Gas consumption optimization question

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  #1  
Old 12-29-13, 02:55 PM
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Gas consumption optimization question

I have this antique boiler and SYSTEM was rehabilitated with the help from this forum especially NJ Trooper. It's working like charm but after getting 2nd gas bill I wonder if there is any way to optimize the gas consumption.

I have 2 AQUASTAT in SYSTEM. Low limit is immersion one and set to 95 F. The high limit one is surface mounted set at 180 F and has fixed differential of 10 F.

BOILER name plate shows boiler being 135000 BTU W/80% efficiency. Since there are no fancy/modern controls I manually noted down the BURNER ON/OFF duration, once water reaches set temperature 1st time. So on average burner is OFF for 97 seconds and ON for 155 seconds.

1. Is this burner ON/OFF frequency excessive?
2. Is there a way to add single modern control AQUASTAT that has variable differential and can be used to control both BOILER/BURNERS and PUMP?
3. If #2 is feasible, then where and what control can be added to the system.




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  #2  
Old 12-29-13, 04:20 PM
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Now how on earth did you get that boiler to run laps ?

You say running like a charm... ALL radiators are 'smokin'... no problems at all with the heating of the home? Pressure all good... ? Not hearing any air circulating ? you know, general report...

I have 2 AQUASTAT in SYSTEM. Low limit is immersion one and set to 95 F. The high limit one is surface mounted set at 180 F and has fixed differential of 10 F.
Keep in mind that the 'low limit' aquastat is actually controlling your PUMP. It has no control whatsoever over the boiler temperature. When your thermostat calls for heat, the pump will not run unless the boiler is above the setpoint on that control.

You would most likely benefit from running an aquastat with an adjustable differential that you can set to at least 20F ... even 30F might help...

I need to ask about the run times you are seeing. Are you setting the thermostat back deeply, and are these run times indicating activity during a recovery from setback period?

IF SO: Once the home is up to temperature, does this activity cease and do you then have 'normal' run times and off periods?

I don't fully understand the lap times... first column is burner ON, second is burner OFF?

What's with that first lap? Seems odd that on and off times are the same to the hundreth of second.

If I'm reading correctly, lap 10 is ON for 2.5 min and OFF for 21 minutes?

Unless I'm misinterpreting the display on your lap counter, I don't see anything near the average on and off times you're describing.

By my abacus, I'm seeing a little over 2 min ON, and over 12 min OFF, on average, throwing out the first lap which doesn't seem real.
 

Last edited by NJT; 12-29-13 at 04:37 PM.
  #3  
Old 12-29-13, 04:24 PM
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What's up with the aluminum pan under the pump?

The simplest thing you could do is replace the high limit a'stat with a similar model that has adjustable diff.

With your boiler, one of the 'HeatManager' devices might help to tame the short cycling... DON'T BUY ONE yet!

BUT if the activity you are noting is during the setback from recovery period, what you are seeing could almost be considered 'normal'.

How bad was the gas bill? Break it down into 'therms' for us. We don't care what you're paying, just how many therms you used.

Remind us if you are also using gas for other purposes... cooking, domestic water heating, etc
 
  #4  
Old 12-29-13, 05:06 PM
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I need to ask about the run times you are seeing. Are you setting the thermostat back deeply, and are these run times indicating activity during a recovery from setback period?
Since I have family members at home all the time I set thermostat to 71 around 7 AM and turn it down to 68 around 10 PM. That being said and as I indicated in my original post I completely disregarded the recovery time, in another words I only captured ON/OFF times once water reaches set temperature (i.e. 180 F) when there is a heat call.

I don't fully understand the lap times... first column is burner ON, second is burner OFF?
Sorry about confusion but lap 1 is BURNER OFF duration, lap 2 is BURNER ON duration and so on… 2nd column in display is cumulative duration, since I was using stop clock.

You would most likely benefit from running an aquastat with an adjustable differential that you can set to at least 20F ... even 30F might help...
I think that fixed 10 F differential is the main culprit then i.e. in my scenario water is losing temperature by 10 F within 97 seconds and then boiler is taking 155 seconds to bring it back to set level i.e. 180 F.

What's up with the aluminum pan under the pump?
That’s there since PUMP motor was changed to catch any dripping oil just in case. Luckily nothing in the pan.

How bad was the gas bill? Break it down into 'therms' for us. We don't care what you're paying, just how many therms you used.

