[Closed] Underfloor heating controls

I had it installed on my last house. We used a timer to run at the temperature we wanted when we were in, and then a lower temperature for when we were out. The difference was something like 3deg iirc, so you are never heating from cold, just topping up the difference.

Also each room had its own zone control, so the timer was different for each part of the house to suit occupation.

you want a programmable thermostat.

Most people recommend Honeywell CM927 but I wont as mine died after only 2.5yrs and honeywell didnt want to know. A solid state electrical device that only runs for 30months is shit IMO. Especially when they cost about £100.

Instead I recommend either a [s]heatmiser unit (I have fitted them on UFH for a friend)[/s]* or a Salus RF500. Both more like £40 and work fine.

There's not much point winding UFH up and down with wide temp ranges. And I tend not to use it to hit a full comfort temp of 19deg. Mine is set at around 14deg for the day or 18deg in the evening. BUT I also might have mine boost for an hour just to get some heat into the floor even if I dont really need to aim for a comfort temp as a solid floor can still suck the heat out of your feet even if insulated unless you take the chill off it for a while. I then use wood stoves to hit a comfort temp in the evenings.

In mid winter then the UFH is working much harder and it will be on all evening, but again watch out for using secondary heating source like a woodstove, making air temp 19-20degrees, so the UFH doesnt run and the floor temp drops away.

Live with it and learn how to get the best out of it.

http://www.salus-tech.com/products/thermostat/rf-thermostat/_c1_34_wireless-programmable-room-thermostat-868mhz/

PS the last Salus I got off eBay for £5. s/h in perfectly good condition.

* RE Heatmiser, they seem to have put their prices up a lot. And someone will probably pop up to say that they are hackable - some of the WiFi connected ones have v poor network security to just go for a dumb device instead.

Editt - too slowwwww 🙁

I dont get the shutting down thing - that makes not sense.
Is he also confusing it with heat pumps which are often linked to underfloor heating.

If it is working at the moment then fine, but as the floor will have a much larger thermal mass than a radiator it will take longer to heat up. you might find in winter that it looses so much temp when the system is off it cant heat up in the two hours you have the heating on in the morning.
A better controller is a thermostat timer that does not simply turn the boiler on or off but allows you to selct a lower night temperature which probably means your boiler is off for most of the night but when there is a really cold night then it kicks in and stops the floor getting too cold so it has a chance to warm up in the morning

N

The builders left it with a simple room thermostat to control, which i've only just turned up as the weathers taken a colder turn and it seems to work fine.

If you need to "turn up" a thermostat when it gets cold, it's not working properly.

Ours works off both room temperature and floor temperature. You can set limits for both mapped against time of day and day of week etc. Think that covers everything.

We're just about to get wet underfloor heating installed in our new basement.

Can you have individual room thermostats? From the OP it sounds like you can, but it's something that just occurred to me and is important for us.

individual room thermostats

Yes - you can specify as many zones as you want. Each will be its own loop back to the manifold and each can be individually controlled.

Yes you can.

Each thermostat sends signal to a control unit at the manifold/boiler to call for heat individually. Any single thermostat can call for heat but each water circuit is controlled by a servo on the manifold valve so only those rooms that are switched to open by their respective thermostat will receive hot water.

these guys have a good site to learn more. They also supply good VFM kit.

http://www.underfloorheating1.co.uk/

Yak and Stoner - many thanks, that is fab news!

Thanks all for the replies, its given me food for thought. Just to clarify, the U/F heating works fine. The thermostat was turned down to zero until recently as heating wasn't needed until the last few days as the weathers turned colder, so i've now turned the stat up to 20 degs turn the u/f heating on and its working nicely. However running just on a stat means its trying to maintain a constant temp 24/7 hence my query about a controller. I'm aware of the thermal lag so want to avoid messing around too much with varying the temperature too much, but at the same time it doesn't make sense to maintain a comfortable temp 24/7.

We had underfloor heating when we lived in Germany.

Switched it on in the autumn; switched it off in the spring.

We are going to continue with our central heating on the ground floor and have underfloor heating in the basement and I have a couple of questions:

should our current combi boiler be able to cope with the extra rooms? (currently heating 4 rooms via radiators; we will be adding a further 4 rooms with underfloor heating)? Sorry I don't know what size it is. Can anyone recommend a minimum size required?

If the current boiler can cope, what would we need to install in order for it to operate the 5-zone UFH in addition to the radiators? We've been quoted 500 pounds + VAT and that seems a lot if all they need is an UFH controller. This 500 + VAT is totally separate from the cost of actually installing the UFH.

what has the UFH installer quoted for? manifold? manifold valves? pump? room/zone stats and controller?

should our current combi boiler be able to cope with the extra rooms?

No idea. Sizing is a combination of science and art based on as much information as possible, including construction tech/insulation associated heat loss, vent loss, local climate etc.

Give us a hand, what boiler do you have now and how big are the current radiators and the new rooms?

What pipe centres is the UFH being laid at?

Really your UFH guy ought to be best placed to answer all of these since it sounds like your install is more than just adding one room and nor is it as "simple" as a "from scratch" or new build install.

We asked why they were charging an extra 500+VAT for the UFH controller and he apologised and said we didn't have to.
We're going to try it with the current boiler. If it doesn't work well buy a bigger one.

wobbliscott , you can get what is called a setback stat. which is designed to set the temperature back 3-4 degrees when the programmer is "off". It requires a 4 core cable to the stat. which might be a show stopper though.
[url= http://www.heatmisershop.co.uk/heatmiser-ds-sb-flush-mounting-setback-thermostat/ ]Heatmiser DS-SB Setback Stat.[/url]

Rich.

