Control Options

[silverback18]

The folk who slag off weather compensation are those who can't be bothered to keep up with improvements in technology during the last quarter of a century, and who also can't be bothered to set it up properly.

That is a rather bold statement. As it so happens, I promoted he boilers before most others did, and dito for digital controls, programmable roomstats and wireless.

It is so simple, and so effective.

Simple, maybe. Effective? Adding wc to he boiler decreases the gasbill by a maximum of 2%. On installations with "ovesized" rads where the boiler is permanently set to a return temperature of below 50, the savings are virtually nil.
I would not call a saving of 0.something % very effective.

The heat requirement of a house is directly proportional to the temperature difference between outdoors and indoors.

True as that may be, it does not automatically make wc a useful addition.

People are incorrect or misinformeed who state oversized radiators, the radiators are not oversized, they are sized correctly to give the required heat output for the room at a flow temperature 50°C doing this gives the customer a more efficient heating system and is more suited to condensing boilers

 

[D_Hailsham]

I hadn't realised this about the Opentherm Protocol although it makes sense now that you've highlighted it. I was thinking of Opentherm as just a communication standard rather than as a complete standard for boiler control.

The Opentherm Protocol is very tightly controlled by the OpenTherm Association. Manufacturers have to submit their products for testing before they can say they are Opentherm compliant.

The idea of using the 957 is appealing as my guess is that it's the most user friendly. Although I guess using all one manufacturer's gear is also a good idea in the event of problems.

The big advantage of OpenTherm is that you can use any OT controller with any OT boiler.

 

[dumbrill]

I've now found a somewhere in Holland that can sell me a wireless iSense:

http://www.cv-sanitairkorting.nl/product_info.php?cPath=96_110&products_id=3119

As long as I specify the 'International' version I will get the option of English. It's also possible to buy a Remeha SmartPower adaptor that provides the 5V supply needed for when the boiler is not to the latest Opentherm standard.

My next question is where can I get the NTC thermistors that I need; one for the outdoor WC sensor and one for the HW cylinder. I thought I had read somewhere that these are standard across a few boilers, but I've found nothing on Google.

If I can get this resolved then I will probably go for the Avanta.

 

[bengasman]

Lots of controls are based on the same few thermistors. But from all I have heard/read, it seems that the "universal compatibility" of opentherm is specifically designed in such a way that it will only work with boilers that are accepted in the club.
Afaik, the components don't work with Honeywell, Siemens, Salus or any of the main boiler brands. It looks suspiciously like that "open" in opentherm is about as open as the door of an exclusive Mason's lodge.

 

[dumbrill]

Lots of controls are based on the same few thermistors. But from all I have heard/read, it seems that the "universal compatibility" of opentherm is specifically designed in such a way that it will only work with boilers that are accepted in the club.
Afaik, the components don't work with Honeywell, Siemens, Salus or any of the main boiler brands. It looks suspiciously like that "open" in opentherm is about as open as the door of an exclusive Mason's lodge.

I'm not sure that it is an Opentherm related query or not. I've scanned the section of the Avanta manual that shows the connections for terminal block X9 and copied it below. This makes reference to the 'outside sensor' and an option to have a 'DHW sensor'. The reference to 'red band' I assume relates to accuracy.

Untitled

• dumbrill
• 4 Dec 2010
• 1

Are these sensors both the same sensor and/or what is the correct part no? Obviously the outside sensor will be in a box for outside and the inside sensor needs to be buried under the insulation on the hot water tank. But I assume that they are both NTC thermistors. I just tried ringing Remeha, but unfortunately they are closed until Monday.

 

[MJN]

You can find the part numbers in the Layout/Wiring guide (pg 3), and they can be purchased at BHL. Naturally, they are exorbitantly priced for the same reason a dog can lick its balls.

Lots of controls are based on the same few thermistors. But from all I have heard/read, it seems that the "universal compatibility" of opentherm is specifically designed in such a way that it will only work with boilers that are accepted in the club.

The thermistors are analogue devices connected directly into the boiler hence not covered as part of the Opentherm spec for master/slave interoperability.

Mathew

 

[D_Hailsham]

But from all I have heard/read, it seems that the "universal compatibility" of opentherm is specifically designed in such a way that it will only work with boilers that are accepted in the club.

You have to understand what what Opentherm is all about. It is a protocol for two-way digital communications between boiler and thermostat. While standard mechanical and digital stats are one-way - stat to boiler, Opentherm works both ways. For example: it will send flow and return temperature to the stat.

Obviously the boiler has to have more sophisticated electronics to be able to send and receive the signals, which must comply with tightly specified criteria. This is why both controller and boiler manufacturers have to submit their products for testing.

