Maybe the manifold pump is circulating a total of (1.065+7.45+7.45), 15.965LPM??, but calcs are probably still OK.
This is what I might expect when I view the UFH, the oil boiler has a TMV (bypass) as well to maintain the return temperature to 40C to prevent corrosion, I think the UFH TMV bypass flow is the UFH flow minus the boiler flow (downstream of the boiler bypass), in this case, 7.45-1.065, 6.39LPM.
That helps to explain why the return to the boiler from the UFH manifold is taking the ‘Mixed Flow’ at roughly 30C rather than the ‘UFH Return’ at more like 25C
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I think it was possibly put together incorrectly.
I’d be inclined to get a new manifold etc
Its worked for the past 10 years, of course won’t know until I see it if its maintaing 30C, the remote sensing capillary TMV probe might seem to indicate that it can??.
But if the return temperature to the boiler is higher than it needs to be, that could be impacting efficiency.
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Finally, some numbers from my son in law.
UFH (only) on for 4 hours when data taken
Boiler inlet temp taken at UFH, 54.5C. “cold” return to boiler taken from UFH bottom manifold 24.0C. Temperature just below manifold pump, 18.5C. None of the 3 flowmeters register any flow. The 20.5kW (oil) boiler cycled (average of 4 cycles) 1.563 min on & 7.01 min off, which by calc gives a boiler output of 3.738kW. The UFH input of 3.738kW at a dT of (24-18.5), 5.5C gives a total loop flowrate of 9.74LPM, an average of 3.247LPM/Loop.
Again , can’t figure out why the temperature at the circ pump isn’t 24.0C, it possibly is a faulty temperature gauge but all three temperature gauges were reading exactly 20C with UFH off so unlikely that it would read a lower temperature if faulty? As I said previously, I havn’t verified that the UFH circ pump is pumping downwards but 99.9% sure that it is. The non reading of any of the flowmeters might indicate that the flow is reversed??.
Assuming the UFH pump is pumping downwards - in the same direction as the boiler’s pump:
- It’s odd that none of the flow meters are registering any flow
- They appear to be in the right location if the bottom manifold is the ‘flow’ to the UFH loops
- Might they be ‘stuck’ as Brian suggested previously?
- It seems a coincidence that they’re all stuck though…
- It’s odd that the temperature reading near the pump is only 18.5C
- We’d expect the TRV to (try to) make that more like 30C, based on the capillary probe sensor
- If the TRV is only receiving boiler flow at 54.5C maybe it’s not able to achieve 30C? But you’d think it would manage better than 18.5C…
- 18.5C sounds about right if it’s (mostly) the return from the UFH, coming into the upper manifold via the white valve heads, then through the pump
- But why isn’t it closer to 24C, the same as the return to the Boiler?
- Might the bypass flow from the TRV be Downwards, into the return to the Boiler, raising the 18.5C to 24C?
- But that would be against the flow direction of the UFH pump, so seems unlikely
- We’d expect the TRV to (try to) make that more like 30C, based on the capillary probe sensor
I’d say the lack of flow indication on the flow meters is the thing to look at first. If there’s really no flow going through any of the UFH loops that’s definitely not right.
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I will be down there on Saturday next to do a service on the boiler so will have a good look at the setup.
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That is a problem. Are the actuators actually opening? Do the return pipes start cold and warm up?
All will be revealed tomorrow, hopefully, boiler is outputting ~ 3.7kW and the rooms are fine and cosy, so the heat must be going somewhere.
Glad to report that this UFH is operating fine. The manifold pump is pumping downwards, the 3 flowmeters are reading a total of (2.5+2.7+2.5), 7.7LPM, the UFH loops are operating at a dT of, (25.5-19.5), 6.0C, this gves a calculated Boiler/UFH output of (7.7*60*6.0/860), 3.22kW.
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