Underfloor heating

[jpdw]

We're due to have a kitchen-knock-through-extension type thing done in the coming months, and are strongly considering "wet" underfloor heating, partly as it's *apparently* efficient and partly because we can't see where to put the radiator!

I will be looking to get the UFH controlled by Cortex as part of gradually moving rooms to individual cortex control. I assume this will mean getting valve actuators on the manifold controlled by Idratek connected relays.

Has anyone already got UFH cortex controlled and have any advice ?

- Positioning of temp sensors?
- Manifold/actuators & control via idratek


Thanks

[chris_j_hunter]

useful overview of options here :

http://www.heatweb.com/techtips/Underfloor/underfloorheating.html

[Viv]

The Idratek hardware controlled by Cortex s ideally suited to controlling underfloor heating and has been in many properties.

When calling for a room to be heated the manifold (if you have one) valve is opened together with the recirculating pump. Other pumps can also easily be controlled.

Underfloor valves on a manifold are often thermally operated (heating coil plus wax cylinder).
This can take 5 minutes to open etc. Not normally a problem. Just tell Cortex the typical open and close times for efficient operation.

Be careful not to heavily insulate this type of valve and manifold, that is don't box it all in. If you do, you run the risk that the valves do not shut off completely if others are on due to the ambient temperature being high. The result is rooms being hotter than expected due to leaky valves.

Also such heating does not lend itself to occupied and unoccupied profiles being used as much as radiators. This is because the thermal mass of the floor does not respond in a timely manner to new occupancy.

Viv

[toscal]

I have underfloor heating in one of the kids bedrooms and also in my office. It is electric and stand alone, but some of the principles should apply to you. I installed it myself, and made for allowances so that is could be controlled via HA at a later date.
The temp sensor is embedded in the floor between 2 of the heating wires. The controller is an Aube TH132F. IT also has a function where it looks at yesterdays temp when it was switched on to see it reached temp by say 7am. If not then it adjusts the on time by 10 or 15 minutes and adjusts today's on time accordingly. So it can turn on early or late. Aslo the Aube controller will decide if the heating needs to be on full or partially on (think dimmer for heating control), maybe you could do something similar via Idratek.
A client of mine who was also where I got the underfloor heating cable from has fitted a wet system in his house and wired the controllers from each room to a control valve on the manifold, he uses a similar Aube controller.
As for placement of temp sensors, I would put one in the floor and have one sensing room temp. And use both to decide when to turn the heating on or off.

[jpdw]

useful overview of options here :

http://www.heatweb.com/techtips/Unde...orheating.html

Thanks... that's useful background. I'm pretty familiar with multizone radiator systems but this would be my first encounter with underfloor, so the background this web link is very useful. [ first encounter and I'm determined not to just have the default standalone-non-automated type thing the builder would fit by default!]

The temp sensor is embedded in the floor between 2 of the heating wires. The controller is an Aube TH132F. IT also has a function where it looks at yesterdays temp when it was switched on to see it reached temp by say 7am. If not then it adjusts the on time by 10 or 15 minutes and adjusts today's on time accordingly. So it can turn on early or late. Aslo the Aube controller will decide if the heating needs to be on full or partially on (think dimmer for heating control), maybe you could do something similar via Idratek.
A client of mine who was also where I got the underfloor heating cable from has fitted a wet system in his house and wired the controllers from each room to a control valve on the manifold, he uses a similar Aube controller.
As for placement of temp sensors, I would put one in the floor and have one sensing room temp. And use both to decide when to turn the heating on or off.

Sounds like 2 sensors is the way to go. Do "default" installs get a sensor in the floor as well or just a sensor in the controller unit put somewhere on the wall? Whilst I'm wanting the UFH to be Cortex controlled I also want a designed-in "reversion" to a standard system for when we eventually move (I doubt Joe Public will have latched on to better heating control by then, more likely govt will focus people on changing every light bulb to save 1w instead)

The Idratek hardware controlled by Cortex s ideally suited to controlling underfloor heating and has been in many properties.

