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Tech support

Online support - cylinders

We’ve collated a set of frequently asked questions to help you to diagnose any system issues. If you’re still experiencing any problems, please contact our technical support team via techsupport@nu-heat.co.uk or give them a call on 01404 540745 (available from 8am to 5pm, Monday to Friday).

EnergyMaster 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

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-pressurize 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 repressurize using a foot pump it 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 – (click to expand)


[click image to enlarge]

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  FS13-C  Flow switch 22mm brass push fit (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


[click image to enlarge]

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  FS13-C  Flow switch 22mm brass push fit (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


[click image to enlarge]

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  FS13-C  Flow switch 22mm brass push fit (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


[click image to enlarge]

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  FS13-C  Flow switch 22mm brass push fit (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

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