heating stystem

kayabram

i have a heating system to wire up , i understand all wiring through stats and valves , but i have seen some drawings where boiler needs a perm feed , aswell as the swith feed that kicks in the boiler when called for , why is there need for both switch and perm feeds??

2011

kayabram wrote: »

i have a heating system to wire up , i understand all wiring through stats and valves , but i have seen some drawings where boiler needs a perm feed , aswell as the swith feed that kicks in the boiler when called for , why is there need for both switch and perm feeds??

Switched is to turn the boiler on and off. Permanent is for the pump (in the boiler) so that it can keep running for a while after the boiler is switched off.

grousedogtom

Some boilers have per feed connection to feed built in frost stat to over ride the time clock

Randyleprechaun

Most likely for the pump, to allow it to run on untill all hot water is gone from the boiler.

But as posted above, sometimes used for built in frost stat or could also be used for an added frost stat on models that don't have one.

I generally run 5 core cable to boilers even if I don't know what type of boiler is being used.

M cebee

ya .some have a switched live. and a perm. feed


some have a 'volt-free'(hopefully!) call- loop and a perm. feed

boiler must be wired so it can be safely 'isolated':eek:

kayabram

isolated , as in spur to turn off the power entering the timeclock ?? or later in the wiring , just before the boiler ??

2011

kayabram wrote: »

isolated , as in spur to turn off the power entering the timeclock ?? or later in the wiring , just before the boiler ??

Normally:
Spur - timeclock - 3 pole isolator (like fan isolator) - boiler.

The timeclock can then be mounted far from the boiler. The boiler must have local isolation. If the timeclock is local to the boiler then the isolator is not required as the spur isolates.

kayabram

ah yes thanks i understand , just have to have isoler near the boiler so it can be switched off if the boiler needs to be worked on etc??, so in normal case isolater is just left in on position always

2011

kayabram wrote: »

ah yes thanks i understand , just have to have isoler near the boiler so it can be switched off if the boiler needs to be worked on etc??, so in normal case isolater is just left in on position always

Exactly. Local isolation is a regultion for fixed appliance such as cookers, showers etc.

M cebee

last boiler i wired for 'sw live /perm live' in a garage

i brought 'garage 10sq feed' and boiler 'switched live ' into a DP 'main switch' in garage

boiler switched live goes into modular relay(neutral from heating control cct) then and boiler wired in 4-core from garage mcb

that way garage and boiler can be safely isolated -as per rules

2011

2011 wrote: »

Exactly. Local isolation is a regultion for fixed appliance such as cookers, showers etc.

In a ideal world the isolation switch for a domestic boiler should be at arms length of the boiler and it should isolate the entire heating/hot water circuit and not just the boiler, if the isolator just cuts power to the boiler you can still have power coming back to the boiler from external controls.

If you are working on a boiler and are going to remove the link wire for external controls then i would always bring back to the call side what is coming out of other side of the link and not just bring a call feed back to the call side of the link, lastly i would separate the cable for the link from the boiler feed if i haven't confirmed it's 240v on the, Gary.

2011

In a ideal world the isolation switch for a domestic boiler should be at arms length of the boiler and it should isolate the entire heating/hot water circuit and not just the boiler

Why do you say that?
This is not normal practice when heating controls such as zone valves are used.

The isolation switch for the boiler is to isolate the boiler. The spur outlet for the heating system (feeding the timeclock) is used to isolate the entire heating system.

if the isolator just cuts power to the boiler you can still have power coming back to the boiler from external controls.

This is not permitted. If installed properly there will be no power present in the boiler when it's local isolator is in the off position.

To achieve this the heating system can be wired in this order:

Spur - timeclock - stat(s) - zone valve(s) - isolator - boiler.

This way the timeclock calls for the stats at the appropiate times, the stats switch on the zone valves at the correct time and temp. and the boiler only fires when it should. Because the boiler is a the end of the circuit the isolator can isolate it completley.

