Drayton Wiser operating questions

[mcprinter]

Has anyone with Wiser TRV’s noticed the reported temperature is about 2c higher than the actual room temperature since firmware ea64 was rolled out.

Noticed this too.

 

[Mister Banks]

Having now read online multiple reports that the Wiser TRV's temperature accuracy is very suspect i would have thought Drayton would have done something about it as a matter of urgency. I am also experiencing the issue with the app settings and Heat Source Type not being visible or configurable and the sporadic indication of when a zone is and is not calling for heat, both issues still not resolved. Come on Drayton, step up!

I'm not sure there is any saving on my gas consumption either. I'm struggling reconcile how a zone calling for heat individually of all other zones which also call for heat individually can possibly result in less gas being consumed. Surely the boiler heating 2 or 3 radiators concurrently is cheaper than heating 2 or 3 radiators consecutively. I'm starting to consider removing all the Wiser TRV's and going back to mechanical TRV's, whilst still using one of the Wiser room thermostats as the master temperature control for the whole house.

 

[Mister Banks]

Cant decide whether to use smart TRV's on all my radiators or just use the smart room thermostats. Is zoning a good idea?

 

[oldbutnotdead]

Lot depends on how efficiently (if at all) your boiler modulates and how low it will go. Zoning is a good way to control your heat consumption but if you go too mad with it you can end up compromising comfort (for instance, if you have a downstairs room you don't use much so decide not to heat it the bedroom above may be slow to warm up).
I've gone the wireless TRVs everywhere- they work really well with the thermal store heated by woodburner- no worries about modulation ratios and cycling.

 

[Mister Banks]

Lot depends on how efficiently (if at all) your boiler modulates and how low it will go. Zoning is a good way to control your heat consumption but if you go too mad with it you can end up compromising comfort (for instance, if you have a downstairs room you don't use much so decide not to heat it the bedroom above may be slow to warm up).
I've gone the wireless TRVs everywhere- they work really well with the thermal store heated by woodburner- no worries about modulation ratios and cycling.

I dont know how well my boiler modulates, its a Worcester Bosch Greenstar 24i system boiler. I cant find any info in the installation or user manuals. I dont want to compromise boiler efficiency which needs low return temps but if only 25% of the radiators are "on" that must have an impact.

 

[oldbutnotdead]

I dont know how well my boiler modulates, its a Worcester Bosch Greenstar 24i system boiler. I cant find any info in the installation or user manuals. I dont want to compromise boiler efficiency which needs low return temps but if only 25% of the radiators are "on" that must have an impact.

Minimum input on the 24i is 7.3 kw (page 6 of the install manual) so if you are only heating 1 or 2 rads the thing will cycle.
You will save energy by heating fewer rooms but due to the not brilliant modulation you may not save as much as you expect (eg heating 2 rooms costs x, heating only 1 of those rooms might well cost 2/3x rather than 1/2x). So if you were timeshifting you might want to get both rooms to setpoint instead of room1 then room2.

 

[Mister Banks]

I was watching a video by Heat Geek who, if I understood correctly, basically said do not zone in my situation as the savings made by not heating all radiators will be lost due to less efficiency by the boiler.

 

[MeldrewsMate]

I would argue against using TPI on a system which used to have an ON-OFF thermostat. TPI (time proportioned integral) will reduce the proportion of time that the heating is demanded as the measured room temp (mv) approaches the setpoint (sp), so for a 15 minute time period (4 cycles per hour) and with a calculated load of 33% (needed to keep the mv aligned with the sp) the output relay will be ON for 5 minutes, OFF for 10 minutes. The result will be 2-port or 3 port valves dancing around, up and down like a bride's nightie.
IMO TPI is useful only where Opentherm is in use, the calculated load being used to modulate the boiler's flow temperature. The Wiser hard-wired hubs have OT, I think.

 

[Mister Banks]

I would argue against using TPI on a system which used to have an ON-OFF thermostat. TPI (time proportioned integral) will reduce the proportion of time that the heating is demanded as the measured room temp (mv) approaches the setpoint (sp), so for a 15 minute time period (4 cycles per hour) and with a calculated load of 33% (needed to keep the mv aligned with the sp) the output relay will be ON for 5 minutes, OFF for 10 minutes. The result will be 2-port or 3 port valves dancing around, up and down like a bride's nightie.
IMO TPI is useful only where Opentherm is in use, the calculated load being used to modulate the boiler's flow temperature. The Wiser hard-wired hubs have OT, I think.

Its a good point but surely Drayton, Honeywell, Hive, Nest, etc wouldn't agree as nearly all modern programmable thermostats now use TPI.

 

[MeldrewsMate]

Its a good point but surely Drayton, Honeywell, Hive, Nest, etc wouldn't agree as nearly all modern programmable thermostats now use TPI.

That doesn't make them right though. My Honeywell Evohome is highly irritating in a standard S-plan configuration, for the reasons given above, but a joy when OT is used.

 

[JonathanM]

Its a good point but surely Drayton, Honeywell, Hive, Nest, etc wouldn't agree as nearly all modern programmable thermostats now use TPI.

