Megaflo safety cut out - wiring to valve

[Taylortwocities]

Hi folks, need your assistance with this.

A megaflo is being installed right at the other end of the house to the central heating wiring & boiler. (To serve shower & bathroom at that end).
The plumber has put a two port valve that is supposed to shut if the cylinder goes over temp (thermal cut out).

There is a handy supply near the Megaflo but its impossible to run control wires right back to the programmer.

Am trying to work out how to wire the valve to the megalfo thermal cut-out & thermostat connections. Is it simply:

Live to terminal 1 on thermal cut out block
Brown on valve to terminal 2 on thermal cut out block
Neutral to blue on valve

Grey & Orange not used on valve?

I think then if the thermal trip is in normal the valve will be open, if trip operates the supply to valve will be cut & valve will shut.

trying to work it out from the wiring diagrams in megaflo installation book but they only show S & Y plan wiring and doesnt cover this situation.

Grateful for your help!

TTC

 

[Dan Robinson]

Thats 'cos you are not allowed to do it like that?

 

[Taylortwocities]

Thanks, so how do I do this?
The plumber has put in the valve for me to wire locally at the Megaflo.

Thanks

TTC

 

[Agile]

The plumber has put in the valve for me to wire locally at the Megaflo.

That implies that your plumber is not qualified to install an unvented cylinder!

It should have been notified to Building Control before installation.

Tony

 

[Dan Robinson]

You shouldn't be doing it either. You need to be G3 qualified.

This cylinder has to be notified to building control.

You will need to get a calbe form the cylinder the centralh heating wiring centre.

Otherwise, apart from anything else; how is it going to be controlled by a timer and thermostat to bring the boiler on?

 

[Taylortwocities]

OK. so I am an electrician 'invited' to do this part. I am fully qual electrician but not got too much experiance in the heating wiring area.
I assume the plumber is qualified to do this work. I will notify the electrical bit to LABC if necessary and assume he will do his bit re notification.

Think we are all aware of the notification bit and I spend a lot of time on the sparkies forum warning DIYers about the need to notify LABC.

The existing boiler & controller are in place, situated at one end of the house. The existing hot and cold water tanks will be removed.
The plumber has installed, in fact, two Megaflos. One to provide for one end of the house ane another for the other end. the two megaflos are situated together in the loft space at the far end of the house away from the boiler & CH controller. He has got two because roof height is limited.

So I have two Megaflos and the plumber has put two valves that are supposed to be controlled by the two thermal cut outs. I assume these are the megaflo DHW zone valves.

I really could do with some help on a solution to this.

Thanks!

TTC

 

[oilman]

The wiring has to be exactly as the Megaflo manual. Nothing else will make the installation an approved installation. Just follow the manual, it is self explanatory (except you shouldn't be doing it).

It should be notified to BC BEFORE installation if it's a first fit of an unvented cylinder, and again once the installation is complete. You cannot be invited to do the electric part, you should know this if what you said earlier is true. You provide the fused spur, all work on the cylinder should be by a G3 approved operator.

The G3 lifetime certificates are coming to an end shortly and it's another effin assessment resit and forkin' out of forkin' money for the benefit of penpushing empire builders rant, rant.

 

[Balenza]

oilman wrote

all work on the cylinder should be by a G3 approved operator.

Im fitting one shortly and aint G3 (aint that the name of some bunch of opera singer's) qualified and will be notifying jack ........
Yeeeeee haaaaaaa.

The G3 lifetime certificates are coming to an end shortly

Mine never begun so can't ever end and never will begin.
Yeeeeeeeeee haaaaaaaaaaa.........

 

[Taylortwocities]

Well, thank you. I can't say how much help you have all been, I really can't.

TTC

 

[gas4you]

Yes what you are saying would work, but the grey and orange wires need to connect back to the boiler to shut this off when the valve closes. This is called the boiler interlock. It has to be present on all new installations thesedays. With unvented the valve is acting as the last resort safety device to shut off the source of heat to the cylinder if the heat source fails and cannot be shut down.

Are you sure there is not any possible way to run the cable back to the wiring centre, however awkward this but be?

