Hi limit setting on boiler

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Old 12-08-12, 12:47 PM
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Hi limit setting on boiler

hi, i have been reading on here for a while now and finally got around to signing up. i just finished installing a new boiler ( slant fin intrepid trdv 30 with tankless coil and a riello bf5 burner with a 1.0 gallon nozzle ) in my 2 story home. the honeywell aquastat was preset to 160 degrees low limit and 180 degrees high limit, but the installation instructions from slant fin say the high limit should be set at 200 degrees. i am not sure which setting will be best for performance and or economy. i have good heat and plenty of hot water with the preset limits at 160 and 180. also, if i increase the high limit to 200, should i then also increase the low limit by the same amount? this is my first boiler install and all the info i got came from forums like this and the boiler man dvd from vermont ( by the way his dvd was very helpfull ). i must say there is a lot of good info out there if you take the time to look for it. i would really appreciate any help on this, thanks in advance, chris.
 
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Old 12-08-12, 01:12 PM
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Hi Chris,

honeywell aquastat was preset to 160 degrees low limit and 180 degrees high limit, but the installation instructions from slant fin say the high limit should be set at 200 degrees.
I don't know why SF is recommending 200. IMHO that makes no sense to me at all. For how many decades systems have been designed around a 'standard' high limit of 180? A: many.

I can't imagine why anyone would opt for a tankless coil in a boiler to produce domestic hot water. It's VERY inefficient... but it's done, so it is what it is I suppose.

No, don't raise the high lim to 200. If it's heating fine at 180 leave it right there.

About the 160 LOW setting... did you also install a THERMOSTATIC TEMPERING VALVE on the hot water supply to the home? If not, you should, and set that to 120-125. Water any hotter that that can cause severe burns, particularly for the young, old, and infirm.

Raising the LOW to 180 is even more dangerous!

My suggestion is to try 140 LOW and DIFF at 20 (leave high at 180) and try for a week or so. If you have adequate hot water for the home, leave it alone. The LOWER you can run the LOW and still have hot water needs met, the less you will spend on fuel.
 
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Old 12-08-12, 02:03 PM
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boiler high limit

hi and thanks for the quick response. i will leave the high limit alone as you say. i dont have the tempering valve, and never did ( there was a ball valve on a pipe between the hot and cold on the original setup, but the valve was always left shut for the last 20 years, so i eliminated it when i repiped the new boiler. ) i now know i should have installed a tempering valve and i am going to do that in the near future. as far as the tankless coil, it is what i had for the last 20 years and it always gave us plenty of hot water with no trouble ever. it is also basically free hot water in the winter months. i know a boilermate or something similar would be more efficient but i was looking for the least labor intensive as well as least costly replacement. thats why i installed it myself. several estimates i got for installation of a new boiler ranged from 7- 10 grand. it cost me about $3500. to do it myself with some help from family. it took us three days and several trips to the hardware store but we did pretty good in the end. i was a little intimidated about such a big project ( my first plumbing job ) but i have always been pretty handy and it seems that it turned out okay. by the way is there any particular hot water maker that you would recomend ( electric is crazy high here in r.i., and we dont have acess to natural gas, only propane which is also very costly here so these are not an option ). thanks again, chris
 

Last edited by ingersollman; 12-08-12 at 02:06 PM. Reason: add more info
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Old 12-08-12, 02:10 PM
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Take some pics.... We always like to critique installs to make sure all is safe and such.

I think if you compare oil to electric for HWH , electric would win out. Thats from what I read here anyway...
 
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Old 12-08-12, 02:11 PM
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it is also basically free hot water in the winter months.
If you really believe this I have some prime swamp land and a couple of bridges to sell you.
 
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Old 12-08-12, 02:55 PM
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hey, i'.m up to my eyeballs in swamps and bridges right now, but thanks for the offer. seriously though the boiler is maintaining temp all winter long anyway, so it cannot cost that much for hot water in the cold months,right? maybe i'm nuts.
 
