Author Topic: New Electric Booster Boiler  (Read 972 times)

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Offline rossw

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Re: New Electric Booster Boiler
« Reply #15 on: October 27, 2016, 01:03:17 AM »
I was working on a rheem instant hot water unit, and noticed the nameplate stated that it uses over 55kw for the 25lpm model for 25C temp increase.... it is not easy stuff.

17:00:28-27/10/16| [RossW]   !kwheat 55 25
17:00:28-27/10/16| -RossBot- 55.00 Kilowatts input will heat water at 25.00 litres/min by 31.55 deg C

I wonder what their losses are... or if they're leaving some "wiggle room"?
(45kW should manage 25.8 deg C rise)

Offline oztules

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Re: New Electric Booster Boiler
« Reply #16 on: October 27, 2016, 03:48:23 AM »
This is not a calorimeter.... it's a gas hot water  unit, and as such has burning hot gas pouring out the top exhaust... I'm guessing this is where it is.
 To heat on the run we need a big delta T or a long time of interface between the "heat source and the heated material".

As we are heating water running past quite quickly before it exits the heat zone, we need a big differential to transfer the heat across the barrier quickly.... and so any of the gas still hotter than the water is lost energy... and there is a truck load of that pouring out the exhaust.

Incomplete burning due to excess gas compared to the  storchiometry, ie being a bit rich to keep it burning nicely, but still hot means a slight smell of gas in the exhaust. It has a 3 stage burner system to allow for throttling, and this won't help either, as the flame bed is not always complete at the lower regions... ie being a low pressure system, the flow rate suffers when all three flame beds are active.... so they need to be a bit rich in the "slower" range, so they lean off, but are still effective when the three fire up all together on the same gas stream... clutching at straws now......

The safety system includes a forcing fan, which will also cause the flame heat to be air cooled and scattered about. I think it is there to scavenge any excess gas out of the units, and stopping heat spots near the flame areas and casing.

Sound convincing???.. I have run out of ideas now....


...........oztules
Flinders Island...... Australia

Offline rossw

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Re: New Electric Booster Boiler
« Reply #17 on: October 27, 2016, 05:40:07 AM »
This is not a calorimeter.... it's a gas hot water  unit, and as such has burning hot gas pouring out the top exhaust...

Ahh, yes, and that perfectly explains the difference. (For reasons unknown, I thought you'd found an electric one - most of the ones I've seen are rated in MJ, not kW)

(Part of the reason most gas burners *NEED* hot flue gas is because of the sulfur (SO2)  disolves in the water vapor and forms sulfuric acid which eats out the heat exchanger, flue etc. (I wonder if the various nitrogen oxides (NOx) form nitric acid too?))


Offline oztules

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Re: New Electric Booster Boiler
« Reply #18 on: October 27, 2016, 02:05:27 PM »
odd...
"Ahh, yes, and that perfectly explains the difference. (For reasons unknown, I thought you'd found an electric one - most of the ones I've seen are rated in MJ, not kW)"

It's taken 10 years to see you fluff your lines like this.... so I'm gonna make the most of it, as I know it won't happen again :) :) :) :)


 MJ is a measure of energy, which is pointless in a lpm temp change calculation. It's equivalence would be kwh... which tells us nothing about how fast we can heat how much water..... only that we have energy available to heat an unknown amount of water an unknown amount of degrees above perhaps ambient T... so there would have to be a time base there as well such as MJ/H ..... ie the difference between a mars bar and a hand grenade... similar energy, different power outcomes. :)

Actually we have propane, (LPG not LNG) here, so really only CO2 and H2O.... energy for bond dissociation of N2 is probably not there except for minuscule conversions.... it is not like the temp and pressure available in an engine (  otto cycle) environment.

The sulphur is also not in the fuel persay, but there will be  tiny amounts because of the perfume they add ( C2H5SH) ethyl mercapton  ( stench gas)... so we have essentially   C3H8 only. The N2 bond is one of the strongest bonds in chemistry, so unlikely to be broken in this sort of reaction... add shock and pressure to the heat, and I suspect a different outcome.... but not at 1atm.   Stench gas is toxic, but at the concentrations ( tiny) they use is harmless.

We can thank vultures for this... it was noticed that vultures would circle around areas that had gas leaks in the early natural gas lines in USA, and so they realised it was a useful thing to add to LPG as an indicator too... and they increased it in the natural gas where it was lower ppm in some gas reserves. It occurs naturally in natural gas apparently.

I have completely and totally used up all my  smartarsedness  with your energy-power snafu.....so it boils down to this.... .

It is still a big whack of power in a little box... just for a shower......





