Folks, sorry about this long-winded question.
When I bought my house, it was piped for natural gas for two furnaces (basement and 2d floor) and two hot water heaters (next to each other in the basement). I turned off the gas to one of the water heaters and have never used it. The main pipe (iron) from the meter to the basement furnace room is 1â€. There it splits off into ¾â€ and then ½â€ pipes to feed the furnace and water heater, as well as another ½â€ pipe traveling upstairs to the second furnace.
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A while back, my wife asked if we could replace her electric cook top with a gas one. I installed the cook top myself but decided to leave the piping to the pros. I got three estimates on the work. Since the path to the stove had a lot of turns in it, the solution described was to use a flexible pipe connected to the ½â€ pipe that used to feed both water heaters, but now fed only the one. Two of the estimates were pretty reasonable. The third guy indicated we would never have sufficient volume (or perhaps pressure) with the existing piping and we would have to upgrade all of it from the meter in.
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Naturally this upgrade option was a lot more expensive, so we went with one of the other two less expensive options. The cook top we installed is a Jenn-Air four burner with a down-draft exhaust between the two pairs of burners.
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Here is the problem: The burners don’t seem to put out sufficient heat so it takes longer than expected to cook things. A worse problem is that if you turn the exhaust fan on high, it actually pulls the flame noticeably in the direction of the fan, effectively providing even less heat to the pans.
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So I am wondering if the guy who said we need more capacity was right.
But I am puzzled. I am sure there are times when the water heater and both furnaces run all at the same time without obvious problems. So if there is sufficient capacity for them, why wouldn’t the cook top work fine when some of these devices are not using gas?
Could the flexible pipe be the problem? Or tha fact that the stove and water heater are boith fed with a single ½â€ pipe? The flex pipe is yellow and has the following markings on it: 13 meters IAPMO GAZ COMBUSTIBLE (EHD19) C221 (1250 ER-153LCI). It was a bit smudged, so I may have gotten a couple of the characters wrong.
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Any suggestions would be greatly appreciated.
Replies
Have you compared your cooktop with one that is installed "correctly"? You may be simply experiencing the normal operation of the unit. I have about 50' of 1/2" black iron piping, off a 3/4" main that feeds the furnace, to run my commercial 6-burner Wolf stove, and a gas grill, and have no problems with low supply. Is the flex ribbed? If not, I would suspect that the cooktop burners are just not putting out as much heat as you expected.
Mike Hennessy
Pittsburgh, PA
Mike, thanks for your response. Perhaps you are right about my perception of the amount of heat it should put out, however I can't imagine its own exhaust fan would be designed to visibly deflect the flame towards to the fan if it is working properly.
"I can't imagine its own exhaust fan would be designed to visibly deflect the flame towards to the fan if it is working properly."
I don't want to discourage you, but Jenn-Air is often slammed for the design of their downdraft cooktops. They have to be pretty much overpowered to work, since they are fighting the natural tendency of the hot gasses to rise. Everyone I know who has one has been disappointed to some degree. (I have a Jenny fridge that has left me cold.) (Did I say that? Groan!)
Mike HennessyPittsburgh, PA
Hmm, That reply could have been a bit "crisper" try putting it veggie drawer next time. ;-)
Dunno, seems to me like it's been in the veggie drawer too long already.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I have a Jen-Air downdraft cook top installed in 1999 and the fan moves the flame even with no pan on the stove. The fan is variable speed. I normally do not use it, and if I do, I use it on slow speed. Mine is set up for propane. If a fan is going to move byproducts of combustion sideways to an exit, the flame front has to move also.It works fine for me, although the btus are down from natural gas ratings. The boiling water test does take a long time. I did adjust the two smaller burners, details in instruction manual, to be simmer burners. The flame is so low it goes out when opening the cabinet doors, but reignites with the electronic ignition immediately. Works great for long simmering.Frank DuVal You can never make something foolproof because fools are so ingenious.
If there's no noticeable difference in the stove operation when both furnaces are running vs both shut off (thermostats not calling for heat) then your meter and main supply piping is almost certainly OK.
It is possible that the flex pipe is too small for the stove and is restricting flow.
It's also possible that your stove isn't set up right, or you have a unit with propane jets in it or some such.
I think you are right that I am getting enough gas in the house. Now I just need to figure out how to determine the size of the flex pipe to see if it is adeqaute. I guess I'd better go looking for the cook top specs and see what it dsay. And also ensure I got the natural gas model.
Most of them come with jets for propane AND nat gas; read the manual, and look for a baggie with the other jets in it, see if yours might be set up for propane.
Thnaks for the suggestion. Will do.
Let's see; you had an expert on site calculate that it was not possible for the natural gass to deliver enough BTUs thru a 1/2" line.
You went with the 1/2" line anyways.
Now you don't have enough BTUs.
Seems pretty simple to me!
I had to have a line re-done in 1" once because of faltering burners and insufficient supply. Now I get it done right the first time.