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Old 12-08-12, 02:59 PM
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elec vs oil

i will try to post some pics tomorrow, but please promise not to laugh too loudly, as this was my first effort and i am by no means a plumber, i only play one in my basement. thanks for your interest and any input or critique would be welcomed. after thinking about it i just paid $3.40 per gal for heating oil this week so perhaps there is no economical way to heat water here in r.i.
 

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Old 12-08-12, 03:03 PM
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seriously though the boiler is maintaining temp all winter long anyway, so it cannot cost that much for hot water in the cold months,right? maybe i'm nuts.
The infux of cold water during a hot water call will cool the boiler and cause it to fire. This uses oil. Common sense.

Oh we will not laugh... We are here to help. We want you to be safe and comfortable.

Health, saftey and comfort is the plumbers motto....


 
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Old 12-08-12, 03:14 PM
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ok i give up, you guys definitely know more than me about this stuff, that being said they are quite popular here in my area. maybe it's just the ease of installation? i would like to hear from anyone who can steer me in the right direction. i have heard that the amtrol boilermate ( this a separate tank which i believe is also oil fired ) is pretty economical to run. anybody have something like this out there i would love to hear what experience you have had with it. thanks, chris
 
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Old 12-08-12, 03:36 PM
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A indirect will still use oil but when the tank is heated it retains the heat. It would take less oil to maintain.

But even that is if you have high demand.

Electric may be a better bet in savings.

Wait for the oil guys to chime in. They sleep this calculation stuff on oil vs electric rates vs indirect...etc

Whats your electric rate there? Here in NJ we are at 15 cents a Kw.
 
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Old 12-08-12, 04:00 PM
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hi, we don't have much demand, just the wife and i most of the time. my daughter is away at college but spends summers here and an occasional weekend. our electricity costs about the same as yours, 14.24 cents. call me the cheap yankee that i am, but the electric co. has no competition and i can still shop around for oil. you might be surprised to know that oil prices here can vary as much as 40 cents a gallon depending on who you buy from and how you pay. cash is king and thats how i pay. that being said i will consider an electric unit, i'm not sure how to compare the cost to my setup. oh ho the laptop needs a charge. talk more tomorrow, thanks again, chris
 
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Old 12-08-12, 04:20 PM
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Here is a spreadsheet to compare heating costs: Fuel Comparison Calculator for Home Heating

Best to also run your own numbers. For oil, I would assume unless you know better, 75% efficiency and 139,000 Btu/gal. For electric, 3413 Btu/kWh and 100% efficiency. If you already have oil heat, then you'll have to replace your baseboards and perhaps upgrade your electric service if it's not already 200A.

Many people will tell you right off the top of their head that one or the other alternative is more economical - including the electric company, oil company, others here, and me. Don't believe any of them. (But, I would tell you that electric heating will not be competitive with oil.)
 
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Old 12-08-12, 04:23 PM
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several estimates i got for installation of a new boiler ranged from 7- 10 grand. it cost me about $3500. to do it myself
About the same here in Joisey. I too just installed my own and figure I saved about $4000 doing it myself. If only I could get the Treasurer to cut me a check! My total came to a little under $3K but I had most of the bits and pieces I needed "in stock". If you want to look at my saga, check this thread:

http://www.doityourself.com/forum/bo...n-finally.html

We have no NG here, or city water, or sewers, and LPG is pretty much the same price as oil and price tracks with it (a byproduct of petro refining).

I run an electric WH myself, costs about $35-40 / month to run.

basically free hot water in the winter months.
Of course not free... but when weather is cold and boiler is for the most part warm/hot most of the time anyway, the 'hit' isn't nearly as bad as in the summer. I mean, how much oil to burn to keep that boiler hot 24/7 just for the few gallons of hot water needed during the course of the day?

Furd usually compares the tankless ( I call them "thankless") coils to a kettle on a woodstove. He thinks the tankless is slightly better... I'm not so sure! But then, I'm all for the 'old ways' and if I could have a copper bathtub in the kitchen and have the Treasurer boiling pots of hot water while I bathed... well, I might kinda like that! I just hope her 'aim' is careful when pouring that hot water in!

