Having difficulty wiring a Alpha Etec 33 hybrid for an S-plan

[mp282]

Hi all,

I've been struggling to wire up a Alpha Etec 33 hybrid to an S-plan so I can incorporate 2x 2 zone valves for central heating and underfloor heating. Alpha technical haven't been much help and the engineer they put me in contact with no longer replies to any messages. All he advised was the receiver and thermostat would need to be changed to allow for a switch live with it being opentherm (have limited information as a visit was agreed and was a no show). I am at loss at the moment as I am unable to commission the underfloor heating and struggling to figure out how to wire the boiler to the wiring centre.

I've attached photos below of where I've got to so far.

P.S. I am currently training to be a gas engineer but have limited knowledge of s-plan/ y-plan wiring.

 

[muggles]

It's probably a good thing he's not replying as his advice is incorrect anyway. The heat pump won't work without that receiver. You can't wire it as a standard S-Plan for your two heating zones either, as that will put 230v onto a terminal that's not designed for it which will kill the PCB. Alphas need to be wired for volt-free switching or OpenTherm. You can connect grey & orange across A & B but if you're going to do it that way grey must not be connected to permanent live.

There's quite a lot wrong with what you've already done, not to mention that it's very messy if you're doing this for a customer.

 

[RandomGrinch]

The heat pump won't work without that receiver. You can't wire it as a standard S-Plan for your two heating zones either

I've just been trying to think this through...
Ignoring the OP's wiring centre mistakes; could the UFH wiring centre be powered up from the e-tecs configurable relay and the zone valve for C/H left open?
At least then, you wouldn't be tempted to operate thermostats that appeared to be on, but wouldn't do anything.
I'm also wondering how these boilers would comply with the dual zone requirements of part L; Alpha don't seem to sell any bus connected wiring centres, that others do?

 

[RandomGrinch]

You can connect grey & orange across A & B but if you're going to do it that way grey must not be connected to permanent live.

Apologies if I've misunderstood, but do you mean terminals A and B on the boiler?

These are a live and neutral supply to the Smartec receiver and shouldn't be connected across.

See @4:30...

 

[mp282]

Thanks for the response. It's not a customers house so it's not too much of a problem.

In terms of messiness, what is your advice on cleaning it up and making it better?

How do I go about wiring this up to make it all work?

I do appreciate you guys taking time out and responding.

 

[RandomGrinch]

How do I go about wiring this up to make it all work?

I have extremely limited experience with these systems, so I will defer completely to @muggles and other professionals.

But from what I see, it looks as if you are stuck between a rock and a hard place.
For the hybrid boiler to utilise the heat pump, it needs to have the Smartec OpenTherm receiver in place - as that includes a link to the heat pump.
OpenTherm (at least with previous versions) is a point to point protocol. If your boiler has one OT connection, it can only connect to one OT controller.

Other manufacturers, such as Vaillant have a bus connected wiring centre, that allows a system to open zone valves through digital commands.
There are also UFH wiring centres that can connect via OT, but again, there would be no way to incorporate this into your boiler and control the heat pump.

As the installer you contacted suggested, it may be possible to remove the Smartec receiver, and convert the boiler to on/off switching, but then you completely lose any benefits of the heat pump, and the costs that went with its installation.

The only way around that I can see, is to treat it as a single zone system - it doesn't mean that you totally lose control of the zones - just as with having TRV's on rads, you can always use the zones to turn off the heating in certain areas, it's just that the individual thermostats won't be able to send a call to heat to the boiler, if the Smartec stat is off. You could keep that stat in the coldest room in the house.

My only other suggestion may be to play with the configurable relay output of the boiler, to provide some sort of on/off control of the zones, but that may not be possible.

I'm sorry, there doesn't seem to be a straightforward answer, that will give you a system that's not a bit of a cludge.
But again, I could be wrong and I will defer to the experts.

In terms of messiness, what is your advice on cleaning it up and making it better?

Compared to some of the DIY (and professional!) installs we see on here, it's definitely not the worst.
I like the use of ferrules on the wires and it's pretty easy to follow what's been done.
Keeping a load of slack on the wires is understandable, in case you make a mistake and need to move a connection, but overly long wires within a wiring centre can look messy.
Also watch your cable grips - they are there to grip the outer cover of the flex, not the wires - i.e. the two core flex to the UFH actuators should be going through the zig zags of the cable grips.

