OpenTherm RF Stat available in the UK?

[tourcd]

Can anyone confirm whether there's an OpenTherm compliant wireless thermostat available in the UK?

I've got a Remeha 39C combi boiler and want to install a OpenTherm modulating thermostat. Their iSense product is only available in mainland Europe and they couldn't come up with an alternative.

There seem to be plenty of OpenTherm products out there but is there a reliable one available to the UK market?

 

[D_Hailsham]

As far as I know, the Remeha iSense RF is the only product available at the moment. Honeywell announced one about 18 months ago but it is not in the shops and recent enquiries to them produced the reply that they have no plans at the moment to sell it in the UK. Something about not being compatible with the latest Building Regs requiring two heating zones.

The way round it is to buy the Multilingual version of the iSense RF from an online supplier in Holland.

You will also need to buy a 5Vdc power pack (similar to the ones used for Routers) from somewhere like Maplin. This is because the PCB installed in UK versions of Remeha boilers does not have ability to supply the iBase receiver with the required 5V.

 

[tourcd]

Thanks for the reply. I have since spoken to Salus who are about 3-weeks away from updating their ST620RF unit with an OpenTherm compliant software release.

Don't know much about Salus but looking around they don't seem to get favourable reviews.

 

[D_Hailsham]

Thanks for the reply. I have since spoken to Salus who are about 3-weeks away from updating their ST620RF unit with an OpenTherm compliant software release.

Don't know much about Salus but looking around they don't seem to get favourable reviews.

Salus will need more than a software release to make it Opentherm.

Most installers have a very low opinion of Salus products.

 

[tourcd]

okay - if I don't go OpenTherm for my Remeha what's a good option? Honeywell/Siemens?

 

[D_Hailsham]

okay - if I don't go OpenTherm for my Remeha what's a good option? Honeywell/Siemens?

You could fit an external sensor and a programmable stat. See Remeha Suggested Schematics

As for make, Honeywell are very good. I would suggest the CM927, which is a wireless programmable stat.

The receiver would be wired volt-free (NO LINK between L and A) - A to X9-7 and B to X9-8

A link would be needed between X2-1 and X2-4. (There should already be a link between X2-3 and X2-4)

The external sensor connects to X9-1 and X9-2.

 

[dumbrill]

I've been using an iSense RF with an Avanta 18S for about 6 months now and it works very well. Fit and forget really, although with the colder weather I will no doubt fiddle with the curve settings a bit more. I bought it from the Netherlands. It controls both CH and HW. The only negative is that it doesn't have a HW boost function, but that doesn't bother me as we have the HW on permanently during the day/evening.

If you're looking for alternatives that aren't OT then I wouldn't go for a CM927. I don't think the cycling approach adopted by the CM927 works well with the modulating approach of the Avanta. I used a CM 927 for a while as an interim solution and I thought that the CM927 turned off the boiler before it ever really got going. This is because the Avanta starts off at mid output and only slowly works it way to full power. In the absence of an OT input presumeably the output is calculated as some function of input temp and output temp, but it doesn't start off at full output initially. Often the boiler would start and as the output cranked up over a few minutes it would get stopped 'early' by the CM927.

With my previous 20 year old Glowworm boiler that was either off or 100% on the CM927 worked fantastically for 5 years. So I'm not criticising the CM927 as a control for on/off boilers,

Anyway in summary the iSenseRF works well and the zoning issue sounds like an excuse. It's more likely that the cost of it is uncompetitive and that it's too complex for the UK market. Also we can hook up an OT control straight into our UK boilers, but in The Netherlands they need to buy a 'gateway'. So who knows why it's not sold over here?

 

[dumbrill]

okay - if I don't go OpenTherm for my Remeha what's a good option? Honeywell/Siemens?

You could fit an external sensor and a programmable stat. See Remeha Suggested Schematics

As for make, Honeywell are very good. I would suggest the CM927, which is a wireless programmable stat.

The receiver would be wired volt-free (NO LINK between L and A) - A to X9-7 and B to X9-8

A link would be needed between X2-1 and X2-4. (There should already be a link between X2-3 and X2-4)

The external sensor connects to X9-1 and X9-2.

Just one comment on this. Wiring in an outside sensor will allow the boiler to adjust CH water temp based on outside temp. This is based on the curve that can be adjusted with various parameters. But use a simple on/off programmable state and not one like the CM927 with TPI control (or turn it off).

