UFH house seems cold

[Dan Robinson]

You probably will need the water at 45 degrees going into the floor with 40 coming back to the manifold.

The valve appears to be set to 50.

If the flow and returns to the manifold are at 60 or so, then the blending valve is guffed.
You cod try temporarily removing the capillary probe from the manifold above the pump and see if that helps.

 

[dk1uk]

I don’t have a thermometer to check, but to the touch, the flow out and the return are definitely different temperatures.

I’ve tweaked the flows a bit on some of the loops to increase the flow to see if it makes a difference. The landing is very open with a floor to roof open void so that’s going to be difficult to keep warm so maybe I’ll never solve that one.

The bedrooms are the most problematic - could that we the carpet??

I notice on the downstairs manifold there’s a Wilo pump which is set to max speed. On the upstairs manifold there’s a Lowara 7-speed pump, which is on speed 6. Is switching it to 7 likely to help (if it is indeed the carpet limiting the heat coming through)?

 

[Gasguru]

It might be worth you contacting Emmeti in the UK to see if they can recommend anyone nearby.Randomly fiddling with pump speeds, TMV heads could make things worse. There's also a flow valve just above the TMV head that requires setting too....and this has an influence on the top rail temperature. Does the boiler get up to high temperature?

 

[dk1uk]

Yes the boiler gets up to a high temp. As do the top rails on the upstairs and downstairs manifolds.

 

[Gasguru]

The picture you posted shows a temperature of only 35 degrees...it's normal to run at 45 to 50 degrees.

 

[dk1uk]

Ah I see. Just taken a pic of the gauge on the upstairs manifold and it’s running at closer to 50 now (some loops are calling the boiler).

The downstairs manifold is in the second pic below running at 35 (no loops currently calling the boiler).

 

[snb]

Change timings so underfloor is on 24hrs. Will make a huge difference. Normal for upstairs flow,to be set at 50 as probably spreader plates, and ground floor at 35 to 40 as it will be screed.

 

[dk1uk]

Just checked and upstairs there is only one loop calling for heat. Earlier this morning when I posted the temp pic, several loops were calling for heat, could it be that the temp drops when it’s under greater demand?

 

[dk1uk]

Change timings so underfloor is on 24hrs. Will make a huge difference. Normal for upstairs flow,to be set at 50 as probably spreader plates, and ground floor at 35 to 40 as it will be screed.

It’s normally on 2am to 10pm so almost 24 hours. Tweaking the flow for one of the downstairs rooms has brought it up to 20 degrees for the first time since the weather cooled.

 

[snb]

On the flow meters with all loops demanding downstairs adjust so you get about 2.5lt flow min on each. Upstairs manifold will need closer to 3 if that's possible with all open

 

[dk1uk]

On the flow meters with all loops demanding downstairs adjust so you get about 2.5lt flow min on each. Upstairs manifold will need closer to 3 if that's possible with all open

Thanks, will give that a try. On both manifolds is a pink sheet left by the installer where they’ve written flow rates anywhere between 1.9 and 0.5. Unless there’s another problem, these flow rates are clearly not enough and the date on the sheet is 10th Oct 2016 - would it have made a difference that he/she made these adjustments when the weather wasn’t too cold?

 

[dk1uk]

I’ve been able to spend some time again looking at this and something I’ve noticed.

Even though the UFH heating loops have been calling for heat all day, the boiler fires up to about 70c, then stops firing and the temp drops to about 38c and keeps repeating the loop. Each cycle takes about 4 minutes.

It’s as if the boiler can’t maintain a consistent temperature. I don’t know if this is a boiler fault or whether the UFH is causing the boiler to behave this way.

Does anyone have any ideas of how to check please?

 

[Dan Robinson]

Possibly a case of the boiler being grossly oversized and with totally inadequate modulation ratios.

What power rating is the boiler? What sort of heat requirement does the house need?

Does the boiler and UFH perform better when the cylinder is recharging from near cold?

 

[dk1uk]

Thanks Dan. I’m afraid I’m not so technical as to be able to answer those questions. However, it’s a new build house and my neighbour has exactly the same house with boiler and UFH. He popped round, I showed him the boiler firing up and down in temperature and he confirmed that his boiler doesn’t do this, it reads 68c consistently.

So I’m guessing that mine has a fault or something has been set up incorrectly

 

[Dan Robinson]

The boiler is probably not broken, however, there is a flow rate problem.