Gas HW Boiler constantly cycling on cold days to keep temp.

riclyo

I Live in an area that has been seeing 20F days consistently. My boiler usually doesn’t have too much problem keeping up until it starts to drop below 32.

The house is about 800 sq ft. and has r13 in the walls and r32 in ceiling vapor barrier is in place. I think the heat loss is due to the windows which are not very good and are pretty large.

I have a HW gas boiler rated at 112,000 BTU with a ¾” pex loop baseboard setup. The baseboards a cheap contractor grade crap and I am contemplating upgrading the baseboards to higher output based on some online calcs I have been using.

An odd thing I noticed when I cleaned my boiler in spring is the output gas pressure was turned down from the suggested pressure listed on the nameplate. I can only assume this occurred by the hands of the previous person who serviced it.

I am looking for the most cost effective solution to my problem and appreciate the help.

Gordy

Short cycling of the boiler is what happens when the boiler is to large for the load. Yet your initial post indicates the heating system can't keep up with temps below 32?

The boiler is plenty big for 800 SF. Much oversized. You indicate the btu input has been changed? How do you know if this was done on purpose? Did you do a combustion test.

Gordy

How was this answered?

riclyo

Yes I agree but am no expert that the boiler is way to large but according to individual room heat loss calcs the baseboards are also insufficient.

How does furniture placement effect baseboard outputs?

I measured gas output pressure with a monometer, not BTU input. Again not being an expert I assume/guess this was done because boiler is larger than needed.

Gordy

In sufficient emitter will cause the boiler to cycle it can't get rid of the Btus it's making. Yes furniture blocking baseboards impedes their output. They depend on convection currents to disperse the heat. So that does not help. Also have they been cleaned?

riclyo

I pretty good about keeping my baseboards clean. And according to some calcs I've done the baseboards are emitting only about half the btu's required for the heat loss of the room.

I am also looking at interior storms as a cost effective way to solve my cold winter heating issues.

But if install the correct baseboard with a higher btu output how big of a problem is the oversized boiler going to be?

Also is there any piping changes that can be made to improve my situation.

Thanks

Gordy

What's the boiler aquastat set at?

Harvey Ramer

You should try to oversize your emitters to match your boiler output. They have some high output baseboard that will make this possible. So what you do is figure the heatloss for each room and size the emitter. Then adjust the emitter sizes proportionally upward till you realize the boilers output. Your distribution piping will have to be taken into account as well and perhaps adjusted.

That will prevent the boiler from short cycling and allow more efficient operation and comfort, especially with the use of ODR.

The other way you can do it is to size the emitters to the rooms' respective heatloads and then add a buffer tank to compensate for the oversized boiler.

riclyo

Gordy
Aquastat is set at 140 (lowest possible) and 170 ish (due to any higher gets noisy.

Harvey
So if the boiler is almost twice the size (my inexperienced boiler sizing is based on what is recommended for my 800 sq ft house) I would need to double the recommended output of the baseboard for heat loss of each room? (round abouts of course)
That would seem costly is such a small space

Even though the boiler seems to be in good working order would the cost effective steps be to increase baseboard output then get a smaller boiler without changing the exiting piping.

I noticed in general if all room doors are left open things seem a little more balanced but since people in the house value privacy and zone control seems a bit crazy for such a small house what are other options...

Thanks

Gordy

You stated the present baseboards are in sufficient, and crap. So if your replacing anyway. Also higher output base boards mean you may need less of it compared to the present ones you have. Look at the smiths.

Gordy

Lets look at the facts.

112K boiler. Input, or output DOE? For 800 sf home.
3/4" pex feeding the baseboard 42K at exceptable flow rates.
Assuming series baseboard. How many feet of baseboard in a loop? or is all baseboard continous one loop?

Circulator type, and size? Taco 007?

if boiler is gross input thats 89k out.

icesailor

A 800 sq. ft. (around 22'X36") insulated the way you claim, doesn't loose a lot of heat. It doesn't have a lot of rooms. It doesn't need a lot of emitting baseboard to do the job.

