Delay timer for heating pump

[John.g]

If you get a pot of water holding 1 kg (~1 litre) and heat it to 100C it will be at atmospheric pressure, 0 bar, but no more, if you put a (tight) lid on the pot and boil it until it reaches 110C it will be at 0.42 bar.
The heat content at 0 bar, 100C, is 418.55 Kj and at 0.42 bar is 460.86 Kj. remove the lid from the pot and what happens?, some of the water flashes into steam, the water in falling from 110C to 100c will give up (460.86-418.55), 42.31 Kj and because it requires 2256.47 Kj to convert 1 kg of water into steam at 100c then, 42.31/2256.47, 1.88% flashes off as steam in falling to 100C.
I won't repeat the dreary calcs but if you had a electric water heater that was heated to 184C then the pressure is 10 bar and 16% of its contents will be released as steam if it ruptured with resultant great propulsive force in expanding while falling from 10 bar to 0 bar which is why you occasionally see a 10 litre water heater heading for Mars. The boilers I serviced operated at 44.8 bar so if one of those ruptured then over 30% of the contents (of 16 tons) would be released as steam and so on.

 

[SJB060685]

If you get a pot of water holding 1 kg (~1 litre) and heat it to 100C it will be at atmospheric pressure, 0 bar, but no more, if you put a (tight) lid on the pot and boil it until it reaches 110C it will be at 0.42 bar.
The heat content at 0 bar, 100C, is 418.55 Kj and at 0.42 bar is 460.86 Kj. remove the lid from the pot and what happens?, some of the water flashes into steam, the water in falling from 110C to 100c will give up (460.86-418.55), 42.31 Kj and because it requires 2256.47 Kj to convert 1 kg of water into steam at 100c then, 42.31/2256.47, 1.88% flashes off as steam in falling to 100C.
I won't repeat the dreary calcs but if you had a electric water heater that was heated to 184C then the pressure is 10 bar and 16% of its contents will be released as steam if it ruptured with resultant great propulsive force in expanding while falling from 10 bar to 0 bar which is why you occasionally see a 10 litre water heater heading for Mars. The boilers I serviced operated at 44.8 bar so if one of those ruptured then over 30% of the contents (of 16 tons) would be released as steam and so on.

I'm drunk at the moment and awaiting the grand national. I will go over this later mate.

 

[SJB060685]

I like your maths John but do you really mean 418.55kj for example? That's is over 400kw.

 

[John.g]

418.55/3600 = 0.1162 kw.

 

[SJB060685]

If you could mate please explain your comment 4 above in extra detail. I'm sort of with you but missing crucial information. Again thank you, you're one of only a few with this level of knowledge.

 

[John.g]

What is comment 4, SJB?

 

[SJB060685]

4 above mate. I'd like to know the maths as to how you arrived at that in depth

 

[John.g]

Sorry, still not with you, do you mean where I got the figures/numbers from or what?

 

[SJB060685]

Yes where you got the figures from. I'm almost with you but not quite 100%

 

[John.g]

Ok. Will do shortly after counting my G.national winnings.

 

[SJB060685]

Haha. Thanks to a friend I won a little myself.

 

[John.g]

The first three are the only numbers that interest us just now.
"Saturation Temperature" is the temperature of the water.
"Specific Enthalpy of Water" is the energy content of the water. (Sensible heat)
"Specific Enthalpy of Evaporation" is the energy required to turn 1 kg of water into 1 kg of steam at the same temperature. (Latent Heat)
They all come from.....

Steam Table Calculator| Dry Saturated Steam Line | Spirax Sarco

Use our Dry Saturated Steam Line steam table calculator to help you plan and design your steam system.

www.spiraxsarco.com

If you want me to explain it further, fine.

 

[SJB060685]

I will get my thermodynamics book out again. What is the website you found that calculator on?

 

[ShaunCorbs]

I will get my thermodynamics book out again. What is the website you found that calculator on?

Steam Table Calculator| Dry Saturated Steam Line | Spirax Sarco

Use our Dry Saturated Steam Line steam table calculator to help you plan and design your steam system.

www.spiraxsarco.com

Steam Table Calculator | Wet Steam Region | Spirax Sarco

Use our Wet Steam Region steam table calculator designed by steam industry experts to help you plan and design your steam system.

www.spiraxsarco.com

 

[Ric2013]

Analogue multifunction timer relays Selec 600XU-A-1-CU

Multifunction timer relays, analog, 13 time functions, 10 time ranges, 20-240 V AC/12-240 V DC, 1 x changeover contact, DIN rail mounting, IP20 protection, Screw-type terminals, Functions: On-delay/interval/flashing with off…

www.automation24.co.uk

GEYA On Off Time Delay Relay ACDC12-240V 1xSPDT Multifunction Timer Relay 1SPDT | eBay

Output: 16A 1SPDT. 1 function of latching relay ( I ).

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Something like this is what you need

This was what I wanted years ago to give my own bathroom fan an over-ride function. Unfortunately Rapid Electronics had nothing of this sort and I didn't know where to look. I suspect this plus a separate non-timer fan would prove more reliable than rely on the cheap internal circuit of an all-in model, and at least when one unit breaks you don't need to change the whole lot. So thanks, Shaun. Next time...

 

[SJB060685]

So John, I've taken on board what you've said. IF I have a 200 litre cylinder at roughly 110°c how much of that volume flashes to steam if the pressure drops below saturation point?

 

[John.g]

If the pressure/temperature falls from 0.42bar&110C to 0.0bar&100C then the % of flash steam (using steam tables, above) will be, ((460.86-418.55)/2256.47)*100, 1.88%. So 200 litres will flash off 200*1.88%, 3.76 litres.

 

[John.g]

Suppose should/must mention the qualities of steam for heating purposes where it is almost universally used in plants/factories normally at 8 bar which gives a temperature of 175.4C necessary for some processes.
As you are aware steam gives up its heat at constant temperature (isothermally) so if you compare a heating requirement of say 20Kw with steam vs hot water then only steam at a rate of 0.59 kgs/min (~0.6 LPM) is required as it gives up 2030.25 Kj/hr/kg (0.564 kw), if water heating is used then ~ 29 LPM at a deltaT of 10C will be required. Also steam heating reacts very rapidly to changing heating demands as its controlled on pressure, hence lower/higher steam temperatures instantly , the coil outlet is normally fitted with a float type steam trap which (traps the steam) will only pass water and ensures all the steam's latent heat is extracted.

 

[SJB060685]

Suppose should/must mention the qualities of steam for heating purposes where it is almost universally used in plants/factories normally at 8 bar which gives a temperature of 175.4C necessary for some processes.
As you are aware steam gives up its heat at constant temperature (isothermally) so if you compare a heating requirement of say 20Kw with steam vs hot water then only steam at a rate of 0.59 kgs/min (~0.6 LPM) is required as it gives up 2030.25 Kj/hr/kg (0.564 kw), if water heating is used then ~ 29 LPM at a deltaT of 10C will be required. Also steam heating reacts very rapidly to changing heating demands as its controlled on pressure, hence lower/higher steam temperatures instantly , the coil outlet is normally fitted with a float type steam trap which (traps the steam) will only pass water and ensures all the steam's latent heat is extracted.

Yes I can wrap my head around this but will read over what you've mentioned above a few times. I thought what I knew above was enough, clearly I was wrong 👍

 

[plumb_know]

Hi everyone,

got to the bottom of the wiring for this relay should anyone else do one.

perm live goes to A1 with link to 15
neutral = A2
switch live to S
pump feed on 18

thanks for everyones help