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How would you improve this anti-efficient gas system?

  1. Sep 8, 2014 #1
    Hi folks,

    I recently got a job on a Hotel, it has 5 floors:

    level -1 underground, we have the water tanks and the restaurant
    level 0 street level, we have only 3 rooms there
    level 1 first floor, we have 4 rooms
    level 2 second floor, we have 8 rooms
    level 3 third floor, we have a special room for the Spa
    Above this level we have the roof with the gas tank and the heaters.

    We have been working there a month and we have arrived to a conclusion: that Hotel is a disaster, from the energetic point of view.

    The big problem is how the building is designed to heat the water which means the gas bill is extremely expensive.

    I will try to show it with an image. (Attach Files)

    Basically the heaters work with gas, and they are on the roof of the building. I am not sure about that but I think that it is for safety reasons.

    Well, the problem is that the water tanks are on the lowest floor, undergrownd, they can't be more far away from the heaters.

    There are 16 rooms in that hotel and the best ones (8) are on the third floor, very close to the heaters... but far away from the water tanks.

    It is impossible to do it worse since the hot water needs to travel the longest possible distance, which is like twice the height of the building, I guess there is a massive loss of energy in that travel which means the heaters must work a lot and the pumps too.

    What ideas would you suggest to improve the efficiency of that system?

    I have two ideas but I don't know if they are possible, or even if they could work:

    1.- Change the water tanks to the level 3 which means they would be very close to the heaters and the hot water only should travel once the height of the building, since we have 8 rooms on the second floor we would host our customers on those rooms as much as we could.

    The doubt is if it is possible to put 1500 kg of extra weight on a floor, which is the weight of those water tanks. Maybe it is not possible.

    2.- Using sensors to start-stop the system only when necessary. I have no idea about how exactly implement that.

    Any other idea? What do you think about the system? Is that something common on Hotels or is it just the engineer in this one missed the efficiency classes?


    Attached Files:

  2. jcsd
  3. Sep 8, 2014 #2

    Doug Huffman

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    I suspect that your employer's facility was not planned or engineered but grew as demand required and technology was available. Remember that improvement investment money must also be efficient.

    Insulate the heated water pipes may be the cheapest improvement. Schematically, add a circulating pump from the right hand end of 'rooms' to the heaters inlet to make their hot water instantly available. Might the rooms be heated with the hot water?

    Remember that your guests' comfort is the benefit in your cost/benefit considerations.
  4. Sep 8, 2014 #3


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    It could well be the best solution to the problem.

    It's impossible to know without knowing the constraints on the original design (cost, building regulations, install timeframe etc etc).

    Don't assume you can improve the design with some simple changes.

    How do you know the gas bill is high because of a poor system and not simply high use?

    You need to analyse the system to find your losses and only then you'll know what and where improvements can be made (If any..).
  5. Sep 9, 2014 #4
    Yes that is very possible. I agree, the investment should be efficient but I guess every penny invested in saving energy is worth it since now the bills for electricity and gas are a disaster.

    The pipes are insulated. I have to ask about the circulating pump, at the moment I don't have enough information about that.

    The rooms are heated with a cold/hot air system which basically works using electricity.

    Yes their comfort is extremely important!

    Thanks for your reply!

    Yes I know I didn't provide with enough information, I am just working at the front desk and I tried to had a look at the overall building but I don't have any drawings or something, I apologize for not giving more information.

    THanks for that advice, I think I have been a bit ingenuous thinking this could be solved easily.

    I know that the problem is not the use because we opened recently the Hotel has been empty a lot of days, we have had only 31 rooms or 31 uses if you want and we have found we have expent 1300 dollars in gas.

    Yes we need a deep analysis. At the moment there is a project to repair the Spa, I will suggest to the architect not to spend a single penny on the Spa and try to improve the efficiency.

    Hopefully with the money they had prepared for the Spa we will be able to do something with this disaster.

    Thanks for your replies!
  6. Sep 9, 2014 #5
    I'd suggest you talk to your building manager instead. The spa helps to draw people to stay in the hotel. If nobody stays there, the hotel is minus all operating costs. If people come stay there, those costs are offset by their patronage. If nobody wants to stay there, it doesn't matter what your energy costs are, you're losing money.

