Wet underfloor heating mixing valve settings

[dazzler9000]

Actually, the numbers are easier to see on screen (I need glasses).....

 

[dazzler9000]

Bit of an update. I had my boiler replaced this week and the gas engineer had a nose at my UFH. He noticed that the feed to the pump (1) was cooler than the return (2) and this was confirmed by a thermal camera. He thinks the hot/cold have been installed back to front.

He's happy to come back and swap them over for me, but would it even work at all if it was wired back to front?

 

[Johntheo5]

It might work to a fashion if there are rads on somewhere else, but only to a fashion, what are the flow meters reading when its on? Even if connected wrongly if these flowmeters are reading then the bottom nanifold should feel colder than the top manifold.

 

[dazzler9000]

I'm pretty sure they don't move. This is something the engineer noticed, he seemed to think these should move when providing heat?

 

[Madrab]

If you look at the diag on the ESBE mixing valve, you can see hot in from below and mix (cold) in from the right. So the return on the manifold would be the cold mix that the valve uses to set the flow temps, blending with the system hot flow. So the manifold and blending valve pump etc should be correct.

Could the flow and return to/from the boiler be wrong whereby the Blue valved pipe is actually the boiler flow and the red is the return, always possible. I'd be tempted to make up a small bridge to connect the flow and return together (red and blue valve) and then confirm the direction of flow or trace it back to a branch if there is one and with a cold system, fire the system up and see what pipe heats up. Is it a mixed system with rads as well as UFH?

What's under the blue cap on the left, a vent? Looks like it could host a temp gauge?

 

[tolly123]

No, if the input temp is 58deg and output is 48deg then you need to reset the flow meters and the pump setting to slow things down to allow the UFH pipework enough time to release its heat.

If your wooden floor is 25deg, then you're probably getting near to the max that the wooden floor can safely take (~27deg), not so much for the tiles of course.

Not sure about this advice, a F&R delta t of ten degrees is an acceptable design for UFH. You dont want it lower than this generally as the floor coverings surface temp will have a noticable temp gradient depending on whether its a single meander or snail pattern.

 

[dazzler9000]

If you look at the diag on the ESBE mixing valve, you can see hot in from below and mix (cold) in from the right. So the return on the manifold would be the cold mix that the valve uses to set the flow temps, blending with the system hot flow. So the manifold and blending valve pump etc should be correct.

Could the flow and return to/from the boiler be wrong whereby the Blue valved pipe is actually the boiler flow and the red is the return, always possible. I'd be tempted to make up a small bridge to connect the flow and return together (red and blue valve) and then confirm the direction of flow or trace it back to a branch if there is one and with a cold system, fire the system up and see what pipe heats up. Is it a mixed system with rads as well as UFH?

What's under the blue cap on the left, a vent? Looks like it could host a temp gauge?

I'm no expert as you can tell, but I can't see how pipe no.2 can't be the hot feed from the boiler as it was considerably hotter than pipe no.1..... Surely that can't be correct?

Seems like it's time to call in a pro I think. Hopefully, they can make sense of it

 

[Madrab]

Not sure about this advice, a F&R delta t of ten degrees is an acceptable design for UFH. You dont want it lower than this generally as the floor coverings surface temp will have a noticable temp gradient depending on whether its a single meander or snail pattern.

A wooden floor will naturally have a temp gradient but their limitations are normally down to floor temps that are too high and creates problems with the construction makup of the wooden flooring itself causing warping and delam. The floating floor should be laid in such a fashion that it will absorb different expansion rates, regardless of the delta.
Even then though, a 10deg delta may not be achieving the design m2 output that the room requires as far as heat loss is concerned, regardless of the floor covering type and it seems that the output doesn't satisfy the client and the system isn't working efficiently with the flow and return temps being too high.

I have engineered oak in 3 rooms and I run the system @ ~45Deg flow with a ~25deg return with floor probes set to 26deg and the floor performs well giving an average 20deg air temp.

 

[Madrab]

I'm no expert as you can tell, but I can't see how pipe no.2 can't be the hot feed from the boiler as it was considerably hotter than pipe no.1..... Surely that can't be correct?

Seems like it's time to call in a pro I think. Hopefully, they can make sense of it

Yes, it would make sense if the blue valved pipe is hotter but it seems such a basic schoolboy error to make but agreed it certainly needs confirmed and if found to be the case then at least its a relatively easy fix.

 

[tolly123]

A wooden floor will naturally have a temp gradient but their limitations are normally down to floor temps that are too high and creates problems with the construction makup of the wooden flooring itself causing warping and delam. The floating floor should be laid in such a fashion that it will absorb different expansion rates, regardless of the delta.
Even then though, a 10deg delta may not be achieving the design m2 output that the room requires as far as heat loss is concerned, regardless of the floor covering type and it seems that the output doesn't satisfy the client and the system isn't working efficiently with the flow and return temps being too high.

I have engineered oak in 3 rooms and I run the system @ ~45Deg flow with a ~25deg return with floor probes set to 26deg and the floor performs well giving an average

Im not quite sure specifically what you were getting at by your comment about the 10deg DT not achieving the correct output but just to be clear, slowing down the flow rate, either by reducing pump speed or throttling the flow meters to say a 20 deg DT will reduce heat output, not increase it.

Difficult to comment on required flow temps without knowing the floor construction and pipe centres etc though but the return to the blender should definetly not be hotter than the flow.

 

[Johntheo5]

A typical loop flowrate & dT might be 2.0LPM and 8C, a 7 loop output will then emit 7*2*60*8/860, 7.8Kwh and so on, Kwh = (no of loops)X(LPMX60)XdT/860, if you want to estimate your own.

 

[Johntheo5]

A wooden floor will naturally have a temp gradient but their limitations are normally down to floor temps that are too high and creates problems with the construction makup of the wooden flooring itself causing warping and delam. The floating floor should be laid in such a fashion that it will absorb different expansion rates, regardless of the delta.
Even then though, a 10deg delta may not be achieving the design m2 output that the room requires as far as heat loss is concerned, regardless of the floor covering type and it seems that the output doesn't satisfy the client and the system isn't working efficiently with the flow and return temps being too high.

I have engineered oak in 3 rooms and I run the system @ ~45Deg flow with a ~25deg return with floor probes set to 26deg and the floor performs well giving an average 20deg air temp.

That's a big (20C) dT, what kind of loop flowrates are you running at?

 

[Madrab]

Im not quite sure specifically what you were getting at by your comment about the 10deg DT not achieving the correct output but just to be clear, slowing down the flow rate, either by reducing pump speed or throttling the flow meters to say a 20 deg DT will reduce heat output, not increase it.

Depends if we are talking about deltas as being the amount of heat being transferred into the space rather that saying it's saying a delta of 40deg where the flow is 60 deg and the air temp is 20 so the the deltaT is 40?

If the former then a delta of 20deg where 20 deg of heat is transferred out of the flow through the floor into the air then that would indicate faster heat up times and a more achievable heat loss replacement and easier to achieve the set temp.

 

[Madrab]

That's a big (20C) dT, what kind of loop flowrates are you running at?

Anywhere from 1.5L/min to 2.5-3 L/Min loop size dependent, the delta is optimum and tends to be on the larger loops when it's cold, as the temp rises that delta seems to become more dynamic once it gets close to target and the stat modulates the system on and off to maintain set.