When calling for a room to be heated the manifold (if you have one) valve is opened together with the recirculating pump. Other pumps can also easily be controlled.

Underfloor valves on a manifold are often thermally operated (heating coil plus wax cylinder).
This can take 5 minutes to open etc. Not normally a problem. Just tell Cortex the typical open and close times for efficient operation.

Be careful not to heavily insulate this type of valve and manifold, that is don't box it all in. If you do, you run the risk that the valves do not shut off completely if others are on due to the ambient temperature being high. The result is rooms being hotter than expected due to leaky valves.

Also such heating does not lend itself to occupied and unoccupied profiles being used as much as radiators. This is because the thermal mass of the floor does not respond in a timely manner to new occupancy.

Viv

I'm anticipating that there will be a manifold of some sort situated in the back of a built in cupboard. We'll probably have 2 zones, so is there a valve type/make you'd recommend to avoid the ambient temp issue you mention?

Do you recommend a temp sensor in the floor (similar to what Toscal mentions) or just one to measure the room temperature? And what's the best position?

I'm not too worried about occupied/unoccupied as I the kitchen will be "visited" frequently albeit often briefly, but I do want to be able to vary the set-point by day/time and use Cortex to go to a much lower set point when we're away (something I currently set up as a manually in Cortex's scheduler)

I'll probably still have some presence sensing in the kitchen anyway as I want to have a few low wattage LEDs to come on to save turning on all the lights just for the 30 seconds it takes to get the wine from the fridge and leave again....

[JonS]

I've just completed the automation of a wet UFH system that was installed with standard controls and I can now switch between automated and standard using change over (aka light) switches.
The HVAC object, zone valves and slave valves make the automation straightforward with pump run-on, wait for valves to open and more options that I could imagine all catered for.
The default you'll get from a builder / plumber will almost certainly not include a floor temp sensor (never saw it offered) and I am not sure how you would include that in the heating scheme as the floor will approach the water temp (40C) but the air temp could still be quite low, you certainly wouldn't want to average the two sensors in the zone. It may be useful to help confirm correct operation, but your feet will soon tell you that.
What are people using floor sensors for?

On the manifold front, ours is in an understair cupboard. I was planning to box it in further, but not now!!
HTH
JonS

[Karam]

For electric underfloor heating systems the controller needs feedback from the floor to know when it should switch off the electric heating elements - typically the controllers control the floor temperature (well the temperature in the vicinity of the heating elements) as a starting point. If a room sensor is used (as well) then I imagine this will then have an effect on how long the floor heating is kept on and not contravening condition one (exceeding floor setpoint - though this may then be allowed to go to maximum rather than a user setting). Obviously if you are using electric UFH for your main room heat source then a room sensor is a must and you would likely not have access to the floor set point.

For a wet system the floor sensor is not needed because the circulating water temperature is normally controlled and how much heat is delivered depends on its tempertaure and how much of this you circulate. The circulation also helps even out hot spots e.g. where you may have more insulation above particular areas of the heat source.

Note: My comments are based on limited experience with such systems and reasoned judgement so it may well be that some different schemes exist

[__CA__]

We completely refurbished our Victorian semi last year and knocked through the substantial chimney breast at the back, removed the dreadful lean-to kitchen and made most of the space (approx 9m x 3.3m) one open plan kitchen diner with bi-fold doors to the garden. At the house end of the space is a separate small lobby and WC. The whole area had to be dug down, DPC installed, thick insulation and concrete slab laid, wet underfloor sytem laid, screed and then car-showroom spec 60cm sq tiles laid. It really adds the 'wow' factor and I'm so glad we did it.