M cebee

ya-boiler isolator doesn't need to shut down heating controls

it just isolates the boiler

3-poles will isolate an additional switched live


if there's significant induced voltage on a call-loop -it should be eliminated rather than the boiler isolator shutting down the heating system

The boiler must be earthed.
All system components shall be of an approved type and
all wiring to current I.E.E. wiring regulations.
The boiler must be connected to a permanent 230 V ac,
50 Hz supply.
Connection of the whole electrical system of the boiler,
including any heating controls, to the electrical supply
must be through one common isolator and must be
fused 3 Amp maximum. Isolation should be by a double
pole switched fused spur box, with a minimum gap of
3mm for both poles. The fused spur box
should be readily accessible and preferably adjacent to
the appliance. It should be identified as to its use.
Alternatively connection can be made through an unswitched
shuttered socket and 3A fused 3-pin plug both
to the current issue of BS 1363 may be used, provided
they are not used in a room containing a bath or shower.
The colours of three core flexible cable are,

blue - neutral, brown - live, green and yellow - earth.

I'm not making this up just to annoy yee:D, i can only advise on domestic gas boiler installations as thats my thing, above is the wiring instructions from a vaillant gas boiler, as far as I'm aware any gas boiler or wiring requirement for a domestic gas installation would be looking for one isolation switch to isolate the power to the boiler and external controls, i have not seen a wiring diagram for a domestic installation that allows for two isolation switches on a installation, it would be a requirement now under gas regs to wire a boiler to manufactures instructions, they take president over any other regs you may be following.

No body isolates the call going back to the boiler from the external controls so if like i had a few years ago the valve is stuck open sending 240v back to the PCB which in turn was feeding the live on the 3 pin plug for the boiler which i had in my hand causing me to do the funky chicken, fuse didn't trip and i luckily squeezed the plug out of my hand.

As for the arms reach thing, manufactures tend to give a measured amount of cable to be used to wire the boiler, it's that long to meet regs, i know of two sites where the electrician was made to rewire the isolation switches due to position to meet regs.
Lastly as a heating technician i hate playing find the switch when i want to work on external controls. Gary

eoghan.geraghty

gary71 wrote: »

If you are working on a boiler and are going to remove the link wire for external controls then i would always bring back to the call side what is coming out of other side of the link and not just bring a call feed back to the call side of the link

I'd have to agree with Gary here, especially on the above point, often overlooked.

M cebee

gary71 wrote: »

The boiler must be earthed.
All system components shall be of an approved type and
all wiring to current I.E.E. wiring regulations.
The boiler must be connected to a permanent 230 V ac,
50 Hz supply.
Connection of the whole electrical system of the boiler,
including any heating controls, to the electrical supply
must be through one common isolator and must be
fused 3 Amp maximum. Isolation should be by a double
pole switched fused spur box, with a minimum gap of
3mm for both poles. The fused spur box
should be readily accessible and preferably adjacent to
the appliance. It should be identified as to its use.
Alternatively connection can be made through an unswitched
shuttered socket and 3A fused 3-pin plug both
to the current issue of BS 1363 may be used, provided
they are not used in a room containing a bath or shower.
The colours of three core flexible cable are,

blue - neutral, brown - live, green and yellow - earth.

I'm not making this up just to annoy yee:D, i can only advise on domestic gas boiler installations as thats my thing, above is the wiring instructions from a vaillant gas boiler, as far as I'm aware any gas boiler or wiring requirement for a domestic gas installation would be looking for one isolation switch to isolate the power to the boiler and external controls, i have not seen a wiring diagram for a domestic installation that allows for two isolation switches on a domestic installation, it would be a requirement now under gas regs to wire a boiler to manufactures instructions, they take president over any other regs you may be following.

No body isolates the call going back to the boiler from the external controls so if like i had a few years ago the valve is stuck open sending 240v back to the PCB which in turn was feeding the live on the 3 pin plug for the boiler which i had in my hand causing me to do the funky chicken, fuse didn't trip and i luckily squeezed the plug out of my hand.