 

[D_Hailsham]

This is because the Avanta starts off at mid output and only slowly works it way to full power.

That's interesting to know; how did you find it out?

The assumption has always been that, with possibly one exception, modulating boilers start off at max output every time they ignite and then reduce output as the temperature increases.

I was thinking about this recently and realized that this does not make sense. When the room stat turns the boiler off, the water temperature sensors are still operational, monitoring the water temperature. So, when the room stat asks for the boiler to run again, the boiler should already already know the required modulation level. There should be no need to start at max and then close down. The only time it should start at max is when the boiler has cooled completely.

Also we can hook up an OT control straight into our UK boilers, but in The Netherlands they need to buy a 'gateway'.

Where did you get that from? The Dutch installation instructions show the connection for an OT controller direct to the PCB.

 

[dumbrill]

Also we can hook up an OT control straight into our UK boilers, but in The Netherlands they need to buy a 'gateway'.

Where did you get that from? The Dutch installation instructions show the connection for an OT controller direct to the PCB.

When I was looking into the iSense I came across various references to a 'gateway'. Here's one I've just found http://home.xmsnet.nl/openthermprotocol/.

 

[dumbrill]

This is because the Avanta starts off at mid output and only slowly works it way to full power.

That's interesting to know; how did you find it out?

Only from observing what the boiler does when it starts. One of the readouts available (t6?) shows the fan speed and 35 is the maximum. The boiler is setup to always start at '22' and it never goes directly to 35, but creeps there slowly. I assume it only goes to '35' if it can maintain the right temp diffential and stay within the max temp.

 

[mickyg]

The assumption has always been that, with possibly one exception, modulating boilers start off at max output every time they ignite and then reduce output as the temperature increases.

its a feature unique to most dutch boilers. Atag, remeha and i think intergas all modulate this way on initial firing.

 

[D_Hailsham]

Also we can hook up an OT control straight into our UK boilers, but in The Netherlands they need to buy a 'gateway'.

Where did you get that from? The Dutch installation instructions show the connection for an OT controller direct to the PCB.

When I was looking into the iSense I came across various references to a 'gateway'. Here's one I've just found http://home.xmsnet.nl/openthermprotocol/.

I have done a bit more digging - on the Dutch website - and found what they are talking about.

It's not Opentherm which is the problem, the Avanta series have connections, it's the external sensor. Some versions (CW3, 4 and 5) do not have a connection for the external sensor, so you have to use a gateway. The CW6, which appears to use the same PCB as UK versions, does have connections.

 

[dumbrill]

The assumption has always been that, with possibly one exception, modulating boilers start off at max output every time they ignite and then reduce output as the temperature increases.

its a feature unique to most dutch boilers. Atag, remeha and i think intergas all modulate this way on initial firing.

Except that in the case of the Avanta range they don't. The start up fan speed is set to 22 against a max of 35.

 

[DeltaT2]

I've been using an iSense RF with an Avanta 18S for about 6 months now and it works very well. Fit and forget really, although with the colder weather I will no doubt fiddle with the curve settings a bit more. I bought it from the Netherlands. It controls both CH and HW. The only negative is that it doesn't have a HW boost function, but that doesn't bother me as we have the HW on permanently during the day/evening.

If you're looking for alternatives that aren't OT then I wouldn't go for a CM927. I don't think the cycling approach adopted by the CM927 works well with the modulating approach of the Avanta. I used a CM 927 for a while as an interim solution and I thought that the CM927 turned off the boiler before it ever really got going. This is because the Avanta starts off at mid output and only slowly works it way to full power. In the absence of an OT input presumeably the output is calculated as some function of input temp and output temp, but it doesn't start off at full output initially. Often the boiler would start and as the output cranked up over a few minutes it would get stopped 'early' by the CM927.

With my previous 20 year old Glowworm boiler that was either off or 100% on the CM927 worked fantastically for 5 years. So I'm not criticising the CM927 as a control for on/off boilers,

Anyway in summary the iSenseRF works well and the zoning issue sounds like an excuse. It's more likely that the cost of it is uncompetitive and that it's too complex for the UK market. Also we can hook up an OT control straight into our UK boilers, but in The Netherlands they need to buy a 'gateway'. So who knows why it's not sold over here?

Their iSense stuff is good but oh my gawd their technical guys are clueless. I'm sure one guy can only answer questions on Baxi 552 BBUs!!!! Why can't Baxi just get calls transferred to an English speaking guy in Holland??...............