DIY UFH Pump

[Bodgit]

Commercial UFH controllers (pump + valve + thermostat + wiring) seem to be quite expensive for what they are. As I've already got a perfectly serviceable Grundfoss pump hanging around somewhere, I want to make my own.

As far as I can make out, I just need the pump, a thermostatic mixing valve and a flow thermostat. I was going to connect them up as follows (ASCII art), and use ...

+-------------------------------+ | | |C | +-----+ +----+ +----------+ | | Mix |O |Pump| | UFH Pipe | | | +---+ +---+ +----+ | | | | | | | +-----+ +----+ +----------+ | |H | | | +-----+ | |Flow | | |Temp | | +-----+ | | |

Flow Return

I welcome any comments on the design, and any suggestions on what I need to watch out for. Also, can anyone recommend where to find the flow thermostat?

Cheers, Dave.

[The Natural Philosopher]

My packaged system (polylumb) consits of pump, mixing valve and not a flow temp stat, but a simple two port motorised valve, which is connected to the pump and a relay to wire OR the UFH call-for-heat with the other motorised valves controlling ordinary CH and HW circuits.

I think two isolation valves are also included. But no drain pint: that's on the manifold

The mixer is a 4 port though, it essentially bridges flow and return, and the UFH flow and return, so as to allow more or less super hot water to mix with the UFH return to form the UFH flow.

See here

You can get the important bit - the mixer - separately for 75 notes or so.

Remember you also need a relay in the wiring center, or the UFH pump will run whenever the boiler pump does.. I built my own out of DIN rail and DIN mounted barrier strips, and a lot of link wires.

I certainly think if you have the bits and the time, a DIY approach is cost saving. Go to it.

[Bodgit]

Thanks for the reply.

I wanted to use a flow temperature sensor rather than a motorised valve because with a motorised valve I'd need to run a wire back to the boiler room, which would be a royal PITA! I want it to be self contained if possible. I'm a bit concerned, though, that the flow stat won't get hot enough if the pump is switched off.

Can you please explain the advantage of a 4-port mixing valve over a 3- port?

Will I need a relay? I thought I could just connect the flow thermostat and a room stat in series to control the pump.

There seems to be a lot made of the rubber mounts to make the thing quiet. I wasn't going to bother - the pump is quite a powerful one, so I was just going to turn the speed down. Any comments?

[The Natural Philosopher]

You have to do that anyway to ensure that call-for-UFH heat switches the boiler on.

I want it to be self

Muy Bad. I have what in the link I posted above. Its a 3 port.

So what will turn the boiler on? I have independent UFH and CH though, which may make a difference. Nope it doesn't..Otherwis UFH pump will run completely independently of boiler..

I run mind pretty darn hard and hot. Big installation and a lot of pipe.

I cant really advise beyond saying the setup in that link is what I have and its been fine, apart from the motor on the motorised valve packing up. A new and better head fixed all that.

I also have a 8 way manifold: That I love because of the little flow valves on each circuit and the fact you can pop a controller on any of them: Couple that to a wireless room stat and that's a sort of room by room TRV

In my case I have the living/dining room as the master thermostat, the kitchen with an Aga is separately regulated to avoid it going ballistic, but at this time of year the floor IS warm,

The rest of the circuit is corridor and a back utility room. That is turned off manually. The corridor has a bit of its own circuit but all the feeds and returns run down it so that's where the cats hang out. It heats the landing area up the stairwell, too.

[Tabby]

I lack exerience on this, so tell me where I'm wrong. I would have thought this could be done more simply without the tmv, like so:

1. Use only the return pipe for hw feed, you dont need anything hotter.
2. The pump circulates water round the ufh loop, and is controlled by room stat and pipe stat
3. Connection between ufh loop and CH return pipe is simply:

ufh ch | | | | | | | | | | | | | |______| | | ______ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |______| | | ______ | | | | | | | | | | | | | | | | | | | | |

this means most of the water simply passes by the connection on each side, but some does intermix.

Note no boiler firing or zone control signals need exporting to this self contained unit, as it only pumps round when both the room is too cold and the ufh pipe too cold.

NT

[The Natural Philosopher]

Simple solutions often work well on small installations as simple 'addons' to an existing circuit but in largee installations you need a completely different time regime for UFH as especially with solid floors, the heat up time is measured in hours. Likewise a LOT of pipe means you do need an auxiliary pump.