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Piff, I don't think implying that he's remiss for ignoring "expert" advice is exactly fair. From his original post it appears that there were two other "experts" on site that said the existing pipe was adequate. Why is it your presumption that the guy who wanted to replumb is right, and the other two are wrong?
I never implied that he was remiss.I simply analysed the facts as reported. You then ask, "Why is it your presumption that the guy who wanted to replumb is right, and the other two are wrong?"Answer, because the results proved him right.It is so flaming simple there is no reason to chase other solutions when it is right under your nose.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Re JenAir and flame to the blower vent, I am in the process of remodeling my kitchen and the JA is the first thing to go to the dump, what a pice of crap. The blower vent is too low and will pull the heat directly into the vent (I found out that all vent piping for downdraft blowers now require 5/8's 1hr sheetrock chase, thanks to JA fires in the vent pipe). I installed a GE Monagram downdraft vent with the telescoping unit in back of a 6 burner Monagram natural gas cooktop and there is no comparison to the JA. The vent raises up about 8-9" and is 36" wide and will pull steam off the front pot. I mounted the blower outside about a 10' run and I can't even hear it. The JA sounded like a B29 winding up and the blower takes up about half the undercounter area. The grease mess in the pans is another problem too. The electric igniters quit after a couple of years and the fan switch would short out when you washed the grill. The knobs melted (replaced them twice). Maybe you can get the supplier to take it back and get a good cooktop.
Jim
To Piffin, you may be right about me making the wrong choice, but as Freestate1 (thank you) points out, the other two experts did not have any issue with the existing piping/pressure and both pointed out I could disconnect the extra water heater and reconnect the piep to the stove without problem. It seemed reasonable to me and of course that option was cheaper.
To the question on pressure, I did not set anything on the regulator and I don't see how you would do it. It just has one big brass nut in the center of it. Unfortunately the only manual that came with it was a user guide that contains no useful technical info. And I could not find any alternate parts in the box for Nat Gas vs LP.
A label on the stove bottom says "the appliance pressure regulator supplied must be used with this appliance". And it was. The label on the regulator itself it says:
Maxitrol, RV47CL, 1/2PSIG, NAT 5.0" LP10.0"
Not sure what all that means. Perhaps my first step should be to have the gas company check out the meter as someone suggested. Then go from there.
This may be of some help to you: the max capacity of Schedule 40 pipe inc. fittings for 1/2 in is 10' 120,000 btu based on a pressure drop of 0.5 inches of WC and a rel density of 0.6
20' 85000 btu
30' 70000 btu
50' 54000 btu
60 49000 btu
90' 40000 btu
100' 37000 btu
find out what your stove is rated at add to that the water tank and see how it looks
But for comparison, our 2000 sq ft house in Minnesota is heated with 60K BTUs (delivered the last 10 feet in 1/2" pipe).
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
The pipe size is determined by the total Btu at the meter ,the distance to the first appliance,then downsized after each takeoff as the demand becomes less.Gas volume, like water, is reduced by a function of pipe diameter and length.If the diameter is reduced for a very short distance the gas just speeds up like a venturi.Hence 10 feet of 1/2 will handle 120000btu(double your furnace size)But 100 ft only 370000 maybe this helps to clarify it .
My point is that even 37000 (your 100-foot number) is a lot of BTUs. One Jenn-Air downdraft unit I'm seeing the specs for has two 9000BTU burners and two 7500BTU burners. That's 33000 BTU with four burners wide open. And the unit has a 1/2" gas connection.I kinda wonder if the OP's unit is a return, and someone had previously set it up for propane (the default is apparently NG). Instructions are available online for converting.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
i think it would be painfully obvious if it was set up for propane and run on natural. what i remember of making those conversions is that LP is about 3 times as hot as NG.
so if you are running NG with LP orofice's and pressure it will barely keep a flame lit if at all is my estimate.
The 1/2" connection is fine but if it is after the water tank (typically 41000 or 33000 btu )and they are fed by a 1/2" line that makes a difference.They may be pulling 70000btu on a small line. Another way of testing is to hook up a manometer at the stove when all is running and see if it reads 3 1/2 " WC .(a good guess for working pressure)That would check the working pressure at the stove.Yet again run the stove and the water tank and time the !/2 cuft hand on the meter ,calculate the cuft per hr,from that the btu per hour and compare with the published total btu/hr for the watertank and stove.
I have scheduled my utiliy to come in Friday and check my meter and pressure. If that doesn't prove to be the problem, I guess I will start looking at the pipe sizes. Thanks to all of you who responded.
Look at the installation instructions and you'll find instructions for adjusting a couple of things on the burners. It's worth a shot to check these adjustments.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
PS: Compare the flame with one burner going vs all four. If the one burner doesn't change much as you turn on the other three then it's very unlikely that restricted flow is the problem.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Also the WH does not run all the time.Turn the thermostates down for the test. Likewise the furnaces (don't remember how the gas runs).If it does not burn correction on one burn with everything else wrong the problem is not the size for the supply lines (but it could be a badly machined valve or something like that..
.
A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
What pressure do you have the regulator for the cooktop set at???
