After previous discussions
on boiler replacement, I have now taken the plunge. Some of this info might be usefull for someone in the same position.
Finally decided to go for a new boiler for various reasons. The old boiler was a combi but since fitting a cylinder for my thermal a few years ago I have only used it as a system boiler.
I had a few requirements:-
Needed to modulate to a lower level than my existing boiler (<9Kw)
Only needed 18Kw Max (Combi was 25Kw on the CH side)
Ability to link in to my HW Cylinder to control the top up of the solar heated water.
I spent ages looking around and finally decided on the Remeha Avanta 18S for various reasons.(modulates down to 6kW)
I believed that in order to control all I needed I would need the Isense controller to make it all work.
Whilst the kitchen was being done I helped my mate fit the boiler.
It was very simple and easy to fit. Redundant pipework removed and all plumbed in, condensate pipe inside to stop it freezing in the winter.. I decided to start off using my existing 2 channel programmer just to get it all working.
All worked well and is very quiet in operation.
I then started to learn:-
Wired in the external temp sensor and found the boiler PCB then activated the weather compensation settings. The 4 set points are adjustable. I have set the flow temp to 60deg C at 0 deg outside temp, and 35degC at 20deg C outside temp. I will tweek these settings over the next year to optimise it all.
Wired up the cylinder temperature sensor and found the boiler then is able to control the set temp of the cylinder.
Have set the hysteresis to 2degC and all works well. There is an option to activate “anti legionella”. Either, ON, cylinder taken to 65degC every time. AUTO, takes the cylinder to 65degC once a week.
Whilst doing the radiators the flow/return temps are controlled by the weather compensation and the return is always below the 55degC required for condensing. When the boiler heats the cylinder the return temp can obviously be higher(than 55 deg C) due to the cylinder temp.
I have used the boiler PCB output to operate a relay to deactivate the CH zone valve when calling for HW, so as to make the system HW priority. This allows the boiler to be on HW for the shortest time so the higher return temp is also there for the shortest time.
There is an inhibit circuit on the boiler PCB, so have used this, so when my heat dump is operating the boiler is inhibited. The old boiler was used for the heat dump circuit. With the new boiler I am reluctant to modify the boiler to use the boiler pump for heat dump. All I have done is to fit a Zone valve and circ pump (controlled by the Resol) that links the HW supply pipes to the CH supply pipes. The boiler is inhibited and the HW and CH zone valves shut automatically during heat dump.
The installation book is translated from Dutch and something is lost in the translation. Some technical guys at Remeha don't understand what all the adjustable parameters of the boiler do exactly so it took quite a while to get all the information to understand how to set up the boiler to do what I wanted.
It does seem a very flexible and good control system on the boiler and does all I want of it.(now I have set it all up!)
When it is “commissioned “ it should have a 5 year guarantee so seems quite good when compared with other boilers.
If anything does go wrong in the boiler it all appears very accessible. Any item could litterally be changed within 10 minutes. It does seem a very well designed boiler.