Hive/Nest Powermax 155x

[Belle427]

Brother in law fancies a smart controller to switch the powermax 155.
Is it better to just replace the room stat with the Hive/Nest and leave the hot water alone?
Generally the hot water is set to constant.

 

[stem]

That's up to you and what you want to achieve really.

It's a long time since I've seen one, but if I remember correctly the Powermax has an in built thermal store for hot water, but still has a two channel programmer for timed control of the hot water. In which case it would be slightly unusual to leave an existing programmer in place that has heating and hot water control, and only use the hot water part, whilst controlling the heating from elsewhere, but you could.

Normally the Nest / Hive (other makes are available ) replaces the existing programmer & thermostat completely. The wires are moved from the original programmer to the terminals at the new one that have the same function, and the existing room thermostat decommissioned. If your boiler is one that has the existing programmer as an integral part of the boiler it can be more difficult to replace than one that is mounted separately elsewhere.

The Nest comes with both heating control and hot water control as standard. With Hive you choose from a single channel (heating only) or a dual channel (heating and hot water)

If you really wanted to, you could use Nest / Single Channel Hive in place of an existing room thermostat and just use it to control the heating. If you did this, the existing time control for the heating and hot water would be left as it is. However, the heating part would need to be set to be permanently 'on' thus allowing the new controls to take over control of the heating.

 

[Belle427]

Yes it does have a thermal store, I believe the timer mounted on the boiler panel failed shortly after they moved in so a plumber linked it out. A common issue I believe, they were going to replace the boiler but funds won’t allow at the moment.

 

[ianmcd]

yes it can be done but as @stem says it is different to normal set ups, if you go for the dual channel you have to leave the HW at the boiler switched to off or the HW will be constantly on and the CH switched to constantly on, then wire the nest or hive into the boiler control panel, certainly not straightforward for a Diyr but it can be done

 

[Gorners]

I got a Nest to my brothers 155x this time last year - see post here where I got clarification around the lack of neutral from the thermostat:

https://www.diynot.com/diy/threads/replacing-thermostat-with-nest-no-neutral.493963/

As others have said, it’s my easier just to replace the heating side and leave the hot water alone. I just hooked into the existing thermostat wires with the heat link and sent the 12v supply down to the Nest from the heat link.

If you’ve got any specific questions I’ll gladly try and help you out as I spent a fair bit of time studying the best way of doing it with this boiler. Mine isn’t the only way but it’s worked fine for over a year now.

 

[Belle427]

Thanks thats a great help. The Hive seems to be a fair bit cheaper than the nest so may look into those but the principle is the same.

 

[Gorners]

No worries - I’d say the Hive is just a thermostat that you can operate whilst you’re not at home, not really a ‘smart’ thermostat like the Nest, hence the price difference IMO.

I had Hive and soon switched to Nest after a week - each to their own though

 

[bbraganza]

That's up to you and what you want to achieve really.

It's a long time since I've seen one, but if I remember correctly the Powermax has an in built thermal store for hot water, but still has a two channel programmer for timed control of the hot water. In which case it would be slightly unusual to leave an existing programmer in place that has heating and hot water control, and only use the hot water part, whilst controlling the heating from elsewhere, but you could.

Normally the Nest / Hive (other makes are available ) replaces the existing programmer & thermostat completely. The wires are moved from the original programmer to the terminals at the new one that have the same function, and the existing room thermostat decommissioned. If your boiler is one that has the existing programmer as an integral part of the boiler it can be more difficult to replace than one that is mounted separately elsewhere.

The Nest comes with both heating control and hot water control as standard. With Hive you choose from a single channel (heating only) or a dual channel (heating and hot water)

If you really wanted to, you could use Nest / Single Channel Hive in place of an existing room thermostat and just use it to control the heating. If you did this, the existing time control for the heating and hot water would be left as it is. However, the heating part would need to be set to be permanently 'on' thus allowing the new controls to take over control of the heating.

Hi @stem
I plan to replace the wired thermostat on my powermax SS 155X with a Tado Wired Thermostat as the current Honeywell TS seems to be way off the temp readings. Based on what I had read through it looks to be fairly straightforward as we only need 2 wires( Live and SL) on Tado. Drawings Attached. Can you please let me know if my understanding is correct?


The next task I have is to replace the inbuilt programmer with Tado receiver to have DHW control. as per the manual, we can disable the inbuild programmer using the ON/OFF switch on the back of the programmer itself. The reason for this is I can't run CH independently without running the HW. I could use the inbuilt timers to match the time I want the CH to be ON or leave HW ON on all the time, but I don't think that's very efficient and the Tado has less control. I have a connection drawing for the receiver attached with DHW control. Do they look correct?

Can I also use CH control on the Tado receiver. That means I would have 2 relays in parallel( Tado receiver for CH and Tado wired Thermostat).if that going to be an issue, I can leave the CH on the smart thermostat

Thanks again for your help

 

[stem]

Normally the Tado receiver replaces the existing programmer, and your sketch with the wires from the CH NO and HW NO terminals to 28 and 24 look good to me, as does the live link to the two common terminals. The switch you mention would be set to disable an inbuilt programmer.

However, from the Powermax 155X manual below any programmer used with it needs to be set to 'gravity' this setting would mean that the HW would come 'on' automatically whenever the CH was 'on'.

Unfortunately AFAIK Tado doesn't have this facility. There are several versions of the Tado receiver out there now, and if you have the installation manual for the receiver you have, it should tell you if it does have a gravity mode. If it doesn't mention gravity mode it probably doesn't. I have got a hardwired workaround that I've used with the Nest Receiver (aka Heat link) that has the same wiring arrangement as Tado and switches the HW on, whenever the CH is on. Post back if you would like it.

To remove the old room thermostat, I would do this by disconnecting the existing thermostat cable and reinstating the link between terminals 27 & 28 as per the manual.

For you information, as I see this is your first post, you should really have started your own new thread and not posted your question on the end of someone else's. This is known as hijacking and is against the forum rules. Don't start a new thread now though otherwise you will be breaking he rules again by starting a duplicate thread.

 

[bbraganza]

Thanks @stem for the info. I don't see any gravity settings on Tado receivers. does that not mean we can't use Tado receivers? Can you pls send me a hardwired workaround? Sorry about hijacking this port as I thought this was the closest discussion to what I was looking to achieve.

 

[stem]

Here's the hardwired workaround. With this arrangement the HW can be 'on' on its own. But whenever the CH is 'on' it will also put the HW 'on' automatically at the same time.

Based on your earlier diagram, the wires shown below are:
CH Control = 28
HW Control = 24

Make the links between the terminals carefully, it's easy to get them wrong.

 

[bbraganza]

Thanks @stem

 

[bbraganza]

Hi Stem. Did a check on the wireless receiver manual - https://cdn.brandfolder.io/607DGEMS...AL-WRP01IB01-INSTALLER_MANUAL-TA-UK-00-V2.pdf and it looks like they do offer a gravity fed config as well - on section 6. That being said can I just go with the wireless receiver wiring as per my original plan?

Appreciate your help

 

[stem]

Perfect; there you go then, back to plan A.

 

[bbraganza]

Perfect; there you go then, back to plan A.

View attachment 291727

Excellent