Halogen Lamp heating system, diversity?

[timhoward]

I'm in the middle of preparing a quote for installing 12 x 3Kw and 4 x 2Kw halogen heaters in a church.
The system design was provided by a specialist company.

This sort of thing:

The system is specified to be split into five zones to be turned on depending on occupancy. Unless the church is packed it's likely only 3 zones will be in use. I'm trying to work out what degree of diversity I can reasonably apply to the total possible load of 44Kw.
I'm currently erring on very little as it seems possible to fire all up 5 zones at once. I'm not yet clear on whether they are thermostatically controlled.

Which leads onto the next topic. I turned everything on (lighting, organ blower, under pew bar-heating which they are retaining, water heaters etc) and measured 45 amps max demand.
The existing supply is a little 'curious'. At present the supplier fuse is unknown but likely 60A and only one phase is connected and metered on the customer side.
There's:
- two phases coming in using newer tails (only one in use)
-a phase coming in using an older cable (not in use)
-the neutral using another older cable.
-One of the fuses in the newer head is linked to another one.
It feels as though something prompted an upgrade but it's curious the Neutral is still an old cable.
I've confirmed all 3 phases are present with 400v between them all.

What I intend to do, unless wisdom from you fine bunch tell me I'm being silly, is ask them to apply for a supply upgrade to the (worst case) 55KVA and seeing what the DNO make of the current setup.

My hunch is that this project will need a 3x100A supply and if phases are carefully balanced that leads to max demand of 80 amps per phase.
Am I over-estimating max demand? The under pew heating is a constant load with just an over-heat safety stat on each unit.

 

[nicebutdim]

Can't see thermostatic control helping much when these are being used to heat a large space. I'd imagine they'll run flat out for quite some time.

 

[Mikegh]

I'm thinking you can't apply any diversity to the zones as church can reasonably be packed

The heaters themselves. I'm assuming they're full-on radiant heaters and no diversity there either?

 

[brianmoooore]

You have to calculate for mid winter funerals, not the congregation of three or four there every week. Weddings as well, but these are normally in the warmer months.
As Mikegh says above, not much scope for diversity.

 

[Mikegh]

The others shouldn't be too hard to calculate ?
Presumably there's next to no diversity allowable on the total lighting load and nothing on the Pew heating?

There'll be diversity on the water heating anyhow presumably

 

[timhoward]

Thanks everyone for clarifying my thinking. It seems clear that the supply needs to be capable of firing up the whole lot and it all staying on for some time.
The new system is 191 amps, so that alone balanced across phases exceeds the total that the head claims to be able to deliver, even if the new head was 3 different phases.
So we'll get off an upgrade form and see what happens.

I'm presuming that the energy provider will also separately need to be asked afterwards to provide a 3 phase connection and metering to the upgraded 3 phase supply. I haven't handled a single to 3 phase upgrade before so this is all a bit new to me.

Slightly academic but I can't help wondering what would have happened had the max demand fallen comfortably within 180 amps.
Would the energy provider have just happily connected a 3 phase meter even though the new head is only 2 phases, without DNO involvement at all?!

 

[Simon47]

I'd agree - no diversity. Even if thermostatically controlled, cold church, switch on, everything comes on together and stsys on for some time. Personally I hate sitting under a grill, but that's what many places install - we also had that recommended some time ago and I was "not in favour" (and that was before noting we only have a 60A supply).

 

[Mikegh]

I'm assuming they don't have thermostatic control ?

Would be of little value and a distraction , the heaters cycling on/off

There's probably half-full heat control on the units ? which is of little value also

Half- full heat control would be some use if you could control it centrally based on ambient temperature. Wouldn't change diversity though.

 

[nicebutdim]

This whole plan is typical of a church committee. Set a load of people down with a sum total of zero experience between them and let the best salesman win.

In 20 years they'll decide the system is unsuitable and eventually replace it with something even less suitable.

 

[Simon47]

Have you been spying on our meetings !

 

[nicebutdim]

Have you been spying on our meetings !

My father regularly laments similar meetings

 

[Vortigern]

That link from L1 to L2 is bothering/confusing me. Any clues as to what is going on with that? I mean if L1 is supplying labelled L2 then L2 is L1 also?
Hate those heaters, they heat your head and it feels like it is baking...

 

[Marvo]

Maybe to mitigate some of the max load you could install a contactor to shed the waterheaters when the room heater load exceeds a pre determined value? and I'd agree as mentioned above that application of any diversity formula would be inappropriate in this application.

 

[Mikegh]

That link from L1 to L2 is bothering/confusing me. Any clues as to what is going on with that? I mean if L1 is supplying labelled L2 then L2 is L1 also?
Hate those heaters, they heat your head and it feels like it is baking...

L2 is looped on incoming side to other L2

3P supply is present in pic and it's fused independently of the 1P that's currently in use(connected to L2 on right)

 

[brianmoooore]

You need to apply inverse diversity to some of these places.
Local chapel (the one that's pictured in media stuff referring to the Morocco undersea link) was complaining of the MCB feeding their kitchen tripping off occasionally. Went to investigate and found no less than SIX electric kettles, all used simultaneously and plugged into three 2G sockets, along with a microwave and a small table top oven - all on a 20A MCB. I split the circuit and installed a second 20A feed to half of the sockets, along with a bit of advice on loading.