I don't understand your comment of "" Aquastat is set at 140 (lowest possible) and 170 ish (due to any higher gets noisy. ""

Is it set for 140 degrees or 170 degrees. If it is set for 140 degrees and the boiler is cycling when it is cold, but doesn't heat the structure at 20 degree OAT, but does when it is 35 degrees OAT, the boiler is too big and the baseboards are not putting out enough heat energy because the boiler water is too cool. Raising the boiler water temperature increases the theoretical size/length of the baseboards. So raise the boiler water temperature.

You are missing the concept. There are many people in colder climates that during the next couple of weeks would die to be living with 20 degree OAT's while theirs are in the -0 range.

When it is 35 degrees outside, the boiler is too big. When it is 20 degrees outside, and the water inside is too cool, the boiler is even bigger. Its like a car towing a empty trailer. The engine is the boiler. The emitters are the radiator. If you overload the trailer, you need more power from the engine. If the radiator is too small, the engine overheats. You either stop and let the engine cool down, or you throw stuff out of the trailer. That's why boilers cycle.

Are you another homeowner expert, obsessed with heat appliances cycling because some DIY expert board told you that it is a symptom of wasted heat if a burner cycles? All burners cycle to the load. Try driving your car with one throttle setting. Especially in traffic.

Is this a double wide trailer house that is open underneath?

riclyo

Ok some further information that might help.

Full Basment 1 story house with full hatch access attic.

I have a 30,000 BTU ventless heater in my (unfinished completely uninsulated) basement I run to make things feel more comfortable when the temperature drops below 20.

I Have R13 faced in all outside walls and R32 in attic with 4mil plastic I am sure.

There is 100 sq/ft of drafty windows throughout the house, 1 old wooden back door and one newer metal front door with no storm.

I have approx 80’ 3/4” pex feeding 55' of baseboard on a continuous loop with a aluminum radiator w/ ½” monoflow tee for the bath w/cathedral ceilings.

Circulator is a taco 007

Boiler is lochinvar 135,000 Input BTU/Hr Mfrs Heating Capacity 112,000 Min Input 67,000

140/170ish forgive my lack of knowledge but is boiler fires and heats to 170 and circulator will run till temp drops to 140 and fire again.

Hatterasguy,
I will turn basement heater off and record my finding run times and such. This weekend will be -8 to -13 so that should help?

Icesailor,
I would never claim to be an expert at anything and am more of the curious type of how things work and am skeptical my system was installed/sized correctly.


Thanks and hope additional information will help.

icesailor

IMO, you have more than enough boiler "nuts" to heat the house. And more than enough temperature "Nuts" to heat the emitters. You just need hotter water. The 30 degree differential between 170 degrees and 140 degrees is just too high. Until the boiler starts again, you are heating with 140+ degree water. You need to up the differential so that the boiler restarts at 160 degrees.

Remember, raising the water temperature increases the theoretical size of the emitters due to the increased output from the hot water.

Slant-Fin #30 baseboard is rated at 510 BTU's @ 170' water, per foot @ 1 GPM flow. The same baseboard is rated at 340 BTU's at 140 degrees. It is rated at 450 degrees at 160 degrees.

What is your returning temperature to the boiler? If the system is operating with a 20 degree drop/Delta T, the last emitter before coming back to the boiler is only "seeing", 120 degree while the first emitter is seeing 140 degrees. If the first emitter is noticeably hotter than the last emitter, you need a higher flow. If you are using a multiple speed circulator, increase the speed.

You need to get the system temperature up to be comfortable.

IMO.

Paul48

On a call for heat, most, if not all boiler controls take the lo-limit out of play, and will cycle off the hi-limit, with a fixed 10* diff.

icesailor

@Paul48:

He seems to have a boiler with a triple acting control. The "Lo" is cancelled out to the High Limit. But if the boiler is maintained like a warm start, you don't get the wide swings during operations. Or at least you shouldn't. But those controls have the white differential wheel on them. When rookies get to futzing inside of them, they might spin that wheel to the maximum. Causing such a wide differential. That would be the next thing to check. A photo of the inside of the control might be informative.

riclyo

Some photos before this weekends homework assignment.

i1291.photobucket.com/albums/b544/riclyo/IMG_1293_zps2232f66e.jpg

i1291.photobucket.com/albums/b544/riclyo/IMG_1292_zps0ca8e9c6.jpg

i1291.photobucket.com/albums/b544/riclyo/IMG_1291_zps50c4772f.jpg

i1291.photobucket.com/albums/b544/riclyo/IMG_1295_zpscb5fc336.jpg

riclyo

So here are the results after an hour. Because of the consistency I felt an hour of monitoring was sufficient.

