Electric UFH vs Automation

[Thorfun]

2 minutes ago, SteamyTea said:

Yes, it is a problem now.

Mind you, not all Chinese made stuff is bad, they have very good engineers there.

I agree. Was just wondering how much of the “good quality” stuff is all marketing b******s as it’s all the same stuff. 

[Dan F]

4 hours ago, Nickfromwales said:

That’s a bit OTT? 50-100w max for anything built to ‘low energy’ standards should be ample as the ambient is never that far away from the desired ‘comfort’ temps. 
I only used to install 150w or above when this was the only heat source in the room ( for a crappy b.regs refurb ). 

 

Maybe, but if it's on a thermostat doesn't really matter if it's 50W, 100W or 150W, 150W will simply be on less of the time.  Unless you plan to trigger it to heat up when you turn on the shower or something, in which case a higher W might be advantageous.

[Nickfromwales]

11 minutes ago, Dan F said:

 

Maybe, but if it's on a thermostat doesn't really matter if it's 50W, 100W or 150W, 150W will simply be on less of the time.  Unless you plan to trigger it to heat up when you turn on the shower or something, in which case a higher W might be advantageous.

If they’re controlled ‘on and off’ vs proportional it’ll cause overshoot, that’s all.

[joth]

9 hours ago, Nickfromwales said:

If they’re controlled ‘on and off’ vs proportional it’ll cause overshoot, that’s all.

The OP will be controlling it from Loxone so easy to use a PID controller to avoid any overshoot. However as I mentioned a few pages ago the PID works MUCH better with zero crossing SSR than a mechanical relay.

 

 

[Nickfromwales]

1 hour ago, joth said:

The OP will be controlling it from Loxone so easy to use a PID controller to avoid any overshoot. However as I mentioned a few pages ago the PID works MUCH better with zero crossing SSR than a mechanical relay.

 

 

Ok, so with the Luxone the output can be proportional? Or just a very tight hysteresis? 

[Dan F]

3 hours ago, Nickfromwales said:

Ok, so with the Luxone the output can be proportional? Or just a very tight hysteresis? 

 

I run mine at 25C with a fairly tight hysteresis using a standard Loxone relay output.  The goal isn't to heat the bathroom, just to take the chill off in the morning in the winter.

 

Looking at the stats from earlier in the year:

- It takes 30min to heat the bathroom floor from 21C to 25C at 6.30 am in the winter with (I think) a 150W mat.

- Overshoot is max 0.4C (floor temp, not room temp).

 

So, in practice, is there any real reason to introduce proportional control here?

 

[Nickfromwales]

1 hour ago, Dan F said:

 

I run mine at 25C with a fairly tight hysteresis using a standard Loxone relay output.  The goal isn't to heat the bathroom, just to take the chill off in the morning in the winter.

 

Looking at the stats from earlier in the year:

- It takes 30min to heat the bathroom floor from 21C to 25C at 6.30 am in the winter with (I think) a 150W mat.

- Overshoot is max 0.4C (floor temp, not room temp).

 

So, in practice, is there any real reason to introduce proportional control here?

 

Not with those numbers! Was more a question than a suggestion, as I have a number of new clients who will likely adopt Luxone or Control 4, so I'm just doing a bit of mining tbh. 

 

For anyone with no home automation, it may serve them better to run a lower Wm² mat as it will need less focus on accurate control.

[joth]

5 hours ago, Nickfromwales said:

Ok, so with the Luxone the output can be proportional? Or just a very tight hysteresis? 

Mine is proportional, insomuch as the PID output is pulse width modulated (I think I have set it about 0.2 Hz) and so as the floor is up to temperature it just ticks over putting in a small pulse of heat once every 5s. (Again this is unrelated to room temp, it's just managing floor comfort temperature).

 

Same as the immersion PV diverter, towel rads and a few other PIDs I've configured for various things I can't recall right now. 

 

It's a shame Loxone doesn't have any PID automatic confirmation, ESPHome is superior in this respect with built in Ziegler-Nichols / Åström and Hägglund autotune. (Completely unrelated to Cher's autotune)

 

Edited June 26, 2023 by joth

[joth]

2 hours ago, Dan F said:

 

I run mine at 25C with a fairly tight hysteresis using a standard Loxone relay output.  The goal isn't to heat the bathroom, just to take the chill off in the morning in the winter.