.............oztules
Flinders Island...... Australia

Offline DJ

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Re: New Electric Booster Boiler
« Reply #19 on: October 27, 2016, 05:53:14 PM »
A sobering thought on direct heating of water.
I was working on a rheem instant hot water unit, and noticed the nameplate stated that it uses over 55kw for the 25lpm model for 25C temp increase.... it is not easy stuff.

..........oztules

Water heating takes immense amounts of power as you point out.  This is why I have gone with using a waste oil burner.
I have the heat exchanger from  gas heater that was used in an Olympic pool. It's rated at 200 Kw and my burners can over power it easily. I also have a smaller spa heater and a water heater I have converted.

The water heater is only a small one at 125L but once I get it up to heat, the thing will run as continuous basically.  The kids have tried to run it out but I can run it hard enough that it will keep up with demand.  Just have to watch when they are finished and get out that it does not over heat before the next one gets in.  I'm looking at controls to fix that problem.

The thing works so well I have plumbed it into the house ht water circuit.  I have valves so I can Feed from the electric or the oil burner Heater.
I'm on the lookout for a 400L unit to convert. With this I would only need to do a fire up every 2-3 days on what we use on average.  I would set this up as a feed for the electric heater.  Even if the Oil powered heater was a bit cool, it could be feeding water at say 40o to the electric heater instead of say 15o therefore making the electric heat up faster and cost less.

I have a 70Kl Swimming pool and I can heat that from winter temps to 35+ in 24 Hours.  Takes a 44 gallon drum full of oil and a bit more But it's awesome to have a pool party in winter that's for sure.
I was going to use the pool as my thermal storage for home heating but I have been looking at moving for some time so haven't bothered setting that up.
I did use another 125 L heater this year this winter for home heating.  Had the burner going controlled by a fuel pump on a timer that just pumped for 2 sec then switched off for 4 and circulated the water with a small electric pump.  The high tech heat exchanger was a car radiator with an electric fan.
The system worked really well and we were very cosy but it needed refining.

My house is basically a front and back area with a door between, the back could be too warm and the front too cold. It really needed another radiator in the front section or what I was thinking would be even better, Run the existing radiator into the house and after that have another Under the quite well sealed floor area to allow the whole place to heat up.

Again looking to move so not worth the effort here but the wife has been encouraging me to do it anyway for Summer.
We had a very warm day ( or what seemed like it) a few weeks ago.  I just pumped water directly from the pool  through the radiator and it made for very effective poor mans AC.  I figure the pool will always be cooler than the ambient summer temps and It might be effective to spray the return water to cool it or blow a fan over the top at night.

Evaporation isn't an issue, I put some IBC's Under the downpipes years ago and with the summer rains always have more than enough water to offset the evaporation that occurs. Often one good rain shower overfills the pool level on it's own and theres really no problem with running it a bit low. I have a lot of margin between high and low to play with.
The Mrs wants me to put the Radiator in the front section of the house so we can have the bedrooms Cool to sleep  at night. The front AC broke so no point replacing that now, plus we never liked it on while we were sleeping as it always gave us Chills no matter where we set it.

Not that I'm worried, but it also is a lot less power to run a 300W pump than an AC unit.

The other unit I have is a spa size heater rated at 100Kw which will be plenty of over kill for the home heating and has the various sensors from the gas burner control that I can tap into to control the oil burner.  At this stage I see it as basicaly a constant burn system with safety  cutouts but even a high and low burn rate would make the thing entirely practical.  I could set the low burn under what I normally need and the high above and just have a thermostat switch between the 2 as needed.

That's the great thing with my burners.  Commercial units seem to have about a 4:1 turn down ratio. I have read of some Gas units with a 10: turndown ratio. I can get a 50:1+ on my oil burners without much trouble at all. Anything from a Litre an hour to a litre a Minute on the same burner.  If I had the thing idling at 10 KW and burning at 40, That would be all I'd need and just cycle between the 2.

The other option of course depending on where we end up,  is to just Co gen my Lister engine and make heat with that and tap off the power as a side benefit which is really the best way to look at those sort of setups. 

Offline rossw

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Re: New Electric Booster Boiler
« Reply #20 on: October 27, 2016, 06:13:13 PM »
It's taken 10 years to see you fluff your lines like this.... so I'm gonna make the most of it

It's a fair cop! Yes, of course I "meant" MJ/H but it's not what I said - well picked :)



Quote
Actually we have propane, (LPG not LNG) here, so really only CO2 and H2O....

Same here, and probably explains why I see far far less issue than we did at our old place, which had town-gas (LNG). The old pool heater (gas) rusted up in very short order.


Quote
We can thank vultures for this... it was noticed that vultures would circle around areas that had gas leaks

Well there you go, I've learned something :)

Quote
It is still a big whack of power in a little box... just for a shower......

Absolutely :)




.............oztules
[/quote]

Offline rossw

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Re: New Electric Booster Boiler
« Reply #21 on: October 27, 2016, 06:22:22 PM »
I'm on the lookout for a 400L unit to convert. With this I would only need to do a fire up every 2-3 days on what we use on average.