There are also a couple of problems with how you have attempted to connect up the wiring centre. It may help you to think of the system as a dual zone system, rather than an S-Plan.
If you haven't seen it before, there's a good primer on central heating systems available from @flameport ...

Central Heating Control Wiring

Wiring diagrams and information regarding central heating control wiring

flameport.com

...and what is the make model of the thermostat you were using for the rads?

 

[mp282]

Thanks for taking your timeout and giving me the feedback and info, some very useful stuff there that I can learn from.

The thermostat for the rads was the Alpha Smartec one, where you control pretty much everything for the boiler/ heat pump within.

The 'other engineer' that was meant to come out, did do on Monday and turned out he is one of Alpha's own engineers.

I've since learnt that Alpha boilers are rebranded Immergas boilers sold in Europe. When he visited, he fitted a Immergas controller and has used different terminals to wire the controller to the boiler which works with the heat pump. With the controller fitted there isn't much control over the heating, it's either on or off and has to be done on the controller by switching it to winter mode, no times or temperature can be set on the controller (guess it doesn't function as a thermostat). He has also put a loop in between 1 and 2 and has told me to use 1 as the switch live.

He has also mentioned that I will only be able to keep the heating and UFH on one zone, which isn't end of the world as the boiler only heats 3 rads and the underfloor heating on one floor (putting 2 zone valves in may have been a mistake on my part for such a small system and control over 2 zones which isn't really required)

 

[RandomGrinch]

The thermostat for the rads was the Alpha Smartec one, where you control pretty much everything for the boiler/ heat pump within.

I asked about the rad thermostat, as there was an 'industry standard' backplate i.e. one similar to a Hive, connected to the wiring centre, and I wondered what receiver may have sat on that - the wiring for the Hive for example, would need an additional link between L and terminal 1 to operate correctly.

When he visited, he fitted a Immergas controller and has used different terminals to wire the controller to the boiler which works with the heat pump.

It's good to know there is a way out, even though it still seems a bit of a cludge.
So it appears that the new controller is still connected to OT/Alphabus, but is also using terminals 24 and 25 - I can't find any reference in the manual, to see what these terminals do, it would be interesting to find out!

Edit: the controller manual says a 12 - 24V power supply is required in addition to the data connection, so I suspect this may come from terminals 24 and 25?

Does it also have a direct link to the heat pump?

He has also mentioned that I will only be able to keep the heating and UFH on one zone,

This I find a little strange. As you now say...

He has also put a loop in between 1 and 2 and has told me to use 1 as the switch live.

If this provides a switched live to fire the boiler, and the OT controller is only there to provide setup parameters and control the heat pump; there is now no difference between this boiler and any others controlled from a wiring centre - you could have all the zones you require at the wiring centre, there is still one switched live provided to the boiler, when there is a call for heat.

 

[mp282]

I asked about the rad thermostat, as there was an 'industry standard' backplate i.e. one similar to a Hive, connected to the wiring centre, and I wondered what receiver may have sat on that - the wiring for the Hive for example, would need an additional link between L and terminal 1 to operate correctly.

Apologies, that backplate is part of the underfloor heating for the smart hub switch.

I have done some further digging and found some further info on the Immergas website for the wiring, still doesn't explain what 25 and 24 do but does show 1 and 2 for a room stat to be added.

Does it also have a direct link to the heat pump?

There is a wire linking the heat pump to the new Immergas controller

 

[RandomGrinch]

I have done some further digging and found some further info on the Immergas website for the wiring, still doesn't explain what 25 and 24 do but does show 1 and 2 for a room stat to be added.

Good digging, that shows everything we've been missing from the etec manuals.
24 and 25 are definitely an (extra) low voltage power supply then.

 

[mp282]

Thanks gent for the help and advice.

Managed to get it all connected and everything is working fine.

The only issue I now face is the antifreeze protection that runs when the temperature falls below 5 degrees. The pump in the boiler constantly runs, even when there's no demand. Normally the pump would only run for a few seconds here and there to keep the water moving.

With the zone valve for the central heating being closed, the water just circulates around the automatic bypass valve back to the boiler. The water doesn't circulate around the pipes to the heat pump and the antifreeze protection just stays on until the temperature outside rises.

Alpha have been no use as they just told me to call them whenever an error code pops up and let the pump run whenever the temperature falls below 5 degrees which isn't particularly useful as it just puts more wear on the pump and an increase in electricity bills.

Any advice on how to overcome this?

P.S.
I have called gas engineers who deal with Alpha boilers and in particular the hybrid systems and no one seems to want to come out and have a look or can give any advice.