Why is my boiler hot all summer with an indirect tank?

MattyO

Moved into my house in May and have used about 150gal of oil over summer. Only 2 people in the house and usually shower at the gym, so hardly any hot water usage. No heating during that time either. So it seems alot to just keep the water hot.



We have a 5 year old Burnham V8 boiler attached to a 50gal Alliance Indirect tank.



I have noticed that the boiler comes on about 10 times a day all summer to just keep the boiler temperature at 170deg F.



Can this boiler cold start and only come on when the indirect tank needs it?

Can I adjust the low temperature down?



Appreciate any assistance.



Matt

JohnNY

It was the installer's choice.

They've set up your boiler to maintain a minimum internal temperature to be "ready" to make hot water at all times. It's the old way of doing things. Not the good way.



Where are you located? Someone's got to make a simple wiring change.

icesailor

Old Ways/Good Ways:

You need to post a photo of the front of the boiler to see what kind of control you have on it. If there is no tank less heater coil on it, and the indirect with zone valves an end switch may be stuck closed on a zone valve keeping the boiler on high limit when it should be off. It is better that the boiler be maintained with some temperature. A minimum of 140 degrees to stop cold condensation in the flue gasses.

If you take the cover off the temperature controller on the front of the boiler and there is only a round wheel that only turns. and not two red plastic switch levers marked "HI" and "LO", it is more likely that something is making the boiler controls think that there is a call for heat when in fact, there  isn't.

What is the temperature setting in the indirect water heater? Try 130 degrees.

How do you know that you have used 150 gallons of oil since may? Unless you have filled the tank and it was last filled in May, you can't go by the gauge in the tank. That basically tells you that there is oil in it. When the red or white mark in the gauge glass is as far down as it will go, it is going to run out of oil. And they never fill it to the top. 275 Gallon oil tanks are only filled to 240  gallons or less when new. They need room for expansion.

Robert O'Brien

Long Island?

More than likely!

gennady

Differential

Boiler has to be hot to prevent condensation during hot water call in summer. Just set differential on the boiler aquastat to 20-25 F. On 162 , off 180F. Install mixing valve on indirect, limit domestic hot water temperature according local code. Set aquastat on indirect on140F off 160F. Install automatic vent damper on boiler flue, interlock it with boiler. Check with chimney company condition of the flue.

JohnNY

Cold start.

When using an indirect, on a call for DHW, the pump kicks on and preheats the boiler with energy from the tank, then the flame comes on. I've been doing regular annual follow up maintenance on, I don't know, a hundred set ups like this over the past 10-20 years in addition to the numerous one-offs we service and have yet to see one that shows evidence of condensing flue gasses.



I'm not saying anyone's not right, I'm saying that's my experience. It may be because I tend to install indirects in places where there is a more frequent DHW demand (i.e. multi-families and larger homes with cleaning and laundry staffs). Also, I tend to keep my differentials wide to increase run time.

And I work with gas.



That's my story.

Zman

Aquastat

The aguastat the are taking about has an addition temp to keep the boiler from ever going below the lower setpoint. It is designed for tankless coils. 

MattyO1

Reply

I have had problems getting in to reply, so have set up 2nd account... We are in Stamford, CT.



Thanks for the responses. I attach photos.



I've tried turning down the "Lo" setting to 140deg, but the dials won't move. Don't want to force and break something. "DIFF" moves OK. Am I missing something??



The "Hi" is set at 180deg, "Lo" at 160deg and Diff at 25deg.



For the small amount of hot water we use, it seems crazy for the boiler to come on all the time. This came to my attention when we got the oil topped up this week. Works out a gallon a day for maybe one shower a day.

MattyO1

Reply

So do you think this aquastat is not the right one for an indirect tank?

MattyO1

Stuck dials

Thanks BC. I can understand why you might want to have the boiler hot and ready with a coil, so you don't have to wait for everything to warm up from ambient when you want some hot water.



But isn't that why we have an indirect tank? This all seems wrong to me.



How about my dials that won't turn? Anyone have a suggestion there?

