Biasi Riva Plus - External Thermostat

[matthocker]

I have a Bias Riva Plus which I have connected an external thermostat to. It is a very simple setup - essentially the thermostat acts as a switch, closing the connection between pins 1 and 3 on the external controls terminal block.

I'm going to try to adapt the system to use the new Nest thermostat, see www.nest.com. It uses American style connections which may or may not have an analogue here in the UK.

The Nest requires up to a 24 VAC control circuit. However when I put a voltmeter across pins 1 and 3 on the Biasi, I see 40 VAC. This is obviously too much.

My question is, has anyone ever adapted a US 24VAC style thermostat to a European boiler such as the Biasi that I have?

I can think of two potential ways to do it: either step the voltage down or install a relay in the middle, isolating the boiler's 40 VAC side from the thermostat's 24 VAC side which I would provide with a transformer.

Advice and suggestions much appreciated. Thanks!

 

[compheat]

Why go to all that messing about?? what benefit will it be for you over what you have know.

Doesn't the Riva have a volt free side (low voltage)

 

[matthocker]

There does not appear to be a 24 VAC source in the Riva. I've read the manual and it seems to just expect a switch-type thermostat.

And why go to the trouble? Because the Nest is really cool and allows for remote programming and learning your heating patterns among a bunch of cool things.

I found another discussion which looks like exactly my situation, this is what I'll try unless anyone thinks this won't work...

http://www.justanswer.com/hvac/2w3kl-277v-line-voltage-thermostat-need-convert.html

 

[Boilerman2]

Programmable, and "Self Adaptive"?? Sounds like a Honeywell CM
why bother with the Septic Tank rubbish!! THe Honey well is directly compatible with your Biasi, and availible at all good merchants near you

Have a Good Day!

 

[matthocker]

On a more helpful note, if someone could recommend a source for a good low current 240 to 24 VAC power supply with wires (rather than the wall-wart type, as there is no outlet in the closet with this boiler) which can be wall mounted, that would be helpful.

The RIBU1C/RIBH1C relays look like a good fit from the relay point of view. http://www.functionaldevices.com/pdf/datasheets/RIBU1C.pdf

 

[Boilerman2]

What VA rating is required? have a look at Fire Alarm PSU's they O/P 24Vac usually 1VA but larger PSU' are availible - Check www.rs-online.com