Your solution is ideal for 'adding a bit of UFH in the new conservatory;' but its a marginal solution for anything bigger.

Friends of mine have accidental bathroom UFH. The builder ran all the CH pipes under the floor, unlagged..It works really well.. the radiator does very little.

[ARWadsworth]

I like the sound of that. My bathroom radiator is the furthest one from the boiler and I could easily do that with the pipework supplying the radiator.

[Peter B]

You can have the setup I've just chopped out from underneath the landing floor if you want...

[The Natural Philosopher]

Better still. run it snakelike between a few joists. you can prevent extreme temps if you part insulate it..the woolly sleeves rather than full foam IYKWIM. Or use poly pipe etc etc.

certainly takes the chill off a tiled floor.

[The Natural Philosopher]

Blimey. Couldn't they find somewhere more awkard to bodge that lot in?

[Peter B]

>> Blimey. Couldn't they find somewhere more awkard to bodge that lot in? Probably not - it's only since it's been de-commissioned that we realised just how LOUD the pump was in operation, as its gentle hum resonated first through the trombone-style pipework and then through the joists.

The replacement is the first step (of many) in the right direction.

[Bodgit]

This is just going to be a single room system - there's already a radiator in there, it's just to take the chill off the floor. So I don't want it to be a separate zone.

[TheOldFellow]

I used a Polyplumb Zonal Regulation Unit. Basically it is as per your diagram. There is no wire back to call the boiler as the temperature sensor turns on the pump when 35C water is detected - because the mixer will be 'open' when the system is cold, it always allows a hot flow to the sensor. The mixer ensures that the circulating water is about 35-40C.

In three years it has been faultless. But I do recommend some form of noise isolation for that pump.

R.

- it's set-able.

[Piers Finlayson]

Been idly thinking about UFH for a while, but hadn't thought of a drain point. Doesn't this mean the manifold needs to be below the floor heighy?

[Piers Finlayson]

I sometimes stay in a hotel that's done that with their HW. I only stay there during te winter ...

[Spamlet]

Better to have something that just feels warm under foot - ie low conductivity stuff like wood or carpet. Floors that are actually heated can be very uncomfortable, in my experience, though if yours are tiled something just to take the edge off might be handy.

S

[Tim Watts]

Dunno - my experience of a heated bathroom/kitchen floor in CentreParcs was very pleasant - and the floor dried off quickly.

But - yes, I agree with the bit above re warm to the touch.

I have 3 sets of wood floors on 12.5mm (20mm for one) marmox plus 6mm underlay and despite the slab being bone crunchingly cold and uninsulated, the floor is *extremely* pleasant to walk on - even sit on.

If the room is unheated for a day or two, of course the floor starts off feeling cold, but it comes up to temperature quite quickly once the room heating is on.

Ditto tiles on marmox in the bathroom - feels initially cool but the feet provide enough heat quickly to warm the tile up.

[Peter B]

In an ideal world, I guess, then yes - but not in reality for most ground floor installs.

What they're used for mostly is to provide a filling point to which one can connect a hose (on the flow side) and an exit point that can be directed into a bucket or whatever (on the return side). With the manifold isolated, each loop can be individually flushed or refilled or purged of air or whatever you want to do, and if you swap the connections over, you can backflush the loops too.

[YAPH]

That's pretty much what I do, using a Reliance UFH mixing valve from Toolstation (£60-ish) and a cylinder/pipe stat where necessary

[andrew]

I'm interested in trying something like this, our plumber is quoting GBP1100 just for the manifold, pump and controller.

When we laid the insulation and floor screed I had the guys lay out 4 loops of polyplumb, just in case. Now I'm wondering about how the controller is to function using a simple 24kW combi.

It's a small single storey cottage of about 70m2 area. As I only intend to have one zone I'm assuming the loops are initially balanced at the manifold during commissioning. After that the roomstat switches the ufh pump and this flow triggers the boiler?

The boiler then sends hot water to the mixer which blends it down to a preset temperature of about 35C, as the room warms up the delta T between the floor and the slab reduces so the heat uptake tails off. The return temperature needs to keep below ~56C to keep the combi in condensing mode.

So why not modulate the combi, or switch it off, on a raised return temperature?

In the past I worked with a woodburner with a thermal store and a predictive controller but I didn't pay attention to the wet side. I think the controller compensated for a falling or rising exteriro temperature to anticipate the thermal lag of the system, are they worth considering?

AJH