I'm glad I can turn TPI off on my thermostat. I don't think it can be good for my very old, cast iron boiler, to just come on for two or three minutes at a time, and not really get hot. And there must still be millions of boilers like mine. In my (limited) experience, TPI will provide extremely good temperature control, if left to do its thing, so maybe that's why the manufacturers promote it. But it comes at the cost of lots of cycling of the boiler and the motorised valves. I don't actually think most people need the room temperature controlling to the 0.25 degree level. I can see if TPI were set to say two cycles per hour, that would work OK, but the minimum on mine is six cycles per hour.

 

[Mister Banks]

I'm glad I can turn TPI off on my thermostat. I don't think it can be good for my very old, cast iron boiler, to just come on for two or three minutes at a time, and not really get hot. And there must still be millions of boilers like mine. In my (limited) experience, TPI will provide extremely good temperature control, if left to do its thing, so maybe that's why the manufacturers promote it. But it comes at the cost of lots of cycling of the boiler and the motorised valves. I don't actually think most people need the room temperature controlling to the 0.25 degree level. I can see if TPI were set to say two cycles per hour, that would work OK, but the minimum on mine is six cycles per hour.

On my Wiser hub I can set the cycles per hour to 6 if I select gas or 3 if I select oil so there is some configuration there. My WB Greenstar condensing boiler doesn't appear to mind the 6 CPH setting.

 

[Mister Banks]

That doesn't make them right though. My Honeywell Evohome is highly irritating in a standard S-plan configuration, for the reasons given above, but a joy when OT is used.

True but I would hope that the manufacturers technical staff that design these thermostats would have a pretty decent level of expertise.

 

[harrythefurrysquid]

I was watching a video by Heat Geek who, if I understood correctly, basically said do not zone in my situation as the savings made by not heating all radiators will be lost due to less efficiency by the boiler.

I've seen that video, but I see it as more food for thought than a blanket rule.

Example:

If you have a set of interconnected rooms that you want at basically the same temp, you might consider setting them up in Wiser as a single room. Wiser will average the temps, but any call for heat will be answered with max rad surface area.

Heat Geek's argument would say this is the way to go. I would say it's the way to go if one room has an undersized rad, because it'll avoid kicking on the boiler just to service that one room (particularly in Comfort mode - I have this issue and this was my solution). But if the rooms have similar heating and insulation, why not give control to Wiser and let it do the fine adjustments to keep the temps stable?


Another example:

I want my study hotter (+2 at least). Heat Geek's argument would tend to suggest that I should have that matched to the whole house, but I just don't need it that warm everywhere.

I compromised with a set point graph that initially heats it in concert with the rest of the house so that the boiler is mostly using all rads, and then steps it up over the course of the morning. This gives it a chance to get some heat from the Sun and my PC/monitor, and the boiler can just feed in small bursts (with Opentherm) to keep the rad warm without overshooting.


Re the TRVs, I would personally just stick Wiser TRVs on everything. Even with the not-stellar accuracy of the measurement, I don't really see the point of buying something like Wiser and then not using the smart TRVs - it looks like it's designed to operate as a system. You might as well buy a cheap wall thermostat and some manual or wax TRVs if you just want one zone all at the same temp.

 

[Mister Banks]

I've seen that video, but I see it as more food for thought than a blanket rule.

Example:

If you have a set of interconnected rooms that you want at basically the same temp, you might consider setting them up in Wiser as a single room. Wiser will average the temps, but any call for heat will be answered with max rad surface area.

Heat Geek's argument would say this is the way to go. I would say it's the way to go if one room has an undersized rad, because it'll avoid kicking on the boiler just to service that one room (particularly in Comfort mode - I have this issue and this was my solution). But if the rooms have similar heating and insulation, why not give control to Wiser and let it do the fine adjustments to keep the temps stable?


Another example:

I want my study hotter (+2 at least). Heat Geek's argument would tend to suggest that I should have that matched to the whole house, but I just don't need it that warm everywhere.

I compromised with a set point graph that initially heats it in concert with the rest of the house so that the boiler is mostly using all rads, and then steps it up over the course of the morning. This gives it a chance to get some heat from the Sun and my PC/monitor, and the boiler can just feed in small bursts (with Opentherm) to keep the rad warm without overshooting.


Re the TRVs, I would personally just stick Wiser TRVs on everything. Even with the not-stellar accuracy of the measurement, I don't really see the point of buying something like Wiser and then not using the smart TRVs - it looks like it's designed to operate as a system. You might as well buy a cheap wall thermostat and some manual or wax TRVs if you just want one zone all at the same temp.

In your first example I have a similar situation. I have 2 lounges joined by double doors which are open during the day but closed after about 19:00. The rooms have 3 radiators in total with the main lounge having 2 rads controlled by Wiser TRV's and a Wiser room stat.

I could have downstairs radiators as a single zone, with a Wiser TRV on each, controlled by a Wiser room stat, thats 5 radiators in total on smart TRV's. I could then have a second zone for the 4 radiators upstairs again using Wiser TRV's and a room stat. I would have 4 radiators in bathrooms with no TRV's on them.