Should firirng rate be reduced?

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Old 05-19-13, 08:51 AM
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Question Should firirng rate be reduced?

I have a 23 year old oil fired cast iron Weil McLain boiler model # A/B 368 VW that is in good working order. In early April I had a 53 gal. indirect hwh installed to replace a failing heating coil which has now be valved off on the output side.

Looking at the information stamped on the boiler there is a standard input (Lt oil) of 0.95 gph with DOE htg capacity (water) of 114 mbh. There is also a minimum input of 0.70 gph/86mbh. The burner is a Beckett model AFG.

The house is a 1200 sq. ft. ranch (eastern Long Island) that is very well insulated and has good quality double glazed windows. The heat is hot water using copper fin baseboard. The boiler high limit had been set at 175˚ F and during the coldest nights (about zero F) would run for about 40 minutes and off for about 20 minutes with T-stat set back to 64˚ F.

Does it make sense/$$$ to ask my oil service company to lower the firing rate down to 0.70 gph? In the previous 12 months I used 730 gallons of oil and had to keep the boiler set at 175 to maintain hot water through the now defunct hot water coil. I am now experimenting with lower boiler temperatures. Is there a lot of work involved to lower the firing rate?
 
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Old 05-19-13, 11:31 AM
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Welcome to the forums.

Not really my department buy I think you are confusing firing rate with boiler temperature. You wouldn't necessarily want to change the firing rate in the summer but a lower water temp would seem to be a good idea. I don't know how low you can lower the boiler temperature.

The pro's will stop by and fill you in.
 
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Old 05-19-13, 12:01 PM
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Not really my department buy I think you are confusing firing rate with boiler temperature. You wouldn't necessarily want to change the firing rate in the summer but a lower water temp would seem to be a good idea. I don't know how low you can lower the boiler temperature.
Iím interested in lowering the firing rate as a permanent year round fuel conservation/money issue.

I only gave boiler temperature settings as a way to indicate that the boiler at its current firing rate (0.95 gph) does not appear to be having any problem keeping up with heat or hot water demand and that I am aware that with the new indirect hwh I can now also reduce the boiler temp as an additional way of saving some cost.

Sorry for any confusion.
 
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Old 05-20-13, 04:57 PM
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Lowering the firing rate is not a difficult process. A new nozzle is installed and then the oil burner is "tuned" using combustion efficiency testing equipment. You will need someone who knows what they are doing and has the right tools.

Whether or not it's a good idea is probably an open question that won't be answered fully until you go ahead and give it a try - over the course of a full heating season - while you monitor the results. It's during those zero degree nights when you'll find out whether or not the boiler can keep up heat-wise. And then of course, it's during those frigid mornings that follow - when family members are taking long, hot showers - when you'll find out whether the boiler (and the indirect tank) can keep up in that regard, as well.
 
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Old 05-20-13, 05:12 PM
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The boiler high limit had been set at 175˚ F and during the coldest nights (about zero F) would run for about 40 minutes and off for about 20 minutes with T-stat set back to 64˚ F.
That doesn't sound too abnormal. If you cut back on the firing rate, the recovery time will increase. In any case, I can't visualize much fuel savings (heat in x eff = heat out). If you want to improve efficiency, try reducing the high setpoint of the aquastat.
 
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Old 05-20-13, 06:10 PM
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730 gallons on a 1200 sq ft home with a hot water coil seems high.
I'm 2000 sq ft cape style in NJ with a DHW coil (2 people) and I use about 600 gallon a year.
I'm firing at .75, don't remember the BTU output of my Ultimate, but it certainly keeps up nicely with our demand.
 
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Old 05-20-13, 06:14 PM
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Lowering the firing rate is not a difficult process. A new nozzle is installed and then the oil burner is "tuned" using combustion efficiency testing equipment. You will need someone who knows what they are doing and has the right tools.
Thanks for the info. Assuming the boiler can keep up with the load on the lower firing rate what kind of savings can be expected if any?
 
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Old 05-21-13, 10:05 AM
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hi guys Ė

I am a confessed boiler system ignoramus but isnít that very high usage (730 gals) because the boiler LOW limit was probably set extremely high, to compensate for the inefficient heat transfer through the coil? Or would this boiler not have a LOW limit? (However, I thought you had to have a LOW limit with a coil?)

( Just an older fella always trying to learn!LOL)
 
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Old 05-21-13, 12:59 PM
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Assuming the boiler can keep up with the load on the lower firing rate what kind of savings can be expected if any?
That's pretty much impossible to say without an actual "field test" being performed... there are just too many variables involved.
 
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Old 05-21-13, 01:32 PM
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I am a confessed boiler system ignoramus but isnít that very high usage (730 gals) because the boiler LOW limit was probably set extremely high, to compensate for the inefficient heat transfer through the coil?
Yes, that is exactly the problem. As part of the purchase of the indirect I insisted they install a universal type A-stat on the boiler so I would have more flexibility in setting boiler temp and differential. They put in a Hydrostat 3150. It has differential on both the high and low adjustable up to 30 degrees.

Now that the weather is warmer I have set the high limit at 155 with a 15 degree diff. The low is set at 140 with a 10 degree diff. Boiler now runs once every 4 hours to top off hwh. It use to run once every 45 minuets to keep the coil warm.
 
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Old 05-21-13, 01:37 PM
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That's pretty much impossible to say without an actual "field test" being performed... there are just too many variables involved.
Makes sense, thanks. Oh no message too short so thanks again
 
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Old 05-21-13, 06:23 PM
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Yes, that is exactly the problem. As part of the purchase of the indirect I insisted they install a universal type A-stat on the boiler so I would have more flexibility in setting boiler temp and differential. They put in a Hydrostat 3150. It has differential on both the high and low adjustable up to 30 degrees.