Remind us if you are also using gas for other purposes... cooking, domestic water heating, etc
Average utilization till October was 30 therms/month. Since October it has gone up to 250 therms/month.

You say running like a charm... ALL radiators are 'smokin'... no problems at all with the heating of the home? Pressure all good...? Not hearing any air circulating? you know, general report...
In general house is heating normally except some cold pockets in house, but that’s mainly due to emitters not present and/or back family room that I think is not getting enough hot water circulation. However if my thermostat is set to around 72 F then house is warm and cozy. I figured that there is approx. 5 F temperature difference between room where thermostat is and back family room. But I believe that this is mainly due to not so well designed SYSTEM.

Thanks again!
 
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Old 12-30-13, 12:20 AM
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Let me paraphrase and see if I understand. You are saying that (round numbers) on average the burner fires for about two and a half minutes, shuts down and then one and a half minutes later it fires up again and the cycle repeats? Does this cycle repeat all day long until you lower the thermostat to the 68 degree point? If yes, then that tells me the burner is insanely oversize for the heating load.

What other controls do you have on this boiler? How handy are you with electrical wiring? Do you want a method to be able to independently set the burner on temperature from the burner off temperature?
 
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Old 12-30-13, 05:06 PM
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Does this cycle repeat all day long until you lower the thermostat to the 68 degree point?
Not all day but till heat call is satisfied. Maybe below will make it clear....

Let's say T-stat is set at 70 F. Room temp goes to 69F so T-stat will make heat call. Boiler will fire and run it for a while(since water temperature is no where near 180 F). Once the water temp is 180 Aquastat will cut the burner. From this point onwards till heat call is satisfied(i.e. room temperature rises to 71F) this 1.5 minutes OFF/2.5 minutes ON cycle will continue.

What other controls do you have on this boiler?
This is pretty old system so not lot of fancy modern control other than immersion type aquastat controlling pump set at 95F and surface mounted(on SUPPLY pipe) aquastat set at 180 with fixed differential of 10F controlling the BOILER/BURNERS.

How handy are you with electrical wiring?
Not very handy but can wire the stuff.

Do you want a method to be able to independently set the burner on temperature from the burner off temperature?
How does that would help in my situation.

BTW - this is my old threat that has extensive info about my SYSTEM.
 
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Old 12-30-13, 05:18 PM
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I have this antique boiler and SYSTEM was rehabilitated
That sure was a fun 150 posts, wasn't it?

I think that fixed 10 F differential is the main culprit
It's a big part of it... but as Furd has mentioned, it could well be that the boiler is oversized... I think we know that to be the case from the previous work. nothing you can do about that!

What's your budget? How much you wanna sink into it this time?

My suggestion is:

Replace with L6006C strap on model with 5-30F adjustable diff.

L6006C1018 - Honeywell L6006C1018 - High or Low Limit & Circulator Strap-On Aquastat, 65-200°F range, 5-30°F Adj Differential
 
  #8  
Old 12-30-13, 05:40 PM
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That sure was a fun 150 posts, wasn't it?
Indeed!

Replace with L6006C strap on model with 5-30F adjustable diff.
I think that maybe an option and may help alleviate excessive ON/OFF.

What's your budget? How much you wanna sink into it this time?
Not too much, but if I’m spending $150 to replace aquastat v/s $300 gets me some more reliable solution then I may go that route.

BTW - Is there any way to replace the antique immersion aquastat controlling the PUMP with any modern one that can do all 3 jobs i.e. control pump, control gas valve and has variable differential.

Is BOILER consuming @ 225 therm/month an eye catching or something normal?

Thanks again!
 
  #9  
Old 12-30-13, 05:52 PM
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Is BOILER consuming @ 225 therm/month an eye catching or something normal?
How big is your house and how old is it?

My house is 1600 sq ft and built in 1928. I have made some insulation improvements, but I still need to make more. This past November I used 132 therms for heat, hot water, and cooking. I suspect the bulk of your energy cost is going to be insulation problems. Especially with the cold spots in the house. My bathroom was quite a bit colder than the rest of the house. I discovered that the wasn't any insulation over the shower and there was a chase that ran from the basement to the 2nd floor. Added insulation and it dramatically improved the situation.
 
