Control strategy

[HughF]

Room thermostat with night setback, or standard thermostat and use the ‘night mode’ on the heatpump controller to limit the operating frequency of the fan and compressor during night time?

 

It’s something I hadn’t considered up until this point. My heat pump controller has no knowledge of room temperature, unlike LG, Samsung, Midea, Mitsubishi.

 

This is with radiators in the house and ufh in the new extension.

 

[ReedRichards]

Do you actually want the night time set-back?  Some heat pump zealot is bound to come along and tell you to forget about the room thermostats, that you should be relying on Weather Compensation together with carefully balanced radiators to maintain a constant room temperature.  Me myself, I much prefer a night-time setback and, should you want to abandon your room thermostat, that's only possible if your heat pump controller has a mode which allows it. 

[HughF]

Yes, my wife will expect a wall thermostat and does like a night-time setback. We have a simple Honeywell analog stat at the moment and I need something equally simple, with a dial. Considering the Siemens, or a Nest.

 

I can’t expect her to go into the heat pump controller and bump the WC curve up a notch if she’s too cold.

 

Ideally the heat pump controller would support load compensation for adjusting the WC curve, but I didn’t buy an Ecodan, so I’m stuck with what I’ve got.

 

My unit is supplied with a jumper on the call-for-heat terminals, I’ll just wire that back to the stat.

 

My unit has a quiet mode which limits the extent of the compressor and fan vfd range, but it has no idea about room temperature.

Edited September 4, 2023 by HughF

[JohnMo]

13 minutes ago, HughF said:

Ideally the heat pump controller would support load compensation for adjusting the WC curve

That's ok for your rads, but not the UFH. 

 

To get a set-back you just need a simple thermostat with a timer.  Basically reduce the target temp a couple of degrees at say a hour before you normally go to bed and set it back to the higher setting an hour or so before you get up. Depending on how long your house takes to cool will determine how long your heat pump stays off.  Only thing to concider is your heating curve needs to take account of having to play catch-up to get the rooms back up to temp. So small set-backs are good.

 

Or use your night setting which in effect do the same thing, but will leave the heat pump ticking over 

 

If you run WC, the moving a thermostat temp up will have zero effect on the heating, moving it down will.

[JohnMo]

26 minutes ago, HughF said:

 

My unit is supplied with a jumper on the call-for-heat terminals, I’ll just wire that back to the stat

That is exactly the way mine is wired up. I am using a Computherm thermostat it has an adjustable hysterisis which is good, I am using 0.1 for the UFH great for limiting temperature over/under shoot.

[JohnMo]

29 minutes ago, HughF said:

We have a simple Honeywell analog stat at the moment

Leave that in place, let your wife twiddle to heart's content, just don't connect to the heating system.

[JamesPa]

6 minutes ago, JohnMo said:

Leave that in place, let your wife twiddle to heart's content, just don't connect to the heating system.

The good old placebo thermostat - best control strategy ever.  I'm genuinely surprised it's not used more often.

[joth]

Any interest in ever using cheap overnight electricity like octopus Go?

If so you want a nighttime boost rather than setback mode. 

[DanDee]

5 minutes ago, joth said:

Any interest in ever using cheap overnight electricity like octopus Go?

If so you want a nighttime boost rather than setback mode. 

 

I think the topic is comfort rather than cost.

[HughF]

37 minutes ago, joth said:

Any interest in ever using cheap overnight electricity like octopus Go?

If so you want a nighttime boost rather than setback mode. 

Probably, but I need to get off prepayment with BG first, then start the long winded procedure of getting getting a smets2 installed and a new octopus tariff in my name.

 

It will be used for ev charging though, I’ll probably need close to 30kWh/ day for my commute.

Edited September 4, 2023 by HughF

[JohnMo]

6 minutes ago, HughF said:

long winded procedure of getting getting a smets2 installed

I booked an appointment last week, they come on 26th September to install, so just under 4 weeks.

[HughF]

1 hour ago, JohnMo said:

That's ok for your rads, but not the UFH. 

 

To get a set-back you just need a simple thermostat with a timer.  Basically reduce the target temp a couple of degrees at say a hour before you normally go to bed and set it back to the higher setting an hour or so before you get up. Depending on how long your house takes to cool will determine how long your heat pump stays off.  Only thing to concider is your heating curve needs to take account of having to play catch-up to get the rooms back up to temp. So small set-backs are good.

 

Or use your night setting which in effect do the same thing, but will leave the heat pump ticking over 

 

If you run WC, the moving a thermostat temp up will have zero effect on the heating, moving it down will.

Planning a 2-3 degree setback… rads sized for 45 flow at -4 so we should be hovering around 38-40 on the WC at normal winter temps.

[DanDee]

10 minutes ago, JohnMo said:

I booked an appointment last week, they come on 26th September to install, so just under 4 weeks.

 

31th may I moved to Octopus through referral, 10th June I was able to book the appointment, received the confirmation for 16th June.

[HughF]

Step 1. Get my wife to contact BG and move us to a credit account in my name…

 

I suspect this will take ages to do and be impossible to get right.

[HughF]

Back to the thermostat choices, this one looks ideal. Has a nighttime mode with programmable times and setbacks, and a simple to use dial display.

 

It’s either this, or a nest gen3 with the smart scheduling disabled. I suspect the nest will look nicer on the wall.

 

 

Edited September 4, 2023 by HughF

[joth]

6 hours ago, DanDee said:

 

I think the topic is comfort rather than cost.

Sure, my thought is it'd be a shame to install thermostat now then have to rip it out and redo it in a few months if a change to variable rate billing is imminent 

[HughF]

The more I look at this 'stat, the more I think it will be just the job.

 

Datasheet attached, it has adjustable upper and lower limits (ideal, stops the wife turning it down to 10deg to turn the heating off, like she does at the moment. Stops sister-in-law turning it up to 25 thinking the place will heat up faster), and either on/off or PID control.

 

And it's under £40...

A6V10954415_Room temperature controller with 24-hour time swit_en.pdf

[JamesPa]

1 hour ago, HughF said:

The more I look at this 'stat, the more I think it will be just the job.

 

Datasheet attached, it has adjustable upper and lower limits (ideal, stops the wife turning it down to 10deg to turn the heating off, like she does at the moment. Stops sister-in-law turning it up to 25 thinking the place will heat up faster), and either on/off or PID control.

 

And it's under £40...

A6V10954415_Room temperature controller with 24-hour time swit_en.pdf 750.04 kB · 0 downloads

Just don't use it on PID control.  That will mess with the heat pumps controller!

[JoeBano]

I’ve got nest on my radiators and heat miser on the Ufh. Nest works great really. If you have been away and turned the heating off you can switch it back on your phone. 

Edited September 4, 2023 by JoeBano

[Alan Ambrose]

>>> heat miser on the Ufh ... you can switch it back on your phone. 

 

You can do that with Heatmiser also if you have the hub thingy.

[HughF]

‘Smart’ controls are not required…

[JoeBano]

I wouldn’t have a nest then the smart features can be a pain to turn off then randomly come back on. 

[HughF]

6 hours ago, JoeBano said:

I wouldn’t have a nest then the smart features can be a pain to turn off then randomly come back on. 

Yeah, I think I’ll stick with the Siemens.

[Wil]

I have a nest which has decided to give up connecting to wifi. Works wonders as a pretty ‘dumb’ thermostat though.

 

Google refuse to fix it as it’s old. Now my nest hub has started playing silly buggers with wifi. It’s almost as if they design in failure after 3 years…

[HughF]

I must admit, they are pretty, and that outer ring is very satisfying to operate...