The "Open" just means the protocol is available to any manufacturer and that all products which carry the Opentherm Logo are compatible.

Contrast this to the Vaillant Ebus, which is unique to Vaillant.

 

[dumbrill]

You can find the part numbers in the Layout/Wiring guide (pg 3), and they can be purchased at BHL. Naturally, they are exorbitantly priced for the same reason a dog can lick its balls.

Thanks, I've been looking at that and I hadn't spotted the list of parts.

So in summary it looks as if I can buy a WC sensor and a DHW sensor in the UK and a RF ISense from the Netherlands. That will then give me all the functionality of the Vaillant system except that the WC sensor has to be hardwired to the boiler. I'll have to think on whether it's worth the extra risk over the known quantity of the Vaillant system (and it's no cheaper).

What I don't understand is why Remeha don't offer the wireless ISense for sale in the UK. There doesn't seem to be a technical reason unless I'm missing something.

Also having looked at the Dutch version of the Avanta I see that a WC sensor cannot be directly connected to the boiler PCB. A 'gateway' module has to be bought. Why bother to make two different types of the same boiler?

 

[mickyg]

just to throw in another option, you could use an ATAG Q series boiler weather sensor and keep your existing honeywell rf controller.

 

[dumbrill]

just to throw in another option, you could use an ATAG Q series boiler weather sensor and keep your existing honeywell rf controller.

At the moment I have a CM927 with my 25yr old Glowworm and I want to get a modulating control with the new boiler. So at the moment all my options are open.

I'm not sure that I follow you're comment on the ATAG control. Their equivalent is the WiZe, but it's not wireless.

 

[mehran]

this link may help you with honeywell stat:

http://www.honeywellbv.nl/uploads/files/aansluittabel-april-2009.pdf it is a comparability list between honeywell and makes

 

[mehran]

also, the isence will work with intergas and also have WC but you can't change the dhw setting from it for intergas

 

[mickyg]

just to throw in another option, you could use an ATAG Q series boiler weather sensor and keep your existing honeywell rf controller.

At the moment I have a CM927 with my 25yr old Glowworm and I want to get a modulating control with the new boiler. So at the moment all my options are open.

I'm not sure that I follow you're comment on the ATAG control. Their equivalent is the WiZe, but it's not wireless.

Well it depends what your trying to achieve. The suggestion was a simple slution to provide weather compensation. You won't get modulating control from the controller, but with your heat curve set right it shouldnt be necessary. Its a very simple solution I've used a few times to allow basic easy to use controllers but with weather compensation. You cant do this on most boilers as the Q series has a seperate contact for hw and ch, so the boiler will know when its heating what and can adjust flow temp accordingly.

 

[D_Hailsham]

What I don't understand is why Remeha don't offer the wireless ISense for sale in the UK. There doesn't seem to be a technical reason unless I'm missing something.

Also having looked at the Dutch version of the Avanta, I see that a WC sensor cannot be directly connected to the boiler PCB. A 'gateway' module has to be bought. Why bother to make two different types of the same boiler?

The Dutch are miles (or is it kilometres?) ahead of the UK when it comes to control systems for boilers. The main difference between the UK and Dutch versions of the Avanta is in the PCB. The UK version does not support SmartPower,which is required for the iSense RF Relay box.

The gateway module also allows the boiler to interface with a modem.

 

[dumbrill]

also, the isence will work with intergas and also have WC but you can't change the dhw setting from it for intergas

It looks as if this is true for the Avanta boiler as well.

I now have a new Avanta 18S that since it's installation I've been using with a CM927. Earlier this week I finally received a iSense RF from Holland and I've spent a few nights this week temporarily hooking it up and seeing what it does. A quick summary:

It controls the CH in either room thermostat or WC mode and appears to work OK doing this.

It doesn't however control the HW. Whatever the settings, time, etc on the iSense a link across pins 3 and 4 of X9 (cyl stat) causes the HW heating to trigger. It seems that a time clock is still required for HW to keep it off when not required. The only thing that does happen is that a little HW symbol appears on the iSense when the boiler is in HW mode.

This afternoon I bought another outside WC sensor and put it across pins 3 and 4 of X9 as I guessed that the thermistor inside a real HW sensor would be the same (the WC sensor is off the shelf and a lot cheaper). It was and this gave a temperature reading for the HW and I could see this both on the boiler and the iSense. BUT the boiler doesn't do anything when the temperature rises. In HW mode the manual indicates that the sensor should cut the HW at the preset temperature, but this doesn't happen.

In summary the iSense RF works ok for CH, but not HW. With or without the iSense a HW thermistor gives a reading, but the boiler doesn't act on it. So for HW an on/off cylinder stat is still required.