    You have to look at the potential for savings and the expected payback period. A cheap modification that saves $100 a month may be better than an expensive modification that saves $300 per month (or it may not, but there's no way to tell before hand without doing a little economic analysis). Maybe the hotel would rather have $10,000 cash in hand (to be spent on things like room upgrades, food services, etc) than spend it on a new water heating system which wont show positive return for 5 years, regardless of how inefficient it is.
  7. Sep 9, 2014 #6
    Well we should talk with the architect, you are right.

    Without the Spa we also have had some people, not as much as we want but the Hotel is very nice even without the Spa. They spent 4 million $ on it, as you can imagine it is a luxurious Hotel plenty of nice details, furniture and so on. It was a palace on the XVI century.

    Thanks for your point of view. I don't know why but I tend to think a big investment to save as much energy as possible is the best option... but maybe I am wrong.
  8. Sep 9, 2014 #7


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    I'm guessing your hotel isn't marketed as 'eco-friendly' or similar so business decisions are based solely on ROI rather than intangible feel good factors like greenhouse emissions?

    Why would your hotel invest in reducing energy costs if a much better ROI could be gained from an advertising campaign?

    I've worked in a few large, expensive hotels and they are notorious for wasting energy. The air con is left on in all rooms all the time simply because it's considered easier than sending someone up to turn on the AC the day before guests arrive (or alternately installing a control system for hundreds of AC units). Energy costs are too low on the list of outgoings to be given much thought.
  9. Sep 9, 2014 #8
    I'm saying you, as a desk clerk, probably shouldn't suggest to the architect not to upgrade the spa lol. That is a suggestion that you bring to your boss or the building manager directly and let them decide whether to use your advice.

    People tend to think that. Many times it does lead to a net positive outcome financially, but the payback period is of major concern to most places.

    I work in mining and I've seen projects which offered millions and millions of dollars in returns over the expected mine life. However, they were major capital expenditures with unsatisfactory return periods. Many times this has to do with stockholders in this industry, but as often as not, it has to do with the fact that a company only has so much money to invest in projects per year, if they are going to spend their cash on something, they'd prefer to spend it on items which have faster rates of return.

    Engineering isn't about making systems perfect, especially when we are working with existing and even-more-especially old systems. Engineering is about optimization.

    With that said, it's probably very true that the water system is outdated and energy inefficient. Could significant gains in efficiency be gotten from major modifications? Yes, certainly. Will it be cost effective? That depends on your specific system and the extent of the work required balanced against the expected savings in gas and electricity.
    Last edited: Sep 9, 2014
  10. Sep 10, 2014 #9
    My Hotel is marketed as eco unfriendly :rofl:

    I am working on an adwords campaign too. But as I said the gas-electricity bills are the main issue with this Hotel.

    In those Hotels you have plenty of guests... our Hotel is in a small town, it is not a tourist destination. There are nice things here, if we work on that maybe it could be more attractive for tourists. Today I talked with the Tourist Info worker about that.

    In this case energy costs are not low, are very high.

    I, as a front desk clerk, MUST suggest that and I will explain why:

    1.- It is obvious the building is designed to work like it is always plenty of guests---> in practice that almost never happens.

    2.- Three different companies have tried previously to manage the Hotel---> All of them failed AND all of them had the Spa working.

    Maybe there is a problem with that building and its design, maybe!!:cool:

    We all agree this is not simple, the experts should make calculations and decide what is better. But if you know all previous companies have failed you fear it will happen again, it is just I don't want to do the same mistakes they did.
  11. Sep 10, 2014 #10


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    So were the ones I worked at, at least superficially, like yours. They asked customers to reuse towels and had a short spiel on their pamphlets, but they didn't sell rooms on it.

    They wanted to appear eco friendly to non-discerning clients but had no interest in actually being eco friendly, it's lip service, nothing more. Much like your hotel otherwise you wouldn't be here with your problem.

    Genuinely eco friendly hotels have PV panels, exceed insulation regulations, solar HW, compost on site, deliver excess food to shelters daily, use sustainably produced foods, have heat recovery systems, have automated heating control systems etc etc. Customers come because of it.

    Maybe they couldn't see the forest for the trees and thought a spa or heating system was what they needed but in reality they needed to move 100km down the highway.

