问答系统过度设计 - 第291期短讯

你好。

Hello.

欢迎收听暖通空调学校播客，这个节目时不时会解答一些问题，顺便帮你温习那些可能已经忘掉的知识。

This is the HVAC school podcast, the podcast that answers some questions every now and again in addition to helping you remember some things you might have forgotten along the way.

这期节目很短，我会尽量回答埃文关于系统 sizing 的问题。

This is a short episode wherein I answer a question from Evan about system sizing, and I'm gonna do that to the best of my ability, of course.

不过在听埃文的问题之前，先来感谢一下让我们能做这个节目的赞助商。

But before we hear from Evan, we're gonna hear from our great brand sponsors that make this podcast possible.

制冷科技公司，特别是他们的 Viper 擦巾，这种万能清洁布清洁能力真的很强。

Refrigeration Technologies and specifically Viper Wipes, the all purpose wipe that is really amazing what it can cut through.

从密封胶、油污、沥青到各种污垢，它都能轻松搞定，而且用起来对皮肤很温和。

Everything from mastic to oil grease tar, grime, and it's nice on the hands.

用完之后，双手会变得柔软舒服。

Makes them nice and soft when you're done.

这样你下班回家后，还能精神抖擞地去跳舞。

That way, you can go home and head out a dancing when you get back to the house.

更多详情请访问 refrigergetech.com/viperwipes。

Find out more at refrigergetech.com/viperwipes.

regergetech.com/viper-wipes。

Refrigergetech.com/viper-wipes.

Carrier 和 carrier.com。

Carrier and carrier.com.

我做 Carrier 的经销商已经很多年了。

I've been a Carrier dealer for many years.

Carrier 最近推出了新款 GreenSpeed Extreme 超高效热泵，已经上市了。

Carrier has their new GreenSpeed Extreme super high efficiency heat pumps out on the market now.

想了解更多信息，请访问 carrier.com。

Find out more by going to carrier.com.

NAVAK，官网是 navakglobal.com。

NAVAK at navakglobal.com.

Copeland 和 White Rogers 的热泵组合产品。

Copeland and the White Rogers hot rod combo.

这个型号是21D64C-843。

That's, of course, the 21 d six four c dash eight four three.

这是一体两用的设计。

It's a two in one deal.

它集成了一个通用的120伏表面点火器和通用火焰传感器，全部打包在一起。

It comes with a universal 120 volt hot surface nitride igniter and universal flame sensor in one package.

每个部件能替代150多种原厂零件，是库存的绝佳选择。

Each part replaces over 150 OEM parts, so it's a great truck stock item.

当火焰传感器或表面点火器损坏时，它能让炉子重新恢复正常运行。

It gives furnaces a fresh start when either the flame sensor or the hot surface igniter fails.

火焰传感器可以轻松调整，确保完美贴合。

Flame sensor is super easy to customize for the perfect fit.

直接剪裁并弯折即可安装，还配有一个保护套，方便你弯折时保持表面清洁。

Just cut it and bend it to fit, and it comes with a sleeve protector to keep the surface clean while you bend it.

这款120伏表面点火器是直接替换件，也能为你的客户带来性能升级。

The 120 volt hot surface igniter is a replacement and can be a worthwhile upgrade for your customers.

它比碳化硅更坚固，也不容易腐蚀。

It's stronger and less likely to corrode than silicon carbide.

这套件配有通用型和标准型安装支架。

The kit comes with universal and standard mounting brackets.

更多详情请访问 hvacrschool.com/wrhotrod。

Find out more at hvacrschool.com/wrhotrod.

hvacrschool.com/wrhotrod。

Hvacrschool.com/wrhotrod.

本产品由 Filtrete 空气过滤器提供。

Brought to you by Filtrete Air Filters.

嗨，布莱恩。

Hey, Bryan.

我叫埃文·巴克维格。

My name is Evan Buckwig.

我是德克萨斯州达拉斯持证的霉菌评估顾问。

I'm a licensed mold assessment consultant in Dallas, Texas.

你们是我学习暖通空调知识的主要来源，真的很感谢你们所做的工作。

Y'all are my main source of HVAC learning, so thank you guys for what you do.

我最近给一位开发商做培训时，有人问到：如果空调系统选大了，该怎么办？

I was recently doing a educational session with a builder, and the question came up, what can be done when a HVAC system is oversized?

我告诉他，其实能做的不多。

I told him not a whole lot.

