Underfloor heating pump wiring

24 Mar 2022
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United Kingdom
Hello everyone, i have installed underfloor heating, and cant figure out how to wire manifold pump so that it only turns on with the heating on and not with hot tap water it is a ideal logic + combi 30 boiler. Anyone know if its even possible?
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It seems there are many ways to plumb and wire under floor heating, most use a dedicated controller/relay box, and this runs the pump when required, but there are so many versions can't answer your question, and if I knew which version I would be down loading and viewing the instructions to find out, and clearly you can do that yourself.
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I think this is the diagram for the boiler. Yes i have radiator as well first floor and ground floor is UFH pipes are all connected so when the heating turns on everything turns on as the UFH manifold is connected to the same pipes, its the additional manifold circulating pump that i dont know how to connect so that it turns on at the same time because now it is plugged in to socket and i switch it on manually

Are there zone valves installed ? can you post a pic of the pipework/controls?
The only was you can control the UFH pump separately from the combi boiler power is use what was suggested before and have a thermostat/zone valve (switched relay) that controls the CH that can send a 3A 240volt supply to the pump when the CH is calling.

How are you currently turning on/controlling the UFH/CH?
We use one of these.
Just a wireless remote switch,

Just replaces your finger on the switch, when our combi boiler pump runs our UF pump runs.

We also use one outside its spec to run a zone/thermostat/timer for an office space...they are just a remote switch.

as with all things there are others out there...

we have used their products before on a remote kill for a hovercraft I kid you not...very good kit lasts all sorts of abuse..
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Thank you @martygturner they seem the answer to my DWH problem.

As to @zig122 I would expect to find some thing like this

It is in essence a bank of relays which can select the heating required and work the second circulating pump, as shown here
the second pump circulated the UFH water to keep the temperature even in the floor, and as the temperature drops more hot water is added from the boiler, the problem is you want radiators at around 70°C but in the main the floor should not exceed 27°C using two pumps is not the only way, but does seem to be most popular method.
Can I presume then it's just a switch on and everything comes on and off all at the same time? Is there a thermostat?

Make and model of thermostat if there is one.
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@ericmark, I installed the RF version of the UH8, it links in with the neoair stats, very good system so far. Has a separate boiler and pump feed and 3 separate valve feeds, one for a HW cylinder, one for the rad circuit and one for the UFH, if the system isn't a Y/S plan that can be wired back to the standard wiring centre of course.

That and it obviously controls 8 actuators.
@zig122 if I remember rightly (would need to check the manual) there is a switched live option for the logic + combi that allows a live to be take from the boiler and run through the stat and back to the stat terminal on the board. If so then that setup could probably be utilised to provide a switched live out to the pump.

Unless your GSR'd tho then you shouldn't really be in past the case playing around. That and unless you know your way around the PCB and are handy with a voltmeter and know what to check, then you may want someone that does in to wire it up otherwise you could fry the board.
Can I presume then it's just a switch on and everything comes on and off all at the same time? Is there a thermostat?

Make and model of thermostat if there is one.
Sorry not sure if that was answer to me or @zig122 as far as I am concerned it was thanks for the info about wireless remote, but do not want to ask questions on @zig122 tread, as far as @zig122 goes, not seen any reference to any device to allow two different temperatures which for mixed radiators and UFH is required.

However have seen a cheap method, where the water is fed to radiator first, so radiator cool the water then return from radiator further cooled under floor, I know it works, but not sure if really permitted as the floor temperature could exceed the permitted limits.

The case I saw was more down to being a heat sink for the Aga cooker, a way to get rid of heat if cooking. I have seen some odd systems including a radiator pressed hard against a steel hull of a narrow boat to get rid of excess heat.

Over the years I have needed to wire up many heating systems, but only once had to install the pipework, it is normally here it is, now you wire it.

However one needs to understand the pipe work to know how to wire. In the early days I would do all sorts, including using PLC's to control things, however working away from home showed me the error of my ways, if some thing went wrong, the guy repairing it often did not have a clue what I had done, so only way was rip out and start again.

OK should leave plans, which I did, but having a program needing Medoc to read it, is only any good if the new guy has Medoc (The original Mitsubishi PLC programming software).

It does not matter if I have a degree in electrical engineering and can use the device, it needs to be standard so anyone else can use it. So one needs to follow standard practice, which with UFH is to use a manifold and control panel similar to what I have shown.

Really not interested in boiler wiring, it is the type of manifold and controller we need info on.

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