Short Cycle Oil Vs Gas

Walt_4

Howdy all. I was laying in bed this morning listening to my boiler short cycle and becan to wonder if there is not an economic reason to switch to gas for a part of the year.

Our system has a good number of zones (11) so, even though I have a 40 gal buffer in the primary loop, I'm not surprised to see it short cycle during this time of year. The system is designed with a primary loop with the zones pullng off of the loop and the boiler injecting into the loop. The boiler is a Buderus. I probably could have gone one size down in boiler and been OK. I've piped it so that I can add a backup boiler.

For controllers I have 2 Tekmar 369s as zone controls, 362 running a 4 way valve for radient and a 262 outdoor reset staging control. We have domestic water priority.

Here is my Q: Even though gas is a little bit more expensive here in Boston, wouldn't I save some money by putting in a slightly undersized modulating gas boiler as my backup (I am thinking a Trinity since my local supplier carries them and there are installers in the area that seem to know them). I could run it as the primary boiler in OCT and NOV. Then I wouldn't be blowing as much heat up the chimney during pre and post purge. During DEC, JAN and FEB, once we are out of stop and go traffic, I could switch to the rail dragster. The for MAR and APR I would go back to gas.

I'd like to have the backup boiler anyway, so doesn't this make sense? I'd appreciate your thoughts.

P.S. Happy Labor Day.....hope you all are taking the day off.

Firedragon_4

Gas in Boston is 40% higher,

wait until the dual fuel burners re-emerge, then you can switch back and forth, but not now.

Firedragon_4

BTW,

read this:
http://www.massoilheat.org/Saugusheatsoars.pdf

lchmb

opening that one

Can you imagion the look on someone's face when they opened that bill!!!! OH MY!!! Although I must admit something seem's way out of wack with that!!

Firedragon_4

Yeah, it's called;

fools rush in!

J.C.A._3

And sometimes.....

They win. Doesn't look so good now, EH?

I've spoken with customers that got the "free" boiler from the gas comany, and frankly, they aren't too impressed with the "savings" either. What goes around comes around, and if doing business in the northeast for the last 20 years has taught me a few lessons, one of them is that the prices reflect and will keep pace with each other.(usually with gas being a bit higher) The only difference is that the gas companies have to appear in front of a regulatory board to get their increases. Somehow, the increase manages to keep up with or surpass the same "cost analysis",(RE: profit margins, and sometimes WAY more in the long haul, because RARELY do the prices go DOWN after that) even when the price of oil seems to come down.
Like the addage goes..."If it seems to be too good to be true, it probably is". JMHO. Chris

Jack_21

Another way

Check www.ductlessheating.com and look at the Energysaver line of modulating gas fired direct vent wall furnaces. I would have the same problem you are having if I ran my boiler in the shoulder seasons. I use the Rinnai in the primary living area (Fam rm, Kitchen)and heat about 750-800 sq ft with the model 556WTA. I don't need a lot of heat at this time of the year and I won't light off the boiler until it gets cold. They are a very high quality product and they work extremely well. BTW, I represent them in the New England market. I've sold about 85-90K of them.

Bill Nye

On man's definition............

of short cycling may be different..........? What does it do ?

Why would changing fuels correct a control or piping issue? Don't mind me, I just have a different slant on things sometimes. Bad day so far.

hr

I'm with you Bill

Why and how is it short cycling? What kind of load do you have this time of year?

What's the boiler aquastat delta T? Should be able to plug your system into Siggys "Buffer Tank" sizer and come up with any run time combinations.

hot rod

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Walt_4

I'm missing something

Oil has about 149K btus per gallon. Our oil fired boiler is 86% efficient, based on our oil company's reading (which sounds correct to me). That means we get 128,140 btu's usable per gallon. We paid $1.59 a gallon for our last delivery. Based on that price we paid $.0000124 per usable Btu.

Gas has 100K btus per therm. A modulating Trinity Boiler would be 95% efficient (so the literature says). That gives us 95K usable btus per therm. According to KeySpans website, for our zip code we would pay about $1.25 per therm (that's my guess based on a blending of 1.37 for the first 30 therms and 1.19 after that). Based on that price we would pay $.0000132 per btu.

According to these numbers gas would cost us 106% of oil...or 6% more....not 40% more. I'm sure I'm missing something?

Unknown

Is the gas supply cost included ?

They list the gas supply and gas delivery cost separate on their bill , at least on Long Island . Do they list them separate on the website too ? The price sounds kind of low . My coworker uses gas for heat and his average cost was a little over $1.80 per therm in February .

Walt_4

Bill/Hotrod:

Thanks for the thoughts. The reason why I think using gas might help is only because there are modulating gas boilers and no modulating oil boilers that I know of.