OST is 5 degrees F and dropped to 1 after the hour.

Thermostat read 68 in house temp at the beginning of test. Thermostat was set to 76 During test.

I started the test with boiler water temp at 90 degrees output temp and 80 Input temp.

Initial run time was 4:08 and with temperatures reaching 170 degrees output and 140 input before shutting down. These temperatures are consistent throughout test.

Peak input temperature was 154 degrees around 1:30 after shut down throughout the test.

Circulator runs entire time during test.

Boiler off time is 8:55 to 9 Minutes between restarts with input temperature at 130 and output at 126 throughout test.

Boiler run time is 2:00-2:10.
These reading are consistent throughout the hour and the thermometer went up a ½ degree but house temp was noticeably more comfortable.

hot_rod

80 feet of pex, probably a bunch of ells? And 55 feet of baseboard. Plus a mono flow fitting and bath rad. That is a pretty long loop.

That 007 may be flowing around 3.5 gpm or less against all that pressure drop, moving maybe 35- 38,000 BTU/ hr.

Is it a multi-speed circ? You might squeeze some more performance with a bit more flow.

icesailor

Have you developed an obsession with boiler burners starting and stopping while attempting to do their jobs? From what you describe, that's how boilers are supposed to operate. The big question that some don't understand is that it is the circulator that is providing the heat on a continuous basis. No one ever mentions if the circulator is running or not. Is your circulator running? It should be. Because if it stops, either you have a bad control, or the boiler is wired wrong.

You have been observing what some would be considering a normal 20 to 30 degree Delta T.

The system is acting like the thermostat in your car. It controls the flow of cooling fluid through the engine from the radiator. In the summer, it might run wide open because of the high OAT. In the winter cold, when driving fast on a highway, if might slow the flow of coolant to a trickle. Because the cooling water was too cold so to keep the engine running at the proper temperature, it has to limit the flow.

You have to think of your house as a car. The boiler/burner is the heat source. The house is the radiator that will bleed off the heat. The thermostat is the device that controls the bleeding off of the excess heat. When you stop the car, or the house is satisfied, the thermostat shuts off the engine. As long as the thermostat is calling, the circulator is running. Just like the water pump on your car engine. Unless your car has electric water pumps and they are supposed to run too.

Jamie Hall

One might add to Ice's comments... if the circulator is running all the time, but the boiler isn't, what you are seeing is that the radiation in the building is not capable of using all the heat that the boiler can produce. Several possibilities. Not enough flow through the building radiation. Temperature in the building radiation too low. Insufficient building radiation. (these will show up as insufficient heating in the building). Boiler oversized for otherwise satisfactory radiation.

Gordy

so the boiler ran for an hour pin balling off high limit, and raised the house temp1/2*?

Like HR said that BB loop is on the edge for loop length. Ice is aluding to it also. Gotta move the BTUs of the freight train.

Gordy

What has me perplexed is if there is not enough radiation is his supply return temps should be higher.

icesailor

Gordy said:

What has me perplexed is if there is not enough radiation is his supply return temps should be higher.

The question is. "Is the circulator running"? The OP says yes.

If the high limit is set to 180 degrees (or 170 degrees for that matter), the discharge temperature should not be leaving the boiler at a lower temperature than the high limit setting, minus the differential. If it is dropping to 154 degrees DWT, then the High Limit is bad. Or it has a fixed differential that is too wide.

IMO, if the house is under radiated, then the RSWT would be high. If the piping was undersized, then the RSWT water can be cooler, but the boiler supply discharge would be running at the high and cycling. Which it does, but the burner is stopping. Its the lack of high enough system entering system temperatures that cause the problems. That, and way too much 3/4" PEX.

