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Normally closed or normally open underfloor heating actuator

Updated: October 2026

The room will not switch off, or a parcel has come back because the floor stayed hot all night. Normally closed or normally open underfloor heating actuator is the choice of what the valve does with no power on the head. You match the unpowered position your wiring centre expects, then you check the mark on the head you actually received. Voltage is a separate question, on the [24V or 230V](/hub/heating/underfloor-heating-actuator/sub/underfloor-heating-actuator-230v-vs-24v) page. Both heads can be 230 V and still be the wrong way round. The listings are on the [underfloor heating actuator comparison](/hub/heating/underfloor-heating-actuator). Products Compared updated this page in October 2026. A purchase through our links can earn a commission at no extra cost to you.

The room will not switch off, or a parcel has come back because the floor stayed hot all night. Normally closed or normally open underfloor heating actuator is the choice of what the valve does with no power on the head.

Our top picks

Wengart Wengart WG2208 Red Head 230 V

Best overall

Wengart Wengart WG2208 Red Head 230 V
7.2/10about £9.99
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Wengart Wengart WG2208 Blue Head 230 V

Rank 2

Wengart Wengart WG2208 Blue Head 230 V
8.3/10about £10.99
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RIMEX RIMEX ZL-2033 230 V Normally Closed Actuator

Alternative

RIMEX RIMEX ZL-2033 230 V Normally Closed Actuator
7.9/10about £12.95
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On this page
  1. 1.Shut until powered, or open until powered
  2. 2.What the wrong type does in the house
  3. 3.The mark on the carton is not the last check
  4. 4.What to buy from this set

Shut until powered, or open until powered

A normally closed actuator leaves the loop shut until the head is powered. Power warms the wax, the pin withdraws over a few minutes, and water flows. When the room is satisfied, or the head fails, that loop goes cold. Warmhaus describes this as the usual room-by-room default. Nordic Tec's definition is the same shape, and it is a description of the mechanism, not a UK legal requirement. A normally open actuator leaves the loop open until the head is powered. Power closes it. The Underfloor Heating Company says normally open belongs only on systems designed for it. If your old head is marked NO, or the centre manual asks for normally open, you buy normally open. Write that mark down before you compare prices on the buying guide.

What the wrong type does in the house

Fit a normally open head where the centre expects normally closed, and rooms heat when the stats are satisfied, then go off when the room calls. Warmhaus says this looks like a wiring fault. A normally closed head on a centre that expected normally open fails the other way: the loop stays shut whenever the control removes power. The same always-hot symptom has other causes. A first-open tab left engaged holds the valve open. A permanent live keeps a normally closed head open. A pin that is mechanically stuck open is a valve fault. Nu-Heat's sheet also describes crossed zones: one room always hot, another always cold, fixed by swapping those two heads after about three minutes.
Wengart Wengart WG2208 Red Head 230 V

Testsieger

Wengart Wengart WG2208 Red Head 230 V
7.2/10about £9.99
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The mark on the carton is not the last check

On the Wengart WG20 listing, which is titled normally closed, one review says a head marked NC behaved as normally open. Look at the mark on the actuator itself, and watch one loop with the power off. A normally closed head should leave that loop shut. A RIMEX buyer sent an order back after choosing the wrong normal state. The review describes normally open as staying open, so the actuator would have to be powered all the time to keep the floor off. One head, one loop, power off, then the rest. A stuck pin can imitate either type. The replacement page separates them: a pin that springs back can take a head, and a pin that stays down is an insert job.

What to buy from this set

The amazon.co.uk titles in this set that state a fail position say normally closed. None is titled normally open. You will not find the NO head by sorting this grid. Go to a listing that prints normally open, at the same voltage you have already confirmed. The Voltrique listing claims 230 V, a 3 mm stroke, and a VA10 adaptor, and it never says normally closed or normally open. The Heatmiser two-wire listing at £9.71 states no voltage and no fail position. A star line on either row does not fill that blank. A normally closed 230 V actuator on a 24 V output stays shut, which feels like a dead room and is the voltage question.

Common questions

What does normally closed do when the power is off?
The valve stays shut. Power opens it over a few minutes, and removing power lets it close again. Match the old head if the system was designed the other way.
Why do UK wiring centres usually expect normally closed?
Room-by-room centres send voltage only when that room calls, so the head should be shut the rest of the time. If the centre manual specifies NO, that is the instruction you follow.
What does the house do if you fit normally open by mistake?
Rooms heat when the thermostat is satisfied and go off when the room calls. A normally open head stays open, so you would have to power it all the time to keep the floor off.
How is that different from a head that is stuck open?
A normally open head closes when it is powered. A stuck pin does not. Take the head off: if the pin will not move, the valve is the fault.
Can the printing on the box be wrong?
Yes. One Wengart WG20 review says a unit marked normally closed behaved as normally open. Read the mark on the body, and watch one unpowered loop before you fit a manifold full.
Does a first-open tab feel the same as a normally open head?
The complaint is the same. The tab is a clip that holds the valve open for filling, including on a normally closed head. Power off at that zone: a true normally open head stays open, and a normally closed head with the tab removed should shut.
Are any of these amazon.co.uk listings normally open?
None of the titles says normally open. The Voltrique row and the £9.71 Heatmiser two-wire row do not state a fail position. An NO head has to be a listing that prints it.
Should you change every head if one was the wrong type?
Change the ones you have proved wrong on a single loop, and leave heads that already match. Crossed zones are different: swap the two heads that are on the wrong rooms, after the three-minute test.

Related pages

What an underfloor heating actuator does

Underfloor heating actuators

Read 24 V or 230 V on the underfloor heating actuator

Best underfloor heating actuator: 230 V, M30, closed

Underfloor heating actuator buying guide for the UK

How to replace an underfloor heating actuator head

Sources

Public UK sources and the amazon.co.uk listings in this comparison. Listings captured 15 October 2026. Page updated October 2026.

  1. Approved Document L, Volume 1 (2021, 2023 amendments) (retrieved 15 October 2026)
  2. Approved Document P (2013) (retrieved 15 October 2026)
  3. BEAMA underfloor heating controls guide (retrieved 15 October 2026)
  4. Heatmiser TA230 actuator datasheet (retrieved 15 October 2026)
  5. The Underfloor Heating Company: install an actuator (retrieved 15 October 2026)
  6. Warmup wiring centre manual (retrieved 15 October 2026)
  7. Grant UFLEX UH8 installation guide (retrieved 15 October 2026)
  8. Consumer Rights Act 2015 (retrieved 15 October 2026)