I did not know of Siggy's sizer. The size of the buffer tank is one of the few things I guessed at.

One thing I did not anticipate when I designed the system was that my wife (two baby's in tow), would want the zone that our bedroom is on to be at 72 degrees. I tried to make the zones as even as possible. I don't recall the Btu requirement for this zone...I would guess about 25K btus. I'll have to dig out the calc.

The zone has two large radiators. I kept the large cast iron radiators even though I insulated the place with Icynene and put great storm windows on, in the hope that I could run cooler temps. This has been true. I think the Icynene insulation did more than I thought it would. The heat loss calc (done room by room) called for about 199K. I put in Buderus that has a 207 K output. It was firing 3 or 4 times an hour on the coldest Boston days, so I figured I was oversized. I downfired it with a smaller nozzle (actually, our oil guy did). It should be putting out about 171 K now. It did not have any trouble keeping the place toasty on the coldest day last winter.

This moring, I think it fired five of six times in an hour.

Where can I find Siggy's sizer? Sounds like good stuff.

I must admit, I picked the 40 gal Superstor because it had big inlets and outlets and because it was stocked locally. I should use a 400 gal and insulate the hell out of it....the boiler could fire for three houes in Sep and that would be if for the year!

Wayco Wayne_2

Modulating boiler sounds good

It will also give you redundancy if the other fails. You could also just add another buffer tank. WW

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Walt_4

Good question. I'll give them a call. I just looked at our last gas bill. You would need a PHd in accounting to figure out how much we are paying per therm. We only used 2 therms in Aug. We grill most of the summer. If you take the total by and divide by the therms.....it would be $6.35 a therm! Must have been how it worked for that school.

The heating rate is suposidly cheaper per therm than what we are paying now. We seldom hit the Keyspan minimum monthly charge since we heat and produce domestic hot water with oil.

Unknown

Yeah , I'm looking at my buddy's bill now

He let me borrow it to compare his gas price to oil . The price per therm for delivery drops the more you use , up to a point . The gas supply cost stays the same , no matter how much you use though . Let us know what the real cost is .

Walt_4

> Why and how is it short cycling? What kind of

> load do you have this time of year?

>

> What's the

> boiler aquastat delta T? Should be able to plug

> your system into Siggys "Buffer Tank" sizer and

> come up with any run time combinations.

>

> hot

> rod

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 144&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Walt_4

Delta T

It is 25. I just pushed it up to 40 to see if this makes a difference. the Tekmar controller also has an "Auto" setting that you can put it on. I haven't been able to understand what this might do, so I've never used it. I wonder if this would maximize run times?

hr

Best to store BTUs

in the chemical form when possible Converting oil to hot water that has to be pumped, insulated and stored is not always ideal. As you know modulating burners excel at matching load to load provider. But, your case a buffer size adjustment may be the best solution.

Try www.hydronicpros.com for a free demo download of the HDS. It will allow you to input all the various loads and toggle them on and off to show run times. Play with tank capacity, delta T and other variables to see the change in burner cycles. Just keep modifing until you get the burner cycles you feel comfortable with. Much easier and cheaper to play what ifs on a keyboard as opposes to a torch and tubing cutter!

Keep in mind the heat loss is ever changing. Addressing short cycling gets involved in the shoulder season where loads are small and infrequent. Reset control is another good option for hydronics to help them simmer down now


Make sure the wide delta T agrees with you boilers spec. Shouldn't be a problem with those cast iron/ rubber alloy Buderus units

hot rod

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Firedragon_4

No matter how much you BS this subject

a BTU, is a BTU, is a BTU and BTU per cost is what it's all about, FACT!

Modulate, step-fire it, crank it, yank it, pull on it til the cows come home and you still pay based on what you use and how cold it gets.

Two biggest mistakes made in the last few years by the utilities in Boston and their minions.
1. Thought it would never get cold again and 5600 degree days was just a fantasy.
2. Thought that a poorly running gas modulating burner (Saugus H.S. and others) would beat the pants off a properly setup oil two-stage and made ludicrous claims to a person that's now longer even around, hmmmmm???

Technology is great, but the hidden item in the Saugus H.S. case is that the modulator still isn't temperature compensating like it's supposed too, FACT!

Oh, BTW, all the Kings horses and all the King's men..................

Firedragon_4

Keep in mind that 'spikes' and 'seasonal fuel charges'

were made exempt by most states in the 1970's. They are the utilities 'best friends' and why you DON'T get what you pay for.

Constantin

Thanks for reaffirming my choice!

Firedragon, I originally specified a oil-based heating system when the oil prices were considerably lower than they are now. I still worry a bit whether I made the right choice going that route considering the wide swings in fuel prices this summer.

