points (L).
4. Remove the 1" top heat exchanger Flow and Return pipework, and
attach the 2 x Flushing connectors (A), and fi bre seals (B) to the
Flow and Return connections of the top heat exchanger (M).
5. Attach the fl ushing device hoses (G) to the 22mm copper tails (A)
J
using suitable fi ttings (not supplied).
6. Flush and descale the heat exchanger using chemical and fl ushing
device suitable for potable water.
M
7. When completed, fl ush with clean water and then remove fl ushing
B2
connectors (A) and retain fi bre seals (B).
8. Inspect original fi bre seals for damage and replace if necessary
L
with spare fi bre seals supplied in fl ushing kit (B). (The part number
to reorder spare fi bre seals is: 7720038)
Q1
9. Re-attach the Flow and Return pipework to the top heat exchanger
K
(M) with fi bre seals placed between the fl at faces.
10. Close drain off points (L) and Open isolation valves (K) checking
Q
for leaks.
B2
11. Repeat process for the lower heat exchanger by isolating (N) and
draining water from lower heat exchanger using hose drain off
points (P).
N
12. Remove the 1" lower heat exchanger Flow and Return pipework,
and attach the 2 x Flushing connectors (A) and fi bre seals (B) to
the Flow and Return connections of the lower heat exchanger (Q).
P
13. Attach the fl ushing device hoses (G) to the 22mm copper tails (A)
using suitable fi ttings (not supplied).
Q1
14. Flush and descale the heat exchanger using chemical and fl ushing
device suitable for potable water.
15. When completed, fl ush with clean water and then remove fl ushing
connectors (A) and retain fi bre seals (B).
16. Inspect original fi bre seals for damage and replace if necessary
with spare fi bre seals supplied in fl ushing kit (B). (The part number
to reorder spare fi bre seals is: 7720038)
17. Re-attach the Flow and Return pipework to the lower heat ex-
changer (Q) with fi bre seals placed between the fl at faces.
M OR Q
18. Close drain off points (P) and Open isolation valves (N).
19. Check for leaks and open Mains Cold Water supply, the Domes-
B2
tic Hot Water FLOW and the Domestic Hot Water SECONDARY
RETURN connections to the heater.
20. With the GAS supply isolated, and in order to remove air from
the pipework, turn on POWER to the heater and operate the Q1
circulation pumps by disconnecting the connectors of the front fl ow
B
sensors (B2) of both heat exchangers. This will automatically oper-
ate both of the pumps (Q1).
21. Continue to operate the pumps until all the air has been removed
from the heat exchanger and pipework.
22. Open DHW outlets to remove all air from tank. Close DHW outlets
when all air is removed. Vent (E) as necessary.
23. Replace the fl ow sensor connectors of both heat exchangers (B2)
A
and press the reset for 1 second (J) when bleeding is complete.
A
24. Check again for leaks before refi tting inner cover and door.
25. Open GAS supply and return heater to operation.
G
CAUTION
It is ESSENTIAL that all air is removed from the water before proceeding with operating the heat
engines, otherwise permanent damage may occur to the heat exchangers and this damage is not
covered by warrantee.
70 MAXXfl o EVO 150/302