我建议加装辅助除湿设备。

I recommended supplemental dehumidification.

这些都是新盖的建筑，建筑围护结构的气密性比较好。

These are newer builds, so the building envelope is relatively tight.

我想问问你们这边，遇到系统选大了的情况，通常怎么处理，才能更好地控制湿度，让住户更舒适？

I was curious from y'all's side of the equation, what can be done when the system is oversized to help control humidity and keep the occupants comfortable?

再次感谢。

Thanks again.

嗨，Evan。

Hey, Evan.

谢谢你把我们当成信息来源。

Thanks for trusting us as your source for information.

我不确定这是否明智。

I don't know how wise that is.

在你所处的领域，还有很多其他非常棒的HVAC信息来源，比如Energy Vanguard。

There's a lot of other really great sources out there for HVAC information in the space that you're in, people like Energy Vanguard.

Allison Bales是个非常好的资源。

Allison Bales is a great source.

The Energy Conservatory有很多优质内容。

The Energy Conservatory has a lot of good content.

Retro Tech也提供大量优质内容。

Retro Tech has a lot of good content.

AC维修技师Craig是个很棒的信息来源。

AC service tech, Craig, is a great source.

Ty Brannerman也是个非常值得参考的人。

Ty Brannerman is a great source.

我只是提一下这个情况。

Just gotta throw that out there.

不过，你既然信任我，

But, hey, you trusted me.

你问了我这个问题，那我就尽我所能回答。

You asked me the question, so I'm gonna answer to the best of my ability.

首先，我给个简单的答案：这真的要看设备情况，问题有多严重，这很明显。

So first, I'm gonna give the simple answer, which is that it really does depend on the equipment, how bad the problem's gonna be, obviously.

你说设备太大了。

You're saying it's oversized.

你说你知道设备太大了。

You're saying you know it's oversized.

如果这设备有变频功能，或者分档运行，再加上它的除湿能力设置方式——比如有没有专门的除湿模式——这些都会影响问题的严重程度，具体要看你遇到的是什么情况。

If that equipment has any sort of turndown, if it has any sort of staging, and depending on how the latent capacity is set up on the equipment, whether it has maybe dehumidification modes, things like that, it could make the problem better or worse depending on what you're experiencing.

所以，第一步，为了让设备发挥最佳性能，得确保风量控制在每吨325到350立方英尺每分钟的范围。

And so first things first, to make the equipment work the best it possibly can, make sure that we're getting our airflow down in the probably three twenty five range, three fifty to three twenty five per ton.

如果设备确实偏大，而且你有除湿模式并设置得当，风量甚至还可以再调低一点。

Again, if it's oversized, you can maybe go down even a little bit more than that if you have dehumidification modes that you can make sure you have set up properly.

但风量越低，机箱结露的可能性就越大。

But again, the lower the airflow you've got, then the more likely you're gonna get cabinet sweating.

冷风管也更容易结露。

More likely you're going to have cold ducts that then sweat.

所以设备过大带来的另一个难题就是这个。

So that's always the challenge with oversized equipment as well.

这里头影响因素挺多的。

So lots of factors here.

把设备换成合适的尺寸，效果会特别好，尤其是你现在已经装了大功率设备的情况下。

Rightsizing equipment is pretty magical, especially now that you've already got big equipment in place.

这意味着你的风管，希望它们本来就是偏大的，这样换成合适尺寸的设备后还能用。不过你提到这是新房，结合最近制冷剂的更新，虽然可能性不大，但理论上还是有可能只换冷凝器，保留现有的空气处理机。

That means your ducts, hopefully, are gonna be oversized when you do put the right size in, but the one thing that you said that I think could make the answer slightly different is that you said these as brand new houses, and in brand new houses, it's possible, not really likely with the whole recent refrigerant change that we've had, but possible, that they could just swap the condenser and keep the current air handler.

所以建议你查一下厂家提供的性能参数表，或者先上AHRI网站找找匹配型号，看看能不能只换冷凝器，不换空气处理机，然后调整一下风机的转速，把风量调到你需要的范围。

So the thing to do is to check the expanded performance data from the manufacturer, or you can just start with AHRI just to look for matches to see if potentially you could just swap the condenser without having to swap the air handler and just set down the fan settings on the air handler to get the air flows that you want.

这其实就是关键所在。

And that's really the answer there.

你提到过安装除湿机这类办法。

You mentioned things like putting in dehumidifiers.