Now that the weather is warmer I have set the high limit at 155 with a 15 degree diff. The low is set at 140 with a 10 degree diff. Boiler now runs once every 4 hours to top off hwh. It use to run once every 45 minuets to keep the coil warm.
Wow! What a great improvement. Good for you. Got to get me one of those! If I set my low limit below 165 my DHW is hardly warm enough for a quick shower. The coil concept stinks!!
 
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Old 05-22-13, 09:14 AM
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The coil concept stinks!!
I upgraded from an older coil several years ago when I got a hold of a used indirect tank. The difference in comfort level was immediate. Even though the tank was already several years old, it nonetheless felt like I had a whole new DHW system!

After I installed the indirect, I continued to run the boiler as a "warm start" w/Low Limit for a few years. I can't say how much oil I saved by having the indirect tank verses the coil, because at that time I just wasn't paying close enough attention to those kind of details.

Later on, when I replaced the ancient oil boiler with a new gas-fired unit, it enabled me to go with a "cold start" control setup for both the boiler and the indirect tank, and that's when I really noticed some considerable savings in energy costs.
 
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Old 05-22-13, 10:19 AM
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The difference in comfort level was immediate.
I'll second that! It's the first time in 35 years that I can really enjoy a shower. A tempering/anti-scald valve was installed with the indirect and I have it set at about 120 F. I have endless hot water in the shower and the temperature never varies unless I move the shower handles.
 
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Old 05-23-13, 09:32 AM
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Ok you guys are making me jealous !LOL

NJ Trooper calls them ďthankless coilsĒ. So true!

Getting some good ideas here from you guys about what to do about mine in the future. There is hope.LOL

Iím sure everyone with the coil appreciates your inspirational comments! I do.
 
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Old 05-25-13, 12:44 AM
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2YsUR,
With the indirect you should be able set your lower limit to zero/off. The indirect should be wired that when it calls for heat on it's own t-stat it will tell boiler to fire. It should also be set as a "priority" call so it won't let other circulators turn on. Most of the IWH have about a 10 degree swing before they call. Your boiler should be able to heat up fast enough to supply that demand. The reduced firing rate might not have enough BTU's if it's buy the low differential of the water heater AND boiler is cold (room temp). Only one way to find out.

When I went from tankless coil to IWH, I saved 400 gal/year by going cold start. During summer boiler turned on 1-2 times day just for hot water recovery after showers. After that I added an Intellicon HW+ (saved another 300 gallons) and then an Oil Vent Damper (saved 50 gallons). I was in a not the best insulated 1700sf colonial. 1400 gal/year when purchased, 650 gal/year when I sold it. Original boiler Repco with tankless, new Weil Mclain WGO-4 with Amtrol boilermate. WM was put in 2 years after buying house. Heat was basically 70 degrees all the time.

The Intellicon and/or Heat Manager might help if you have an oversized system which 98% of the older one were. YMMV

Also elaborate for my own knowledge "valved off on output side". What was failing on the tankless? Is water still supplied to it? Some coils fail and increase pressure in the boiler causing pressure relief to give (since domestic water is not pressure reduced the same as boiler). With your low limit at 140 your boiler still needs to maintain that min. cold start would knock out 4-5 "runs" during the warmer months and some in colder also. The OVD will help retain the heat in the boiler instead of out chimney all day/week/year long.
 
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Old 05-25-13, 12:11 PM
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Sequoiasoon,

Thanks for the very informative reply.

With the indirect you should be able set your lower limit to zero/off.
Iíve read many posts about running a boiler as a cold start but Iím not comfortable that my 23 year old WM will handle it well, so Iím holding off for now.

The indirect should be wired that when it calls for heat on it's own t-stat it will tell boiler to fire. It should also be set as a "priority" call so it won't let other circulators turn on.
Yes, it is setup as you describe and has a priority override after 1 hour.

When I went from tankless coil to IWH, I saved 400 gal/year by going cold start.
Wow Ė thatís amazing!

Original boiler Repco with tanklessÖ
Thirty-six years ago the builder had put in a Repco. Brookheaven town declared them a fire hazard and I had it replace with my current WM (23 years ago) when the Repco showed signs of burning through the side!

The Intellicon and/or Heat Manager might help if you have an oversized system which 98% of the older one were.
I have my eye on one of those or the Hydrostat 3250 but Iím willing to wait to see what my fuel usage will be like with the indirect and lower boiler settings over the next heating season.

Also elaborate for my own knowledge "valved off on output side". What was failing on the tankless?
The hot water coil was left in the boiler and still has a cold water supply open to it. On the hot water output side a ball valve was added and is closed. The coil was producing less and less hot water and I finally opted for an indirect. Iím super pleased with the indirect!

At the time the indirect was installed (early April) I replace my thermostat with a Honeywell digital thermostat model RTHL3550d. This maintains the room temperature at exactly the set point without varying. No more overshooting the set point two degrees or waiting for the heat to come on as the room temperature falls 1 or 2 degrees below the set point. The comfort level is fantastic.

Thanks again for the input.
 
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Old 05-25-13, 04:54 PM
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2YsUR,
Since your not using it, I would consider if possible to close off the supply to coil but leave one side open. Many threads posted about leaking coils and pressure relief etc.

With the indirect supplying your HW it should recover fine. I would leave your high limit at about 180 but set your low limit for now maybe to 100 if you don't want to try cold start. Keep an eye on the rubber seal areas (like your tankless gasket). If you see any drips from anywhere then you know to keep it warmer.

My new house the boiler got down to 65 degrees (ran out of oil) and I saw some drips from the tankless coil gasket. I have a new gasket and blank plate that I will install this summer when I put in indirect water heater. Never had an issue with my WM in old house but it started life as cold start.

Check you PM also.
 
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