Indirects or Turbomax - Any Experiences?

jp_2

nrt

3. Finally I do not agree that the tank at 180 uses any more energy IF it is better insulated than the 140 tank.

rob, it takes more energy to get to 180 than 140. the higher the temp, the higher the total system losses and the higher the flue temp, but I know you know that. therefore it does use more energy.

Unknown

Really?

What temp is the boiler running at with the 140 degree tank?

markotah

Glen: Indirect Comparison

I have an excel sheet that does the calculations similar to yours and can email it to you. Based on 100K BTU 40* in and 110*supply in 10 min you will get about 46 gal from a T23 and continiously draw at 2.7 gpm.
Take a 50 gal conventional indirect with the same parameters and and you will get about the same. The big difference is with the Turbomax is after the peak the shower is still useable and you can't do that with a conventional indirect. I like using the T-33 for most applications because of the additonal thermal storage.
Also you don't seem to factor the benefit of thermal storage and how it helps to pick up temp in your boiler.

Glenn Sossin_2

Rob Normally

when I am specifying equipment with a low output boiler, I will suggest 50, 65 gallon indirect or more, depending on expected demand loads to compensate for the low btu input.

Following this logic, specifying a larger Turbomax will not have an measurable effect on water delivery, but certainly will affect the cash outlay. Buying a larger indirect will provide more usable hot water, but will not affect the wallet as much as a larger Turbomax would.

I agree, the Turbomax can deliver more heat transfer for a given temp drop due to large surface area, but it sounds like you are ignoring that fact that the conventional indirect has an heat changer surface too. For example, I don't know the numbers, but I'm sure an SM40 can absorb just as much heat energy as the Turbomax 23 with 100,000 btu input.....

I just checked sqft of surface area values. The Turbomax 23 has 19.6 sqft of area. The SM-40 has 16 sqft. On this size, and probably all the sizes going upwards, the Turbomax has an advantage in heat transfer - no dispute.

I have a job now, 4500 sqft house, super insulated, Marvin hurricane windows, we calculated a heat loss around 40,000 btu's. We are supplying a PS-110 Prestige. He has a shower with a rain forest head - and body sprays. His son gets up to take a shower before work the same time as him. Real world example, real situation where you can't use a Turbomax no matter what size it is.

He is looking at a 120 gal indirect, 2 Nortiz N0751 instantaneous heaters or 1 Noritz N0931. He is going to decide in the next day or so. We gave him the facts, he is making the decision.

But, in looking back at this whole post, we veered away from the original intent of my comment - my opinion, 2 simultaneous draws was a marginal scenario for a small boiler with a Turbomax. Que sera sera

Glenn Sossin_2

Mark again, you are citing

a boiler with a larger btu value then I was commenting on. I based my comments on a boiler size of 100,000 btu input or less. You refer to a boiler with a net rating of 100,000 btu's, probably an input closer to 140,000 btu's.

I understand and agree with your commments, its just that your using a boiler 30 - 40 % larger than I specified in my comment. Its interesting all the banter this has created but I don't think, throughout this whole post, we were comparing apples to apples.

I would like to see your spreadsheet. I've collected quite a few great charts, graphs, pictures off this site. I've posted alot as well. Yes, please email that to me.

Thanks

Glenn

markotah

Apples and Oranges

Your comparison and assumption of heat exchange being the same from SM-40 @16 sq' and T23 @ 19sq'is way off base. Heat exchange area is only part of the equation. The copper exchanger in Turbomax has a 17 times better rate of exchange than Stainless Steel. The diffuser in Turbomax also creates turbulence (wind chill as example) which is why it can exchange so effiectly. Basic physics.
From the literature you will see SM-40 max BTU 112,000. T-23 300,000!
Caution: Typically when selecting a unit you want a max of 5 gpm per coil to avoid a high pressure drop. T-23 3 coils x 5 gpm max flow 15 gpm. I personally try to stay at 3 gpm max flow per coil or 9 gpm. You only want to design at max if you are supplying (or re-charging) a storage tank or you will have to much pressure drop.
As far as the job you are working on now based on the BTU load I would agree the Tankless to be a better option. In my experience with Rheem Tankless Units it is better to use 2- RTG74 DV units or the 2- Noritz instead of one.
Why? The two units will give you a little bit better flow rate,have reduntancy should one unit ever go out, and are a don't require an ASME rating because they are under 200K. Your customer would also be able to replace a single unit at far less cost when it does come to replacement time. The only down side is two vent penetrations.

PTN

Mark Bruder,

Could you talk a little more about the thermal storage part of turbomax and how it helps to pick up temps in the boiler. i would like to get a better understanding of how this specifically benefits the 133K/156K boiler example.

Thanks.

jp_2

?

Unknown

my point there jp is that you are going to run the boiler at a high temperature with a regular indirect too. There might be some additional loss at the top end of the curve with a higher storage temp, but it's not like you're running the boiler at 140 with a standard indirect. You're still running it at high temp.

Unknown

I"m not at all saying the turbomax's output is necessary or even cost effective in every situation.

But, under no equivalent circumstance will it provide less hot water than an equivalent indirect, which is what you were insinuating in some of your earlier posts. That is the distilled point of my posts.

If you would rather have efficiency with lower storage temps rather than more stored BTUs, then the turbomax would allow for the lowest boiler temp for the same amount of transfer.

In short, it outperforms any equivalent size indirect I've seen. Whether it output performs ENOUGH to warrant its cost... that is an entirely different question and one I'll grant you any way you want to go with it, as long as you're using real info and not thinking the substitute indirect will outperform the turbomax AND save money... it won't. not ever.


and edit: we match large turbomaxes with 12 GPM spa showers and a secondary shower all the time. You start at about 350,000 kBTUs of boiler plant for a continuous draw and size up from there for additional loads. The turbomaxes at the high end can take up to 600k or so... that's a whole lotta flow. Of course, you need huge boilers, but hey, if they are going to want 15 GPM of hot water that requires some heat output. Might as well meet it efficiently at least, so that therm a day in the shower doesn't escalate even further...