Maybe a hydraulic mining pump would overcome the resistance of all those short pattern plastic PEX fittings. Unlike all those expensive copper short pattern 90 degree ells had with the nice radius inside to help the water along in its flow. I'll bet that the restriction from turbulence from 4-3/4" plastic PEX 90's is equal to a whole box or bag of 3/4" Copper 90's. No wonder you need high head pumps to push the water around in some new modern hydronic systems.

icesailor

Hydraulic Turbulence:

For any of you out there in Wethead Land who like to play with Google Earth, and want a natural example of Mother Nature and her reaction to turbulence, look no farther than any marsh with water flowing through it. Especially tidal marshes. The tides make them perfectly flat. With fresh water draining out of the land, into the sea.

Like the Barnstable (MA) Marsh at 41' 42" 57.N, 70' 21" 33.W. from 4,000' +/-. Notice all the extremely crooked streams flowing through it. And all the straight parallel man-dug mosquito control ditches to let the little fishy's in at high tide. And at low tide, they can stay there and not be eaten by the bigger fishy's while the little fishy's munch on mosquito larvae. Cheaper than spraying. The County Mosquito Control Board has to keep the straight trenches open. Not the curved streams. But they are all crooked. Because water does not like to go too fast or too straight. Look to the NW (if you have bothered) and notice a stream that has sand bars along the flow, where the water wears away one side and deposits it along the back side. It scours the end/point, making the passage of the water even more convoluted. If the flow speeds up, there is more erosion. If the flow goes down, there's less erosion. If given the chance in a river or stream, the erosion will slow the flow down to what is needed. Anywhere in the world. Increase the flow and get more erosion.

Bypass's:

And notice where the Mosquito Control folks tried to put in a by-pass to short circuit the stream flow The water preferred to take its own path rather than the new one provided. Water DOES care where it goes. Maybe ME's lazy brother is on to something.


Everything is related. You just have to connect the dots to see and understand the relationship.

riclyo

Icesailor,
Just obsessed thinking of dollar bills flying out of my chimney every time I hear the boiler fire.

I have been contemplating interior storms to help combat heat loss. Also I want to know if my heating system is optimized as much as possible and given the boiler would be the most expensive to replace and am curious as to possible tweaks that could be made to radiators or piping as a possible economical solution.

I come to this board as where else could you get multiple opinions and solutions to stew over where if I was to call a local contractor I’d feel they would be more likely to sell me something I don’t need. Yes I am skeptical as I too work in a specialized filed just not HVAC.

154 degrees is the highest the return water temp reaches at approx 1min 30sec after the boiler has shut down and the circulator must be doing its job as the return water temp slowly declines to 126 degree before the boiler fires again after 9 minutes has passed.

How long should it take the average heating system to raise the indoor temperature say 3 degrees? I'm assuming OST plays a role but is the a rule of thumb?

If the Boiler(engine) to big…So what is the downside of upsizing the radiators? (since I don't have to pass a emissions test)

According to my online calcs some of the rooms are good with the slant fin 30's while the living room where the thermostat is, my sons room where a bed is covering most of the radiator and my office/closet seem undersized.

Hatterasguy
“Increase the size of the emitters and provide more BTU's to the space allowing you to do setbacks and a proper recovery if you so desire.”

If setback mean constant thermostat adjustment then yes I do. When I leave in the morning I set the thermostat to 65 and when I come home 68-70 depending on OST.

2- Black iron 90’s
1- 1” Copper 90
2-1"-3/4" reducers
10- ¾” Pex to sweat fittings
2- ¾” pex-pex 90’s
3- ¾” copper 90’s
2- ¾”x1/2”x3/4” mono tee’s
11- ½” 90’s
In addition to 80' of 3/4 and 55' baseboard

Another thing I always knew was my entire heating and water system is Kitec! Should I panic now?
I’ve read you only need to worry about the fittings made in Taiwan while other sites say I’m completely doomed.

hot_rod

Can you draw a piping diagram? Where are those 11- 1/2" ells the system?

Also 3/4 pex fittings reduce the OD, sometimes quite a bit.

There have been a few different problems with that brand of tube other than fittings. I have seen pics of it delaminating causing a blister and eventual leak. also some pictures of the blister forming inside and greatly reducing flow.

I don't know that all the tube they manufactured has issues, and some of the problems were traced to the improper fitting or assembly, the brass fitting reacted with the aluminum layer causing the barrier to fail. Did high operating temperatures cause more of the tube to fail, who knows?

