CCTs, separation, bypass, and all that guff

[HughF]

Making some progress… hopefully this will work.

 

[JohnMo]

Only thing I would have different is made the tees 28mm not 22mm. To get a step change in velocity at the tees.

[HughF]

1 hour ago, JohnMo said:

Only thing I would have different is made the tees 28mm not 22mm. To get a step change in velocity at the tees.

Consider it done…. Nothing pressed yet and I’ve got 28 Ts in the bucket.

[HughF]

@JohnMo better?

 

 

[HughF]

All pressed up…. Didn’t even need my angled jaws 🤣

[John Carroll]

What temperature are you running the UFH (flow) at and what total flow rate through the two loops and return temperature do you expect?. 

[HughF]

45 minutes ago, John Carroll said:

What temperature are you running the UFH (flow) at and what total flow rate through the two loops and return temperature do you expect?. 

I’d need to check my calcs from loopcad, don’t recall them off the top of my head. 2.5l/min at 33 flow rings a bell.

 

16mm @ 150 ish centres in 100mm concrete, on 200 pir. 2 loops, 50m each. 15m2 floor area in a new extension.

Edited November 4, 2023 by HughF

[HughF]

Just put a plug into this and got it flowing…. It’s taking heat from the flow. But the loop temps aren’t coming up, is that normal? I’d have expected it to take as much flow as it can in order to satisfy the flow temperature, is that an incorrect expectation?

 

The pipes into/out of the manifold are hot/cold…. And there is some warmth to the flow, but it’s not rising above 22.

[HughF]

Well, it appears to be doing something…. Heat pump is happier now there is more of a sink for its energy to go.

 

[JohnMo]

If it's the first time heating it will take quite some time to get heat back to the manifold. You are heating a few tonnes of concrete.

[HughF]

23 minutes ago, JohnMo said:

If it's the first time heating it will take quite some time to get heat back to the manifold. You are heating a few tonnes of concrete.

Yep, I figured as much…. I think I had an incorrect assumption about how it blended the water, assuming that it would in fact feed water at the requested flow temp (I’ve set the dial to 33) until the return from the loop was at that temp. Instead it seems to be flowing quite cool. The heat must be going somewhere, the flow line is hot and the return from the manifold is cold.

[John Carroll]

What temperature is the HW (from the HP) going to the mixer?, if its 45C then it should give a mixed flow of 33C if the index on the TMV is accurate, once the slab is heated up then you might expect a return of 25C/27C, a dT of maybe 6C to 8C, if the flowmeters are flowing 2.5LPM each then the UFH input will be 2.1 to 2.8kw.

Edited November 10, 2023 by John Carroll

[JohnMo]

 

16 hours ago, HughF said:

But the loop temps aren’t coming up, is that normal?

Just seen you have an Ivar mixer, you need to adjust the mixer to suit your flow rates.

 

They are very adjustable, if you didn't get instructions with the manifold you can normally download them.

[HughF]

7 minutes ago, JohnMo said:

 

Just seen you have an Ivar mixer, you need to adjust the mixer to suit your flow rates.

 

They are very adjustable, if you didn't get instructions with the manifold you can normally download them.

I’ll have a look and see what I can download. Some energy appears to be going into the floor, but I can’t get the flow temp into the loops above 26 ish.

[HughF]

10 hours ago, John Carroll said:

What temperature is the HW (from the HP) going to the mixer?, if its 45C then it should give a mixed flow of 33C if the index on the TMV is accurate, once the slab is heated up then you might expect a return of 25C/27C, a dT of maybe 6C to 8C, if the flowmeters are flowing 2.5LPM each then the UFH input will be 2.1 to 2.8kw.

Varies between 38-50 depending on the weather comp.

[John Carroll]

Have you tried turning up the mixing valve setting until you achieve 33C, it should react fairly rapidly.

[HughF]

3 hours ago, John Carroll said:

Have you tried turning up the mixing valve setting until you achieve 33C, it should react fairly rapidly.

that’s what I was expecting, it to respond quickly to a demanded flow temp when being fed with a considerably higher flow temp than the mixer was calling for.
 

 

It seems completely disconnected from the flow temperature I see through the loop, which again is sitting at 27. Getting dT 3 between flow and return, and the floor is doing a nice job of keeping the extension warm, so I guess it’s working… it seems that no matter what I set the mixing valve to, it sits at 27.

Edited November 11, 2023 by HughF

[JohnMo]

13 minutes ago, HughF said:

that’s what I was expecting, it to respond quickly to a demanded flow temp when being fed with a considerably higher flow temp than the mixer was calling for.
 

 

It seems completely disconnected from the flow temperature I see through the loop, which again is sitting at 27. Getting dT 3 between flow and return, and the floor is doing a nice job of keeping the extension warm, so I guess it’s working… it seems that no matter what I set the mixing valve to, it sits at 27.

I used a couple of different mixers last year, including Ivar, feeding from a buffer charged via WC, but I had to have the mixer flow turned down to minimum and still had the flow cooler than I really wanted.

 

One of the reasons, when I went heat pump, I removed the mixer and pump and added to my big pile of good but useless heating bits.

[John Carroll]

24 minutes ago, HughF said:

that’s what I was expecting, it to respond quickly to a demanded flow temp when being fed with a considerably higher flow temp than the mixer was calling for.
 

 

It seems completely disconnected from the flow temperature I see through the loop, which again is sitting at 27. Getting dT 3 between flow and return, and the floor is doing a nice job of keeping the extension warm, so I guess it’s working… it seems that no matter what I set the mixing valve to, it sits at 27.

A dT of 2C with a assumed total flow of 5.0LPM = UFH output of 0.7kw.

[John Carroll]

3 hours ago, HughF said:

that’s what I was expecting, it to respond quickly to a demanded flow temp when being fed with a considerably higher flow temp than the mixer was calling for.
 

 

It seems completely disconnected from the flow temperature I see through the loop, which again is sitting at 27. Getting dT 3 between flow and return, and the floor is doing a nice job of keeping the extension warm, so I guess it’s working… it seems that no matter what I set the mixing valve to, it sits at 27.

If you are getting 3C dT then UFH output is ~1.1kw, have you a link to the mixing valve, it seems to have a adjustable bypass (if like the one below)

there is only ~ 0.7LPM of hot water at 45C mixing with 4.3LPM of UFH return water at 23C so requires very tight control, you would require 1.0LPM mixing with 4.0LPM to get 33C mixed temperature.

 

Edited November 11, 2023 by John Carroll

[HughF]

I’ll post up the user manual when I’m in front of my laptop… the ivar mixer does indeed have two internal bypass’ both of which are adjustable.

 

If it turns out I can heat the extension with only 27 degree flow then that’s all good, less losses all round. It would just be nice to have another pair of eyes looking over the manual with me. 
 

Appreciate everyone’s input on this.

[HughF]

Well, it works... floor is staying warm, house isn't cold...