New evohome FW - update WiFi 02.00.17.00 and Application 02.00.17.03

[DBMandrake]

If would be great if we could then use the new information to help our set ups. For example I think my Atag would be a lot more efficient if evohome called for max heat when there is hot water demand, but called for say only half if the demand was radiators only. It would be even better if we could also control / set some parameters around how it acts.

Doesn't the OpenTherm spec already differentiate between a call for hot water and a call for central heating ?

In that case because the boiler knows whether the OpenTherm master is calling for hot water or heating it should be able to apply independent boiler set maximum flow temperature limits for CH and HW...

Of course that doesn't necessarily help if there is a call for both at once, unless you are configured for hot water priority...

[bruce_miranda]

The OT spec may differentiate between CH and HW demands. But I've not seen that difference coming through on the Vaillant side. Mind you, on the Vaillant there is the VR33 that is converting OT to eBUS as well. So what I am seeing are the translated eBUS commands and there I see only a single heating command (treated as CH), if it's trying to heat just HW. The eBUS protocol does allow for a CH and HW message because when you use the Vaillant controls you can see the differences and then the boiler uses either the CH dial or the HW dial. Maybe someone with an OT monitor can confirm? @dty or @The EVOHOME Shop has one.

[fergie]

I've started a new thread about it, but I guess its down to boiler design that means OT seems to override the built in boiler control based on return temps.

I don't think OT is clever enough to tell the boiler it wants say 20%, 50%, 60% or 100% heat to an exact percentage. I'm guessing the boiler is reading the OT signal in bands:

Say 0-20% band low set point, 20-40% med set point, 40-60% higher set point, 60%+ FULL POWER!

[Jahill]

On our OpenTherm system with the Ideal Logic System, it is definitely able to differentiate between hot water and central heating demand and the temps are set accordingly. Next step is to change the system to hot water priority, so that we're not pumping 80c heat around the rads when it's really trying to heat the hot water!

[fergie]

On our OpenTherm system with the Ideal Logic System, it is definitely able to differentiate between hot water and central heating demand and the temps are set accordingly. Next step is to change the system to hot water priority, so that we're not pumping 80c heat around the rads when it's really trying to heat the hot water!

I have HW Priority and also the Hot water kit. Currently the system is showing 100% for HW and 100% for the boiler - which is what I would expect.

Maybe an easy solution for Honeywell would be to give a parameter so that when it is CH calling, it halves the value sent to the boiler via the bridge? This could then be calibrated as appropriate.

[Giel538]

Wow ! Which country are you in? That’s the most basic ufh system I’ve ever seen . What is controlling the bypass? I’m not surprised you are having problems.

If definitely not good practice to run direct from boiler without a mixer/pump. In fact I believe there are even special mixers for Opentherm boilers.

I live in Holland. It seems kind of basic but it is working quite good. The pump is strong enough for my total of 600 meter UFH system to pump it around at the right Liters/minutes for each zone. The good thing about this boiler is that i can limit the temperature with a parameter so it don't need a mixer. Also the boiler don't have to heat up the water to 60+ degrees (but only to 45 in my case) to mix it with cold water (which is a waste of energy). The bad thing is that the pump is controlled by the boiler so i cannot start or stop it manually unless i change my setup to on/off mode instead of opentherm. The bypass is like an overpressure valve which can be set from 0.1 to 0.5 bar and therefore not controlled by anything.

The problem i have (And other people as well) is that for some reason the HCE80 is closing (by use of the MT4-motor) the zone valves while the Evohome is still sending a setpoint. This results in no water flow (only trough the bypass) and a boiler which is still heating up the water. And after a few minutes the valve opens again. Are you sure that you don't have this problem as well? Maybe you never noticed this because you use a radiator as a bypass?

From info i found so far is that when you use multiple zones and don't use hr92 radiator valves you have to use the on/off mode from the boiler which means i have to use a BDR91. I have on of them and i will try this next week to see if it works better.

[HenGus]

I've started a new thread about it, but I guess its down to boiler design that means OT seems to override the built in boiler control based on return temps.

I don't think OT is clever enough to tell the boiler it wants say 20%, 50%, 60% or 100% heat to an exact percentage. I'm guessing the boiler is reading the OT signal in bands:

Say 0-20% band low set point, 20-40% med set point, 40-60% higher set point, 60%+ FULL POWER!

OT does over-ride the manual CH control on the Atag but as far as I can tell the two profiles are different. When HW is demanded, TSet Calc immediately matches TSet Max (in my case 70C). When CH is demanded, there is a progressive increase towards TMax Set as zones demand heat. TMax Calc then falls away as zones come within the TPI range. Isn't this the Fuzzy Logic used by all Honeywell TPI controls?

That said, I agree that there is a difference between heating 12 zones up from 'rest' in the morning to their set temperatures, and 'say' turning up a single zone by 5 degrees during the course of the day. The latter doesn't need a massive increase in boiler flow temperature. This is why I have stopped using Economy. Gas usage monitoring suggests that it is more efficient just to leave the house at a stable temperature unless out for more than 3 to 4 hours.