 

[timhoward]

This whole plan is typical of a church committee. Set a load of people down with a sum total of zero experience between them and let the best salesman win.

In 20 years they'll decide the system is unsuitable and eventually replace it with something even less suitable.

Yes and no. There are couple of engineers that I rate on the committee, and there are a number of difficult things to balance.
I have to admit heating that place is a difficult challenge.
This is a large 19th century stone building (Gd 1 listed), with abysmal insulation meaning any conventional means needs to be on a long time in advance to actually do anything, which is expensive.
Any retro-fitting of conventional means needs to get through listed building consent AND the church of England faculty process. Advice from both parties is apparently that it isn't likely to be granted.
The real mistake was physically removing the old radiators (see below) as now they are gone, permission to reinstate them is likely to be difficult to get. Replacing them would have been a different story.

You are right about the likely lifetime. So far I've found:
-a huge 3 phase distribution circuit leading to the crypt which looks like it was under floor heating (apparently abandoned beyond repair). I've advise re-visiting this.
-an oil tank outside and an abandoned oil-fired boiler that once ran large radiators (now unfortunately removed)
-the existing under-pew heating
So it would be something of a miracle if this is the last attempt at heating that ever happens.

(The best system I've seen in a similar space is a rarity in the UK, gas fired blown air. You get the instant-on heat and heating from the bottom up with minimal aesthetic change. Decent heat and reasonable bills.)

Half- full heat control would be some use if you could control it centrally based on ambient temperature. Wouldn't change diversity though.

There is very little useful detail in the proposal, though there is mention of a "remote control unit". So 'maybe'.

I'm going to be suggesting that if they are determined this is the way, the plan needs tweaking. Having two of those things in the vestry is overkill, and having one pointed straight at a pipe-organ is just nuts, it will play havoc with tuning.

I've tried various permutations on paper, and nothing I do ends up with the existing 60amp 3ph supply being suitable (though in fact I'm doubting all three phases could be safely used as things stands ). So however this transpires it looks like an upgraded supply.

You need to apply inverse diversity to some of these places.

Agreed. I had a callout on Christmas day to a church that was cooking Christmas lunch for anyone who was alone at Christmas and homeless people. All good stuff. But the sub-main to the kitchen board was a C60 and was tripping! I found 10 slow cookers, 6 air fryers on extension leads, an industrial dishwasher and 2 ovens on.

On the plus side if this goes ahead I get to modify some MICC which will cheer me up for a week or two.

 

[UNG]

Given that the heater pictured is designed to heat people using the infra red light spectrum and not the space around them it cannot be controlled via a thermostat
Fitted quite a lot of these back in the late 80's and early 90's mainly in commercial and industrial buildings with some success especially when controlled with PIR / microwave movement detectors and staff / people are moving around, as mentioned

Hate those heaters, they heat your head and it feels like it is baking...

When your sat down in an area and it is difficult to move around you can end up overheating / irritating people

Another thought would be how they may affect any photography or video during weddings or other special occassions given the operating light spectrum of these heaters

Heating churches is always a difficult one especially given the high / vaulted ceilings I have often thought that pasteurisation fans would help push some of the lost heat down but they may not fit in with the character and architecture of the church

 

[Mikegh]

Given that the heater pictured is designed to heat people using the infra red light spectrum and not the space around them it cannot be controlled via a thermostat
Fitted quite a lot of these back in the late 80's and early 90's mainly in commercial and industrial buildings with some success especially when controlled with PIR / microwave movement detectors and staff / people are moving around, as mentioned

When your sat down in an area and it is difficult to move around you can end up overheating / irritating people

Another thought would be how they may affect any photography or video during weddings or other special occassions given the operating light spectrum of these heaters

Heating churches is always a difficult one especially given the high / vaulted ceilings I have often thought that pasteurisation fans would help push some of the lost heat down but they may not fit in with the character and architecture of the church

All you could possibly do is step-control them switching in 1-3 elements depending on the prevailing temperature, if the units facilitated this. 3P units might if safe to do so, but don't seem available in 3kw .

Blunt switching on-off isn't great

Any control on the units (probably only half-full heat if at all) is of no use here

 

[Simon47]

There are couple of engineers that I rate on the committee

That's a good starting point

and there are a number of difficult things to balance.

Most people (and I was one of them until a few years ago) who don't realise the extra constraints many churches operate under - and how "complicated" church finance is.

I have to admit heating that place is a difficult challenge.
This is a large 19th century stone building (Gd 1 listed), with abysmal insulation meaning any conventional means needs to be on a long time in advance to actually do anything, which is expensive.
Any retro-fitting of conventional means needs to get through listed building consent AND the church of England faculty process. Advice from both parties is apparently that it isn't likely to be granted.
The real mistake was physically removing the old radiators (see below) as now they are gone, permission to reinstate them is likely to be difficult to get. Replacing them would have been a different story.