I have two, 2000 litre tanks. They are heated by whatever "available heat" we have. A 60-tube evac tube solar collector feeds directly to one. The generator (complete with exhaust heat recovery) and the 50kW wood-fired boiler both heat both tanks (via heat-exchangers in the bottom).

You'll want to super-insulate your tanks. We seem to lose a fair bit of heat - even if you use almost none, if we don't add heat at all, we only get about 4 days storage of water hot enough for normal domestic use. (I'll just add in here - that we don't actually store any "hot" potable water. Our domestic "hot" water is the domestic "cold" water passed through a copper coil in the top of each storage tank).


Offline DJ

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Re: New Electric Booster Boiler
« Reply #22 on: October 27, 2016, 11:30:56 PM »

The tanks I was referring to were actually gas hot water heaters which will already be Insulated... to a point anyway.

I see a gross inefficiency in them being the tube that runs through the centre where the flame/ vent normally is.  On my 125 heater, you can feel the thermo siphon effect once the flame is off with the air being drawn through  which would be a heat loss. I have read that is significant which I don't doubt for a second and also that the pilot light normally running when they are on gas is a significant amount of energy a day that compensates.

I was thinking I would need some sort of Solenoid operated shutter on the top of the flue for this to seal off the vent and stop/ significantly slow the draft losses.

I did think about insulating regular IBC tanks.  Do you think a layer or 2 of house fibreglass roof batts would be sufficient? I guess there is going to be a point where the heat loss happens no matter what you do. The thing would be to get as neat that as cost effectively as possible.

I have been looking at the evacuated tubes as well. Here they are not economical compared to used PV I can backfeed and use a normal cheap heating element but I am interested in them none the less.  What I can't seem to find is any sort of specification on their output.
Panels are all rated so I know how much power they produce but I can't seem to find anything that tells me what a Tube does.

All I have found is something that says the output of a 10 tube collector is equal to 648W. this is bugger all and seems to conflict with my other belief from what I have read that these things are super effective at heating water.  Is there something else at play here? The same article said a 30 Tube collector had a 2Kw output.  Given the cost of that and the cost of even a new installed PV system, there has to be something else or why would you even think of Tubes for water heating?

At least with PV, once the water is up to temp the power can go to other things. With Tubes it just does nothing..... which is something else I can't figure, how does the thing shutdown or stop heating once the water is up to temp or do you get 150o Water at 30PSI in the right conditions?

Offline eraser3000

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Re: New Electric Booster Boiler
« Reply #23 on: October 28, 2016, 08:55:40 AM »
The specifications on mine show differently:
Category(Ti-Ta),  Clear Day 2000Btu/ft2/day,  Mildly Cloudy 1500 Btu/ft2/day,  Cloudy Day 1000 Btu/ft2/day
A (-9F) 47,000 36,000 24,000
B (9F) 46,000 34,000 22,000
C (36F) 43,000 31,000 19,000
D (90F) 36,000 25,000 13,000
E (144F) 29,000 18,000 7,000

(Ti) – Temperature Inlet: Refers to temperature of fluid entering manifold.
(Ta) – Temperature Ambient: Refers to the ambient temperature, or the outside air temperature.
(Ti-Ta) – Refers to the inlet fluid temperature subtracted from the outside ambient temperature. For example, if the temperature
entering the manifold is 100F, and the outside air temperature is 80F, the Ti-Ta would be 20F.

http://www.solarpanelsplus.com/pdfs/spec-sheet-spp-30a-revb.pdf

From experience I think that is pretty accurate.  I am normally in the D Category.  So for me 36K btu each is great. That 10.5 KW.  It really starts adding up when you have several in series as you can get huge deltas at fairly substantial flow rates.





Offline eraser3000

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Re: New Electric Booster Boiler
« Reply #24 on: October 30, 2016, 06:38:30 PM »
A little more progress.

ila_rendered

Offline bj

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Re: New Electric Booster Boiler
« Reply #25 on: October 31, 2016, 06:25:39 AM »
  Looking great.
"Even a blind squirrel will find an acorn once in a while"
bj

Offline eraser3000

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Re: New Electric Booster Boiler
« Reply #26 on: November 17, 2016, 09:43:29 AM »
Looks like spaghetti.
ila_rendered
But its functional.  Next step will be to clean it up and insulate a little more.
ila_rendered
Handles a load nicely.
ila_rendered

Offline bj

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Re: New Electric Booster Boiler
« Reply #27 on: November 18, 2016, 06:55:12 AM »
  Functional has to be first, otherwise continuing would be fruitless.  ;)
  Coming along nicely.  Very interesting project.
"Even a blind squirrel will find an acorn once in a while"
bj