MAX_CH Water Setpoint

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CaptainSlow
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MAX_CH Water Setpoint

Post by CaptainSlow » Monday 09 January 2017 19:26

Hi there,

does anybody know what the MAX_CH Water Setpoint actually exactly does?...I was playing altering it from 80 to 75 degrees via domoticz sending a command to the OTGW which seems to work well. See pictures.

I reckon it's a sort of Maximum water temperature of the central heating system as the name implies preventing the CH from boiling water in the radiators.
The question is ...is there anything lese i should know about this setting?

thx in advance

willem
CH-temp.PNG
CH-temp.PNG (78.87 KiB) Viewed 426 times
CH-75.PNG
CH-75.PNG (27.72 KiB) Viewed 426 times
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Raspberry PI 3, Domoticz Beta, Open Therm Gateway with ESP wifi-bridge, Milight Ibox(V6), Wundermap

tiga
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Re: MAX_CH Water Setpoint

Post by tiga » Wednesday 29 March 2017 21:24

max central heating water setpoint.......or maximum temperature of supply water for the heating of your radiators.

TyzzyT
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Re: MAX_CH Water Setpoint

Post by TyzzyT » Thursday 06 April 2017 9:47

This is especially relevant when you want to tweak your central heating system. Because HR-ketels have the best efficiency when the retour-temperature is below 45ºC.

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najtram
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Re: MAX_CH Water Setpoint

Post by najtram » Friday 11 August 2017 10:53

TyzzyT wrote:
Thursday 06 April 2017 9:47
Because HR-ketels have the best efficiency when the retour-temperature is below 45ºC.
This is interesting information! Could you indicate where there is more of these kind of information. I'm not an expert on such knowledge, so a simple reference guide could help.
Domoticz on Raspberry Pi 3 with USB RFLink Gateway at 433 Mhz for several KAKU switches. Bluetooth Soma Smart Shades. USB Opentherm Gateway connected to Remeha iSense with Remeha Tzerra boiler. Almost running homebridge.

jb274
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Re: MAX_CH Water Setpoint

Post by jb274 » Saturday 12 August 2017 10:03

An HR-ketel uses the burner exhaust gasses (CO2+H2O+NOx) to heat the return water using an heat exchanger. If the return water is below a certain temperature (Around 45ºC) the H2O from the exhaust will condense (that is why these type of heaters are connected to the sewer, check the amount of water coming out of it when it is running high). This condensation - or phase change - delivers extra heat (the same heat that is needed to evaporate water into gas) and is what makes an HR-ketel reach its 115% efficiency.

If the return temperature of the water is too high for the H20 in the exhaust gasses to condensate the efficiency will drop and your heater will fall back to being more like a VR-ketel with a lower efficiency. White water vapor plume will be rising from the pipes outside (indicating presence of water vapor which didn't condense). So it is important to make sure the return water temperature isn't too high. You can tune the outgoing water temperature of course and the flow rate as well on modern heaters (to give the water more time to exchange it's heat in the radiators).

jake
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Re: MAX_CH Water Setpoint

Post by jake » Saturday 12 August 2017 11:39

I tuned my system the same way, my CH setpoint (set @ the CV-ketel itself) is 50'C. More than plenty to supply the floor heating with hot water. The device mixes it down to safe temperatures anyway. The result is a return temperature , 35'C. In winter times there is hardly any steam plume to be seen from the exhaust. Condensation is crazy, a constant drip-drip sound can be heard.

Take care: there is a big relation between max. water temperature and power of the connected radiators / convectors. At low temperatures, a convector, like Jaga produces them, has a higher efficiency. On their website they offer an Excel spreadsheet where the supply/return termperatures are variable. New radiators/convectors are specified at 75/65/20 (supply / return / room temperature).
I am renovating my house, room by room. I replace in every room the old-skool 90'C spec'd radiators by the calculated 55/45/20 Jaga convectors that used to be on sale at Marktplaats big time. (I hope the increased production of new houses will create extra Marktplaats supply to be able to pick the best suited model for my room)

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