这确实是个可行的方案。

That is a solution.

你可以把湿度负荷和显热负荷分开处理。

You can decouple the latent from the sensible.

约翰·阿瓦克这些人经常提到这一点，这确实是一个选择。

That's something that John Awak and others talk about a lot, and that certainly is an option.

但安装时必须得规范，而且要让除湿机完全独立运行，现实中往往很难做到。

They have to be installed properly, and again, getting a dehumidifier set so you can completely decouple it is often not practical.

这跟妮基·克鲁格从圣达菲常讲的观点一致，也是她导师教她的：空调才是除湿的主力。

That goes back to what Nikki Krueger from Santa Fe talks about all the time, which goes back to what her mentor taught her, which is that the air conditioning really has to be the king of dehumidification.

所以设备的容量必须得选对。

So it really needs to be sized right.

它需要被正确设置并运行，而除湿机则能在春秋过渡季补充不足。

It needs to be set up to operate properly, and then a dehumidifier helps fill in those gaps in the shoulder seasons.

这才是你应该采用的设计方式。

That really is the way that you should design it.

但你能不能装一台除湿机，把问题大大缓解？

But can you put in a dehumidifier that will do the job and make the problem much less prominent?

当然可以。

Absolutely.

我们再次强调，安装时一定要规范，尽可能把除湿机接入设备的送风管道，这样能解决好几个问题，比如让送风温度不至于太低，又不影响空调主机的正常运行。

And again, we talk about making sure that you install it properly, making sure that whenever possible, that you duct it into the supply ducts of the equipment, which helps solve a couple different problems, including tends to keep your supply temperatures a little bit warmer without derating the actual AC equipment.

这样能减少管道和出风口的结露，也让空调主机能充分发挥作用。

So it reduces duct sweating, reduces vent sweating, and keeps the AC equipment doing its job fully.

但同时，它也会增加本就可能偏小的风管系统的静压负担。

But it also adds to the static pressure of what already may be a bit of a challenge depending on how the ducts are sized.

对吧？

Right?

所以我们这里做了不少假设，因为我并不清楚具体情况。

So we're making a lot of assumptions here because I don't know the specific situation.

现在我们稍微聊聊理论层面，好让这个解释更完整一点。

Now let's go into the theoretical side of this a little bit, just so that way I'm filling this in a bit.

你能故意让一台设备降额运行，来让它工作得更好——也就是降低它的能力吗？

Could you take a piece of equipment and intentionally de rate it to make it work better, to basically make the capacity worse?

你可以做一些事情，比如开启电加热。

Well, you you can do things like you could run electric heat.

或者使用再热模式。

You could run reheat.

对吧？

Right?

还有没有其他方法，能利用空调本身产生免费的再热，从而让它变成更好的除湿机？

Are there other ways that you could potentially get free reheat turning your air conditioner into a better dehumidifier?

当然有。

Sure.

确实有办法这么做，但你还是在向空间里输入更多的热量。

There are ways that you can do that, but you are still adding BTUs into the space.

我常开玩笑说，如果你的设备太大了，干脆把阁楼的保温层拆掉一点，或者把窗帘都拉开。

And so sort of a joke that I often say is like, if you have an oversized unit, just remove some insulation from the attic or take the shades off your windows.

问题是，像窗户这种东西，会让某些房间变热，其他房间却没变化，而每多输入一单位热量，都会增加能耗，无论是为了让空调尺寸合适，还是让它运行更久。

Now the problem is is that things like windows, now you're gonna heat up certain rooms and not others, and all of that has a power penalty when you are adding BTUs to make the AC the right size or to make it run longer.

但在潮湿气候下，这未必是坏事，因为有时候我们需要让空调多运行一会儿，才能更好地除湿，所以系统越大，除湿能力就越强。

Well, in a humid climate, that's not always a bad thing because sometimes we need it to run longer in order to dehumidify better, and so just having a bigger system means it's just gonna be a bigger dehumidifier.

但就像所有事情一样，这中间得找平衡。

But it's a balance like everything.

不过，除了加回热量、用电加热、用再热盘管这些方法，还有没有别的办法能降低设备的输出能力？比如在上面加一个水盘管，用热水供暖系统的热水来重新加热空气。

But are there things, again, that you could do to de rate the equipment other than just adding heat back, running electric heat using a reheat coil, adding a water coil above it that runs hot water from the water heating system to reheat the air.

