UFH Manifold Flow & Return Temp help

[richo106]

Hi All

 

I have jumped on a previous thread but thought I would start a seperate one as I need some help/advice on an issue I think I have

I have UFH upstairs and downstairs, downstairs in a concrete slab and upstairs in aluminium spreader plates below 22mm T&G floorboards. I have an ASHP with 100L buffer (set at 35deg). I have been running the ASHP hot water and heating in line with the octopus cosy tariff and has worked well like this, I know it wouldn't run like this when we hit cold snaps like now so my plan was to just leave it on and ticking over.

The GF seems to be working well and the floor warms up nicely and all the rooms easily reach the temperature but the upstairs rooms are struggling a bit to get to there set point

I was looking at the GF manifold and the water temp in was 30 deg and return temp was 23 deg 

However the first floor manifold was slightly different as the flow and return temperature was same (both 26 deg at 9pm, both 30 deg at 11pm)

I have a common pump that does both manifolds 

 

I am after any kind of advice/information on this potential issue as there seems to be no heat transfer and the upstairs struggling to heat up. It all looks there is flows on the indicators 

 

I have ran this all night and still no difference in flow temps this morning

 

Thanks in advance

 

 

 

 

[Super_Paulie]

so you have flow but the Δt is 0... im not sure how that would be possible. Have you tried removing the actuators from those loops and just running them open to see if its actually flowing, is there any warmth at all?

[ProDave]

That is a recent (post Brexit) install so are we to assume a new house or is it a retrofit to an old house?

 

Are bedrooms carpeted?  If so lift a carpet if you can ans I bet it is cosy warm underneath and the heat is just not getting through the carpet fast enough, hence the floor is heated up to flow temperature giving the low Dt but the heat is not getting into the rooms quick enough.

 

If so higher flow temperature, or thinner carpets is the answer.

 

As a sanity check, turn the upstairs heating off. Let it all cool down, say over night, then when you first turn it on, I bet you will see a Dt between flow and return while it heats up the spreader plates and the floor.

 

Our previous house had UFH and carpets upstairs and we ran that at 40 degrees flow on the upstairs UFH and lower on the downstairs with solid floors.

[richo106]

12 minutes ago, Super_Paulie said:

so you have flow but the Δt is 0... im not sure how that would be possible. Have you tried removing the actuators from those loops and just running them open to see if its actually flowing, is there any warmth at all?

Daft question...if i take the actuators off will the loops just be open? 

I will do this later when i get home

[richo106]

6 minutes ago, ProDave said:

That is a recent (post Brexit) install so are we to assume a new house or is it a retrofit to an old house?

 

Are bedrooms carpeted?  If so lift a carpet if you can ans I bet it is cosy warm underneath and the heat is just not getting through the carpet fast enough, hence the floor is heated up to flow temperature giving the low Dt but the heat is not getting into the rooms quick enough.

 

If so higher flow temperature, or thinner carpets is the answer.

 

As a sanity check, turn the upstairs heating off. Let it all cool down, say over night, then when you first turn it on, I bet you will see a Dt between flow and return while it heats up the spreader plates and the floor.

 

Our previous house had UFH and carpets upstairs and we ran that at 40 degrees flow on the upstairs UFH and lower on the downstairs with solid floors.

Its a new build

Yes all bedrooms are carpeted but they are specific UFH underlay and carpets

The bathroom is tiled and the tiles still feel cold!

Regarding turning it off, I would expect to see Dt yesterday evening as the upstairs floor was pretty cold

 

I will try remove the actuators as mentioned above, i have one area of floor (another bathroom) with no flooring yet apart from the T&G flooring so ill see if there is any warm there

If not I will try upping the temp to 40 to see if this makes a difference too

 

Many Thanks

[JohnMo]

Are you running constantly or cycling the heating on and off?

1 hour ago, richo106 said:

both 26 deg at 9pm, both 30 deg at 11pm

The above would indicate on/off, based on Cosy time periods.  Those low flow temps for a couple of hours at a time will do nothing heating wise via UFH. I have said a few time that Cosy is really a battery tariff, but can be used to reduce heating costs. Running UFH on off for short period needs high flow temps to work, not low ones more suited to continuous heating. You may need to think of Cosy differently - the cheap periods are just that, cheaper periods, the other periods except the high priced one are normal costs (not expensive). You setback the heating temp during the expensive evening time and all the rest of the time operate normal WC.

 

26 deg flow temps will never feel warm underfoot, nor will 30.

[richo106]

It looks like the actuators are working correctly, when I opened a few zones upstairs there was a slight temp difference in flow and return temps to start with but soon gets back to almost the same

 

ill change my water temp to 40 to see if that makes a difference at all 

[richo106]

I have had my UFH on all day (apart from the expensive period 4pm - 7pm) and my electric usage for today will be around £11 (around 55kWh) compared to around £4 day all last week (25-30kwh) by timing my hot water and heating with the cheap periods

 

Sorry for the daft question but do you think this is normal jump in usage during a cold snap. Since Monday night it has ranged from -2 at night and got no warmer than 2 in the day

 

Would welcome some opinions on this if possible and how cold snaps effect other peoples usage etc

 

I know usage will fluctuate during the year but i am just panicking now it will be very expensive to run during the winter months

 

 

[JohnMo]

28 minutes ago, richo106 said:

Sorry for the daft question but do you think this is normal jump in usage during a cold snap

Our calculated heat demand triples from 10 Deg average temp outside and 0 average outside. By the time it's -5 the heat demand is around 4 times that used on a 10 deg average day.

 

But in reality it's more than that. As background heating from fridge and general stuff proportionally gets way smaller. So at 10 degs if you needed 1kW of heating and general stuff in the house gave you 200W you only need to supply 800W of heating, on day where you need 4kW, the general stuff still gives you 200W, so you need to supply 3.8kW. So 4.75 the heating input is required.

 

The more heat leaky the house, the steeper the heating curve.

 

We are are on an average daily temp of -0.5, our coldest so far. But looks to dropping to -6 on Friday