I am still not sure that I understand the boiler demand temperatures.

[rvb99]

I live in Holland. It seems kind of basic but it is working quite good. The pump is strong enough for my total of 600 meter UFH system to pump it around at the right Liters/minutes for each zone. The good thing about this boiler is that i can limit the temperature with a parameter so it don't need a mixer. Also the boiler don't have to heat up the water to 60+ degrees (but only to 45 in my case) to mix it with cold water (which is a waste of energy). The bad thing is that the pump is controlled by the boiler so i cannot start or stop it manually unless i change my setup to on/off mode instead of opentherm. The bypass is like an overpressure valve which can be set from 0.1 to 0.5 bar and therefore not controlled by anything.

The problem i have (And other people as well) is that for some reason the HCE80 is closing (by use of the MT4-motor) the zone valves while the Evohome is still sending a setpoint. This results in no water flow (only trough the bypass) and a boiler which is still heating up the water. And after a few minutes the valve opens again. Are you sure that you don't have this problem as well? Maybe you never noticed this because you use a radiator as a bypass?

From info i found so far is that when you use multiple zones and don't use hr92 radiator valves you have to use the on/off mode from the boiler which means i have to use a BDR91. I have on of them and i will try this next week to see if it works better.

I dont seem to have problem, but then I'm not using opentherm. Firstly I have a T87RF2033 for each evohome zone. The UFH system is a mixer with its own pump and it is set to provide a manifold temperature fixed at 45deg. ie I like to think of the ufh system as a separate independent heating system (almost like an electric zone). it has a preset ufh internal pipe flow and temperature. Clearly it needs the heat from the main CH flow, but it operates almost entirely separately from it .This allows Evohome to easily learn and fully control the system. E.g as soon as heat is demanded the ufh zones are already preset in terms of manifold temperature and ufh pipe flow. The bolier provides CH water at around 75deg and there is a separate CH modulating pump that switches on when the boiler is fired that feeds the UFH system The HCE80 opens the manifold valves for the required zone, then switches on the mixer pump (and also a ufh feed zone valve for the manifold) , and then calls for boiler heat (+ CH flow pump). The CH circuit is also used to feed 14 other radiators with HR92s, and indeed one bathroom radiator is used as a bypass.

What I see from your graphs is that the ufh pipe temperature is changing and going up to 50deg. This seems a little high - what floor temperature does this produce ?

One of the other reasons for using a mixer pump is safety. It seems with your system it is quite easy to change the ufh temperature which could risk in the worst case damage the floor (assuming it is laid in a screed). In addition there is also a risk of a boiler malfunction leading to overheating. There are also health issues with running the ufh tempeature too high. As a minimum there should be a cutoff thermostat either in the floor or fitted to the manifold that runs independent of Evohome and shuts the system down in case of overheating. Is one fitted ? - is this perhaps the reason for the boiler to shut down or the valves closing ? . For example in my system the safety thermostat is fitted to the manifold and set at 50deg. If by way of malfunction the temperature goes higher than this, the ufh mixer pump will stop and the ufh feed zone valve will close.
btw there is no reason to have modulating actuators in the ufh system. The warm up and cool down lag times are so slow that there is no sense in trying to adjust an actuator to partially open

[JosP]

I have the same setup as Giel538 with the same boiler, also living in Holland. My system is used with 1250 meter UFH system and also with the right flow for each zone. I have only floor heating with 2 times a HCE80 in my house. My max. temperature on the boiler is set @ 40 deg.c. My experience is the same as Giel538. I was waiting for the last application update but my feeling is that it doesn’t work better. Next week I will change the system and use the internal on/off contacts in both HCE80 and set them parallel on the boiler and test if this is working better then with the opentherm module. So I don’t need a BDR91.

[fergie]

OT does over-ride the manual CH control on the Atag but as far as I can tell the two profiles are different. When HW is demanded, TSet Calc immediately matches TSet Max (in my case 70C). When CH is demanded, there is a progressive increase towards TMax Set as zones demand heat. TMax Calc then falls away as zones come within the TPI range. Isn't this the Fuzzy Logic used by all Honeywell TPI controls?

That said, I agree that there is a difference between heating 12 zones up from 'rest' in the morning to their set temperatures, and 'say' turning up a single zone by 5 degrees during the course of the day. The latter doesn't need a massive increase in boiler flow temperature. This is why I have stopped using Economy. Gas usage monitoring suggests that it is more efficient just to leave the house at a stable temperature unless out for more than 3 to 4 hours.

I am still not sure that I understand the boiler demand temperatures.

At the moment its telling me only one zone is calling for heat (Master Bedroom already at temp), but it is asking for 88% and the OT Bridge is asking the boiler for 88%. The result is the boiler is showing 70deg demand and 65deg return temp. To me, that just doesn't seem right and something that could easily be improved on.