It is... and one should design circuits such that at full load they still meet the basic requirement of showing no more than 4% or 5%[1] voltage drop.
Since it does not appear that yours are meeting that requirement, it would suggest that either the cable run in the circuit itself or that of the sub main feeding the CU at the origin of the circuit is underspecified for the length of cable in use.
[1] Used to be 4% on all circuits. These days its 5% on power circuits, but 3% on lighting circuits.
That will make matters worse in this circumstance.
(also not going to help reduce costs either since the heaters will just need to run longer to provide the required energy transfer).
What it says. It's a thermal switch that cuts out (in this case) when the temperature reaches a certain point and cuts back in again when the temperature has dropped back to a certain (lower) point again (just like a thermostat). You can get them that are wired in reverse to control cooling fans etc.
Not new (other than to you possibly and in this specific message), just 'another'.
Yes, where the 'overheat protection' is provided by an overtemp / thermal / cut-out / switch *and / plus* a one way (non-resettable), thermal fuse.
Not really ... once you have taken the measurements you just need to do the sums. What you can measure (and it seems like you have been able to do that bit) you can manage. ;-)
You would have to decide that based on other factors that you haven't yet covered (less I missed or forgot), like the need / usage, environment (building type, thermal characteristics etc).
Like, my mate used a waste oil burning space hearer (blown air) in his garage but it got old and I think they banned them (or were going to if not heavily updated etc). He got the gas board in and (long short), much to my mates questioning, they fitted two blown air gas heaters that were never going to be up to the job. The sales rep suggested he set the timer to come on at say 6am so the place would be warm for
8am, completely ignoring that the first thing my mate typically did was open up the end of the garage to move cars in and out (and in so doing losing any heat). So, they eventually ripped out the new units and fitted bigger ones that were up to the job.
So, to 'feel the affect' of the heating effect you might be better of with industrial fan / space heaters or IR heaters etc.
Never seen a plastic handle on a hot air gun or soldering iron?
See above. Not all 'plastics' are created equal mate. ;-)
But 'a reason' to take it apart would possibly to prove that it wasn't wired correctly? To do that you would first have to speak to the suppliers and they in turn to the wholesalers and possibly the manufacturers.
That wasn't what I was talking about and couldn't without you telling us more about the entire scenario (including the thermal values for the rooms / building etc). I gave you most of the tools, costs and options within my first few posts and I couldn't do much more without more information (you know, like knowing the likelihood of us leaving the EU to be likely to be a 'good thing' or not before deciding to do it). ;-)
It might just be a few more to send back. ;-(
Maybe they could get a 2-3kw garage / workshop fan heater in to try?
The OP said somewhere in the thread that the lab was supplied by an autotransformer. (This is of course a completely stupid idea. The electronic equipment will simply use its usual power, perhaps slightly less efficiently. And heaters will produce slightly less heat, so that a thermostat either in the heater or the room will leave them on longer. So it can never save money. And because it is less than 100% efficient it will always lose money.) This is clearly becoming overloaded with five 700W heaters, so will never provide significantly more electrical heating however many radiators they buy.
Step one is to either put in a new supply with several suitable ring or radial circuits bypassing the autotransformer or remove the latter. It may have some scrap value.
It seems he already has as much electrical heating as that autotransformer will ever supply, and is probably exceeding its ratings. Perhaps someone who knows where it is could have a quick look and see if any smoke comes out when the voltage drops to 202V?
I think it was more when they were on 2kw but actually (intermittently) drawing 1.6kW or somesuch.
Quite ... and why I suggested they try something else.
A 'problem' with all radiators, especially small ones (for the space) is you don't actually feel the effect until they have warmed the entire space, especially if you have high ceilings and no real airflow around the space (and why tall buildings / rooms sometimes have fans in tubes blowing the heat back down to the lower levels). So, for the same volume of room and the same wattage of heater, a fan heater might be 'noticed / felt' by the inhabitants more / sooner than that from a straight convection heater. If the situation is worse, many don't try to heat the space at all but heat the people, often using radiant heaters (I can often feel the IR heaters in the ceilings of DIY sheds and the like because I'm folically challenged). ;-)
If they bought an autotransformer I'm not sure anyone is going to hold their hand up and pay again to have it taken out. ;-(
Hehe ... only any real value if it's actually filled with copper. However, if they bought the autotxfmr in the first place they may have bought the 'aluminium cored one because it was better as it was lighter. ;-(
We still don't know what sort of building we are talking about and if other 'improvements' could be made to conserve the heat they do have? Like, if there is a draughty doorway I wonder if you could fit something like a forklift curtain, or another set of doors to form an airlock, especially on any doors going directly to the outside?
What about workmats on the floor, especially if it's a solid floor etc?
Or a hot air curtain on the external doors to stop the cold air coming in (and the warm air going out)?