JohnNY

Here ya go.

Taco SR501 relay

Capeesh or no?

JohnNY

This way...

The aquastat sits in a boiler tapping and only closes TT on the boiler on a call for heat from the indirect. From there, it allows the boiler to run until it reaches its setting. I like 170°. It breaks on rise.

JohnNY

I'm dead against...

....keeping the boiler warm solely to prevent condensation.



It's a far bigger problem in theory than it is in practice. I promise you that.



Eventually the boiler's going to die. Why commit to wasting fuel maintaining boiler temperature for the entire life of the boiler.



Again, come see my boiler/indirect combos after 5, 10, 15 years. Wired like this. Cold start every morning. No problem. No a shred of evidence of anything but normal flue condensation.



As for the pre-heating, my point is that the water being circulated through the coil and into the boiler has a reverse effect and warms the boiler water quickly. It's as if the indirect were the heat source until the boiler temp quickly equalizes, then surpasses the indirect and the boiler then becomes the heat source and transfers energy to the domestic water.

icesailor

Condensate/Cleaning:

If someone hadn't needed my camera more than I, I could have shown you what happens when they condense.



The "Delay" you notice is with the more advanced "Pre-Purge/Post Purge controls. The control gets the call. The control does a self check while the pump runs, sucking heat from the indirect back into the cold boiler, to waste up the chimney. The "Pre-Purge" starts, 15 to 30 seconds, and the solenoid opens with the burner starting. It isn't planned to be some exceptional idea on oil burning equipment and energy savings. Its just what it is.



Every Weil-McLain WGO cold start boiler run on oil for a year, needed a soot saw to just get through between the sections. Between the pins took a piece of 1/4" or 5/16" threaded rod on a file holder handle. Sometimes, you can't get it all out. If you've never opened the front to clean out the floor, you've never cleaned one properly. I've put a florescent trouble light in the bottom and not seen the light through the Kibbles and Bits.



Some don't even bother to try to clean them. They just condemn a perfectly good dirty boiler and sell them a new cheap one.

icesailor

Cold Start Aquastats:

The Cold Start Aquastat is just a high limit with a TT connection to a relay to start the burner and circulator. When it gets powered up, it runs. When it hits the set point, it stops. 8124? I can't remember numbers.

icesailor

Flue Gasses:

I hate to **** any balloons but any flue oil boiler with internal water temperatures that are under 140 degrees will condense water and make this magnificent slurry that grows kibbles and bits inside the boiler. It will form on any cold surface until the boiler is warm.

A well maintained cast iron boiler like a W-M WGO 3 or 4, will go from room temperature in the boiler to 140 degree boiler temperature with the circulators stopped, within 5 minutes.

The piping/wiring scheme that you suggest is a real energy sucker when you use multiple zones and an Indirect, and don't use the Priority Control because because if the indirect tank is hot and both a cold zone and hot water tank start together, a large portion of the already heated and stored heat will be lost to the boiler and heat piping zone.

How much do you save by running it cold start and not warm start for the summer?

Most spend more on beer than they will ever save.

icesailor

120 * Condensation:

Well, I'll be darned. The laws of weather and physics changed when I wasn't paying attention.



There's an easier way to do what you want. I've never seen anyone do it, but it might work for you.



Good Luck.



What's that freezing temperature of water again? -40 degrees?

JohnNY

Yeah.

I don't use multiple zones with an indirect on a steam boiler. Who does?

And there's no way anyone's going to tell me that constantly maintaining 140°f in a cast iron atmospheric steam boiler doesn't waste a lot more energy than going cold start.



What are you spending on fuel to avoid such a small amount of condensation that may or may not happen sometimes?

Bob Bona_4

simple

Swap out the control for a cold start version. (It's not technically cold--the indirect/ambient temps keep things warm). Then, assess the circulator control strategy to see if indirect pump is prioritized. Then, investigate an outdoor reset control to further save fuel.



We are in Norwalk and work with these all time. Contact me if you need more assistance.

Bob Bona_4

exactly

What John said.

