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If you’re experiencing issues with a Nu-Heat cylinder, please contact our Technical Support Team via techsupport@nu-heat.co.uk or call 01404 540745 between 8am and 5pm, Monday to Friday.

EnergyMaster cylinder troubleshooting

Faulty flow switch

When the hot water tap is opened does the shunt pump operate and when the tap is closed does the shunt pump stop?

Shunt pump – boiler pump on older systems – gate valves closed

When a hot water tap is opened does the 2-port zone valve open and start the boiler pump?

Blending valve fault

Can you alter the input temperature to the manifold? If not, remove the white head and check that the pin valve is moving freely.

Air in the top of the cylinder – faulty AAV

Make sure that the black cap on the AAV is always on loose – remove the red cap and poke a small screw driver down the hole to rapid purge. If air is present then replace the AAV.

Heat exchanger blocked or restricted

Double check the inline strainer – remove all pipework and blow down the HX with your hand over the hole to check resistance. If the HX is blocked then an acid cleaner can be used to unblock it.

Cylinder thermostat faulty or temperature set incorrectly<

Make sure that the cylinder thermostat is set at least 5°C higher than the boiler setting. Turn the thermostat up and down and listen for a click. If it will not click then replace.

Boiler fault

Please call a gas safe engineer.

Zone valve faulty

Remove the actuator head and exercise the mechanical valve underneath. Otherwise replace the whole valve.

Faulty wiring connection on wiring board

Remake all connections.

Faulty relay on wiring board

The relay will be either permanently on or off – replace the wiring board.

Non-return valve on DHW loop letting by

Replace the non-return valve with a new one.

Pressure loss on system

  1. Visual check on manifolds, cylinder including PRV, AAV and expansion.
  2. Re-pressurise system and isolate all manifolds. Check which side drops in pressure.
  3. Temperature pressure relief valve letting by – check for a weep from the connected pipework.
  4. Check expansion vessel on boiler side.
  5. Check boiler blow off valve.

Pressure rise on system

  1. Filling loop left on or letting by – double check that the filling loop has been left on – make sure that both black isolation valves are at 90°C .
  2. Restriction.
  3. Expansion vessel failure.

Circulation pump failure

Check the air side for pressure. If no pressure, try to repressurise using a foot pump. If this does not work then replace the expansion vessel. With the system cold the expansion vessel should hold a charge slightly over system pressure.

Choose your cylinder from the list below to determine your spare part requirements

Assembly for Nu-Heat 300 litre Solar EnergyMaster thermal store

Assembly for Nu-Heat 300 litre Solar EnergyMaster thermal store

Assembly for Nu-Heat 300l Solar EnergyMaster thermal store
No. Code Description Buy online
1 C28-C 28mm compression coupling N/A
2 CZV02-C 1″ zone valve Buy online
3 BU05/075-C 1/2″ to 3/4″ brass hexagon bush N/A
4 BU05/038-C Brass hexagon reducing bush, 1/2″ x 3/8″ N/A
5 AAV-C Auto air vent 3/8″ with shut-off valve Buy online
6 C22-C* 22mm compression coupling* N/A
7 ELC22-C 22mm compression elbow N/A
8 PV22-C 22mm pump valve N/A
9 JB4-C Junction box, 5A, 4 terminals N/A
10 FS05-C Flow switch 22mm brass compression fitting (3A) Buy online
11 BV22F-C 22mm ball valve & filter N/A
12 NRV22-C Non return valve 22mm N/A
13 T222205F-C 22x22x1/2″ FI Tee N/A
14 SVPG6-C 6-bar safety valve/pressure guage N/A
15 FI05/15-C 15mmx1/2″ FI compression coupling N/A
16 EVP02-C 2 litre potable water expansion vessel Buy online
17 PRV05-C 15mm pressure regulating valve with gauge N/A
18 DOM-C Drain-off/filling valve N/A
19 DSTAT-C Dual cylinder thermostat / limit stat N/A
20 LSTAT/90-C Cylinder limit thermostat – manual reset 90°C cut-out N/A
21 EVK35-C** 35 litre expansion vessel kit with filling loop** N/A
22 MP1CP-C 7 day, 24hr or 5/2 single-channel timeswitch Buy online
23 G2580M1-C Grundfos Magna1 UPE 25-80 modulating pump N/A
24 SBLVA22-C Solar mixing valve 22mm N/A
24a EPC/SOL5-A Additional component sub-assembly for solar EnergyMaster thermal store (Type 5) N/A
25 SZV22-C 22mm solar 2-port zone valve (3-wire) N/A
26 C22(B)-C 22mm compression coupling with brass olives (for solar) N/A
27 SPI22-C 22mm brass pipe insert for use with compression fittings in a solar circuit N/A
28 LSTAT/80-C Cylinder limit thermostat – manual reset 80°C cut-out N/A
29 LSTAT/90-C Cylinder limit thermostat – manual reset 90°C cut-out N/A
30 G3TD22/15C 15/22mm tundish N/A
* – Two couplings have been provided to ensure the pump can be installed without clashing with the cylinder. If the pump can be suitably positioned the installer may determine that these couplings are unnecessary.
** – Only supplied when purchased with underfloor heating. Depending on the volume of the underfloor heating system a larger expansion vessel may be supplied.

