Independent comparisons. We may earn from shop links. More info

How to replace an underfloor heating actuator

Updated: October 2026

One room is cold and the others are warm, so you are looking at a single head on the manifold. This is how to replace an underfloor heating actuator when the new head already matches the old one. You can usually leave the water in the system. You still isolate the electrics, check the pin, and wait several minutes before you call the new head dead. The [underfloor heating actuator comparison](/hub/heating/underfloor-heating-actuator) is where the listings sit. Match voltage on the [24V or 230V](/hub/heating/underfloor-heating-actuator/sub/underfloor-heating-actuator-230v-vs-24v) page and fail position on the [normally closed or normally open](/hub/heating/underfloor-heating-actuator/sub/underfloor-heating-actuator-normally-closed-vs-open) page before you start. Products Compared updated this page in October 2026. A purchase through our links can earn a commission at no extra cost to you.

One room is cold and the others are warm, so you are looking at a single head on the manifold. This is how to replace an underfloor heating actuator when the new head already matches the old one.

Our top picks

Wengart Wengart WG2208 Red Head 230 V

Best overall

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

Rank 2

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

Alternative

RIMEX RIMEX ZL-2033 230 V Normally Closed Actuator
7.9/10about £12.95
View offer
On this page
  1. 1.Confirm you are changing the head, not the valve
  2. 2.Remove the old head and test the pin
  3. 3.Fit, wire like-for-like, and wait
  4. 4.When a new head will not fix it

Confirm you are changing the head, not the valve

The actuator sits on the loop valve, above the water seal. The Underfloor Heating Company says a head swap usually needs no drain for that reason. Replacing the brass insert is a different job: isolate flow and return, stop the pump, and release a little pressure, with no call for heat. You still make the supply dead. Isolate the wiring centre and confirm the actuator conductors are dead before you disconnect them. Stop if you cannot prove that. Approved Document P treats a new circuit, a new consumer unit, or work in a bathroom zone as the notifiable class. A like-for-like replacement elsewhere generally is not. Nu-Heat's fault sheet says actuators take about three minutes. If you remove only that head and the zone then warms, the head or its wiring was holding the loop shut. If you are unsure which loop feeds the cold room, swap the two heads after that wait. The buying guide is where you match the replacement first.

Remove the old head and test the pin

Take the power off, note which cores landed in which zone terminals, and unscrew the ring by hand. The Underfloor Heating Company says not to force a nut that will not start. Pliers on the collar are how plastic rings split. With the head off, press the valve pin gently and let go. A healthy pin moves and springs back. A summer-stuck pin can sometimes be freed by that press. If the pin stays down, you have left the head-swap. Isolate flow and return, stop the pump, drop a little pressure, and treat the insert as a heating engineer's job if you do not already drain loops. Another actuator will not cure a pin that stays down.
Wengart Wengart WG2208 Red Head 230 V

Testsieger

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

Fit, wire like-for-like, and wait

Screw the new ring on by hand until it is seated. VPS describes the order as cap off, ring on, then wire to the centre. Put the cores back into the same zone terminals. If you found four cores and you cannot say what the extra pair did, stop. This page does not give a terminal diagram, because the centre in your cupboard is the diagram. Some heads ship with a red tab or a first-open latch that holds the valve open for filling. VPS says to remove the red tab on a Salus head after wiring. Warmup's manual says its latch needs at least two minutes of power, or the test switches, before the head can close. Wait about three minutes, and up to five if the listing says 3–5 minutes. The room can take hours to feel different. Thermotech's sheet calls a warm head that never moves a failed element, if you can judge that without opening a live cover.

When a new head will not fix it

Stop when the pin does not spring back, when the cores are not a pair you can put back, or when the job has become a new circuit or a bathroom zone. Those are the points for a heating engineer or an electrician. A room that stays hot may still have the first-open tab fitted, a normally open head on a normally closed centre, or a permanent live on that zone. If one room is always hot and another is always cold, Nu-Heat's fix is to swap those two heads after the three-minute test. The moment the insert has to come out, the job is no longer dry.

Common questions

Do you have to drain the floor to change an actuator?
For the head itself, usually no, because it sits above the water seal. Isolating flow and return starts when you replace the valve insert. You still prove the cores dead.
Which port does the head screw onto?
It replaces the manual cap on the valve for that loop. If you are not sure which loop feeds the cold room, swap the two suspect heads after a three-minute test. A nut that will not start means the thread is wrong.
How long should you wait before deciding it is dead?
About three minutes, or up to five when the listing says 3–5 minutes. The pin can move in that window while the room stays cold for hours.
What if the pin does not move?
Press it gently once. If it sinks and springs back, you can fit the head. If it stays down, stop. That is an insert job, not another actuator.
What is the red tab for?
It holds the valve open so the loop can be filled. Remove it once the actuator is wired. Left on, the room heats after the thermostat is satisfied.
The room is always hot after the swap. What now?
Check the tab, then the fail position, then whether that zone has a permanent live. If one room is always hot and another is always cold, swap those two heads after the three-minute test.
When do you stop and call an electrician or a heating engineer?
Call an electrician for a new circuit, a consumer unit, or a bathroom zone. Call a heating engineer when the pin will not spring back. Four unidentified cores are a stop as well.

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

Normally closed or open underfloor heating actuator

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)