UFH - do I need floor probes?

[Great_scot_selfbuild]

We’re installing UFH in a dry screed with an ASHP that has reversible function and may be used in a cooling mode.

 

Ive read a little about floor probes, but our ASHP installer is saying they’re not required as dew point just requires us to know the air temp. 
 

1. When are they required?

2. What for?

3. Where should I put them? (I’m having a single zone with 11 circuits across 6rooms).

[SteamyTea]

The floor temperature will be pretty close to the mean flow temperature, so no real need for extra sensors.

Extra sensors would be good for data collection and analysis, but not many people are as nerdy about that as me.

[Nickfromwales]

If I can walk about in my cream and brown Y-fronts in Jan then I really wouldn't give 2 hoots what the mean flow temp is. I'd be warm and happy, the neighbours not so much as apparently that's not a good look.

 

It's not just the probes, it's what you need to connect them to, if you actually do want to geek-out, but the novelty will wear off PDQ. 

 

 

[Great_scot_selfbuild]

37 minutes ago, SteamyTea said:

Extra sensors would be good for data collection and analysis, but not many people are as nerdy about that as me.

I’ll leave the data analysis to my wife. She’s the clever one…

 

33 minutes ago, Nickfromwales said:

cream and brown Y-fronts

🤢🤮…

 

34 minutes ago, Nickfromwales said:

if you actually do want to geek-out, but the novelty will wear off PDQ.

🧐

 

I think I’ll install one probe and have a connection to the plant room in case we decide we want to. 
 

thanks all - I’ve whittled the UFH quote down quite a lot thanks to input from here and it comes to just £1060 ex VAT for a 115sqm area coverage. Over £1k cheaper than some of the quotes I had in!

[-rick-]

1 minute ago, Great_scot_selfbuild said:

I think I’ll install one probe and have a connection to the plant room in case we decide we want to. 

 

If you do this the advice I've seen which seems like a good idea is to put the sensor inside a pipe/conduit with the end sealed to stop concrete getting in. That way if something goes wrong with the sensor you can pull it out and push in a new one. Can use either an extra length of PEX or flexible electrical conduit. PEX might be the better option as long as your sensor fits inside.

[JohnMo]

For the information it gives, would not bother. Certainly no need for cooling as your plumbers says. Pump at 17 degs, humidity will never be an issue - ever. I did short bursts at 12, with zero issue.

 

Heat pump off, circulation pump on, will tell you way more than the odd probe in the floor, you can see solar gain and chart floor temperature drops and rise rates for heat and cool.

 

Generally if you need more than a manifold and possibly a single thermostat (if the heat pump controller doesn't do that function) you are over thinking it. The thermostat should do heat and cool with in build humidity sensing. Humidity sensing is belt and braces for cooling and serve as as safety cut out off, if you or someone has been messing with controller

[joth]

As others say, the main use is for nerdy stat collection. I also use mine to protect the bamboo floor finishes when I'm overdriving the flow temp during cheap rate (to maximise energy delivery) but that's really just because I can, not something I'd design into a system.

 

TBH the single biggest use I have for them in other installs I'm involved in is it gives me some independent data on whether the heat pump is working, and whether individual loops have issues. When I'm working remotely it doesn't matter how many times the local plumber says it's all working, if I can see the floor in a room is not warming up I know there's an issue on the hydronic side (probably air trap or the flow balancing valve screwed down too tight) and I can feed this back without an extra visit to site to confirm as much.

Without the temperature probe expect a bit more time staring at the floor with a thermal camera while debugging the system. But in normal operation, it's not needed.

 

[JohnMo]

18 minutes ago, joth said:

if I can see the floor in a room is not warming up

Why do you need a floor sensor for that? A room sensor does that anyway.  If a room sensor breaks its an easy job to replace, not so sure about a floor sensor.

[joth]

29 minutes ago, JohnMo said:

Why do you need a floor sensor for that? A room sensor does that anyway.  If a room sensor breaks its an easy job to replace, not so sure about a floor sensor.

Because if I'm not onsite it's easy for the local contractor to say "oh yes, the heating and floor loop is working, the problem must be with {insert excuse here: poor insulation, high heat losses, bad room sensor}."  if I can show the floor screed itself is not getting hot, it's much easier to save myself a call out. Not saying this is how it should be, just how I've found it to be in practice.

Also, somewhat counterintuitively, floor sensors are in many ways easier to install as they happen much earlier in the programme. A room air sensor needs to be sympathetic to aesthetics, and coordinated with plastering and decoration, and that sometimes results in them being  significantly delayed or even omitted, so functionally useless when the heating is being commissioned.

 

FWIW when I've specified floor temperature probes I think they ended up being direct buried without the install tubes, yet I've had 0% failure rate. That's not a recommendation, just observation. This is with Dallas type encapsulated 1-wire probes.

 

 

Edited 3 hours ago by joth

[Nickfromwales]

39 minutes ago, joth said:

FWIW when I've specified floor temperature probes I think they ended up being direct buried without the install tubes, yet I've had 0% failure rate. That's not a recommendation, just observation. This is with Dallas type encapsulated 1-wire probes.

I direct bury the ones for UTH in bathrooms, but as they're so cheap I just put A - in use and B - spare each time. I just prefer the nub on the end to be wrapped in tile adhesive or SLC for the most accurate reading possible.

 

The last job where I was asked to do this, we just used offcuts of 16mm ufh pipe and made long sweeping bends. The probes then got taped to piano wire and pushed into the depths; if these fail, you just pulled out the piano wire, re-attach, and poke the wee beastie back in.