As for the arms reach thing, manufactures tend to give a measured amount of cable to be used to wire the boiler, it that long to meet regs, i know of two sites where the electrician was made to rewire the isolation switches to meet regs.
Lastly as a heating technician i hate playing find the switch when i want to work on external controls. Gary

you're referring to a gas boiler fed via a fused spur -with a live call loop

not familiar but yes the 'local spur' should isolate the switched live(it should originate from the fused spur /boiler )

alternatively it may not originate at a boiler -in which case you can use a local 3-pole isolator(all lives from same circuit) and the heating spur may be remote


there is no need to isolate a volt-free call loop -they usually pull-out of the boiler controls if induced voltage is a concern

i hope this makes it clearer for you
l

M cebee

M cebee wrote: »

you're referring to a gas boiler fed via a fused spur -with a switched live to fire boiler

Any wiring for a gas boiler should start with the isolation switch for the wiring installation beside the boiler, this opinion is based on the regs i work to as a heating and manufactures technician

M cebee wrote: »

you're actually agreeing with my previous post regarding isolation -though you don't know it:rolleyes:

I'm good like that, really annoys the wife:)

M cebee wrote: »

there is no need to isolate a volt-free call loop
if there is a problem with induced voltage it may be from an unrelated circuit

To clarify i like to see wiring for volt free separate from the feed for the boiler, this is because at times due to induction it can confuse the boiler, and the point about isolating the call feed is nobody will do that and if the call from the external controls is 240v then isolating the boiler only, may potentially not stop the power from being inside the boiler when i go hands on, Gary.

2011

Gary it is simple the fused DP spur with a fuse at 3A max. supplying the timeclock isolates everything (this is your common isolator). The local isolator to the boiler makes everything within the boiler dead. The boiler isolator must be local to the boiler. This conforms with ET101 and it meets all of your requirements as listed above. Please highlight any part that you feel it does not comply with.

2011

To clarify i like to see wiring for volt free separate from the feed for the boiler, this is because at times due to induction it can confuse the boiler, and the point about isolating the call feed is nobody will do that and if the call from the external controls is 240v then isolating the boiler only, may potentially not stop the power from being inside the boiler when i go hands on, Gary.

Gary I have been at this a while too. If you go to any system that I have done and you turn off the boiler isolator everything within the boiler is dead. It will isolate the permanent feed and the switched feed that has cone via the auxillary connnections on the zone valves and the stats and the timeclock. It could not be safer. This isolation switch only leaves the earth connected. If however you want to isolate the timeclock, stats, valves and boiler simply turn off the common DP fused switch spur and you have that too. Boiler isolators are for isolating boilers. Some boilers have conbections from the boiler PCB for external stats, clearly these will be dead if the boiler is as the boiler feeds them.

2011, i am not trying to tell you how to suck eggs:eek:, the wiring you have described is different to my own training, i am not a electrician but i do have a back ground in domestic heating, i personally don't like two isolation switch's on a domestic installation because i have had a belt from this set up and it hurt, so i like to go to the boiler isolate it and get on with my job.

i would say that all wiring diagrams for gas boilers that i have seen would only show one isolation switch and it's this that i follow , the issues i have are with messy slap it any where installations that don't fit any criteria, thats why i tend to tell people just to follow the instructions, a well labeled and well set out system wouldn't bother me, so long story short i would like to see a proper format for installations be it the one the manufactures are asking for or the one you have mentioned, Gary.

2011

2011 wrote: »

Some boilers have conbections from the boiler PCB for external stats, clearly these will be dead if the boiler is as the boiler feeds them.

