The engineer wants 448K I calc 253K ??

Brad White_9

the biggest variable is the infiltration (1.0 ACH across what is it, an open warehouse?). That could be that number or half or even less depending on fenestration, general leakage, what have you.
Personally and absent better information, I would cut that in half. That gets the total down near the numbers you state. No mention of ventilation- is it an industrial fabrication or woodshop? Spray booth exhaust or dust collection?


The transmission methodology is sound (U x A x TD). The assumption of 33% for thermal bridging is reasonable, I have seen as high as 50%. ASHRAE says for metal stud construction to cut the R value in half essentially. Call that an OK for the engineer in this case.

The perimeter factors could be better defined (1.2 x TD x LF?) Is it an insulated perimeter for example.

Personally I take a 10% safety factor at most where I can preduct construction, maybe 15% in areas such as older construction where I have less verification and control. 20% seems too conservative in my experience.

The safety factors are each engineer's judgement expressed numerically- may even say where an engineer got burned in the past, like an indellible tattoo :)

The disconnect I get is, assuming his factors and assumptions are correct, he gets to a 373 MBH base load before safety factors, where is the leap to a 764 MBH boiler? That seems more like a typo than a design decision.

But the infiltration seems to be the root of the over-sizing in my opinion, absent any quantifiable make-up air loads for exhaust.

Just my opinion from the facts presented - it is his design and responsibility.

Brad

hot_rod

9000 square foot of shop

Here are his hand calcs, he wants a 764,000 Raypak, I want two- 150K Lochinvar nights.

I ran the calcs on Siggys program 233K3, and Watts Radiant Works.

PLUS the engineer has seven 100K unit heater in the space also.

Wish me luck I placing a call to him

hot rod

hot_rod

9000 square foot of shop

Here are his hand calcs, he wants a 764,000 Raypak, I want two- 150K Lochinvar nights.

I ran the calcs on Siggys program 233K, and Watts Radiant Works 253K.

PLUS the engineer has seven 100K unit heater in the space also. So the gasline needs to be sized for 1.4m loads!

Wish me luck I placing a call to him

hot rod

mitchb B

Been there too

Just did the same Idea. Eng want 2.4 Million, I calced it at 978,000, and I was generous as this is a retrofit.

We compromised with his 2.4 Million (because he is hard headed), and I used 12 x 200k modcons, sequential stage in control, automatic rotation of boilers, system split to 8 for heating to use outdoor reset, 4 for DHW (they use a LOT)

Splitting the system this way gave full modulation from 80k to 1.6 Million and even wear. same with the DHW.

He had them all parallelled and firing simultaneously.

We are going to ponitor the sitch with cycle counters and run time monitors and see who is right and who is out of the ball park.

hot_rod

thanks Brad

I am waiting to speak with him before I cry foul! I've not seen that 20% contingency figure before. That alone is 75K. That fudge seems odd with the 7 UH back-ups.

I also used a lower infiltration.

I do have a track record of 5 other buildings in this area + or - a few hundered square feet that heat fine with 1/2 that power, including some with additional overhead doors and exhaust systems for truck repair.

hot rod

Christian Egli_2

Are we talking about windows that open?

I just love the words Brad used. This thread calls for defenestration, the radical clean up one gets by tossing everything out the window.

I have no way of judging the numbers, of course, and I'm not even against oversizing the whole system, but the idea of having multiple boilers trumps the one-for-all scheme. It's better for modulation and it's better for saving face when loads don't match up as imagined.

If you can make the customer understand all this, it would be best to go way undersize on the initial machine, but pipe things for easy expansion. Then, whenever and if ever needed, a new additional boiler can be brought in.

At that point at least, fuel cost savings should taste pretty sweet. It depends on who the end user is, though.

Weezbo

that is not an uncommon description of the uncertainty principal



The principle that seems to often guide the material equipment selection is more than over sized and then doubled for redundancy with an alternative means of acquiring another 33% above that...

i like the cascade function of the Knight, for that reason,
(not to make more work for you) let me ask if you considered using three with the thought in mind to extend the life of the equipment.....

you could keep that card under your hat until the feathers reconform to the chicken ...that will sound like you have seen the error of your ways and the engineer will feel like he is not the bad guy because you have evidently seen the light *~/:)

...so, when he has his mind wrapped around that , suggest that you will get him accurate information on the actual gas sizing for the equipment,provided by the manufacturer ...:)

that way all is cool,you do a developed length etc. drop off a couple pieces of paper all is well.

not liking that idea (feathers still flying) then let me suggest you bump it up a notch and offer to have the owner first have the plan review of the mechanicals done by an outside agent...and split...

Brad White_9

Ok Ricardo, I mean Weezbo...

We know it is you. Come out with your hands off the Corinthian Leather. Step awaaaay from the Chrysler...

joel_19

leather

You'll take my vinyl roofed,landau bar, 8MPG Cordoba away when you pry my cold dead fingers from the Corinthian leather clad steering wheel...