Glenn E Sossin

Thanks for the Spread Sheet

As far as the heat exhange surface area, at first I didn't think there was a big difference, then in the next paragraph, I acknowledged there was.

As far as apples and oranges, I was referring to the real world performance with a small btu boiler and the Ergomax versus a 40 gal indirect.

The current job that I referred to is a good example of what I was trying to get at. We have a small boiler and a high draw - the turbomax, no matter what size won't work here.

However, as we were looking at another option, the idea of a PS-399 with Turbomax 43 was considered. Then I would use the Turbommax as a thermal buffer tank for the low radiant btu loads. It would fill his 10gpm flow requirement.

Imagine, this guy installs an 8gpm showerhead in his shower. Its the only head in it.

We considered the 2 N-0751 units because they also would give him the 10gpm, a simple cable connects the two units together and they know about each other, gives him floor space in the mechanical room. It would be my choice, but he doesn't want penetrations through the side of the house. Thats why I came up with the 399 and turbomax. But, on heat demands this boiler is 10 times what he needs, so I was thinking of piping the primary loop right through the Turbomax. This way on small heat loads,the boiler may not have to fire, and if it did, the heat could be absorbed by the mass in the Turbomax.

Anyway, I am surprised about the 17 times better exchange rate between Stainless and Copper. You sure about that ?? Seems an awfully big difference. Whats your source for that info?

markotah

Thermal Storage

It is easier to maintain energy that to bring it from a dead stop. If moving a vehicle more energy is consumed to get it moving but it far easier to maintain motion after that. The same rules of physics hold true with heating which is why you don't want to setback t-stat more than 10*. It takes much more energy to bring it back offsetting any savings you might have seen. The answer to your question: If you have a boiler that has been idle since the morning and it now has to fire from ambient temp. The thermal mass in the Turbomax which has maintained it temp helps to raise the boiler temp much faster. This is more of a benefit with lower water content boilers. Example:A boiler with a 10 gal capacity and a T33 that holds 36 gallons. Additionally any chance of condensing is eliminated.

markotah

Thanks for the spreadsheet

First be careful when looking at Tankless Units. You must look at the worst case senerio. In NE for example 40* incoming and a 75* rise (115*supply temp)you will only see about 4.3 gpm each unit. I understand the h/o not wanting the vents exposed as I run into this once and a while myself. As far as the "17 times greater rate of exchange compared to S/S" it is in the literature so it must be true. All kidding aside there are enineering manuals that publish thermal conductivity of various materials. If you are looking for more than that I suggest an email to Thermo 2000 directly.

jp_2

stainless vs copper no difference!!!!!

mark was right, copper conducts heat far better than stainless.

problem is, stainless steel conducts heat about 25 times faster than water. so heat move through water way slower than stainless steel, oh thats a problem.....

so, we are not concerned about thin walled tubing of 1mm or 1.5mm thick. we are more worried about 'getting' the heat from the water thats 6 or 8 inches away from the tubing!!!!!!

therefore surface area will be far more important than being copper or stainless steel.

so, that comment is more of a sales pitch

added: what I want to know, is it pure copper or copper alloy? that makes a big difference in thermal conductivity, add 10% aluminum and the conductivity drops by a factor of 4.

markotah

stainless vs copper no difference!!!!!

The material is 1/2 od type L copper as used in refrigeration. If you are just radiating heating your right about exchange. The difference is when yo add movement over the coils breaking the thermal narrier. Think back to when you were a kid and it was cold out. If you put your hands in hot water after a couple of seconds it didn't feel as hot but move your hands and break the "thermal barrier" and it was hot again. This is why the Turbomax can eat all those BTU'S. If you don't believe me look at other indirects and look at what the max BTU they can handle.

jp_2

flowing water

how is the water always moving in the turbo max?

Unknown

you've got a pump running on one side of the exchanger and flow through the coils on the other side. right?

If you don't have a pump running, then you are not calling for heat and the whole issue is moot.

jp_2

big tank

rob, if you have a 60 gallon it has to drop X degrees before calling the boiler to recharge temp, so any draw under that amount of hot water won't circulate tank water? correct?

Unknown

Sure, if you are not under any real need for real amounts of hot water, then fine, your exchange rate on any indirect will be bottlenecked by the water's conductivity AND the severity of any convective current it sets up.

Go ahead, in that case, get an indirect with 120 gallons of storage per showerhead to coast through a 15 minute demand on a 20 degree tank temperature drop without having to exchange heat, and if you like, you can make the exchanger out of PEX. Or brick. Or wood. whatever you like! cause all it will have to do is eventually recharge the tank, with turbulent water, without worrying about that "peak demand" you're presumably sizing the tank for. Assuming, of course, that no one will need hot water after that shower for awhile.

Assume you are sizing your indirect to actually exchange heat here in the real world, though, and you can probably assume that the water is turbulent during most of a heat demand. You might consider that there is a reason why exchangers are not made out of materials less conductive than water, right? Perhaps because... it effects the ability of the tank to exchange heat?

I mean... that might be a crazy idea, but what can I say, I'm a crazy guy!

jp_2

real world

keep in mind rob, the "real world" is all the above !

Jed_2

Actually

The copper coils in the Turbomax tanks are "m" copper tubing!

Jed

jp_2

L M ???

but what does that mean alloy wise?

added: Ok, I see they are both pretty much pure copper.