UFH wiring centres explained: what they do and how to choose one

Every multi-zone wet underfloor heating system has the same wiring problem: several thermostats, several actuators, one pump and one heat source, all of which must act together. You could build that from relays and a terminal box, but a wiring centre does it on one labelled board, with an output for everything and an LED to show what is live.

This guide explains what the wiring centre actually does, when you need one, and how to pick between the four in the Heatmiser range we stock. For the terminal-by-terminal wiring detail, see our separate UH4 and UH8 wiring guide; this one is about understanding and choosing.

What does a UFH wiring centre do?

It does three jobs at once, and the third is the one that matters most:

1. Routes each thermostat to its loops. When the thermostat in a zone calls for heat, the wiring centre powers the actuators on that zone's manifold ports, which open the loops.
2. Runs the manifold pump. When any zone is open, a switched live output starts the circulation pump, and stops it when the last zone closes.
3. Enables the heat source. A volt-free switch closes to tell the boiler or heat pump to fire, and opens when no zone wants heat.

That third job is the boiler interlock: the heat source cannot run when nothing is calling. Approved Document L requires heating controls to provide interlock, and a room thermostat wired straight to a pump does not achieve it on its own. Our guide to UFH boiler interlock and pump relays covers the wiring logic in depth.

On the Heatmiser UH8, the pump output is switched 230V live and the heat source output is volt free, so it suits system boilers, combis and heat pumps alike. The manual also recommends a high limit switch on the manifold, so the pump stops if the blending valve ever fails hot.

Do I need a wiring centre at all?

If the system has more than one zone, yes. One thermostat, one pump pack and one zone can be wired without one, but as soon as a second thermostat appears you need somewhere that combines their calls for the pump and boiler, and that is exactly what the wiring centre is.

• One zone: a single room, one thermostat and a single room pump pack can work without a wiring centre, though fitting one keeps the wiring tidy and expandable.
• Two to four zones: the Heatmiser UH4.
• Five to eight zones: the Heatmiser UH8.
• Two manifolds: one wiring centre per manifold, each running its own pump, both enabling the same heat source.

How many zones you should have is a design question, not a wiring one: see how many UFH zones do I need.

Which wiring centre do I need?

Pick by thermostat type first, then zone count. All four share the same core spec: up to 6 actuators per zone, 3A per relay, 5A total board load, 230V supply, DIN rail or wall mounting.

The UH8-RF is the retrofit choice: no thermostat cables to chase into finished walls, and a wireless RF-Switch can even replace the cable to the boiler. The UH8-N suits new installs standardising on Heatmiser's 12V neoStat range. Both the UH4 and UH8 also offer a radiator option on the last zone, so one board can run the UFH plus a radiator circuit upstairs.

How do thermostats, actuators and the wiring centre fit together?

Each room thermostat connects to one zone on the board. Each zone output then feeds the thermal actuators screwed onto the manifold ports for that room's loops, up to 6 per zone within the 5A board limit.

• One room, one loop: one thermostat, one actuator on one port.
• Open-plan room, three loops: one thermostat, three actuators wired to the same zone, all opening together.
• App control: add a Heatmiser neoHub to a system of neoStats and the same wiring centre works unchanged; the intelligence sits in the thermostats, not the board.

Thermal actuators open slowly rather than instantly, so a short delay between the thermostat clicking and the pump starting is normal, not a fault. If a zone never opens, test the actuator before blaming the board; our guide to how actuators and zone valves work explains the sequence.

Where does the wiring centre go and who fits it?

Next to the manifold, almost always. The actuator cables are short, the pump is right there, and one supply feeds the lot. The board is IP20, so it needs a dry indoor location: a manifold cupboard, plant room or utility space, not a garage wall that runs wet.

• Supply: 230V fused at 5A, from a fused spur.
• Mounting: wall screws or DIN rail inside a manifold cabinet.
• Labelling: mark each zone with its room name as you go; your future self at the manifold will thank you.
• Sign-off: this is fixed wiring, so it must be installed by a qualified electrician to BS 7671, and in dwellings the work falls under Part P. The Heatmiser manual makes the same point, and improper wiring voids the product warranty.

Plan the cable runs at first fix: a thermostat cable to each room from the manifold position is cheap in a bare wall and painful in a plastered one, which is exactly when the UH8-RF earns its premium.

Frequently asked questions

What is the difference between a wiring centre and a junction box?

A junction box just joins cables. A wiring centre adds the logic: it combines every zone's call for heat into pump and boiler outputs, giving the interlock that Approved Document L requires from heating controls.

Does a wiring centre work with a heat pump?

Yes. The heat source output on the UH8 is volt free, so it can switch a heat pump's demand input just as happily as a boiler's. Check the heat pump maker's wiring diagram for which terminals it expects.

Can one wiring centre run two manifolds?

Fit one per manifold. Each manifold has its own pump, and the pump output on the board is designed to run the pump beside it. Both boards can enable the same boiler through their volt-free contacts.

Can I run radiators from a UFH wiring centre?

Partly. The UH4 and UH8 let the last zone switch a radiator circuit instead of UFH actuators, which suits a house with UFH downstairs and a small radiator zone upstairs.

How many actuators can one zone drive?

Up to 6 on the Heatmiser boards, within the 5A total board load. Large open-plan zones with more loops than that are better split into two zones anyway.

Do I need a wiring centre for electric underfloor heating?

No. Electric UFH is switched directly by its own thermostat on each circuit; there is no pump, actuator or boiler to coordinate. Wiring centres are a wet UFH component.

Why do my zone LEDs light but the floor stays cold?

The board is doing its job and something downstream is not: usually a stuck actuator, a closed valve or an airlocked pump. Our guide to underfloor heating not getting warm runs the checks in order.

Sources: Heatmiser UH8 installation manual, BEAMA Part L 2021 heating controls guidance