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Henny071021 Feb 2017 09:05Hello,
as a layperson, I have a question for better understanding.
A hydraulic separator of the brand MAGRA is installed.
There is a gas condensing boiler and underfloor heating throughout the entire house.
On the secondary side of the separator, a pump is installed in the supply line.
My question is: Where should the supply temperature sensor be connected? At the separator or at the boiler?
Doesn’t the supply and return flow mix in the secondary circuit at the separator, so that the desired supply temperature setpoint needs to be compared with the actual temperature at the separator?
as a layperson, I have a question for better understanding.
A hydraulic separator of the brand MAGRA is installed.
There is a gas condensing boiler and underfloor heating throughout the entire house.
On the secondary side of the separator, a pump is installed in the supply line.
My question is: Where should the supply temperature sensor be connected? At the separator or at the boiler?
Doesn’t the supply and return flow mix in the secondary circuit at the separator, so that the desired supply temperature setpoint needs to be compared with the actual temperature at the separator?
K
Knallkörper21 Feb 2017 12:34I would not position the sensor directly on the boiler or on the manifold just yet. Depending on the direction of the water flow in the manifold (which varies according to the current relative pump outputs), the measurement might be inaccurate. If you do place the sensor there, it should be positioned at the very top.
In my opinion, you are safer if the sensor is installed on the outgoing pipe to the underfloor heating, at least a few centimeters (inches) away from the manifold. The temperature you really want to measure is the water actually flowing into the underfloor heating.
In my opinion, you are safer if the sensor is installed on the outgoing pipe to the underfloor heating, at least a few centimeters (inches) away from the manifold. The temperature you really want to measure is the water actually flowing into the underfloor heating.
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Henny071021 Feb 2017 13:10The hydraulic separator even has a socket for a temperature sensor. However, my heating engineer thinks it is sufficient to measure the supply temperature at the boiler.
K
Knallkörper21 Feb 2017 13:46But if the boiler pump is running at high power while there is only a low flow rate in the heating circuit, you might have a small measurement error. It’s possible, but if I want to measure the "flow temperature in the heating circuit," I would place the sensor exactly there. I strongly assume that the boiler has its own measurement!
If the circulation pump of the underfloor heating fails, the correctly displayed flow temperature would be close to zero, because the water only circulates between the mixing valve and the boiler. However, the display would correspond to the boiler temperature, which would be much too high. On the other hand, if the heating circuit pump runs at full speed because of high heating demand, cold water from the return flow is mixed into the flow via the mixing valve. If the sensor is placed near the boiler, it might show 75°C (167°F) – all fine. But the actual flow temperature in the underfloor heating might be only 40°C (104°F) due to the mixing, the rooms don’t reach the desired temperature, the pump might increase its speed, and the problem worsens.
I don’t want to confuse you; the system probably works as your heating technician intended. Especially if the pumps run at a fixed speed. But if I had the choice, I wouldn’t set it up that way.
If the circulation pump of the underfloor heating fails, the correctly displayed flow temperature would be close to zero, because the water only circulates between the mixing valve and the boiler. However, the display would correspond to the boiler temperature, which would be much too high. On the other hand, if the heating circuit pump runs at full speed because of high heating demand, cold water from the return flow is mixed into the flow via the mixing valve. If the sensor is placed near the boiler, it might show 75°C (167°F) – all fine. But the actual flow temperature in the underfloor heating might be only 40°C (104°F) due to the mixing, the rooms don’t reach the desired temperature, the pump might increase its speed, and the problem worsens.
I don’t want to confuse you; the system probably works as your heating technician intended. Especially if the pumps run at a fixed speed. But if I had the choice, I wouldn’t set it up that way.
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