Reply With QuoteI have seen that as well but only when a zone has fallen by more than 2 degrees. I would be interested to know if this is the same with Atag One Opentherm control.Originally Posted by fergie
On my system it is telling me also that there is only one zone calling for heat. The Ot bridge is asking the boiler to heat on the same value. If I look on the HCE80 there are more zones activated. Strange thing is that this is not visible on the evotouch (zone calling for heat is 0%).
Last edited by JosP; 21st January 2018 at 08:42 PM.
I have seen that as well but only when a zone has fallen by more than 2 degrees. I would be interested to know if this is the same with Atag One Opentherm control.
Evohome is now saying the same zone is asking for 37% and OT is also asking for 37%. The boiler is now displaying the demand as 20 deg.
Just because the set point is reached doesn't mean the call from heat from the boiler should be low or zero. It probably genuinely needs that high flow temperature to meet the target. After all if it could achieve the set point with a lower flow temperature it automatically would!
It's likely that your bedroom radiator is "weak" and is struggling to meet the set point - either that or it is obscured by something, or you have a window or door open or perhaps poor insulation. In any case, it will only have the flow temperature as high as it needs to be. The negative feedback loop automatically finds the right flow temperature to reach an equilibrium.
Our hallway has the same problem - it's always the first room to "struggle" when outside temperatures get really low, and consequently with it set to 20 it may be producing a heat demand of 80% or so when other rooms are more like 20%! This results in the flow temperature being unnecessarily high for all the other zones (whose radiators close down to a low flow to compensate for this) but the hallway radiator does genuinely need this high flow temperature to meet the set point.
The best solution to a "weak" zone like this is just set it to be slightly cooler. If I drop the hallway from 20 degrees to 19 the heat demand in the same circumstances will be more like 30% instead of 80%.
Drop your bedroom set point by 1 degree - you won't notice the difference but you'd be surprised how much lower the call for heat is even after it has come back on to reach a new equilibrium.
Last edited by DBMandrake; 21st January 2018 at 09:02 PM.
Cheers DBM - Shall try that. Its one of the largest rooms and the radiator is in a bay with a dresser in front of it - though I did take the back off the dresser so plenty room for air to circulate. Its also on the colder (prevailing wind) side of the house.
The dresser would explain it.
Rated output power of a radiator is a combination of both convection and direct infrared line of sight radiation from the panel - even if it can freely convect you'll lose nearly all of the direct IR radiation into the room having a radiator behind a dresser or sofa etc... All the infrared output of the panel will do is heat the back of the dresser.
Although there's some debate about what proportion of the heat into the room is convection vs radiation on a convector panel, I reckon you'd lose about 30-40% of the heat output capability of the radiator by reducing it to convection only.
In our living room we have 3 linked bay window radiators - which cope just fine most of the year but as soon as the Christmas tree goes in they start to struggle to reach the set point and warm up times get a lot longer, despite there being no obstruction to the convection into the room. It's the loss of the direct IR radiation wasted warming the back of the tree that is responsible..
For any given radiator and room situation there is a maximum set point the room can reach with the radiator going full blast - as you get close to that maximum especially within a degree or so the call for heat to try to get the last little bit of the way there will skyrocket, hence if its struggling a small drop in set point can help a lot.
I still haven't built mine, I'm afraid. On the bright side, today I moved the components into the same room as the soldering iron. Still haven't actually opened the boxes to check I got what I ordered... 6 months ago.
remember that HCE80 "zones" do not correspond to Evohome controller zones. The zones on the HCE80 are in effect "ports". You can bind any combination of HCE80 zones to an Evohome controller zone. E.g in my case in one room I have HCE80 zones ("ports") 1 & 2 bound to a single Evohome controller zone. The reason is that I have 5 pipe circuits in that single Evohome controller zone. 3 actuators are conected to zone1 (port1) of the HCE80 and 2 circuits (actuators) conected to zone2 (port2) of the HCE80.
Remember the wiring of an HCE80 allows direct connection of 3 actuators to port1, 2 to port 2 and 1 each to ports 3-5 or 1 each to ports 3-8 with the extender.
In your case it could be that you are seeing multiple "zones" on the HCE light up as they are all bound to the same evocontroller zone. By the way what safety mechanism is used in your system to prevent floor overheating ? Is there a manifold or floor thermostat that can shut off the boiler, pump or valves ?
Last edited by rvb99; 22nd January 2018 at 12:20 PM.
I know that HCE80 "zones" do not correspondent to Evohome zones. It would be better that I had called it ports on the HCE80 instead of zones. Thanks for that.
At the moment there is no safety mecahnism to prevent floor overheating. The only "safety" is that I have set the maximum temperature in the parameters @50 deg.c. On the frontpanel I have set the maximum temperature @ 40 deg.c. for floor heating and it is not possible to set the temperature higher then 50 deg.c. I have asked Intergas what whil happen if the temperature sensor is defect. The boiler will stop heating then. So that is failsafe. If you look in the Intergas manual (see drawing Giel538 #262) they advise to connect a maximum thermostate (A) and connect it in serial with the open/close contact of the thermostate. I am in discussion with the installer of the floor heating/boiler because I am not happy that I don't have a safety mechanism as showed on the drawing of intergas.
Still trying to get to grips with your system
Is the HCE80 connected in anyway directly back to the boiler , either through the pump relay or the boiler feedback connection (depends on the HCC80 version you have)?. Also is the system bound correctly. E.g everything uniquely bound via the Evohome controller. E.g HCC80 is not bound directly to the OT bridge ? or there is no double binding to the OT bridge ? Maybe try unbinding everything and starting again, especially if a 3rd party installed it.
Last edited by rvb99; 22nd January 2018 at 02:19 PM.
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