本人ＨＶＡＣ工程师，想多认识几个同行。

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作者: ACEW

各位HVAC专业的朋友:
新年好.
我是外行,是自控专业的,一不留意,逛到了你们的坛子里来了 .
不过,在空调自控,节能方面我们说不定还有合作的可能呢.
如感兴趣的话,我们是否可以交流交流.
我们电气专业的朋友每月有一次聚会,如有时间的话,请你们过来看一看.愿我们一起合作干点事.

ACEW, I have some questions regarding energy management system, HVAC control, gas detection system, and HVAC system sequence of operation, etc. How can I attend your meeting each month? thank you very much!
kiteincloud@hotmail.com

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作者: baozi

just post your question.

Baozi,
Could you advise me the sequence of operation for heat pump system? the cooling water comes from closed circuit cooler, and the heating water comes from boiler. The heat rejection temperature setpoint is 95F, and the heat injection temperature setpoint is 60F.
Your earliest reply will be appreciated.

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作者: baozi

也可以PM给我

Baozi,
Thank you so much for your prompt response. There are more than 10 different size heat pumps (Manufacturer is Carrier) in one system for various space. I am asking the general sequence of operation for this kind of heat pump system. Or we can discuss by phone? and I sent my phone number to your PM.

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作者: baozi

just post your question.

Baozi,
One story group D commerical building, What is the minimum building area which the sprinkler system shall be required as per OBC and fire code?

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作者: jumpfish

Water loop/source heat pump?

Yes, water source heat pump.
Any idea about sequence of operation of closed circuit cooler? Thanks.

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作者: Peterspan

how many streets it faces? What is the fire-resistance rate of the fire seperation? is it a combustible or non-combustible building? The max building area depends on all these things.

Say, if noncombustible, 1 hour rate, no limited
45 min rate, facing 1 street, 4800 SM

Thank you very much Peterspan, This number is exactly what I am looking for.
Additional question: The building is storage and repair garage area with some hugh overhead doors, aboveground and heated in the winter. The sprinkler system should be wet or dry for this area?

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作者: baozi

不过奇怪啊,你不是在个CONSULTANT里做吗?没有CODE?

有CODE，单位一套，家一套，就是没找到相关条款，不好意思，每天工作太多。

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作者: PerterMan

Hi,my friend,I just have a little knowledge about sprinkler system. for general use of the building, the sprinkler system should be wet,but it should be dry if those stuff that the sprinkler system protects are books, computers, something like books and computers. it should be special extinguishing agents if the sprinkler system protects those stuff, like electrical equipment, water will be hazardous agent. good luck!

my two cents: Sprinkler system should not be designed at computer room. Dry sprinkler system should be used at unheating area to prevent freezing in the winter.

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作者: PerterMan

Hi, you have to use NFPA Standard to design sprinkler system and this is an American standard thta we use it in Canada.

Yes, I use NFPA 13 for sprinkler system design. My question here is dry sprinkler should be used in unheated area to prevent freezing in the winter. Why a lot of dry sprinkler systems are used in commerical storage garages and repair garages in Canada which heating systems are provided in winter.

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Does someone know how to select pressure relief valve for domestic cold water? Thanks in advance.

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Thanks Jsl630226, flywithwind, freda.
We designed PRV (Pressure reduced valve) for 4" domestic cold water piping (94psi to 60psi) without specify any model. Now the contractor installed wrong model and wrong size PRV (Pressure Relief Valve) (Watts 174A 3/4") with discharging piping to floor drain, which is for boiler hot water application.
I need to reselect a correct PRV for cold water application currently. I guess 2" should be correct size, and without discharging piping to floor drain.
Can any friend confirm with me?

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作者: jsl630226

你所说的冷水系统，应该不会是自来水系统，饮用水供水系统肯定不用放气、卸压。
那就应该是空调中的冷水系统。空调中会有两套：冷却水系统、和冷冻水系统。其中冷却水系统多是开放式系统，也不用放气卸压。那就只有冷冻水系统了。因为冷冻水系统是闭合的，放气阀是必要的，分为两种：手动的，和自动的。现在多选用自动的，只用过一个尺寸的4分（15毫米）的，管道再大都没关系，因为不是常用，开始给系统注水的时候，用一次，正常使用的时候，基本上不用。
pressure relieve valve的中文叫安全阀，除了锅炉、热水器、压力容器等使用之外，不会用在冷水系统中。

Thanks, jsl630226. I can see that you have a lot of experience in HVAC. Can you confirm me that I can remove the discharging piping for PRV in domestic water piping which contractor has wrongly installed for pressure relief valve?

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Thanks, Jsl630226.
Do you have experience regarding diesel fire pump suction piping? Is it true that the distance between the flange of diesel pump intake with the flange of gate valve at suction piping shall be the minimum 10 times of piping diameter?

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作者: jsl630226

希望得到更多的信息，比如：这台水泵到底是干什么用的？
进水水位高于水泵吗？
不是的话为什么要在水入口加阀门？
是临时使用的水泵吗？
有安装水表吗？

这台水泵是消防水泵，而且是应急消防水泵，在电力供应也没有的情况下使用。
进水水位低于水泵，但是城市管网水，有压的（60PSI），肯定要加阀门。
我的问题是水泵吸水管设计。现在阀门和水泵距离太近。泵房空间有限，要保证10倍管径距离就的加个弯头。不知是否符合规范。

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作者: jsl630226

这种情况下，加装阀门是对的。同时还应该有减震柔性接头。
阀门与水泵的间距应该没有什么要求，PLUMBER'S CODE 上面肯定没有什么要求。在国内安装的时候，也没记得有什么要求。10倍管径的间距在水表前后，是防止紊流造成计量不准。你为什么会想到10管径的间距？

市政消防局现指出间距不够10倍管径， 而且入口处不能有T管件，只能是弯头。勒令尽快修改，可是在规范里找不到相关条款。
水表处设计没问题。

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作者: baozi

你在哪个CONSULTANT做?把你的CODE卖给我吧,哈
我没有这里的CODE,但国内的规范是,消防泵最少要双泵互备,从HEADER下来,从没看到过用T的,泵到了一定流量以上,要有减震底座,进口要有GATE VALVE, CHECKING VALVE (就是国内叫的角阀),FILTER,减震, 出口有减震和GATE VALVE,其他的是还要有GAUGE,冷热水还要有TEMP,GATE VALVE是做MAINTAINANCE用的,如果有特殊要求还可能加其他的东东
距离是在CODE里的,离进口多远,因为要保证FLOW,才不会出气蚀,入口只能用90度是全世界都用的CODE

你说的这些附件全有，除了HEADER是和水泵入口同一水平高度，自然有用T的（双泵）。这是一个既有工程，水泵，管件全已摆放安装在现场，我们需要花最少的钱改造。
如你需要CODE，我可送你一套复印件，算是交个朋友。

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作者: jsl630226

既然他们勒令修改，就有义务告诉你原因。或者是违犯了，哪一个规范的哪一个条款。问他们一下不就得了吗？
我也希望知道，他们为什么这样要求？

是个既有工程改造，很多问题，我们得一项一项查找，再提出可行方案，不能条条问市政府呀。

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作者: flywithwind

有一次面试，对方问我选取的制冷机是多少吨，他们是指水流量呢还是指冷负荷呢，国内有时会用冷吨btu来表示冷负荷。请明白人赐教。谢谢先

指冷负荷. 标准工况大约12,000BTU/h 是1冷吨