Then I remind myself that Keyspan gas costs $0.90 per therm just for delivery charges (and we know those cannot go down). I also feel better knowing that I will have a choice among oil delivery companies... and with 550 gallons of on-site fuel, supply disruptions are unlikely.

So, Oil it is for now. Furthermore, there is always the possibility of changing the head on the Vitola to gas if oil prices swing WAY out of control. However, I think we'll be dealing with some other issues by then.

Firedragon_4

The next generation of

'fuel burners' will be able to go gas-oil. Minituraziation and technology is now here for that. You can buy and hold a four step mod motor with controller in the 'palm' of your hand from people like Belimo, Siemens and Maxon. My humble opinion is that this will turn the tide against the utilities.

In Europe oil is much stronger and generally more popular than gas due to 'advanced technologies'. It's also that way in the Far East and I just saw an oil furnace from Korea that fires 0.15 gph.

Keep in mind though that service 'over there' is done by factory employed techs, not independents that seem determined to destroy their own businesses. That's not true of all, as these boards attest to, but oh baby, do the bad make us all look bad!

The good news is that faulty materials are about the only thing that make the 'bad boys' look good. There's too much live beta testing going on, we need 'proven materials' a ton more factual education and less sham, all around, JMO!

You did the right thing for all the right reasons and didn't go where salesmen lead 'the sheep'. Congratulations for using your head! :-)

Walt_4

BTU Storage

Thanks for all of the replys...I'm going to toy around with the buffer tank idea for a bit. Still don't have a straight answer as to how much I would pay for per therm of gas if I used it for heating.

Bill NTSG

Walt?

On that real small zone, does the t-stat call the burner On , on a call for heat? Like a switching relay that turns the pump on and starts the burner??

If so, maybe you could disable the call for buner function and just start the pump? Hard to say w/o seeing it but a zone that uses 1/8 of the boiler capacity will tend to short cycle.

Are you doing any continuous circulation w/reset or is this all on/off with t-stats?

4 to 5 starts per hour is "not" really short cycling.

Walt_4

RTUs

Bill:

The zone is on an RTU. The RTU goes to a Tekmar 369 zone controller. It is on outdoor reset. Our last boiler was twice the size as this one (in terms of output). That thing REALLY short cycled...like a rail dragster in stop and go traffic. I guess I just assumed 4 or 5 starts was too much. It may be a little higher than that some times. Any thoughts on what a good target for cycles per hour is?

Thank for you response.

Best regards,

Walt

S Davis

Auto Differential

The auto differential setting in the 262 is for helping with short cycling problems, it will pick the best differential based on boiler load and would probably help with your short cycling issue.

S Davis


Apex Radiant Heating

Walt_4

Auto Diff

Thanks. I'll give it a shot.

Constantin

Oil vs. Gas Differential

Walt, the thing to keep in mind is that Oil and Gas prices fluctuate relative to each other even though they generally rise and fall in tandem.

The 40% price differential was correct in May (when I last did an analysis) as heating oil could be had at $1.15 a gallon and gas was $1.39 a therm with a heating plan (keyspan, Arlington, MA).

Since then, the price of oil has gone up 50% but gas prices have held steady. Hence, there is less of a difference right now. Yet historically, the Boston area has always been better served by oil than gas in terms of pricing. The reasons are many-fold, including:

• no natural gas supplies in the area, it's either piped in from Appalachia/Texas or shipped in via LNG tankers (Everett). I hear we may now get some gas from Canada, too...
• Increasing use of gas throughout NE. The NE was one of the few holdouts for oil heat until recently. Hence, the good infrastructure up here for servicing and supplying oil heat. Now that gas demand is soaring, gas "supplies" will become constrained. Yet, the gas companies do not insist on installing very efficient equipment when they provide "switch" coupons to prospective customers. This is an irresponsible game they play with the regulators to increase demand, IMHO.
• Gas supply constraints will only get worse as power plant sites in the region are "upgraded" to run on gas instead of oil or coal. Either that or Boston turns into NYC and becomes even more heavily dependent on outside energy suppliers like Hydro-Quebec, etc. Even there, the MA area is facing transfer constraints.

I decided to install a new oil boiler I believe that nothing in the current conditions suggests that the gas prices will not return to their traditionally higher price points in this region vis-

Walt_4

Good Thoughts

Thanks for these useful thoughts. Some of this same reasoning went into our decision to use oil as our our main fuel. This boiler would be our backup...and possibly run in the beginning and end of season when we would get the most benifit from a modulating boiler. I'm still on the fence, since I also get some comfort from the idea of being able to switch fuels at the flip of a switch.