IF you plan on some remodeling I would certainly look at replacing the tube.

hot_rod

flow reduction

SWEI

riclyo said:

my entire heating and water system is Kitec! Should I panic now?
I’ve read you only need to worry about the fittings made in Taiwan while other sites say I’m completely doomed.

From what I have seen and what I have read I would say that as long as the heating system has not suffered from excessive makeup water and you do not see evidence of corrosion at the compression fittings, it is probably OK. I would suggest verifying the tightness of the system by valving off the makeup system once or twice a year, perhaps turning it off completely. Make sure your expansion tank is tested annually, properly charged, replaced when needed. Pay close attention to water quality and give serious consideration to water treatment.

The domestic piping is more problematic. Keep a very close eye on that.

Some here have much more direct experience with Kitec. I look forward to learning from them.

riclyo

I've heard upping the boiler temp to 180 has been a cause but I don't know what to believe. Maybe now is the time to get a hold of a plumber buddy of mine and start collecting some materials. I guess I should be glad I have an unfinished basements and no second floor. Only wall that will need to be cut is behind the toilet so I guess it would be about the easiest re-pipe considering the size of the house.

hot_rod

Here is what it looks like on the simulator, I didn't add any near boiler piping and fittings, just the baseboard, fittings and pex. I used 4 feet for the bath emitter.
I used SlantFin #30 baseboard, 3/4" if you know the brand that can be entered, but probably not going to change much.

A room by room load calc would show how closely the BB matches the load for each room.

As we guessed that circ pump is a bit on the small size for that much loop, moving only about 27,000 BTU/ hr.

Did you notice if the fin runs the entire length of the BB. All the fins facing the right direction

SWEI

riclyo said:

Full Basment 1 story house with full hatch access attic.

Have you considered splitting the loop?

riclyo

The bath radiator according to manufacturer is equiv to 6' baseboard. The BB size shown is actual emitter size (not tin case size) so the calc should show??? 5 1/2, 15, 10, 7 1/2, 9, 3, 6, 5 1/2
Supply temp is also set @ 170 in hopes of preserving Kitec.
Slant fin 30's and installed correctly.

So today is 0 degrees and a hellacious wind creating wind chills
-20 Below. Thermostat is set for 72 and in house temp is 67 and has been there all day. Boiler keeps firing away but isn't getting anywhere.

I have considered splitting the loop not sure how to go about it though.

Thanks for the continuing help with this now because of the kitec thing I'm wondering if there is some sort of safety flow switch that will turn off the boiler feed in case the pipe blows? Or can I just turn the boiler feed ball valve off and install a low water cutoff switch since my boiler doesn't have one?

hot_rod

splitting it into 2 zones would help, it's that long loop with 3/4 tube that is limiting the heat output. The boiler has 60K or so to give, but the distribution is constipated.

Kitchen, bath and living on one zone, beds and office on another.

You mentioned a basement with steel access door, are you sealed off as best as possible? The infiltration, especially on windy days really sucks, heat.

I've not known Kitec to just explode or disconnect, seems to be a drip at fittings or a bubble between the layers.

Although a bubble inside like I showed above would certainly limit your flow even more.

Consider limping through this heating season and doing some zoning and re-piping when you can shut down for a few days.

In the meantime tighten up any and everywhere, windows, doors, basement rim joist, etc.

Consider a blower door test, and accurate load calc with that info. Maybe your utility offers that service, or find a qualified energy auditor. Best money spent is toward lowering the load.

It really shouldn't take a lot to keep 800 sq. ft. comfortably warm.

SWEI

riclyo said:

I have considered splitting the loop not sure how to go about it though.

You can split the loop to increase flow by teeing into the middle of it (between LR & BR or perhaps between BR & Office) and running a 1" line back to the boiler. This will halve your flow resistance and give you even more heat on the back half of the original loop (since it will now be starting with hotter water.) You also have the option to make two zones, but there is no requirement to do so. Where you split the loop and which direction you pump the water can sometimes present opportunities to fix previous imbalance issues.

icesailor

riclyo said:

I've heard upping the boiler temp to 180 has been a cause but I don't know what to believe. Maybe now is the time to get a hold of a plumber buddy of mine and start collecting some materials. I guess I should be glad I have an unfinished basements and no second floor. Only wall that will need to be cut is behind the toilet so I guess it would be about the easiest re-pipe considering the size of the house.

