UFH Cooling Control

[volcane]

Hi All,

 

After an extremely tough build we are nearing completion and I am about to order an ASHP for DHW (500 litre UVC)and UFH. The house is 400 sqm with separate bedroom and living areas, 5 bed (3 upstairs). 4 Velux passive roof lights for stack ventilation. We have a larger than average house partly due to disability requirements. The house was planned to achieve 'passive' levels and require little heating, I have been running a couple of 1200 W electric heaters which easily have the house comfortable even during the recent cold spell.

 

I have selected Daikin as the manufacturer due to local support and experience of our plumber, (who has been excellent).  I wanted a reversible pump to have the option of cooling as well as heating, with the view that the house may require a small nudge to stay comfortable. The plumbers usual supplier were going to supply a non-reversible 14kW low temp split, I feel that this is oversized and that that a 8kW Daikin Altherma 3 low temp split (reversible) will provide more than we need (and I still have my electric heaters!) along with the electric towel rails (5x800 watt). All ok so far bar the ability to cool as the supplier says it won't work. In all the Daikin brochures floor cooling is promoted for the reversible units.

 

How can I control the cooling aspect of the UFH? a thermostat that controls cooling only seems to be directed to fan coil control. Do I just switch the ASHP to cooling and then set the themostats to the desired temperature and let the ASHP try to achieve that? Perhaps I can set the minimum temperature flow rate to a level where the risk of condensation is minimised?

I really only want the bedroom block not to overheat and to be slightly cooled.

 

I also need the system to work simply as my wife doesn't want to be left with a complex heating system when I am unable to tinker.

 

thanks for any advice,

 

[SteamyTea]

Is it in here, page 15.

Tell the vendor that it is a non RHI installation.

 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.daikin.co.uk/content/dam/document-library/declaration-of-conformity/heat/air-to-water-heat-pump-low-temperature/ehbh-cb/EHBH-CB_EHBX-CB_4PEN383118-1C_Installation%20manuals_English.pdf&ved=2ahUKEwjc_I6svfHuAhWdQkEAHfyWBjYQFjAEegQIFBAB&usg=AOvVaw2zhfl3ZrOUkvtQGRsPArBy

[volcane]

Thanks Steamey,

 

I now have an updated quote for an 8kW Split Daikin that is reversible. The supplier is still doubtful that cooling the floor a little can work and has never tried it or seen it work in practice despite what the Daikin literature may say.

 

So I have still an issue, in that I'm not sure if simply switching the heat pump to cooling perhaps in June and then setting the room thermostats to my 'max' temperature and hoping that this will direct the cooling from the ASHP. I only want the bedroom area of the house to be cooled. The supplier says that I should use a thermostat with a floor sensor in case the slab gets too cold, my thoughts are that this should not be required as I can't envisage that amount of cooing being required and I plan to set the minimum temperature to 13°

 

All input appreciated

 

V

 

[SteamyTea]

Worth putting temperature probes in the slab anyway.

https://m.ebay.co.uk/itm/DS18B20-2M-Waterproof-Digital-Temperature-Temp-Sensor-Probe-DS18B20-UK/192870453965

[volcane]

Thanks, floors getting tiled next week so likely too late, certainly for delivery from China! Main kitchen dining already done.

 

Might look for something more local.

[Bramco]

20 hours ago, SteamyTea said:

Worth putting temperature probes in the slab anyway.

https://m.ebay.co.uk/itm/DS18B20-2M-Waterproof-Digital-Temperature-Temp-Sensor-Probe-DS18B20-UK/192870453965

 

Buyer beware!

 

There are loads of fake and counterfeit DS18B20 probes around and most are sold through ebay or AliExpress etc.  If you want to make sure you have a real Dallas/Maxim part, then buy through a reputable outlet RS etc.

 

Issues include 'some of the counterfeit sensors actually do not work in parasitic power mode, have a high noise level, temperature offset outside the advertised ±0.5 °C band, do not contain an EEPROM, have bugs and unspecified failure rates, or differ in another unknown manner from the specifications in the Maxim datasheet.'

 

This is from - 'How to tell original from fake DS18B20 temperature sensors.'   at   https://github.com/cpetrich/counterfeit_DS18B20

 

I use software from the open energy monitor crew and there has been a lot of discussion there about failure rates of the fake sensors.

 

You may not have any issues with a fake or counterfeit part - but then again you may...

 

Simon

[SteamyTea]

34 minutes ago, Bramco said:

Buyer beware!

True for everything.

 

All the ones I have use the ROM pattern 28-xx-xx-xx-xx-00-00-xx.

But I do have one that is outside the 0.5°C temp range when compared to the others.

Though I have had this before with Dallas stuff.