Balancing rads - increased cycling/failed starts after balancing

[-rick-]

33 minutes ago, marshian said:

If the CH light is not going out then it's not interveening

 

By the CH light do you mean the flame icon? I don't tend to look at the thermostat but rather the app, but it has a representation of the same.

 

It doesn't appear to be directly connected to the opentherm requests. I've seen plenty of times when the boiler is active (and cycling) when the flame icon is off. I initially thought it was a bug (and my boiler was ignoring opentherm requests) but after a decent amount of observation I think the flame icon represents not matching the setpoint. ie, in a traditional on/off system, when the thermostat calls for heat. But with Opentherm it's trying to modulate the flow to maintain the set point to a much more precise degree (within 0.1C) and as long as it considers itself as successfully regulating that then the flame is off.

 

The relay signal to the boiler has stayed on all day barring once around dinner time when cooking pushed the temp a fair bit above set point at which point the relay switched off.

 

What I think is happening in my case is that Wiser adjusts the setpoint it wants from the boiler constantly based on the heating demand % supplied by the thermostat. Wiser wants the boiler on all the time to maintain the set point. The boiler is willing to exceed the set point by a certain amount but if it goes over that then it shuts off. I think there's more to it than this but feels like the main issue.

 

33 minutes ago, marshian said:

My solution to the issue was to set the room stat or a smart TRV to a higher target temp that cannot be achieved - that way the Wiser Hub doesn't get to screw around making the boiler cycle or stopping it mid burn (which is what it did with my old boiler when I had it set up with a really long anticycle timer to give the rads chance to dump the heat)

 

I assume you mean since you moved to weather comp and not using opentherm at all. That's not really something I want to do (given the amount of disruption running the cable would involve) and I'm not sure weather compensation would help when the CH system can't dump out the heat from the boiler at minimum modulation.

Edited 4 hours ago by -rick-

[marshian]

1 minute ago, -rick- said:

By the CH light do you mean the flame icon? I don't tend to look at the thermostat but rather the app, but it has a representation of the same.

 

It doesn't appear to be directly connected to the opentherm requests. I've seen plenty of times when the boiler is active (and cycling) when the flame icon is off. I initially thought it was a bug (and my boiler was ignoring opentherm requests) but after a decent amount of observation I think the flame icon represents not matching the setpoint. ie, in a traditional on/off system, when the thermostat calls for heat. But with Opentherm it's trying to modulate the flow to maintain the set point to a much more precise degree (within 0.1C) and as long as it considers itself as successfully regulating that then the flame is off.

 

The relay signal to the boiler has stayed on all day barring once around dinner time when cooking pushed the temp a fair bit above set point at which point the relay switched off.

 

What I think is happening in my case is that Wiser adjusts the setpoint it wants from the boiler constantly based on the heating demand % supplied by the thermostat. Wiser wants the boiler on all the time to maintain the set point. The boiler is willing to exceed the set point by a certain amount but if it goes over that then it shuts off. I think there's more to it than this but feels like the main issue.

 

No I mean the CH light on the Hub - flame on the app is just saying room is not at target temp - flame out says at target temp

[marshian]

3 minutes ago, -rick- said:

Then not really using Opentherm at all and relying on TRVs/max flow temp to limit room temp?

 

Old boiler couldn't support Open Therm - so yes I was managing room temps via TRV's however I had one room that needed much longer than all the others to hit target temp - so when other rooms reach temp and the Wiser Hub stopped the boiler it buggered up any chance of getting the one room to actually reach the temp required

[-rick-]

1 minute ago, marshian said:

No I mean the CH light on the Hub - flame on the app is just saying room is not at target temp - flame out says at target temp

 

Yeh that's basically been on all day.

[marshian]

1 minute ago, -rick- said:

 

Yeh that's basically been on all day.

 

If it's on and not clicking off then the cycling is down to the boiler

[-rick-]

1 minute ago, marshian said:

If it's on and not clicking off then the cycling is down to the boiler

 

Somewhat, it's down the the interaction between the boiler and how it meets the opentherm setpoint (which is set by Wiser and changed constantly).

 

When Wisers 'Heating Demand' measure started oscillating so did the boiler. I changed the set point then to force a long continuous burn and after I dropped the set point again we are now back to no oscillation and less cycling. Now I imagine there could easily be a feedback loop where the boiler cutting out due to insufficient modulation for my CH system triggers the oscillation. My comment earlier was that wiser doesn't offer a way to rate limit or filter this setting which makes cycling more likely. Opentherm also offers a way of turning the flame on and off remotely without using the relay. I don't know if wiser is using that ability or not.

 

This is all somewhat off-topic for this thread though. I want to optimise what I have to the best extent possible physically, then explore wiser more. My plan is:

1. Complete tweaking balance, etc

2. See how wiser works if asked to just manage the temp in the warm part of the home. (it should be able to satisfy that with lower temps and the colder unregulated rooms will act as a bigger heatsink to prevent cycling).

3. See what difference these fan kits I've ordered make (GPT suggests they could double the heat output of the radiators at high flow temps but don't help that much at low flow temps).

4. By the time I've done this I will have had more time to think about radiators. Looks like I can replace the two vastly undersized ones for ones with 2.5x the output for about £150 if I don't mind sacrificing matching the existing. I can't justify the cost of matching existing but moving to the cheap ones might get payback (and if I keep the old ones I can always swap them back in if the new ones cause issues with buyers/valuation).

5. If I do upgrade radiators then I go through the above again

6. If still having problems talk to wiser

 

Good news so far is that if I've done my sums right my gas usage is only about 50% more than normal heating the whole place vs what I was doing before. Given the heating is on for >14 hours a day vs maybe 6 before this doesn't seem to bad (more than I'd like long term though). This means I'm not in a huge rush to finalise this process and can take the time to try things out