Bud
i am pretty sure there is an online calculator for sizing natural gas piping systems. you have to measure the lengths and turns and sizes of the pipes and you can calculate what size you need. i remember seeing it somewhere, but don't remember where or the name.
the other thing to check is the regulator(s), both at the house and at the appliance.
what i reccomend is to draw a diagram of the piping system, with all the turns and lengths and sizes recorded. ( a small rough blueprint if you will) this diagram should contain all the information you need to perform the calculation, then you can either perform the calc yourself online or if you have a gas man make a service call to check the unit (it may be a bad or improperly adjusted regulator at the unit) you can give them the information, and ask them to create a report showing the results of the calc based on the diagram.
the recipe for troubleshooting is to list all the possible causes you can think of, and one at a time patiently eliminate things from the list.
Check your pressure at the range under load. I ran into a similar problem when we installed a tankless heater. Our 30 year old gas meter was not regulating properly under the higher load. A call to the gas company got us a new meter and all was well.
Three weeks ago I installed a Jenn-air oven with four buners on top. I did the LP conversion for the home owners. When I test fired it I wasn't impressed with it.
Since I am not an appliance tech, I suggested the home owners try using it for a while, if they were not satisfied they should call a qualified appliance service person to see if it could be fine tuned to suite there needs.
If you have a good service person in your area, there are some adjustments, he could also tell you what you can expect from this unit.
Service calls are not cheap, but it could save you alot of problems.
I noticed in the discussions that some are converting from gas to LP. This is puzzling to me, since here it is just the opposite. Is the reason utility costs?
Generally the conversion occurs because the new appliance is shipped configured for NG and the user has LPG, or the user has moved and brought the appliance with him.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
It's rare in our area for anyone outside the city limits to have NG. Propane tanks have become real popular.
An "average" domestic range uses significantly more gas than a water heater; ~59CFM as opposed to ~37CFM, so that is likely the problem.
So far as I know, the number of bends doesn't matter
And I suspect many newer ranges have higher requirements.
But CSST will only carry about 1/2 the amount of gas as iron of the same size
CFM / length
.....CSST .....Iron
10'...95.......175
25'...60.......108
With my mouth I will give great thanks to the Lord; I will praise Him in the midst of the throng. For He stands at the right hand of the needy, to save them from those who would condemn them to death.
- Psalms 109:30-31
But CSST will only carry about 1/2 the amount of gas as iron of the same size
Yup, all those corrugations reduce the capacity of the tubing.
To the OP
How long is the run of corrugated? Can some be replaced with black iron pipe?
Can you come off a different place (larger) to feed the stove?
Light one burner and watch it, does the flame get smaller as you turn on more burners?
The size & strength of the flame doesn't seem to be much affected by the number of burners in use at a time, so I am thinking maybe it is the stove that is the problem rather than the piping.
To answer your other question, it would be very difficult to replace the CSST with iron pipe, however I could connect the CSST to a 3/4" iron pipe instead of the 1/2" pipe it now shares with the water heater.
It sounds like there is enough gas supply based on the flame. Hard to diagnose over the internet.
It could be you are just used to a electric stove.
What is the rate of the burners? 12k BTU each?
Approximately how long is the CSST run? When you said it was 1/2", is that the large or small corrugations?
How does the flame look? Nice and blue, yellow only at the tips? Smell OK?
edit for spelling
Edited 2/6/2007 11:37 am ET by JAlden
There are two 8000 BTU and 2 10000BTU burners. All have a blue flame.
The CSST runs about 15 feet.
It appears you have enough capacity.
A 10k BTU burner is not all that large. It may take some getting used to.
Thanks for the help. At this point I am not going to do anything before the gas company shows up Friday to check my meter.
Color of the flame is meaningless - we used to think that before CO meters and combustion analyzers beca,me affordable.Now we know differently.
With my mouth I will give great thanks to the Lord; I will praise Him in the midst of the throng. For He stands at the right hand of the needy, to save them from those who would condemn them to death.
- Psalms 109:30-31
I agree. Just trying to get a benchmark.
If it was yellow and rubbery we would know there is definately a problem.
The gas company guys showed up Friday and determined the meter was a bit undersized, so they replaced it with one that allows more gas to get through (their explanation). Anyway, the cook top burners are now going a lot stronger, so this appears to have solved the problem. Thanks to all of you for responding with your ideas and suggestions. Once again, the members of Breaktime come through!
Glad to hear. Wife is happy?
And for dinner?
Yes. And that is all that counts!
BTW: it is very importnat to make sure the gas piping, especially the CSST is properly grounded -
A class action suit on that has just been settled, and it has been argued there is risk of CSST failure in the event of a lightening strike if it isn't bonded to the house grounding system
With my mouth I will give great thanks to the Lord; I will praise Him in the midst of the throng. For He stands at the right hand of the needy, to save them from those who would condemn them to death.
- Psalms 109:30-31
I think that you should have used the third guy, you don't have enough capacity in your system. Sorry.
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"If all else fails, read the directions"