Bob Bona_4

yes it

Is that simple.



you are overthinking it bc. I can tell by your posts you don't work in the field. You are free to have your thoughts, Thousands of trouble free set ups like this between John NY and myself and countless others constitute real world success.

Robert O'Brien

John NY and Bob Bona

Are both absolutely correct. In reality it never really cold starts with an indirect, the standby loss of the indirect as well as the few domestic calls per day really don't allow it. To those who dissent,how do you explain the Energy Kinetics System 2000 that actually does cold start every time?  They work just fine!

icesailor

Well Said: (Bob Bona)

Well Said.

He must have seen or read something that got his shekel saving mind into a conundrum.

And there's no possibility that anyone here knows what were talking about. Like if you take what I do, and use storage tanks on oil boilers with tankless water coils, have the High Limit set to 160 degrees which heats the house just fine in the coldest of cold, and set the "LO"/Operating control to 140 degrees to stop internal boiler condensation, and the water heater set to 125 degrees, he equates any circulator running the same as the burner running, sucking up vast amounts of fuel/money.

And he asks how interesting it would be if any one had any idea about how long things run (save money).

Well, I know how MINE worked. In the AM, after showering and hot water usage, I'd go down into my cellar/shop. The DHW circulator pump was running but not the boiler. Because it was sucking stored latent heat in the 160 degree boiler and transferring it to the 125 degree storage tank. Once the storage tank was satisfied, the DHW pump shut off. I've worked on projects the whole day on a weekend and the burner never, not once came on and ran. Of course, all my clock thermostats were down to 58 or were off in unused zones. 4:30 PM, zones would call and the burner would start, and cycle because I got home around 6:00 PM. But there was no hot water usage.

At my ancient age, I've come to realize that some are born with a switch into their brain that is operated by the sound of a burner running. It sets off the center of the brain that controls anxiety and causes an anxiety attack. The invisible sound of cash being extracted from their wallets. Funny how that same switch doesn't set off an anxiety attack when at Starbucks getting a black Venti French Roast and a stale pastry.



Then, DIY'ers who come to a professional forum where the members are mostly willing to share information with DIY'er. And a DIY'er comes here and starts telling the experienced Pro's how to do things? There's a DIY board on the Internets that I occasionally look at. I look at it to remind me what Steamhead always reminds me/us. "You Can't Fix Stupid".

Sooner or later, some have to give up ALL hope of a better yesterday.

Bob Bona_4

Actually,

Advising someone to stick thier fingers in a high voltage control and alter it's wiring-a critical safety limit control to boot- is what's unprofessional.



The millions of OEM boilers with no tankless coils shipped with cold start aquastats are....?

icesailor

10 Hours:

 "" Do you believe that it can never make it say 10 hours without a call? ""



In MY own personal experience, 10 hours is a piece of cake. If a 50 gallon storage tank or indirect makes a call and the boiler goes to high limit, you must think that the burner goes and runs the entire time the circulator runs. It shuts off on high limit.



 "" Where are the cold start boilers that Ice is referring to that plug themselves ever year? ""

You must not clean oil boilers. Or if you do, they are like some of the ones I see that were cleaned and serviced in less than an hour and it takes me 3 hours to get them satisfactorily clean again. If they can be cleaned.



What you see as "normal" debris, I see as the result and remains of cold start condensation. I've seen complete, fairly new, working boilers ripped out and replaced because someone was too lazy to clean it, or someone else had been too lazy to clean it properly. Steamhead posted some photos here back a while ago of some of the prize gems he's found that were well serviced that he had to rip out. Bet a Starbucks black Venti that most  were on steam boilers with a DHW coil and a wet leg that just called the burner to run like a thermostat and used some sort of high limit water control to stop the burner. Steam Boilers are cold start.

icesailor

System 2000's:

Actually, MOST of them work just fine. Some do NOT for periods of the year. Like the few I saw, undersized because the installer believed all the hype about how efficient they are and was clueless about heat loss. He installed one in a big old un-insulated 3 story house that had been converted from gravity years ago. He added a zone to the third floor. The burner/boiler was rated to fire at well below 1 GPH. On a good day in January, the system temperature might get to 140 degrees. The burner never stopped while I was there. If you shut off the new third floor zone. The house was for sale. I was asked to look at it by a customer of mine who was interested in buying it. The owners kept the heat on all winter at "low" in case they might come down for a visit. The GC friend that was doing the structural agreed, the boiler was way too small.