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Old 12-30-13, 06:09 PM
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utilization till October was 30 therms/month. Since October it has gone up to 250 therms/month.
So around 220 therms for heating then...

That's about 22000000 BTU a month...

Since 9/17 until yesterday I've burned about 21000000 BTU in OVER THREE months.

You sure about your therms? That's for ONE MONTH?
 
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Old 12-30-13, 06:32 PM
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BTW - Is there any way to replace the antique immersion aquastat controlling the PUMP with any modern one that can do all 3 jobs i.e. control pump, control gas valve and has variable differential.
You've been trying to get me to 'go there' for a long time!

OK... I'll bite...

I'm sure that it's possible.

However:

It isn't likely that the immersion well that the pump control is on now is suitable to mount a modern aquastat. It MIGHT be, but I don't think it's terribly likely.

We don't know that the location of the existing a'stat is representative of the temperature of the boiler water inside on AVERAGE. It's mounted pretty low and is more likely responding to the RETURN water temperature at that point.

I'm curious as to where the ORIGINAL high limit control was installed on the boiler before the strap-on was added at some point. I THINK it was on the other side, opposite that one, higher up on the boiler. Take a look see if you can.

If you can find a well, even if it's in a bad location and not suitable for mounting an aquastat on, there are REMOTE MOUNT options for the modern a'stats that utilize a long thermal probe on an electrical cable. You could mount the unit on the wall and run the sensor to a suitable well if you can find one.

For example:

48-3200 - Hydrolevel 48-3200 - Model 3200 Fuel Smart Hydrostat (Temperature Limit, LWCO, & Boiler Reset Control) for Gas Boilers

4' sensor cable and 'flush mount' kit:

48-102 - Hydrolevel 48-102 - HydroStat Wall/Jacket Mounting Kit with 4' sensor

20' sensor cable and 'flush mount' kit:

48-104 - Hydrolevel 48-104 - HydroStat Wall/Jacket Mounting Kit with 20' sensor


This control also has an LWCO feature, but you must use the well designed for it. You CAN simply not use the LWCO function. It will still do everything else it is designed to do.

The thermostat, pump, and burner would all wire directly to it.

Your new relay and transformer would not be needed any longer.
 
  #12  
Old 12-30-13, 07:19 PM
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You sure about your therms? That's for ONE MONTH?
Yes I checked the utility bill again just to make sure... the billing period is Nov 17 to Dec 17( actual meter readings). But if you remember from my previous post #134 boiler is consuming approx. 112.5 CF i.e. @ 1.2 therms per hour. 220 therms/month is approximately 7 therms a day. So per this reverse calculation BOILER is fired 7 hours/day on average.

I'm curious as to where the ORIGINAL high limit control was installed on the boiler before the strap-on was added at some point. I THINK it was on the other side, opposite that one, higher up on the boiler. Take a look see if you can.
I couldn’t find anything outside either but after looking closely noticed this. That copper wire/tube appears to be just bent over that nut.

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I suspect the bulk of your energy cost is going to be insulation problems.
That maybe the case but I believe issues is places without any radiators at all i.e. common hallway above stairs on 2nd floor that is roughly 6’x6’ has no radiator similarly boiler, laundry room right next to kitchen approximately 8’x11’, and pantry room right next to pantry room approx. 8’x5’ has no radiators.
Just an FYI…House was renovated with extensions and bedrooms added in 1992. The guy did everything, except replacing outer brick walls and existing heating system.

The current boiler is 135000 BTU w/80% efficiency. I would think it may still be operating at at least 70%.

I did the heat calculation for the house and with worst possible walls and insulation the heat loss is 80000 BTU. The house is approximately 2200 SQFT.

You've been trying to get me to 'go there' for a long time!
You figured huh
 
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Old 12-30-13, 07:56 PM
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boiler is consuming approx. 112.5 CF i.e. @ 1.2 therms per hour. 220 therms/month is approximately 7 therms a day. So per this reverse calculation BOILER is fired 7 hours/day on average.
Maybe not the boiler? Have you had high consumption before this in previous yrs? Sorry I did not re read the threads..

Note-- A job last yr had a similar issue.. There was a leak at the gas meter. I only found it because of the smell outside.. I thought it was a neigbors house or at the street but after calling the gas company it was her house...

They credit her on the bill even though on her side of the meter...Older home and under ground though the foundation... Was not sleeved...

Just a thought...
 