Our ground floor UFH was installed in 2002 and is never 'off', all year round. It runs off Honeywell (CM67, the old ones) roomstats which basically have the main temp setting and a 'set back' temp which I think is 4 degrees lower so it basically operates on a very shallow sine wave of temperature and gently puts some more heat in only when needed rather than having your boiler (or other heat source) having to try really hard, and therefore expensively, to try and ramp the temperature up.

Just picking this one up again, thanks for the links and suggestions. I think i'll look at one of those setback thermostats, though looking at the spec they seem to need a signal from the C/H timer and I don't think there is one to the current room stat so I guess I would need a setback stat with a built in timer.

As has been pointed earlier up there , it would be far better to have a programmable stat.
Dead simple, L+N in, switched live out.
I fit a really cheap one for my miserly customers, cost around £35, and never had a call-back to them.
https://www.dungannonelectrical.co.uk/cms/cms.jsp?menu_id=19730&prodref=DRT2&proddesc=Niglon-5-35-Degree-Programmable-Room-Thermostat&category=Stats&catdesc=Thermostats

did whole house rebuild with kit from these guys - individual room thermostats (touchscreen on 7 day, multi event timer, different temps, over-ride etc etc). Best price we could find 2 years ago, no probs with kit at all.

http://www.wundafloorheating.co.uk

Out of interest, why are people recommending only setting small temperature differences with the thermostat? What's the downside of having it completely off overnight, and then setting it to be warm by the time you get up?

Radiators operate at a higher temperature (60 degrees?) than underfloor heating (30 degrees?). Underfloor heating takes a long time relative to radiators to heat an area. Radiators on a off-on-off-on cycle will get the house warm but underfloor heating won't warm up sufficiently.

Just spotted this thread. Have just moved into a house with UFH and couldn't understand why the rooms were getting so hot, even adjusting the thermostats down. Then I've just discovered that the servos to the manifold have been disconnected! The only problem is there are three servos and four valves on the manifold. I presume it's just a question of trial and error or is there something more scientific that I should be doing? Apologies for hijacking the thread!

When you say servos do you mean two port valves?

I'm not sure. I was referencing Stoner's description. There are three white dome shaped units attached to electrical wires and there are four valve units on a copper manifold with screw threads that match these units. I have yet to attach / fit the units to the manifold because of the extra valves to units (if that makes sense).

Without a picture it's difficult to tell, but what you describe are the valve actuators that are controlled from a box somewhere that also takes in feeds from the stats. There is probably 4 zones in your system, one of which is an open zone designed to act as a heatsink if the three that are controlled are shut as they are up to temperature. The open zone is going to be the one without the thermostat; possibly the hallway or area where it's likely to be coolest.
To reactivate the zones, put the 3 actuators back onto the manifold on top of the valves corresponding to the controlled zones. ie the open zone should have nothing on it.

Any questions, post away!

Rich.

wot rich says ^

servos are just motorised actuators that push the manifold valve pins up and down. Two port valves are self contained valves installed in a pipe that open or close a single flow.[img] [/img][img] http://www.speedfit.co.uk/getattachment/a33ae695-3832-43be-9087-2134c5c78555/ACTUATOR-VALVES.aspx [/img]

I dont have them on mine as the barn is completely open plan downstairs and zoning is only because you're limited to <100m of pipe run in any one circuit. Instead I have set each depending on the location of the zone relative to the kitchen or TV 😉 It's deeply scientific.

Having said that, Ive just completed building a wall around the kid's play room, so they now have a self contained zone. In theory I should get a second thermostat, 5 actuators and a new master control unit. But that'll cost a bomb so they can just get cold in there 🙂

EDIT: having said that: only £10 each, seems a bargin!!!
http://www.underfloorheating1.co.uk/product/standard-electrothermic-actuator-230-volt-2-wire-5

The valve actuators are like the ones shown in Stoner's latest post bottom two pictures. How do I know which value is going to be the open zone?

you should have some caps to go on top of the valves. Their job is to close off each zone. Put three on and see what zone warms up. Swop around as necessary until you find the one which is the open zone. If you don't have caps, use the actuators and turn the stats down very low which will stop the valves opening.
Rich

edit:
Actually swop them round as necessary until you a) find the openzone and b) associate a stat. with the zone otherwise you'll have a stat. controlling the wrong zone.

Many thanks RWA and Stoner, I'll give it a go and sorry again for hijacking the thread!

rwamartin, should we have an open zone then?

We've asked for 5 separate zones but no open zone.

Ekinspain, I'm an electrician, not a plumber so I'm in the dubious position of knowing enough to be dangerous when it comes to the bits with water in. 😀

I think some systems need them; others not. It depends on the design and I would ask whoever is doing the work for you what you need. If they don't seem to be able to give you a convincing anwser then you might want to seek a second opinion.

Sorry I can't be more helpful but I'm sure there's someone watching this thread that can fill in the gaps.

Rich.

A quick bit of research gives this - remember IANAP -

<GOOGLE> With a heatpump, an openzone prevents short cycling (ie frequent stop/starts) which draws a large amount of current and is not very efficient. The open zone dumps some of the heat causing the pump to continue running. </GOOGLE>

I think open zones are also relevant with gas/oil systems in that they are often used where thermostatic valves (TRVs) are fitted. One radiator is used without a valve. Now, on my system at home (oil - S Plan plus if that means anything to you) - I don't have an open zone; there are TRVs on all the rads. However, I do have a bypass valve which causes the hot water to circle directly back to the boiler. I think that this negates the need for an open zone because excessive pressure from the pump is diverted back to the boiler. An open zone would not necessarily require a bypass valve (though maybe for other reasons it would) because excessive pressure can't build up.

That said, if there's anything worse than a plumber doing electrics, it an electrician doing plumbing......

Rich.