Regardless of what you do, if the depiction of the floor plan and the installed radiation is representative, IMO, I've experienced deep problems with that.

First of all, you have a radiator in the small bathroom? The 3' section under the window adds to the kitchen heat when the bathroom door is closed. If it is a cast iron radiator, it will add little to the heat. But the real problems occur with the back door that enters on to the kitchen, with the stairs that run upstairs. There needs to be a large piece of installed heat in the hallway of the second floor stairway. It needs to be connected to the first floor kitchen zone. Because if it isn't, and it is connected to the second floor zone. it sucks the heat out of the kitchen and puts it upstairs. Then, it is common to put thermostats for second floor bedrooms in a common hallway. Fine if there is a door to close off. Otherwise, the heat from the kitchen goes up to the second floor and heats the second floor. The kitchen appears to be cold. When in fact, a large amount of the heat is going up the stairs, making the kitchen feel cold because of drafts. The door swings are odd and all the stairs are going up in the drawing. That whole corner doesn't make a lot of sense from a drawing point of view. But whenever you have an entrance hallway with an outside door, the space should get special consideration. Like the infiltration factor for that space should be 1 1/2 ACH or more.

hot_rod

Ice, this is a single story home, with basement, no upstairs, from what I read?

icesailor

It gets hard to remember which is which. The drawing is confusing. Either way, more heat is needed in that back hall. Is that radiator connected with Mono-Flows or is it series looped through the baseboards.

I wasn't criticizing the plan. just pointing out that fact about where do you connect the second floor heat in an area that is open to the first floor zone. Its my experience that all the heat rises to the second floor. I've seen it and had them close all the doors that open to the balcony. Especially one Radiant one I was asked to opine on. Aesthetically beautiful. Practically awfully cold. For years before I came along. And no way to correct it.

riclyo

Sorry for the confusion. When you enter the back door if you go straight the stairs lead to the basement, if you go left it's 3 stairs up to the house divided by a heavy wooden door. The aluminum radiator in the bathroom comes off the loop via monoflow tee's. It was put in the small bath because that bath has a cathedral ceiling peaking at 13' and also has a 120v in wall supplemental heater.

So I attached a updated drawing which splits the loop in about half by a 1" copper line tee'd to two separate loops. The living room baseboard is undersized and very close to a couch so it looks like this room could benefit from a higher output rad. The one bedroom I changed to a radiator as a bed currently covers the majority of the existing rad. And lastly the back hallway by the bathroom is a cold area as the bathroom door is always closed in addition entry to the house is always via the back door so heat always leaves that area first. Allot of in and out between people and the dog.



Sealing and tightening things up is part of my summer plan, and unfortunately my utility doesn't offer any home efficiency tests so I will have to see if anyone I know could recommend a good one.

I know I'm getting a little obsessed with this I admit I may have a problem. Check out my drawing if I'm crazy say so, my feelings won't be hurt. I apologize if I'm becoming annoying or a little slow to the concept but I still appreciate the help.

icesailor

IMO, there's nothing wrong with your drawing. I was only pointing out an area of concern to me personally from my experiences.

As far as hiring some "Expert" to come and figure out what you need to do, buy a infra-red thermometer gun and have at it. They are cheap, and will tell you more than you know now.

Its always been my experience that the money spent on tightening up and resistance, usually is cheaper than system repairs. That turn out to not be needed once you have made improvements. Then, you can make some SERIOUS improvements. And not be wasting heat.

Try putting a piece of plywood in front of the termination. If the problem stops, its either the blower or the wind. A cheap experiment. Don't put the plywood against the outlet. Get some saw nags and weight them down with cement blocks or something. Then lean the plywood against the nags. If you get my idea.

hot_rod

All all the baseboards getting good air flow? Sometimes carpet gets shoved below them and blocks the convection. Or furniture blocking the airflow. Any chairs or couches with dust ruffles can limit that convection current.
Cool air needs a path to the bottom of the BB, and clear space above to get best output.

All the doors and windows sealed? Infiltration is often a bigger load than lack of insulation.

A cup with holes will leak no matter how thick the cup is.