 

Looking at the stats from earlier in the year:

- It takes 30min to heat the bathroom floor from 21C to 25C at 6.30 am in the winter with (I think) a 150W mat.

- Overshoot is max 0.4C (floor temp, not room temp).

 

So, in practice, is there any real reason to introduce proportional control here?

 

 

I run mine at 27°C and takes about 16mins to get there from 22°C with the PID controller, no overshoot. (Summer numbers a odd I can dig back for a winter example if helpful)

Still nowhere near fast enough for "on-demand" heating as you walk in the room, but I trigger it from the bedroom alarm/ curtains opening which is usually enough for a warm floor before getting that far out of bed 😅 

I'm not actually sure how many W/m2 ours is. That'd be fairly easy to derive from some measurements tho

Edited June 26, 2023 by joth

[Dan F]

1 hour ago, joth said:

 

I run mine at 27°C and takes about 16mins to get there from 22°C with the PID controller, no overshoot. (Summer numbers a odd I can dig back for a winter example if helpful)

Still nowhere near fast enough for "on-demand" heating as you walk in the room, but I trigger it from the bedroom alarm/ curtains opening which is usually enough for a warm floor before getting that far out of bed 😅 

I'm not actually sure how many W/m2 ours is. That'd be fairly easy to derive from some measurements tho

 

I can see PID is technically better, but for most people simple hysteresis is good enough and easier to implement. In my case, I'd have to buy SSRs and add also add PWM dimmers to implement PID. which I can't really justify.

 

 

[joth]

39 minutes ago, Dan F said:

 

I can see PID is technically better, but for most people simple hysteresis is good enough and easier to implement. In my case, I'd have to buy SSRs and add also add PWM dimmers to implement PID. which I can't really justify.

 

 

No PWM dimmer required, Loxone directly turns the SSR on and off. (In my case it's via a DMX channel but treated as a binary on/off output). The SSRs were like £1 per channel and I had spare DMX outputs already (48 channel decoder of which I'm only using a fraction) so this approach was by far the most cost effective for me. 

I expect different tiles have greater chance of overshoot, certainly when I first did it it was overshooting by a few ° (can't remember how many) and if the element is vastly oversized it will have higher risk as Nick said, but agree it not enough I would have worried about retrofitting if I wasn't trivial for me to do in the first place. 

 

 

[Dan F]

17 hours ago, joth said:

No PWM dimmer required, Loxone directly turns the SSR on and off. (In my case it's via a DMX channel but treated as a binary on/off output). The SSRs were like £1 per channel and I had spare DMX outputs already (48 channel decoder of which I'm only using a fraction) so this approach was by far the most cost effective for me. 

I expect different tiles have greater chance of overshoot, certainly when I first did it it was overshooting by a few ° (can't remember how many) and if the element is vastly oversized it will have higher risk as Nick said, but agree it not enough I would have worried about retrofitting if I wasn't trivial for me to do in the first place. 

 

Well, it's not quite directly from Loxone if you are using a DMX channel.  For anyone that doesn't have DMX channels (or similar) in their cabinet then you'd need a digital output of some sort, and it doesn't make sense to use a 16A relay to control SRR to then switch a max 10A load (especially if trying to avoid anything mechanical for PID control).

 

The other approach is a proportional SSR using 1-10v control but this involves a more expensive SSR and Loxone AO are seemingly £80/output!!

 

20 hours ago, joth said:

Same as the immersion PV diverter,

 

Not using something proportional for this, or you can avoid that given you have a battery as a buffer?

[joth]

15 hours ago, Dan F said:

Well, it's not quite directly from Loxone if you are using a DMX channel

I never claimed it was. Loxone don't have an SSR solution so any SSR output will be non Loxone at some level.

I mean Loxone also don't make cabinet wire or RCBOs or UFH heating mats but we're all okay using those from other suppliers, but they DO make a DMX extension so I feel pretty happy with my choices in using other manufacturer's DMX decoders. (KNX would be similar position, esp as I have a V1 miniserver)

 

16 hours ago, Dan F said:

Not using something proportional for this, or you can avoid that given you have a battery as a buffer?

Yes my PV diverter is just a big 30A rated SSR. That one actually takes 0-10V input to control its PWM, so I drive it directly from one of the miniserver AOs. (A DMX 0-10v decoder would be my next stop if I needed more channels)