Remeha Avanta 18V boiler - frost protection

6 Jun 2007
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United Kingdom
Can anyone give me some advice please. I intend to install a new heating system ths year and will be fitting a Remeha Avanta 18V boiler.

By neccessity, the boiler will be fitted on the external wall of an integral garage. The Remeha Manual has details about the 'Integrated Boiler Frost Protection Device' which sounds just what I need.

This device starts the circulating pump but, assuming it all happens when we're safely tucked up in our beds, all my CH/DHW zone valves will be shut and Iwon't be having a system bypass (it will be a Grundphos Alpha 15-60 pump).

My question is, will it be possible for the integrated protection device to also provide a 230V supply to open one of my zone valves (dowstairs zone) which will normally be opened by a Remeha Celcia 15 Room compensator.

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Download the boiler manual from their site. They cover every conceivable way these things can be wired!
So it all becomes simple, once you've found which of the 384 diagrams it is...
Thanks for responding. I had dowloaded the 'Installation & Service Manual' from the Remeha site but it didn't answer my question. Iv'e just been back to the site and can't find any additional wiring diagrams for this boiler -am I mising something?
By neccessity, the boiler will be fitted on the external wall of an integral garage. The Remeha Manual has details about the 'Integrated Boiler Frost Protection Device' which sounds just what I need.
The MIs say:

The boiler should be mounted in a room which, even during severe cold weather, remains frost-free.

The boiler must be installed in a frost-free area to prevent the condensate drain from freezing.

Presumably the garage is not heated, so you would not comply with the above.

Terminal block X7 may be of use. Terminals 1 and 3 close when the boiler is running. This is intended for an external pump (connected by a relay), but could be used for a zone valve. The only problem I can see is ensuring that it does not open the valve all the time.

Avanta wiring diagrams are Here

You say that you are using a Celcia 15, presumably with an external temperature sensor. All the suggested wiring diagrams show the Celcia 15 used with a HW priority system which required a Diverter valve, not two zone valves.

The reason for this is that, when CH is required, the water temperature is controlled by the external sensor, so it may be as low as 30°C. When HW is required the temperature is automatically raised to the maximum so the water is heated as quickly as possible. If you have two zone valves and both CH and HW are required, the water temperature would be determined by the HW side, so the water going through the radiators could be hotter than required.

It might be a good idea if you spoke to Remeha technical dept.
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Thanks very much for the wiring diagrams.

The garage is frost free. It was built with the intention of using as a year round workshop with the possibility of future conversion to accommodation. It's super insulated, double glazed and draught proofed whereas the wall between it and the original house isn't which keeps it warm.

I was concerned about the external part of the condensate drain freezing so I intend to first drain the syphon into an internal open tundish. If the outside freezes it won't interfere with boiler operation and I'll get a visable prompt when the tundish overflows.

I hadnt' intended using an external censor with the Celcia15. Because of the house insualtion values I think the system would respond too quickly. I just intend to use it as an internal room sensor to modulate the boiler for efficiency purposes only.

The house is large (300 square metres) so I'm compelled to have 2 heating zones (and 22 radiators!). I will also have 2 seperate DHW cylinders. I want to keep it as simple as possible so my intention was to have a dedicated timer for DHW that fed both motorised valves to the DHW cylinders via individual tank stats with the valve auxiliary switches sending the DHW required signal to the boiler (so re-set flow temp to 70C).
For the early morning DHW heat up both CH zone valves will be closed and the DHW timer will be set to switch off before the zone valve timers are set to come on.
For the late afternoon DHW top up the downstairs CH zone valve may be open (the upstairs zone valve has a seperate timer and will be set to not be open). If this is the case then water at 70C will circulate round the downstairs radiators and the DHW cylinders. The relative system resistances means that 90% will flow through the DHW cylinders. If I fitted a diverter valve then the room would not be able to achieve it's design temperature until DHW demand ceased. The only down side is radiators at 70C until the room stat is satisfied.
I know I'll need to play with the timings for a while but it seemed a relatively simple solution but I'd welcome any comments.

Are you completely set on the 18V, I rate Remeha boilers, but not their heat only models. Flue fitting is crap, and they don't seem to modulate properly as they near the max flow temperature.
It doesn't have to be an 18V. The only given I had when looking round was it had to have a stainless steel HE.

I've mostly been guided by comments on sites such as this one. Overall, Remeha came out pretty well but I must admit that I didn't take much notice to see if the comments applied secifically to their range of heating only boilers.

What would you suggest?
If you want to control a zone valve, why not take the simple option and install an external frost stat? That way, you can use it to control whatever you choose.
Thanks for your comments.

Back to the original question about the frost protection. I'd really like to use the boiler's integrated device but now I think I realise that when activated everything happens within the clever electronics and there's nowhere for me to tap into that uniquely identifies that it's the frost protection that's fired up the boiler and pump so there's no signal I could use to open a zone valve.

All I'm looking to do is make sure there's a pumped bypass circuit through the boiler when the frost protection operates and none of the other zone valves are open (but only under these conditions - not at any other time).

I'm considering fitting a 22mm bypass line after the pump but before any of the zone valves, with a further motorised valve in it. The supply for the bypass valve will come from a pair of normally closed relay contacts. The relay will be energised from the auxiliary switches on all/any of the 4 zone valves. The aim is to ensure that when all 4 of the zone valves are closed, the bypass is open just in case the frost protection operates. I suppose I could refine it and only enable the relay during periods at risk of frost.

Does this sound a bit Heath Robinson like? I'm open to more elegant solutions.


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