The manifold has 5 circuits, 4 for the kitchen area and one for the lobby/WC area. However, I have no actuators on the manifolds and run all the circuits together as one, using a zone valve. I take an average of the ceiling temperature at the kitchen end and the other from the panel by the back door. I don't use occupancy settings for the reasons stated in a previous post - response lag.

The only issue I have experienced was cold air in the ceiling void 'falling' through the pattress over the temperature sensor and causing a low reading (and the underfloor system running too much), which was easily sorted. In the rest of the house I have the temperature threshold set to 20 degrees when occupied because of the normal convection radiators sending the heat to the ceiling, but in the kitchen because the heat is generated at floor level obviously the temperature at the ceiling doesn't need to be so high, I think it's at 17.

I think I have the run-on or minimum run time (?) for the UF system to 30 minutes as there's no point in putting heat into the slab for anything less as it will have no effect.

Overall it seems to work very well and the logs often show a slow decline in temperature overnight causing the underfloor to kick in about 5 or 6am for a couple of hours, resulting in a lovely warm floor for the barefoot morning tea run.

The cat LOVES it.

[jpdw]

We completely refurbished our Victorian semi last year and knocked through the substantial chimney breast at the back, removed the dreadful lean-to kitchen and made most of the space (approx 9m x 3.3m) one open plan kitchen diner with bi-fold doors to the garden.

Description sounds very similar (though we're only doing the downstairs)

At the house end of the space is a separate small lobby and WC. The whole area had to be dug down, DPC installed, thick insulation and concrete slab laid, wet underfloor sytem laid, screed and then car-showroom spec 60cm sq tiles laid. It really adds the 'wow' factor and I'm so glad we did it.

Interesting that you've got solid floor -- we've been told suspended (still with lots of insulation) will be more efficient in terms of heating it. Have to say I liked the idea of solid floor under things like the washer, so will have to get them to put more brick supports around that area.

The manifold has 5 circuits, 4 for the kitchen area and one for the lobby/WC area. However, I have no actuators on the manifolds and run all the circuits together as one, using a zone valve. I take an average of the ceiling temperature at the kitchen end and the other from the panel by the back door. I don't use occupancy settings for the reasons stated in a previous post - response lag.

So I take it the fact it's piped as 5 circuits is more about the water flow than zone/area control then. I can't think of an easy way to split out 7m x 5m area into different heat requirements so will probably control as one, though the fitters might pipe them as diff circuits. A singe zone value sounds good and I've an idratek relay unit with a spare relay already.

The only issue I have experienced was cold air in the ceiling void 'falling' through the pattress over the temperature sensor and causing a low reading (and the underfloor system running too much), which was easily sorted. In the rest of the house I have the temperature threshold set to 20 degrees when occupied because of the normal convection radiators sending the heat to the ceiling, but in the kitchen because the heat is generated at floor level obviously the temperature at the ceiling doesn't need to be so high, I think it's at 17.

Are you using the standard Idratek parts in the ceiling ? I remember seeing pics that gumby has done this. Not sure my wife would approve, so I was wondering if I would need to find a "more stealthy" way to put temp sensors on/in the ceiling. Like fitting at least the sensor into the lower profile boxes you often see in commercial buildings (like a slim thermostat without a control knob -- I think Rapid sell something like it now). The point (partly) being that these are probably slim enough to surface mount so avoiding the problem you describe.

Steering further away from the HA aspect, any other specific about the underfloor kit that I should question the builder/installers about ? I've no experience at all with underfloor, so other than wanting to control it, will be completely in their hands here (which I dont like).

[__CA__]

Yes the 5 circuits are for flow rather than control / zoning. The circuits at the far end of the room are run at a higher flow rate because of the long run and extra heat loss, the smallest and nearest is on a much lower flow rate. I set these (and the operating temperature) according to the spec; the whole design / spec was done by PolyPlumb (except the control element).

We have standard Idratek ceiling mounted sensors throughout the house. With tall ceilings people don't tend to notice, particularly in the kitchen where there is so much else to draw the eye...