Low heat demand not heating radiators
How can I fix this and stop Tado wasting gas? Is there a way to disable low heat calls for instance?
Comments
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Sounds like the radiator valve pin might be stuck so when Tado opens the valve to 1 bar, the pin isn't coming up to allow heat through.
I'd check that the pin moves freely and let Tado do another calibration
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Mine had this issue on a couple of radiators last year from the sounds of it - sometimes a radiators in three of my rooms could end up calling for low heat for an hour+ with the boiler firing and nothing getting to the actual radiators. I confirmed the pins moved, I changed the batteries, I did all the things.
It didn't always happen, but it happened often enough it was costing me a noticeable percentage of my daily gas use.
If that sounds like you, here's my learning, and apologies for war and peace - you can just skip to 'in conclusion' if you like :)
A key thing is: when the smart TRV calls for low heat from nothing, can you hear it open? They make a little ...vvvvvv... noise.
- If you don't hear it actually making a noise, then the TRV is not budging. Do a recalibrate, and make sure you are using only the specific batteries Tado support in your problem TRVs, then contact Tado, that's clearly some kind of fault, I doubt they'll argue about it, they'll probably just replace it. This was not my issue.
- If as I did, you DO hear it making the noise on low heat and the boiler is firing up, but nothing's getting to the radiator, then you might be in for some pain getting this sorted, but take a deep breath and contact Tado anyway.
Something I noticed was that my problem TRVs had issues opening, not closing. On the way up, opening to low wasn't always letting heat in, on the way down from medium or high, no problem at all. As if on the way up is wasn't moving to the exact same position as on the way down.
Once I recognised the pattern (which was after many hours of hopping through heat graphs and documenting everything in a spreadsheet and doing graphs and... well you get the idea), and realised from the forums that it might not be be a quick fix from Tado, I decided to make some changes to my scheduling to force the issue.
Workarounds
First: if using rechargable batteries, MAKE SURE you are using the supported Eneloop in problem rooms.
- Switching to the eneloops did help me - it did not eliminate it, but it unarguably helped.
- This isn't so much a workaround as just one of the legs you'll need to knock out before Tado will admit they might need to do anything.
Second: early start is a fools errand if there is a chance of low heat calls not working.
- Turn it off for your problem radiators if you use it at all, and just use gradual set back and step up temperatures if need be.
Third: you want to compensate for any situation where the TRV is going:
- 'I'm not on right now, but I'm nearly at the temperature you wanted anyway so I'll only call for low'; or
- 'I think I'm on low already, so even though the schedule has changed I'll just keep going at low cos the target temperature is still close enough'.
If it's going to from 'gosh it's a bit warm I'll just drop to low', then there's never really an issue that I noticed.
So what i did is:
- Use set back temperatures in the affected rooms of at least 3C difference, if not 4C.
- In the problem rooms, set any heating period longer than an hour to also start with a 15 minute period which is at least +2C higher than the target temperature
- If the planned heating period was longer than 3 hours, I also added similar 15 min spikes at 90 min intervals.
Most times, that forces enough of a differential between current and target that medium heat will kick in and ensure the valve is open, before going back to behaving properly 15 mins later.
- Is that efficient? NO, of course not! I hates it forever, precious.
- Is it more efficient than it calling for low heat for sometimes an hour+ with the boiler firing the whole time and nothing getting to the radiator? YES. And this set up stops that happening.
Obviously I wasn't satisfied with that, so I had a bit of a rant on the forums then reached out to Tado via website chat, then moving to email. There were people on the forums who'd said Tado had adjusted the firmware to make the pins move more on low, and that sounded pretty sensible given what all my poking at the problem had revealed.
What Tado could and couldn't do
Over the course of a month of back and forth... :
- Tado can indeed do tweaks to change how much the pin moves on low heat calls, but it's something they do only if the developer team agree it after being convinced there's a problem, and there's a limit to how effective it can be - and initially the support person denied this was possible at all.
- Once this was agreed as needed and then implemented things weren't solved but definitely improved again - in as much as it now happens far less often, generally in those rooms that we keep cooler like the kitchen which are more prone to only wanting low heat to begin with - so I still keep spikes in the schedule there.
- They can also set your whole system (but not a specific TRV) to ignore all calls for low heat full stop in order to stop the boiler firing, and heating will start when the TRV gives up and calls for medium.
- I declined this one, on the basis that a big part of issue was that they could get stuck on low but not allowing heat into the radiator sometimes for an hour plus before calling for medium heat. If it elevated to calling for medium heat more reliably when the room temperature hadn't changed or kept falling whilst on low, I doubt I'd have even noticed a problem and this change would just mean rooms getting actually cold then bursting into life! Better to just have short spikes in now and again to make sure it's awake.
- They cannot change how fast the Tado will give up calling for low and call for medium. The magic algorithm does that and there's no config for it (at least, none they're prepared to admit or deploy).
- If they could have done this I'd have considered things resolved entirely satisfactorily rather than having to live with manually compensating in my schedule and burning more gas regularly on purpose just in case.
So, to conclude...
If:
- The pin is moving freely
- AND the TRV is audibly moving on 0>L1 heat call,
- AND the boiler's firing,
- AND you're using the right batteries,
- AND you're getting no heat to that radiator sometimes or all the time...
...contact Tado.
But also keep yourself sane and warm by adding short spikes just after a heating period starts and depending on the frequency with which it happens in the middle of a longer heating period, short spikes there too.
It's possible, even likely, that if I changed the whole valve assembly on each radiator for a new one it would stop happening, but that's beyond my ability and is just yet more cost sunk in - certainly more cost than it'll cost to run the spikes until such time as I can afford a heat pump at which point all but one radiator in my house is going to need replacing anyway.
I hope this has helped!
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@Unkledunkle I have the same issue, so I contacted tado for help and to ask if they can recommend any valves to replace my old ones thinking that might be the source of the issue.
tado CS representative said the they can't recommend any valves, but I can try IMI Eclipse TRVs if I want to replace mine because they are old, then repeated that they can't guarantee anything, so I bit the bullet and replaced all the valves around the house but, unfortunately, that didn't fix the problem.0 -
This is so frustrating hearing over people with the same issue. I bought these SRT valves to save money and instead they fire up my boiler for an hour and don't let any heat into the rad that requested it. Means I'm burning cash to heat my bathrooms.
Support just don't seem to understand what I'm talking about and I doubt this will be sorted.
Thanks for the info @Unkledunkle and I have similar findings to you just not in as much depth. To be honest I'm thinking of giving up and sticking with a single zoned house unless I can find a system that actually works. What Tado is doing is a mystery to me and I'd rather the simplicity of simple TRVs and a central thermostat.1 -
@SaulGoodman have you considered unscrewing Tado TRVs a bit to let some waterflow instead of going back to full single-zone system? Not ideal but better than just heating the bathroom rail.0
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If it's happening to 1 or 2 rads, check the pipe which comes from your boiler is getting warm/hot. Check the rad return valve is open and not stuck. Also, the rad which isn't getting hot, could need flushing out (this happened to me).
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