A combination of experience with the current heating system, and some knowledge of the construction of the building (i.e. how much thermal mass it has, and where that mass is with respect to the insulation (if it has any).
For buildings that are reasonably will insulated, and have their thermal mass outside of the insulation, then conventional thermostatic controlled stats will work ok. For more "difficult" buildings then optimising stats that learn the response of the building and adjust the on times automatically can work well. Some places however which have large volumes of masonry and no insulation will frequently take days of continuous heating to get to a sensible temperature. In those cases just setting the heating output based on an external stat (i.e. a weather compensating type of arrangement) is often the easiest way so that you track the general trend in the external temperature to aim at a roughly constant inside temp).
For what, heat loss calcs? General details of the construction, and the areas involved.
If it turns out you need 5kW to keep pace with losses on a cold day, then you know that if you have 7kW available, you should be able to reach the target temperature eventually. Then it becomes a question of optimising start times and working out what your minimum setback temperature is. If it turns out you can only gain 1 deg/hour, then you probably want your setback temp no lower than 15 degrees, and the heating to go to full power at say 7am to get a comfortable temp by 10am.
ISTR that bigclive did a tear-down on one of those voltage reduction units. At some load point it actually had relays to bridge itself out of the supply as a self protection mechanism. So you may find enough load actually takes it out of circuit.
The maximum design load would be 32A. With that load, you should drop no more than 5% for socket circuits. If you overload the circuit, then its not unreasonable to be out of spec for voltage drop.
You said the voltage was 202V. If your starting point was 220V then that is well out of spec (given your actual applied load would probably be close to the 32A design load even with 5 heaters running, since the actual power dissipated by each heater at that voltage would be well under the nominal 2kW)
So is it a cut-out or a thermostat, you seem to be saying tehy are the same .
So you can't tell the differnce between those labels is that it. ? Thermostat, cut-out, resettable fuse.
top over heating I'd get the whole thing to switch off to 0W as a safety fe ature.
As I thought you can;t tell teh difernce between these terms a thermostat i s the same as a cut-out.
ters would be needed,
What measurements, most situations you decide what you want before taking m easurements, because yuo buy based on teh specifications of the product.
Yep, far better than those using theory.
y more to buy and who should pay for them.
Yes and those were prettyy much fixed when it was built, so how would an en gineer predict what sort of heater and what power would be required ?
Suppose he was told that 10KW heater would be required to do what he wanted and then on installign them, he found that after a while the 5x2KW were no longer 2KW but reduced in power to 700W, would that change any calculation , I'msuggesting if that is the case he'd need 13-14 of thse heaters wouldn' t he.
Neither of which are allowed in the teaching lab due to H&S.
Yes but it's insulated from the heat part.
before it was put back into use.
and I doubt the best plastics are in use in his cheap heater.
But in the manual they do list things like the carry handle adn everything else the seem to have missed out the section on how to get to the wiring. Perhaps it;s not user accesable like changing the oil.
ed with working equipment that was up for the job.
I don;t care. I have 5 of them and of the 3 I tested they all do the same.
you don't need to know more that is the point. It's pretty basic maths and even simplier if you think before calculating.
No wonder you can't work it out.
They seem to be working as indicated why would I send them back ?
Not allowed in a teaching lab .
would be handy as my brother works for clarke and he'd get a 10% discount I IRC.
But how do you know what power they are ? in order for your calculations to work.
or their priorities were keeping the costs down or saving money or getting promoted, or that once the lectures offices got enough heat, just extent t he heating system further and any heat left would end up in the teaching la bs, which I think is basically what happened. Tbe teachingmlabs werenlt con sideredd important in 1955 or there abouts. Here;s one of the first pictures I've seen of the lab not sure of the year, so if anyone has any ideas... I think late 50s early 60s rather than 40s This area is now two offices, previosuly it was about 15-20% of the student lab.
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saving on electric and no doubt anyone saving money will get promoted.
Nah that's OK I know how important snake oil is, and we haven't got any squ eeky snakes to oil, obviously your snakes squeek more than ours it seems ;- P
25L thought it was 251 which is actually the number of the teaching lab, well 251, 253 & 255 are the teaching labs in this area
It would depend on where it bridged itself (if it does). It might already have done that, in which case the measured voltage is even more worrying!
(I remember once years ago we were installing a small network of machines in the back of a converted mobile library to make a mobile training setup. It was winter, so we had a rack of 8 systems running, and a 2kW fan heater plus 1kW of halogen lighting on the mains supply to the bus. I remember thinking that the fan heater was a bit feeble for
2kW, but then noticed we had an undervolt warning on the rack mount UPSs. A quick measurement revealed we actually had something around
190V. It was then that the owner mentioned that he had plugged it into his greenhouse sockets, since those were closest, and he had wired the submain to the greenhouse in 50m of spare 1.0mm T&E he had laying about!)
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