ᐅ How do temperature fluctuations occur in a domestic hot water system?
Created on: 2 Jan 2020 12:23
F
fonsi99
Hello,
I hope this is the right forum.
Can someone explain to me how temperature fluctuations can occur in domestic hot water?
The domestic hot water is set to 60°C (140°F). The circulation is at 55°C (131°F).
It receives water from the buffer tank at 65°C (149°F) (limited by a mixing valve), which operates at around 70°C (158°F).
At the apartment outlet, the domestic hot water is delivered at a consistent 60°C (140°F).
However, sometimes the hot water temperature seems to fluctuate slightly while showering.
It’s not constant as it was set at the single-lever mixer.
How can this phenomenon be explained or fixed?
Could it be because when many users demand hot water at the same time, the domestic hot water does not reach 60°C (140°F)?
Or could it be that the demand at that time is actually too low?
Thank you.
I hope this is the right forum.
Can someone explain to me how temperature fluctuations can occur in domestic hot water?
The domestic hot water is set to 60°C (140°F). The circulation is at 55°C (131°F).
It receives water from the buffer tank at 65°C (149°F) (limited by a mixing valve), which operates at around 70°C (158°F).
At the apartment outlet, the domestic hot water is delivered at a consistent 60°C (140°F).
However, sometimes the hot water temperature seems to fluctuate slightly while showering.
It’s not constant as it was set at the single-lever mixer.
How can this phenomenon be explained or fixed?
Could it be because when many users demand hot water at the same time, the domestic hot water does not reach 60°C (140°F)?
Or could it be that the demand at that time is actually too low?
Thank you.
Once again: what does "beforehand" mean? A good fresh water system only requires a temperature difference of 1–2 degrees Celsius (2–4 degrees Fahrenheit) between the buffer supply line and the domestic hot water outlet. But 60°C (140°F) at the fresh water side is quite extreme, both because of the energy demand and also due to limescale buildup. What is the hardness of your water?
Domski schrieb:
One more time: what exactly do you mean by “beforehand”? A good fresh water system only needs a temperature difference of 1–2 degrees between the buffer supply and the domestic hot water outlet. But 60°C (140°F) for the fresh water is quite high, both because of the energy demand and also due to scaling. What is the hardness of your water? Hello.
We were given a requirement of 60°C (140°F) for the fresh water, since this is a multi-family house with 5 units. It is supposedly a regulation for multi-family buildings…
Personally, I would go for 55°C (131°F).
The water hardness is not very high, about 10 °dH (degrees German hardness). So scale buildup is not very severe.
The buffer tank currently holds about 65°C (149°F). A limiter set to 65°C (149°F) is installed between the buffer and fresh water. The thermometer for the supply to the fresh water usually shows 60°C (140°F), but the fresh water supply display actually shows 65°C (149°F).
The fresh water temperature is currently at 58°C (136°F), the circulation is at 53°C (127°F).
So based on these figures, the fresh water should be stable without fluctuations.
However, the hot water temperature must constantly be readjusted because it is not maintained consistently.
That is why I am surprised that these fluctuations occur.
Domski schrieb:
Again: what do you mean by “before”? A good domestic hot water system only requires a temperature difference of 1–2°C (2–4°F) between the buffer supply and the hot water outlet. But 60°C (140°F) at the domestic hot water side is quite high, both because of the energy demand and the risk of limescale buildup. What is the hardness of your water? Addendum: The buffer volume for the domestic hot water was generously sized with 1000 liters (265 gallons). The sensor was moved slightly downwards. That is why a lot of the approximately 60°C (140°F) heating water is available for the domestic hot water.
Then take an inexpensive IR thermometer and observe the actual temperature progression at the hot water outlet of the fresh water during an extended draw-off. It should be approximately the set temperature and remain almost constant.
It is possible that the loading pump reacts too slowly or inaccurately to changes in flow rate.
It is possible that the loading pump reacts too slowly or inaccurately to changes in flow rate.
Domski schrieb:
Then get an inexpensive IR thermometer and monitor the actual temperature at the domestic hot water outlet during a longer draw-off. It should be close to the set temperature and remain nearly constant.
It’s possible that the loading pump reacts too slowly or inaccurately to changes in flow. Alright. Can you send me a message with your email? Then I can send you some photos. Thanks
fonsi99 schrieb:
All right. Can you send me a message with your email? Then I could send you some photos. Thanks No, because that is not the purpose of this forum. You are welcome to post them here.
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