Remeha Avanta18S Wiring - Unvented Cylinder and iSense RF

dumbrill · 10 Jun 2012

It's taken well over a year for me to get around to drawing this up, but I thought it might be useful for others to put down on paper my setup for an Avanta 18S boiler with an unvented cylinder and iSense RF. I've based my diagram on those provided by Remeha for other systems.

The key components are:

Avanta 18S boiler,
iSense RF controller
Santon Premier Plus unvented cylinder with HW thermistor sensor.

Untitled

dumbrill
10 Jun 2012
1

This gives pretty much the optimum system with either fully weather compensated control, simple room temperature control or a combination of both. Over a years use has shown the system works well - fit and forget.

D_Hailsham · 30 Jul 2012

That's very interesting. However I'm not sure why you have wired the pressure switch and condensate pump in series. Also the Manual says these terminals are volt-free and you need a relay. Is this what you have done?

However I am more interested in the hot water side as I recently installed a Remeha open vent boiler and am thinking of the iSense to replace a Honeywell CM927 and a single channel timer for the HW cylinder.

I have read and re-read the iSense Installation Manual and the HW instructions do not make any sense.

At the moment I have the following:

CM927:

Optimized ON for 06.30 - various changes during the day - OFF at 2300.

HW timer:

ON at 1200
OFF at 1400 (tops up water used on waking and during the morning)
ON at 2100 (we all shower at night)
OFF at 0030 (tops up after last shower. The water is still hot enough in the morning and up to lunch time)

My question is: Will I be able to have the same with the iSense, i.e completely independent CH and HW times?

I also notice that you use a sensor for the HW cylinder. Did you ever try a cylinder stat?

dumbrill · 31 Jul 2012

D_Hailsham said:
That's very interesting. However I'm not sure why you have wired the pressure switch and condensate pump in series. Also the Manual says these terminals are volt-free and you need a relay. Is this what you have done?

I assume your open vent version doesn't have a pressure switch that cuts the boiler if the pressure falls below around 1 barg. In my case I do and that is simply a open or closed contact across terminal X9, pins 5 and 6. I also wanted to stop the boiler in the event of the condensate pump failing. The high level switch that detects a failed pump is just a float switch. All I have done is wired this in series with the pressure switch. Either one going open circuit cuts the boiler.

D_Hailsham said:
However I am more interested in the hot water side as I recently installed a Remeha open vent boiler and am thinking of the iSense to replace a Honeywell CM927 and a single channel timer for the HW cylinder.

I agree the manual for the iSense isn't very good. There is however full control across seven days of HW coming on and off several times a day.

D_Hailsham said:
My question is: Will I be able to have the same with the iSense, i.e completely independent CH and HW times?

Yes

D_Hailsham said:
I also notice that you use a sensor for the HW cylinder. Did you ever try a cylinder stat?

No I've never tried, but I see no reason why it won't work. Afterall that is what 99.9% of installations will have. However you can buy about 10 of the thermistors from Digikey in the US for about £20. If you can fit one of these to the tank then you get a temperature reading. In fact that now reminds me that you can control the HW temperature across the various time periods. Unfortunately I'm not at home at the moment and so I can't check the screen. Otherwise I'd post a screen shot.

In summary the iSense is a very good controller. It does either simple room thermostat control, simple WC or a combination of the two. The heating curve can be completely changed from first principles. Although this is also a negative because it takes more knowledge to setup. It's worth googling 'reset ratio heating' to understand how the iSense heating curve parameters translate to the typical curves from other manufacturers.

dumbrill · 31 Jul 2012

I'm struggling to upload a the latest revision of the schematic because the resulting image quality is so poor.

D_Hailsham · 31 Jul 2012

Thanks for replying.

dumbrill said:
I also wanted to stop the boiler in the event of the condensate pump failing. The high level switch that detects a failed pump is just a float switch. ... Either one going open circuit cuts the boiler.

Ingenious!

There is however full control across seven days of HW coming on and off several times a day.

That's good to know

D_Hailsham said:
D_Hailsham said:

My question is: Will I be able to have the same with the iSense, i.e completely independent CH and HW times?

Click to expand...

Yes

So is that.

D_Hailsham said:
D_Hailsham said:

I also notice that you use a sensor for the HW cylinder. Did you ever try a cylinder stat?

Click to expand...

No I've never tried, but I see no reason why it won't work.

You seem to be able to set HW temperature on the iSense. I can see how this would work with the sensor as it sends actual temperature data to the iSense. But a cylinder stat is just an on/off switch, which as relatively inaccurate and could turn the boiler off before the iSense says it should.

In fact that now reminds me that you can control the HW temperature across the various time periods. Unfortunately I'm not at home at the moment and so I can't check the screen. Otherwise I'd post a screen shot.

That would be helpful - if you have the time.

The heating curve can be completely changed from first principles. Although this is also a negative because it takes more knowledge to setup. It's worth googling 'reset ratio heating' to understand how the iSense heating curve parameters translate to the typical curves from other manufacturers.

I did some googling and it was very interesting/informative. The formula for calculating the 'reset ratio' (strange American term

) is obvious when you think about it. The water temperature can never drop below the room temperature, e.g 21C and its just a case of determining the minimum water temperature necessary to heat the house at a given lowest outside temperature.

PS It would appear that the RF version of iSense is now available in the UK! See http://www.partsarena.co.uk/baxi/ : Remeha - Avanta - any boiler except Exclusive - Accessories - New Remeha Accessories April 2012.

dumbrill · 2 Mar 2013

Updated schematic with larger text:

Untitled

dumbrill
2 Mar 2013
1

revo68 · 27 Sep 2015

I know this is a rather old thread but I have just installed the above setup from dumbrill, but for one small fault, I cannot get the boiler to provide hot water. I have a tank stat instead of the thermistor, a time clock for the DHW and a sauter 3 port valve wired up as a diverting valve. On initial start up the boiler repeatedly switches over the valve as it completes it's checks, but with the heating off and the DHW on the valve does not switch over. I have checked and there is power at terminal 3 block X2 for DHW, but not on the terminal 2 block X5, which should switch the 3 way valve over.
I have tried everything I can think of and was hoping someone on here may be able to give me some pointers.
P.S. on the remeha 'suggested schematics' it implies that you leave the link in on teminal block X9 terminal 7 & 8 even though you have connected the iSense rf to this????

D_Hailsham · 25 Jan 2016

Did you solve the problem?

If so, what was the solution?

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Remeha Avanta18S Wiring - Unvented Cylinder and iSense RF

Similar threads