That their be the problem, if that connection is 240v then it's common practice in my experience to bring a call from the time clock/zone valve straight on to the call side of the connection so when you isolate the boiler only you can still have juice on the call feed ouch, thank god for basic electrical checks which i do now because i don't like pain.
Again i would be more than happy to see installations as you described but if i talk to another sparks they could have a different idea to you, i would just like to see all installation following a common route, Gary

M cebee

gary71 wrote: »

That their be the problem, if that connection is 240v then it's common practice in my experience to bring a call from the time clock/zone valve straight on to the call side of the connection so when you isolate the boiler only you can still have juice on the call feed ouch, thank god for basic electrical checks which i do now because i don't like pain.
Again i would be more than happy to see installations as you described but if i talk to another sparks they could have a different idea to you, i would just like to see all installation following a common route, Gary

i don't know what sparkies you're dealing with-but i've never known this to be common practice among competent sparkies :rolleyes:

M cebee

M cebee wrote: »

i don't know what sparkies you're dealing with-but i've never known this to be common practice among competent sparkies :rolleyes:

I don't get to choose, i go out to who ever has bought one of my boilers and can't get it to work or have broken it:(

M cebee

i'm aware of your boiler woes-you've only mentioned it like 100 times in the past:D

I don't know about you sparks but i will happily admit us gas fitters are the biggest moaning bitches out there and this is therapy for me because i can bitch to my hearts content, which i can't do to someone who has just spent money on one of my boilers and is keeping me off the streets:)

2011

That their be the problem, if that connection is 240v then it's common practice in my experience to bring a call from the time clock/zone valve straight on to the call side of the connection

That is against regulations. If it is bringing a live to the boiler it must pass through the isolator or be powered from the boiler. Otherwise part of the boiler will be live when the boiler isolator is off.

Either:
1) The valve auxlillary supplies the the switched feed to the boiler via the bolier isolator switch. That way the boiler isolator is in the off position this switched supply stops at the isolator along with the permanent supply.

OR

2) The boiler PCB supplies power external stat, so when the boiler is dead so is everything that it supplies.

Either way when you turn off the boiler isolator everything in the boiler is dead and no seperate supply from external contols can make anything within the boiler live as it either passes through the boiler isolator or is powered by the boiler (not powered from elsewhere).

so when you isolate the boiler only you can still have juice on the call feed ouch, thank god for basic electrical checks which i do now because i don't like pain.

If it was wired in a way that you could get a shock when the boiler isolator is off then I would agree with you 100% that this is incorrect and against regulations. This is not the way I am suggetsing.

i personally don't like two isolation switch's on a domestic installation because i have had a belt from this set up and it hurt, so i like to go to the boiler isolate it and get on with my job.

The way I am suggesting you could not get a shock form the boiler. If you turn off the spur outlet (isolator) at the time clock then everything after that point is dead which would include, the time clock, all valves, all stats, the boiler, everything fed from the boiler.
If you were to turn off the boiler isolator then everything within the boiler including everything wired from it and powered from it would be dead. Where is the issue?

So either the main isolator or the boiler isolator would make the boiler safe to work on end of story. This conforms with the regulations as agreed by Board Gais, the ECSSA, RECI and people servicing the boiler all of whom have seen and inspected my work at various times over the last 20 years.

i am not a electrician

I think that is the problem (no offence intended). You are not understanding what I am trying to describe. there are many ways to do this that are safe and compliant and many ways that are not! I can assure you that once one of my boilers is switched off at the isolator (either the local boiler isolator or the DP spur for the entire heating system) it is simply not possible to get a shock.

i personally don't like two isolation switch's on a domestic installation because i have had a belt from this set up

You got a belt from something that was wired incorrectly where I would guess the boiler had a switched feed comming from another source that did not pass through the isolator for the boiler.

Remember digital timeclocks are normally only rated to switch 3 amps (aprox), therefore it should be supplied via a spur outlet with a 3 amp fuse. All mains power (switched and unswitched) for valves, stats and the boiler should come from the timeclock and will therfore pass through this spur. Therefore turning it off will have to make the boiler safe to work on. Often the boiler is remote to this so it must have it's own clearly identifiable isolator within arms length. This isolator must ensure that the boiler is dead regardless of what is done with external controls.

In your case someone just fu##ed up!

(sorry op for hijacing your tread:o)

Hi 2011, we both have experiences and expertise in what we do but come from different working environments, as a electrician you would be the top dog here for wiring a heating system where as i am not used to electricians or plumbers coming anywhere near a domestic heating system:eek:, normally only a heating engineer/ technician would work on a heating system and it would be seen as a specialist role, electricians rarely would go near a heating system.