Ah yes, the "I wouldn't start from here" problem. We are only G2 listed, and in part that was done to stop the highways people knocking it down for a bypass.

-an oil tank outside and an abandoned oil-fired boiler that once ran large radiators (now unfortunately removed)
-the existing under-pew heating
So it would be something of a miracle if this is the last attempt at heating that ever happens.

(The best system I've seen in a similar space is a rarity in the UK, gas fired blown air. You get the instant-on heat and heating from the bottom up with minimal aesthetic change. Decent heat and reasonable bills.)

We too have the "poor insulation" - not least we have much larger than usual windows, all single glazed, and many of them long overdue for some TLC (lets just say, we don't have a problem with lack of ventilation !) We do have the luxury of a boring flat ceiling which I believe does have "some" insulation above it.
Our heating was the old large bore cast pipes and oil fired boiler. The boiler was apparently 2nd hand in the early 70s when electricity arrived - before that it was coal/coke fired and someone had to light and stoke it the day before each service. Before I was involved, they had some fan coils fitted which are very effective at heating the place up quickly - the limitation is the heat output from the oil boiler and that it takes about 1/2 hour just to get the 100gallons (as an estimate) of water in the system up to the point where the thermal switches turn on the fans. While this did mean we could get from cold to comfortable in an hour or so, they had major problems :
1) There were too noisy so got switched off at the beginning of the service
2) At this point, the water in the system wasn't hot enough for the old pipes to take over and keep the place warm.
Between these, it meant that it all went cold early in the service and was recovering nicely by the time we finished.
By experimentation, we've arrived at a working setup. I added a resistor to each unit to give an extra low fan speed. Most of the time, they are so quiet people forget they are still running. I added a run-on timer to the circulation pump to keep water going round (and hence through the fan coils) when the room stat turns off. I also changed the thermal switches for a higher temperature, so the pipes are hotter before the fan kick in. Between them, this gets the place comfortable fairly quickly (in practice, we find we only use the extra-low speed and it's enough to do the initial heat up) and it stays comfortable during the service. I can hear (by the pops in the sound system) the room stat cycling the boiler on and off.

I would suggest that as you previously had radiators, it may be worth revisiting options there. I realise there will be some who would be against it, but if done right I'm sure they could be a lot less visible than a load of overhead grill elements. That would be something to raise - if they won't allow reinstatement of radiators, how on earth are you going to get permissions for all those radiant heaters ?

Something else I'd like to experiment with is adding one or two fans to circulate warm (or less cold ?) air down from up high. Access is a problem as the ceiling is about 6m (20ft) high, and the only access to the roof space is via a small loft hatch - I ain't going up there on a ladder One of the things fan heaters do is de-stratify the air - though a lot less so when on the extra low speed.

There is very little useful detail in the proposal

Ah yes, seen that ourselves.

A few years ago we had someone in - I vaguely recall they were recommended as specialists. To be fair, their proposals were reasonably detailed, but impractical (and very unaffordable). One of them was the head grills you've had suggested - and I vetoed that in short order. Another was a new boiler - that would have had to be dismantled to get it through the door into the boiler room.

One of the then churchwardens insisted on getting a quote from the people that fitted heat pumps to his rambling big pile. I did a quick calculation and figured it wouldn't be able to heat the place in cold weather - from memory, it's limit would be something like 8˚C above external temperature. At least our supply would have run it - just. Pity the supplier hadn't done any sensible calcs of their own.
Said person was known for being thrifty, and during Zoom meetings had during covid was noted to appear in a thick coat. His wife also complained about being permanently cold - and was very happy when they downsized to somewhere warmer.

On the plus side if this goes ahead I get to modify some MICC which will cheer me up for a week or two.

Other than when I was an apprentice <cough> years ago, I've never had the opportunity. I always feel like I've missed out.
I feel some of the needed improvements in our place would suit pyro - but of course I don't have the tools anyway There is some in the boiler room, but it's a right mangled mess from when it was moved during a roof replacement and roughly clipped back in place afterwards.
At one or two of the other churches we go to, I find myself getting told off by SWMBO when I'm sat there admiring the pyro work.

 

[Simon47]

All you could possibly do is step-control them switching in 1-3 elements depending on the prevailing temperature, if the units facilitated this. 3P units might if safe to do so, but don't seem available in 3kw .

As long as the unit don't have any internal electronics, they could be managed by burst firing - e.g. on for 1 mains cycle in 2 would give you half output. Synchronise units and you get to run two units at 1/2 power for one units worth of mains load.
But unless you have a fairly complicated control system, you'd not be able to benefit from (e.g.) being able to run some units on full because other areas aren't being heated. And it doesn't get round the problem of needing to heat the whole building when the supply is limited.

Blunt switching on-off isn't great

Agreed.

Any control on the units (probably only half-full heat if at all) is of no use here

Anything that needs user action is going to be of no use. In my experience the only controls the users should have available is a timer for when the system is needed, and limited control over temperature.