By the way, the "indirect" water heater that was mentioned... the BoilerMate is an "indirect". There's a number of good ones out there. They ARE pricey, but when you consider that you don't have to replace them every 6-9 years, the price starts to make sense. I would fully expect that an indirect installed would run around $1000 or more... some of the tanks themselves run that much.
 

Last edited by NJT; 12-10-12 at 03:53 PM.
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Old 12-08-12, 04:39 PM
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Here is a spreadsheet to compare heating costs: Fuel Comparison Calculator for Home Heating


But thats for home heating no? Would it not be different for HWH?

I put in #'s and it would seem electric is more.

Troop what do you have? Electric? Whats your calc? Or are you pleading the 5th????
 
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Old 12-08-12, 05:49 PM
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Spreadsheet is only comparing the price of equivalent BTU, no matter what they are used for.

The Treasurer says I have no rights...

I run an electric WH myself, costs about $35-40 / month to run
I guess we could back that out into how many BTU a typical electric would use in a month, then forward it into how much oil would be the equivalent... where's my abacus?

If the beads are right, that looks like a bit more than 30K BTU per day... can that be right?

That's about 1260 BTUH.

Heater elements are 4500 watts... or 15345 BTU.

Which would seem to indicate that the element is actually ON a little less than 2 hr a day... yeah, I guess that could be right.

So, if an oil boiler were 100% efficient (which we know of course it is not), one should be able to heat domestic hot water with slightly under a QUART of oil a day. Let's say a quart times 30...

That's about 7.5 gallons a month, at say 3.60 a gallon ... that's about $27 a month at 100% efficiency...

Let's say 80% efficiency... Looks like about $32 a month.

Not a HUGE difference, is there?

(but my COLD water is CHEAP! 0.0007 cents per gallon)
 
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Old 12-08-12, 06:05 PM
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Spreadsheet is only comparing the price of equivalent BTU, no matter what they are used for.
What difference does it make in this case?
 
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Old 12-08-12, 06:07 PM
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What difference does it make in this case?
No difference.

A BTU by any other name...
 
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Old 12-09-12, 08:50 AM
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elec vs oil water heater

thanks for all the input, everyone. sounds like not much dif between oil and electric water heater according to nj trooper's calcs. i guess i can go either way when finances allow. i just discovered i have no heat to the second floor and the zone valve is opening when it's supposed to so i'm going to shut down the boiler till it cools off and close the other 2 zones. then open the second floor zone valve manually and try to bleed out some air. hopefully this fixes it. i'll keep you posted and post some pics later on.
 
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Old 12-09-12, 11:33 AM
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Yes, not a HUGE difference, but keep in mind that the 'thankless coil' will certainly run a LOT more oil than my calcs. The difference I calculated would be more in line with a quality indirect. I wouldn't be surprised to hear that a thankless coil used TWICE as much oil to heat the domestic.

Two story home you said?

Is the COLD pressure on your boiler at least 12 PSI ?
 
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Old 12-09-12, 01:28 PM
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no heat second floor

hi, i have'nt checked the cold pressure, at operating temp i have 17psi. i just bled out quite a bit of air and i am waiting a while to go up and see if that worked.if not i 'll shut it down again until it cools off completely. will now try to post some pics.
 
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Old 12-09-12, 02:08 PM
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If yer at 17 HOT, my bet would be the cold fill is OK. An increase of 5 PSI from cold to hot is very reasonable.

By the way, those calculations are VERY hypothetical and subject to a lot of variance... I did take a lot of WAGs with my numbers. They should definitely not be taken as 'gospel'!
 
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Old 12-10-12, 06:27 AM
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no heat second floor

hi, bleeding that zone again seems to have done the trick. the temp up there now is matching the set temp on the thermostat. we're not using that floor right now so i keep it set low (55). i will check it again when it gets cold later this week. thanks again to all who chimed in, i appreciate all the help. bye for now, chris
 
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