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  1. #1
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    Making up for lower dT by adjusting Belimo valves?

    I was wondering if I could get people perspective on a possible solution for a facility that's replacing a steam sourced heating to hot water of approximately 160 degrees. The plans are to replace the HX in each of the basements from shell and tube to plate HX's but my concern is going to be that during peak demand there's going to be cold complaints due to the heating coils not being sized for the lower dT. I was told that it may be possible to fully open the belimo valves during peak demand which had been previously only half open and compensate for this lower dT. Is this reasonable?

  2. #2
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    If you are converting a sytem from steam to hot water you may run into some issues. First as you stated 160* water may not be hot enough. What pressure steam do you currently have. 5lb=227* ,10lb=240*. 15.... Another issue is leaks you are going from LPS to a system constantly under pressure winter and summer im assuming around 15-20 psi. Is your piping sized for hot water, Probably not. For every 1 ºF drop in water temperature, each 1 lb of water will give up approximately 1 BTU. On the other side....At a pressure of 30 psi, each 1 lb of steam will give up approximately
    929 BTU’s. Good luck keep us updated. Keep in mind if you run glycol it will give up less heat than plain old H2O.

    Sent from my SM-G920R4 using Tapatalk

  3. #3
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    Are you responsible for the design?

  4. #4
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    Thread Starter
    No, I think they want to see what I'll come up with but I'm just an intern.

  5. #5
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    Thread Starter
    Quote Originally Posted by Spitz View Post
    If you are converting a sytem from steam to hot water you may run into some issues. First as you stated 160* water may not be hot enough. What pressure steam do you currently have. 5lb=227* ,10lb=240*. 15.... Another issue is leaks you are going from LPS to a system constantly under pressure winter and summer im assuming around 15-20 psi. Is your piping sized for hot water, Probably not. For every 1 ºF drop in water temperature, each 1 lb of water will give up approximately 1 BTU. On the other side....At a pressure of 30 psi, each 1 lb of steam will give up approximately
    929 BTU’s. Good luck keep us updated. Keep in mind if you run glycol it will give up less heat than plain old H2O.

    Sent from my SM-G920R4 using Tapatalk
    Thanks for your input. The biggest change in piping will be from replacing the steam HX with the HW one but I was assuming the Supply and Return lines would stay the same if they can achieve a similar T and Q gain with the lower dT. I was also looking at the option of having a supplemental boiler in the system to add additional heat during peak demand periods. I'll keep you up to date!

  6. #6
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    So far there is not enough information to answer this question. First where are you?. Design heating temperatures vary greatly with location. What is the "heating coil"? AHU, VAVRH, FCU, RAD...? What is the existing HWS Temp Setpoint at design conditions? Is it reset? What is meant by Belimo Valves half open? Termina unit valves? Heat Exchanger valves? Are these valves limited in travel to 50%? Or are they at 50% when the building is running on a design heating day? Why are the Belimo Valves at 50%? (Noise, Controllability, Balancing?)

    With these answers I might give an indication if this is reasonable. But, the PE proposing this ought to answer the question using Temperatures, BTUs, GPMs, balance reports and existing equipment data sheets to do Load Calculations at each building. Someone is going to spend a lot of money to change this system, they need to know it is going to work, not if it seems reasonable.

    The thing is, if the load on a space exceeds the ability to heat the space, it does not just get a little cool, it gets cold. Kinda like, if the leaks on the ship exceed the pumping capacity, the ship does not just sit a little lower in the water, it sinks.

  7. #7
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    Reading your original post I'd like some clarification.
    It sounds like there are existing shell and tube steam to hot water heat exchangers in the building(s) and that the final, existing heating coils are served by hot water already.
    It sounds like the plan may be to delete the steam distribution system between buildings and swap to hot water. (This is popular long term cost savings measure)
    The new hot water distribution system between buildings would then use plate and frame HXs to heat the existing hot water loops in the building.
    It all comes down to how much hot water at what temperature you can bring to the building. If things are sized to provide the same quantity of 160 Deg on the output side of the new plate and frame the building will probably not know the difference. It's doubtful that the existing steam to HW HXs produces more than 160 deg water

  8. #8
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    Just the title of this post had me steering clear, now with a wad of responses I had to peek and I'll add 0.02.

    Your talking about adjusting valves for the change? Exactly what option do your have in a control valve with steam to HW conversion? Steam circuit setter / balance valve...nope. Did the control valve have some sort of limit in the programming...not likely. Its controlling to DAT or some other PV. In that case, reduce the input energy what happens? The valve automatically goes to max if it cannot maintain whatever it was before unless it failed otherwies.

    I have a hard time imaging any case you might have to adjust something with Belimo products for this. The whole hope this flies is things generally where grossly oversized back then.

    That said, I have been using tons of Belimo ePICs & energy valves. With those I can re-balance a whole system on the fly. Being only recently available an not steam rated, certainly not your case.


    Adjust a steam valve for HW, smells like sheet but can work. The maths don't lie and it shouldn't be something that cannot be calculated...unless the design team is pulling crap out the sky and preying at least.
    Last edited by orion242; 12-14-2018 at 12:46 AM.
    Propagating the formula. http://www.noagendashow.com/

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