 

[Agile]

In spite of you apparently being sarcastic we have been very helpful in pointing out that you are not qualified to fit the wiring on the Magaflow and by the sound of it nor is the plumber.

You started your first posting in a way that made us think that its your own house. Now I think that its a customer's house.

If you are a properly qualified electrician as you imply then surely you will do the correct thing and advise the customer that he must have a competent person installing the unvented cylinder and its wiring.

Unlike all gas and some electrical work, as far as I can see there is nothing to stop anyone fitting an unvented as long as its checked and signed off by a qualified person. Thats probably an unintentional loophole!

Tony

 

[Balenza]

Agile wrote

If you are a properly qualified electrician as you imply then surely you will do the correct thing and advise the customer that he must have a competent person installing the unvented cylinder and its wiring.

Yeah, just get someone in who is not qualified but is competent and he/she will sort it out for you.

 

[Taylortwocities]

Thanks for your responses especially gas4you.

I have been dumped in this as the plumbers electrician is away on hols.
I was told the job was just to run in feeds for the two immersions and this little item has been tacked on. I am a qualified spark but, as you may know, central heating controls aren't part of the usual training programme and tend to get learnt the hard way. thats what I'm trying to do here.

I think I understand whats needed and will have to find a way to get control wires back to the programmer. Just tell me if this is correct.

Essentially, in an S plan, the Megaflo safety control replaces the cylinder stat and this is part of the DHW circuit.

In this dual Megaflo situation I will run a wire from DHW ON from the programmer. This will go to thru the safety cut out on the Megaflos so that both the Megaflo zone valves will operate when DHW is ON.

If cylinder goes over temperature that zone valve will realease.

I then run a permanent live from the programmer to the two zones valves with the contacts in series so:
live feed > green (valve 1)
orange (valve 1) > green (valve 2)
orange (valve 2) > boiler & pump

In this way, when DHW is on both valves will operate and the feed will be returned to boiler & pump to come on. If thermal cut out operates on either Megaflo that zone valve will release and cut feed to the boiler & pump.

Still grateful for your advice. I spend alot of time helping folk over on the sparkies forum and was hoping to get a little help back.

Cheers

TTC

 

[ChrisR]

the Megaflo safety control replaces the cylinder stat and this is part of the DHW circuit.

No, it's Normal S plan. Megaflo's normal "Indirect" cylinder stat shuts the valve, and that turns the boiler off.

For two M's, you just have a zone valve for each. The "Indirect" Stat (which also has an overheat cutout in it, in series) closes the valve for whichever is hot enough. The boiler may still be running to heat the other M, but the "happy" M won't get any hotter cos the valve's shut.

The safety cutout there for the immersion heater(s), whose wiring is totally separate from the boiler controls. It's physically in the same box as the immersion heater normal stat, not the M's cylinder stat. If you don't USE an immersion heater, then that Safety stat doesn't get connected to anything.

In other words it's like any other cylinder, except that you have to use S plan not Y, using the 2 port valve which comes in the box because it's part of an "Approved Package".

I don't think you have any choice other than to get a wire back to the boiler. A radio link wouldn't be part of the "Approved system". Bit inconsistent really since you can close the valve locally, without the wire, but you can't shut the boiler off, but since it might be on anyway for the other M, should it matter..?


Sorry TTC, you've helped me in the past where others have just called me a fool, you seem to have come up against the plumbing section's department of circumlocution. Everybody's telling US we can't do this or that any more without paying somebody more money, so you're getting some of that passed on! Yeah I suppose you should be G3 qualified to do the wiring, but I can promise you the "course( )" didn't mention what to do if you have more than one cylinder.

 

[Taylortwocities]

Thanks Chris, hi. Yes I am aware immersion is separate!

The connections i have been talking about are the ones (also in the imm housing) that comprise the Indirect Thermal Cut-Out Button and the thermostat.

So it look like the green & oranges from both Megaflo zone valves are wired in parallel otherwise if one cylinder is "happy" (I like that) then the boiler gets cut off & the second cylinder wont then get any more heat.

Lots of fun, eh?

TTC