Assembly for Nu-Heat 300 litre EnergyMaster thermal store

Assembly for Nu-Heat 300 litre EnergyMaster thermal store

Assembly for Nu-Heat 300l EnergyMaster thermal store
No. Code Description Buy online
1 C28-C 28mm compression coupling N/A
2 CZV02-C 1″ zone valve Buy online
3 BU05/075-C 1/2″ to 3/4″ brass hexagon bush N/A
4 BU05/038-C Brass hexagon reducing bush, 1/2″ x 3/8″ N/A
5 AAV-C Auto air vent 3/8″ with shut-off valve Buy online
6 C22-C* 22mm compression coupling* N/A
7 ELC22-C 22mm compression elbow N/A
8 PV22-C 22mm pump valve N/A
9 JB4-C Junction box, 5A, 4 terminals N/A
10 FS05-C Flow switch 22mm brass compression fitting (3A) Buy online
11 BV22F-C 22mm ball valve & filter N/A
12 NRV22-C Non return valve 22mm N/A
13 T222205F-C 22x22x1/2″ FI Tee N/A
14 SVPG6-C 6-bar safety valve/pressure guage N/A
15 FI05/15-C 15mmx1/2″ FI compression coupling N/A
16 EVP02-C 2 litre potable water expansion vessel Buy online
17 PRV05-C 15mm pressure regulating valve with gauge N/A
18 DOM-C Drain-off/filling valve N/A
19 DSTAT-C Dual cylinder thermostat / limit stat N/A
20 LSTAT/90-C Cylinder limit thermostat – manual reset 90°C cut-out N/A
21 EVK35-C** 35 litre expansion vessel kit with filling loop** N/A
22 MP1CP-C 7 day, 24hr or 5/2 single-channel timeswitch Buy online
23 G2580M1-C Grundfos Magna1 UPE 25-80 modulating pump N/A
24 BLVA28-C Hot water mixing valve 28mm Buy online
25 CRB28/22-C Compression reducing bush, 28x22mm N/A
26 G3TD22/15-C 15/22mm tundish N/A
* – Two couplings have been provided to ensure the pump can be installed without clashing with the cylinder. If the pump can be suitably positioned the installer may determine that these couplings are unnecessary.
** – Depending on the volume of the underfloor heating system a larger expansion vessel may be
supplied