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Weezbo

WHat? Who Me? *~/:)

Huh?

joel_19

and

If it's any help we just entered a 7k or so heavy equipment garrage in the RPA contest. 230K BTU or so . it's Real high big honkin doors they drive d-10's inside. They do only keep it 60f or so. but no problem at 5f in 40MPH wind.

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joel_19

Weezbo

right ,c'mon we all know Weezbo moved up from a Corvair to A Ford Pinto wagon.

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Weezbo

I Love this place:)

ok. Focus guys Hot Rod is making a good point. We have working experience with the original question. I am certain that the Vote from Corporate headquarters would be to LISTEN to his guidance in the selection of equipment and get the second opinion on the review.

the 700K unit heaters and the three inch gas line fund tickets could be spent elsewhere like a few bricks donated to the Wall.

Radiant Wizard

I think he's a little off

> Here are his hand calcs, he wants a 764,000

> Raypak, I want two- 150K Lochinvar nights.

>

> I

> ran the calcs on Siggys program 233K, and Watts

> Radiant Works 253K.

>

> PLUS the engineer has

> seven 100K unit heater in the space also. So the

> gasline needs to be sized for 1.4m loads!

>

> Wish

> me luck I placing a call to him

>

> hot rod

Radiant Wizard

I think he's a little off

I didn't get into the whole structure as I am not sure what you have but based on the wall btu loss he is a little off.

To calculate btu through an outside wall. Formula is

Ti - To divided by R-value = btu sqft

In this case I am assuming that you have 6,264 sqft of outside wall.

If R-Value is R-11 then that comes out to 6.36 btu sqft x 6,264 giving you a loss of 39,839 btus' through the wall.

If R-Value is R-19 then that comes out to 3.68 btu sqft x 6,264 giving you a loss of 23,051 btu's through the wall

Now you he didn't give any glass on the wall but you can use the same formula but take the sqft of glass away from the total outside wall calculate the wall then the glass and add them up.....

Darin Cook_5

Big Heatloss Numbers

We have a 5000 sq ft motorcycle showroom/repair shop (infloor radiant/Morton steel building) heating with a Munchkin T-80.
It is really such a waste to install all that extra boiler power. Driving costs up needlessly for the owner. I hope you can work it out with the engineer and go with your heatloss calcs.







Darin

[Deleted User]

The bottom line...

Who's the owner going to call if the building can't stay warm?

Is the building owner going to go back to the engineer of record if the building always only operates on one boiler and ask for a refund of all the unneccesary mechanicals associated with his overdesign?

I think we all know the answer to both of these questions. I know what I'd do if I were owner.

ME

Kal Row

ok - this is based on hard experiance...

heat loss calcs are a starting point only and not the end all be all they would have you believe, you are thinking radiant, and he is thinking AIR,

heating air to heat people is the worst way, first air is a lousy heat transfer medium, and because of wind chill discomfort , you have to overheat the air, this results in short cycling, his estimate is correct for instant heating of a cold warehouse without blowing cold air at people – this is gives us me major grief in NYC as they require a certain amount of air changes per hour in schools, forcing us into using air

– on the other hand, your radiant is sized for a system that should really be turned on in October and off in May, and only adjust the slab for outdoor temps – as a pilot I always get the weather forecasts in cryptic symbol format known as a TAF or Terminal Aerodrome Forecast – my dream is to have a RESET controller read those forecasts off the net and ramps the slab up or down 12hrs in advance – cause with direct reset – by the time the slab is ramped up – it’s midday and too hot – so it ramps down – and by the time it ‘s cooled – it’s midnight and too cold - this is why a high mass radiant only house simply doesn’t work, you can have slab sensors, indoor feedback, the works, been down that road many time – it’s never quite right if you live like in NYC where the weather turns 30 degrees on a dime, !!! you have to schedule it to death to even get close, so you run it cooler and then you need supplemental heating, and fresh air cooling, and being that there usually is central ac system anyway that’s where it goes – besides you need humidification in the winter regardless, so you anyway have to run the scorched air system , I am doing a Creston BAS system now – will let you know if it’s any better, also it’s a good idea to glue supplemental electric grid radiant right under the tiles all around in the bath – as that is useful even in the summer when the ac is drying the bathroom and you don’t want to freeze when you come out of the shower.

In the end it’s seems that cast iron radiators under windows where they usually are infrared-light visible to heat people – is the best way to go – and if you home run “pex” to each from a radiant manifold you can really balance a house – you can put a stat per room and even have an occupancy sensor per room switch on/off that radiator slot in the manifold – mosses of eny did a system like that in a whole condo – each with a laars mascot – that does DHW also, it works like a dream for peanuts, my neighbor’s daughter moved into one of them an she loves it… see pic – the only glitch was that on of the condo owners boxed it in so tight that the electronics – HO’s always cram our boiler rooms and in this case wanted to make it disappear completely