System 2000's are triple pass and heavily insulated. Because they are smooth, there's less to condensate on. Like massive amounts of pins that cause turbulence, slow down the flue gasses and allow the heat to be absorbed by the pins. Triple pass boilers do it by having large amounts of smooth passageways to give enough restriction for good heat absorption.

I look at it like sailboat racing in a big fleet. The Start is the only time everyone is together. Having clear air is critical at the start. If you haven't muscled yourself into a nice front row position so you have clear air up to the first weather mark, you just won't do well. If you get stuck behind the first row, the air will be so disturbed and bent that you will be the slowest boat in the fleet until you can tack over and get into some clear air. Those pins in a boiler are like all that restriction. Or standing in a forest of trees on a windy day. It might be blowing 30 over the top of the trees, but its just a light breeze on the ground through the trees.

Cold Start soot flakes are different from warm start flakes. Ask anyone that knows how to use a soot saw and Soot Master Vacuum.

Bob Bona_4

yep

At the point now where I'm changing out boilers and ac I put in in 1990. Year after year of routine services and cleanings tell the tale.

Bob Bona_4

i see

Crud in heat only boilers, and boilers hooked to high mass systems with no bypass or three way valve protection. Indirects tend to cycle things enough to keep things dry and cleaner inside. Add an old damp basement to a steel or CI boiler thats been off for the summer and let the fun begin!

ced48

I Get 10 Hours With

a 10 degree differential on my little 20 gallon HTP-I just kind of figured how much propane I have used since the first of May, maybe 25 gallons! I really do love my little Loch 55-

Zman

Condensing

If you are trying to reduce condensing the issue has little to do with hot start vs cold start. In either case some condensing will occur at the beginning of the cycle.The important part is to not have the boiler shut down with an wet acidic flue and heat exchanger.

Modern indirect heaters have a ton of heat exchanger surface area. If they are piped directly to a non-condensing boiler with no boiler protection, it is impossible for the boiler to reach it's operating temp and will turn off  wet every cycle. Every system will seek to find to find thermal equilibrium, it doesn't matter how you set the controls, if it designed incorrectly you will condense, Hot or Cold start.



Personally, I think hot start controls and tankless coils are an incredible waste of energy with little or no benefit.



Carl

Zman

Exactly

The vast majority of boilers used for heat cold start several times a day  with no issues.The emitters, usually baseboards heat up quickly and the on/off cycles from the room t-stats are usually long enough so the boiler runs a good long time in the non condensing zone.

With an incorrectly designed indirect setup, that never happens. The problem is made worse by tank aquastats with tight on/off differentials.



Carl

Zman

Condensing

You really cannot tell using math without more info and a considerable amount of brain damage. The amount of surface area in the indirect exchanger and the thickness of the metal as well as a few other factors determine the exchange rate. If the exchanger is too efficient compared to the output of the boiler. When thermal equilibrium is achieved the boiler can still condense. The manufacture knows all these numbers I did not see it in the literature.

With an existing system, if the boiler is coming out of condensing mode (130 + return) well before the end of the cycle, the flue and exchanger will dry out and there will be little or no risk of damage. I don't see how a hot start vs a cold start make any difference.



Setting the hot water heater temps higher and the differential wider certainly will help as the as the difference in water temp between the two sides of the exchanger will be constant.The temp of the domestic water can vary quite a bit but should always finish the cycle at the same temp.



With an inexpensive temp gauge you should be able to see what's going on and make necessary adjustments



Carl

Bob Bona_4

yup

That's the ticket. Most of the time I see undersized pumps and piping driving the indirects anyway so the boiler bounces off high limit. I can live with a 30 degree delta in indirect land

Gordy

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