Assembly for Nu-Heat 210 litre Solar EnergyMaster thermal store

Assembly for Nu-Heat 210 litre Solar EnergyMaster thermal store

Assembly for Nu-Heat 210lSolar EnergyMaster thermal store
No. Code Description Buy online
1 C28-C 28mm compression coupling N/A
2 CZV02-C 1″ zone valve Buy online
3 BU05/075-C 1/2″ to 3/4″ brass hexagon bush N/A
4 BU05/038-C Brass hexagon reducing bush, 1/2″ x 3/8″ N/A
5 AAV-C Auto air vent 3/8″ with shut-off valve Buy online
6 C22-C 22mm compression coupling N/A
7 ELC22-C 22mm compression elbow N/A
8 PV22-C 22mm pump valve N/A
9 JB4-C Junction box, 5A, 4 terminals N/A
10 FS05-C Flow switch 22mm brass compression fitting (3A) Buy online
11 BV22F-C 22mm ball valve & filter N/A
12 NRV22-C Non return valve 22mm N/A
13 T222205F-C 22x22x1/2″ FI Tee N/A
14 SVPG6-C 6-bar safety valve/pressure guage N/A
15 FI05/15-C 15mmx1/2″ FI compression coupling N/A
16 EVP02-C 2 litre potable water expansion vessel Buy online
17 PRV05-C 15mm pressure regulating valve with gauge N/A
18 DOM-C Drain-off/filling valve N/A
19 DSTAT-C Dual cylinder thermostat / limit stat N/A
20 LSTAT/90-C Cylinder limit thermostat – manual reset 90°C cut-out N/A
21 EVK24-C* 24 litre expansion vessel kit with filling loop* N/A
22 MP1CP-C 7 day, 24hr or 5/2 single-channel timeswitch Buy online
23 G1560A2-C Grundfos UPS2 15-60 energy efficient pump N/A
24 SBLA22-C Solar mixing valve 22mm N/A
24a EPC/SOL5-A Additional component sub-assembly for solar EnergyMaster thermal store (Type 5) N/A
25 SZV22-C 22mm solar 2-port zone valve (3-wire) N/A
26 C22(B)-C 22mm compression coupling with brass olives (for solar) N/A
27 SPI22-C 22mm brass pipe insert for use with compression fittings in a solar circuit N/A
28 LSTAT/80-C Cylinder limit thermostat – manual reset 80°C cut-out N/A
29 LSTAT/90-C Cylinder limit thermostat – manual reset 90°C cut-out N/A
30 G3TD22/15C 15/22mm tundish N/A
* – Only supplied when purchased with underfloor heating. Depending on the volume of the underfloor heating system a larger expansion vessel may be supplied.

Assembly for Nu-Heat 210l EnergyMaster thermal store

Assembly for Nu-Heat 210l EnergyMaster thermal store

Assembly for Nu-Heat 210l EnergyMaster thermal store
No. Code Description Buy online
1 C28-C 28mm compression coupling N/A
2 CZV02-C 1″ zone valve Buy online
3 BU05/075-C 1/2″ to 3/4″ brass hexagon bush N/A
4 BU05/038-C Brass hexagon reducing bush, 1/2″ x 3/8″ N/A
5 AAV-C Auto air vent 3/8″ with shut-off valve Buy online
6 C22-C 22mm compression coupling N/A
7 ELC22-C 22mm compression elbow N/A
8 PV22-C 22mm pump valve N/A
9 JB4-C Junction box, 5A, 4 terminals N/A
10 FS05-C Flow switch 22mm brass compression fitting (3A) Buy online
11 BV22F-C 22mm ball valve & filter N/A
12 NRV22-C Non return valve 22mm N/A
13 T222205F-C 22x22x1/2″ FI Tee N/A
14 SVPG6-C 6-bar safety valve/pressure guage N/A
15 FI05/15-C 15mmx1/2″ FI compression coupling N/A
16 EVP02-C 2 litre potable water expansion vessel Buy online
17 PRV05-C 15mm pressure regulating valve with gauge N/A
18 DOM-C Drain-off/filling valve N/A
19 DSTAT-C Dual cylinder thermostat / limit stat N/A
20 LSTAT/90-C Cylinder limit thermostat – manual reset 90°C cut-out N/A
21 EVK24-C* 24 litre expansion vessel kit with filling loop* N/A
22 MP1CP-C 7 day, 24hr or 5/2 single-channel timeswitch Buy online
23 G1560A2-C Grundfos UPS2 15-60 energy efficient pump N/A
24 BLVA28-C Hot water mixing valve 28mm Buy online
25 G3TD22/15-C 15/22mm tundish N/A
* – Depending on the volume of the underfloor heating system a larger expansion vessel may be
supplied