你甚至能想出一堆荒唐的办法来搞这些事。

You could do all kinds of silly things like that.

当然。

Sure.

你可以在设备里装一个更小的压缩机。

You could put a smaller compressor in the unit.

但在一栋新房子里，这么做靠谱吗？

Now, is that a good idea in a brand new house?

我不是会这么干的人。

That's not what I would do.

这活儿可不小。

It's a big job.

改动起来特别麻烦。

It's very invasive.

而且那时候，你的膨胀阀也会偏大。

And then also, at that point, your valve is gonna be oversized.

制冷剂的回气流速可能不够，导致回油不畅。

You're probably not gonna have now the return velocity for your refrigerant, and so your oil return's not gonna be what it should be.

这里面牵扯到好多因素，但最关键的是把风量调到最低，又不能让结露或结冰出问题。等设备要换的时候，我建议直接换小一点的，别拖着，趁现在就下决心改掉。

So there's all these different factors, but really making sure that you get your airflow dialed in as best you can, as low as you can without having issues of condensation or freezing, and then really suggesting that when that equipment is replaced that they downsize it, or go ahead and bite the bullet and downsize it now.

如果系统还比较新，你可以保留室内机、炉子或者风机盘管，只换一个新的室外机，这样成本会低一些，当然，这种做法也有风险。

And if there are still matches that exist because it's new enough that you can actually keep the air handler or furnace or fan coil in place and just put a new outdoor unit in, then that's a cheaper way of doing that if that's what you wanna do, but it's a tricky one.

设备选大了，完全是两头吃亏。

Oversized equipment is it's a lose lose.

设备更贵，还需要更大的风管，而且运行效果还差。

The equipment costs more, it requires bigger ductwork, and it just doesn't work well.

让设备容量和实际需求匹配，也就是BTU精准匹配，这非常重要，可惜很多房子建的时候设备都选得太大了。

Getting equipment right sized, BTU matching is really, really important, and unfortunately, there are a lot of houses that are built with oversized equipment.

但如果你现在面对的是一栋新建的房子，设备已经偏大，而房子其他方面又挺不错，那最糟糕的做法就是再进一步降低房间的热负荷。

But at this point, if you already have oversized equipment in a new house that already has a lot of other good features to it, the worst thing you can do is try to reduce the loads in the house even further.

在潮湿气候下，确实要控制对流带来的湿气，因为对流正是把湿气带进来的主因。

Now, convective loads, yes, in a humid climate, we wanna make sure that we're not getting more moisture with it, and convection is what carries moisture in with it.

所以对流负荷还是要控制，但如果你能多让一点阳光进来，就别再一味加厚保温层，那样反而会让问题更糟。

So we still wanna control convective loads, but if you can bring in a little extra sunlight, don't start overdoing insulation even more and making the problem worse.

这时候千万别往另一个极端走，奇怪的是，很多人偏偏就这么干。

At this point, don't go the other direction because that's strangely, people do that a lot.

他们遇到湿气问题，却反而试图进一步降低室内的显热负荷，结果让问题变得更糟。

They have moisture problems, and they start trying to remove additional sensible BTUs from the house, and it makes the problem worse.

我常提到一个案例，有个人卧室的湿度特别严重，是个超大的主卧，结果他加了更多保温材料，反而让情况更差。

I always talk about the case where somebody had a really big humidity problem in a bedroom, a huge master bedroom, and they added more insulation, which just makes the problem worse.

减少热负荷、缩小设备规模，同时分阶段进行，这对潮湿气候来说简直是完美搭配，对节能也很有帮助。

Again, reducing loads and reducing equipment size and doing them kind of staging so you can do that at the same time, that's a match made in heaven for humid climates, it's also great for power.

这才是真正的双赢。

That's your win win.

但如果你不具备这些条件，那就只能在各方面做妥协了。

But if you don't have that, then you're always making a compromise one way or another.

不过，像我之前说的，除湿机是项很棒的技术。

But like I said, dehumidifier is great technology.

我经常提到它。

You know I talk about it all the time.

给家里加装除湿机非常值得，只要安装得当，就能带来显著的改善。

It's a really great thing to add to a home, and when installed properly, can make a massive difference.

很遗憾，我这边也提供不了更多内容了。

Unfortunately, I don't have anything else to give you there.

好的。

Alright.

谢谢你的收听。

Thanks for listening.

下次再见，欢迎收听 HVAC 学院播客。

We'll talk to you next time on the HVAC school podcast.