  #14  
Old 12-30-13, 08:08 PM
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Maybe not the boiler? Have you had high consumption before this in previous yrs? Sorry I did not re read the threads..
I purchased the house this year so my 1st winter.

Note-- A job last yr had a similar issue.. There was a leak at the gas meter. I only found it because of the smell outside.. I thought it was a neigbors house or at the street but after calling the gas company it was her house...

If that is the case then don't you think that leak could have caused higher consumption during previous months.

On a side note – for whatever reason I have oversensitive ears and nose. I was smelling something so have called utility company 3 times in last 2 months, they couldn't find any leak but then have tighten every possible unions and gas valves The meter they bring was reading 1 to 1.5 at few pipe fittings around the room but guy said that's just normal.
 
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Old 12-30-13, 08:37 PM
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Your heat loss calculation comes in at 80k but the boiler is rated at 135k output. Right there it shows that under the worst conditions the boiler is more than 50% larger than necessary. You also state that the boiler is 80% efficient; how did you come to this conclusion? I would be quite surprised to find a boiler of that age to be 80% efficient.

No doubt the close differential on the operating control is the cause of the short cycling and substituting a new aquastat with a wider differential would help. My thoughts are to instead incorporating a relay that would be closed by the lower aquastat and opened by the upper thermostat. The relay would then control the burner. You may need a second relay to control the pump. The way the "lo limit" (immersed) aquastat is now wired is to prevent circulator pump operation until the boiler temperature is above the set point. Having it set at 95 degrees pretty much means the control is useless.

That fitting with the broken copper tubing IS no doubt where the original operating aquastat was installed. It may be impossible to remove the bulb from the well and would then require draining down the boiler to remove the entire well and replacing it with a new well and control. There are other options as well. For approximately $30 to $50 you could buy a PID controller and thermocouple sensor (maybe even an RTD sensor) off of Ebay and connect it as the operating control, leaving the existing controls for safety limits.

I would also consider lowering the gas pressure to the burner or (preferably) changing the orifices to a smaller size and thus limiting the gas input to the burner. This would necessitate combustion testing to ensure proper setting of the gas pressure and primary air shutters.

I'll look at the previous thread a bit later.
 
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Old 12-30-13, 08:46 PM
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If that is the case then don't you think that leak could have caused higher consumption during previous months.
Not if it just started leaking recently???

Its just a thought though...

And dont know where you are in NJ but we had constant cold for a while here in NJ... That spike is not normal... Somethings amiss and I dont think its just due to an oversized boiler.......
 
  #17  
Old 12-30-13, 09:03 PM
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Thank you all!


Your heat loss calculation comes in at 80k but the boiler is rated at 135k output.
It is rated at 101K output, but I'd think that gas consumption is based on input rating of 131250 BTU.

You also state that the boiler is 80% efficient; how did you come to this conclusion? I would be quite surprised to find a boiler of that age to be 80% efficient.

Below is some data from plate on BOILER:

AGA Rating Btu/hr - Sea Level: Input 131250, output 105000, so I’d think that with IDEAL CONTROLLER conditions, when it was NEW – this BOILER was rated as 80% efficiency boiler (105000/131250 = .8).

I timed the gas meter and had few comments in previous post.
 
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Old 12-30-13, 09:06 PM
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And dont know where you are in NJ but we had constant cold for a while here in NJ... That spike is not normal... Somethings amiss and I dont think its just due to an oversized boiler.
That's for sure, RIGHT now outside temperature appears to be 24F. I'm in NNJ btw.
 
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Old 12-30-13, 09:29 PM
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I'm in NNJ btw
Grew up paterson/pomptonlakes...
 
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Old 12-30-13, 09:36 PM
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Are you on a slab? Gas water heater? If you have a slab leak the water heater will constantly run...

Just a thought....
 
  #21  
Old 12-31-13, 06:22 PM
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Are you on a slab? Gas water heater? If you have a slab leak the water heater will constantly run...
Section of the house on slab, but since house is ranch BOILER/GAS water heater is on my way in/out everyday and that doesn't seem to be case!

Thanks!
 
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Old 01-01-14, 11:18 AM
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this BOILER was rated as 80% efficiency boiler (105000/131250 = .8)
This is COMBUSTION EFFICIENCY though and not an indication of AFUE (Annual Fuel Utilization Efficiency). They are very different properties!
 
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