Without sounding like a twat, I am a qualified gas service engineer having served a old school 4 year apprenticeship then going onto becoming a manufactures senior technician added to that i have my UK part P to a high level that allows me to work as electrician in the UK if i chose to do so:cool::rolleyes:, so i would be high up the food chain when it comes to system wiring and design, i don't say this to show off as i am only as good as my last job and there's always something round the corner to put me on my arse, but i understand fully all you have posted on system wiring and design, i don't doubt your work for a minute, but the main difference between us apart from the big money you're on;) is i cover all aspects of installation, servicing and maintenance, i would design a system that is easily worked on, you may think i am being petty about having two isolating switch's but in my old working environment nearly every house i walked in to would have all components in the same place as the format was always the same, if i wanted to isolate the system then i would ask where is the boiler, go to the boiler and thats the system wiring off with no hunting for the other switch, the idea of splitting the boiler from the external controls is a unusually one for me as i see the installation wiring as being one thing not two.

I have worked under gas regs for many years and wiring is only an issue when something goes wrong and when a installation is looked at by the powers that be(and i have been that fella with the clip board) it's the manufactures instructions they will take for primary system design unless it's something like a system link then the system link instructions that take president, i have no problem with the system you have described and I'm not saying my way is better than yours i didn't know there was a different way till i came here so your ideas are as different to me as mine would be to you, i like to get the information out there and then the sparky can decide, but as a end user my life is much easier if one switch does all as per manufactures instructions and the s-plan being taught to RGIIs( I'm such a bitch:D) Gary

2011

No body isolates the call going back to the boiler from the external controls

I think what you mean is that when the boiler is switched off at the isolator the call back should not be able to send power into the boiler?? In that case I agree.

f i wanted to isolate the system then i would ask where is the boiler, go to the boiler and thats the system wiring off

So why not simply turn off the isolator that I install at the boiler?? This will make everything in the boiler dead. Then you can safley work on the boiler. If the problem is external to the boiler it is the job of a registered electrician. If you were working on part of the heating control system that is at mains voltage and external to the boiler then you must be a qualified electrician. You would also require access to the timeclock which would be beside the spur that isolates everything.

I fail to see where you think I am not complying with what the manafactuer reccomends. Please highlight.

As you say most houses have the timeclock and the boiler at 1 location so 1 isolator is ok. But some don't and these boilers must have local isolation and the timeclock must be fed from a spur, hence 2 points of isolation either one making the boiler safe to work on. So where is this not safe? How could you possibly get a shock when either isolator makes the boiler safe to work on and the boiler isolator is always at the boiler?

2011

Gary PM sent.

(I now answering a post thats disappeared dohh)

Most modern gas boilers will not be looking for a switch live but have a link as on the PCB as mentioned, this can be either no voltage or voltage switching, some like heatline give you both just to confuse, manufactures are now looking to use the link for more than a on/off on a external switch ie.. room stat/zone valve, with modulating room stats or boilers that are timing how long it takes for the room stat to reach temperature than adjusting the boiler output to match demand, the performance can be effected by wiring a cylinder stat in the mix calling for heat when the room stat is satisfied. Gas boilers are getting very funky so don't assume boilers will operate as they did before.

It's more important to make sure a gas boiler has a permanent live as gas boilers have very small heat exchangers and without the pump/fan over run they can suffer from heat issues, for the old style installation it's important to wire the link/switch live to the orange and the gray on the zone valve(s) because if the boiler doesn't shut down before the valves close you can get valve hammer or again over heating issues.

2011

Sometimes it is difficult to explain what you are saying on Boards.ie

Following a long and interesting phone conversation with Gary71 we agree that what I am suggesting will work and complies fully with the regulations. There are many ways to do it right (and many to do it wrong also!)

Thanks Gary for an interesting conversation. If you ever service boilers out my way let me know, you would be top of my list. An absolute gentleman!