    You need business advice, not engineering or physics advice.
  12. Sep 10, 2014 #11
    this is probably why they keep the water heaters on the roof (hehehe) *take notes at 3:42 of the video!!*

    If a water heater gets neglected, and its outlet gets plugged, with a plugged RV, then it's basically becomes a bomb. if the water inside starts to turn into steam, then you're screwed.

    anyway, I don't see why that's such a bad design (I'm not a designer, so take my input with a grain of salt), but the way I see it, it's not that different from a water tower. you pump the water to the fourth floor, and the head pressure from the top delivers everything that's needed to get the hot water to its users. the only problem that I see is head loss from pumping it all the way up, and letting it double back. that might increase your head loss by... 10 ft? (I don't know, I have no idea what size pipes and flow rates you guys have), but basically, all that translates to is more power usage for the water pumps.

    and your water pipes are already insulated, so you're all set there.. and considering your best rooms are the closest to your water heaters, that means they don't have to wait as long for their water to heat up, so you're good there too..

    so.. what's the problem?
    Last edited by a moderator: Sep 25, 2014
  13. Sep 11, 2014 #12
    -if the hot water can travel from the heater directly to the rooms that is ok

    -if the hot water travels to the water tanks and then is pumped up to the rooms I think it is a bit stupid because there must be energy losses everywhere
    Last edited by a moderator: Sep 25, 2014
  14. Sep 12, 2014 #13

    jim hardy

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    Let's think real simple.... and start at the extreme case of zero hot water use...

    When there's no use,
    Heat energy that goes into the hot water system should stay there.
    How can it get out and make your heaters come on again?
    Most obvious is through the pipe insulation.
    Do you know if the pipes are insulated inside the walls? Feel the wall around the hot faucets in an empty room.

    Where else could that heat go ?

    Gravity makes hot water rise, just as it does hot air.
    Your heaters should be below the hot water storage tank. That way when the heaters are off the hot water stays in the tank.
    As your system is shown, when your tank gets hot enough that the heaters shut off and start to cool down, hot water from the tank will rise up to the heaters keeping them hot.
    My guess is you lose a lot of heat through the heaters when they're off.
    That's because the combustion air passageway through the heater warms the air in the heater and sets up a natural draft that cools the heater. That'd be okay were it only the heater that cools down.
    When the heater cools down the water in it becomes more dense(heavier) than the water in the hot tank four levels below ,
    so gravity pulls the cool water down to the tank and pushes hot water up to the heater.
    Look up the term "thermosiphon" .
    Feel of the exhaust stack when heaters have been off for an hour... if there's lots of hot air coming out, well.... that heat is probably coming from your tank in the basement by natural circulation(thermosiphon) when the pumps are off. Result is you throw away a lot of heat between heater run cycles.

    The most glamorous fixes for that would be to invert the hotel or reverse local gravity.
    Surely you guys can come up with something better - like automatic valves to block natural circulation .

    I'd actually expect the original designer to have included something to prevent that natural circulation, maybe you'll find it not working.
    Look for electrically operated water valves at the pumps. Do the heaters have fans for combustion air? Dampers to trap heat when burners are off? Is all that stuff working?

    I once lived in a house that was touted as having a heat recovery airconditioning system with a freon to water heat exchanger in the water heater. Sure enough the heat exchanger was right there with refrigerant lines soldered in place.
    I wanted to see how well it worked so after dinner one night i turned off electricity to the water heater. Man-oh-man was i in trouble the next morning when the girls took their showers sans hot water. The el-cheapo contractor never hooked up the freon lines on the airconditioner end.

    I hope you find something easy like that. You'll be the hero.

    Keep in mind i'm just guessing. Let us know what you find.

    old jim
    Last edited: Sep 12, 2014
  15. Sep 15, 2014 #14
    but natural circulation is a good thing if you think about what it does to prevent corrosion by keeping the water moving, especially if it's hot water. but I have no experience with city water, which is higher in TDS than the water we end up condensing from steam.

    there's probably an economic analysis you can do from all this. personally, I don't think it's worth the time. I think the best thing to do is to contact the designers, and get their take on why it was designed this way, and if you really want that promotion, consult a few other designers with this setup, and get their take.

    nobody here's an expert on this stuff.
  16. Sep 17, 2014 #15
    Thanks for both replies Jim and spectastic, you talked about fenomena I had not thought about which is very interesting.
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