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Triple Aquastat with No DHW Coil... A Waste of Oil?

Hello there.

Two of my three boilers in my 3-family are cold start boilers. Without a call for heat, their temperatures will drop to nothing.

When they installed the 2nd floor boiler, a newer LAARS oil-fired, they used a triple aquastat, even though none of my boilers have DHW coils. I have three gas hot water heaters for DHW, one for each apartment. I'm assuming they never changed the control even after removing the DHW coil.

The lowest I can set the low limit on this boiler is 120, and it's a total waste of oil for my tenant to keep the boiler toasty warm in the unheated basement on a day when no heat is needed.

Can I remove any wires from the Honeywell triple aquastat (I forgot the model number, it's a vertical triple-aquastat) to basically turn it into a cold start boiler?

My brother installs boilers for a living and he has tons of controls in his van, I just have to find time to get one from him. In the meantime, can I modify the wiring on the triple aquastat to disable the low limit?

Nick, Cranston, RI


  • icesailor
    icesailor Member Posts: 7,265
    A waste of oil?

    I'm sure that some will disagree with me. That's their opinion and right.

    From my experience and conclusions, cold start oil boilers suck in ways that defy my descriptions that I can use here. There is not a competent oil burner technician that will honestly tell you that they would rather clean a cold start boiler over a warm start boiler. If they cold start and run below 140 degrees, they will condense. And it is nasty. The debris in the flue passages will consist of hard black kibbles and bits and soot that you need a soot saw to break through. If it is a well running warm start, there will be a reddish brown or brown ash that may take a few years to accumulate. But it is usually laying on top of the sections and not down on the pins. There is no way that the kibbles and bit and soot don't insulate the boiler. And it doesn't clean well. There are some of us that feel that switching to warm starts save money because of less sooting. In your situation, leave the control set on the low at 140 degrees. Set the "hi" at 160 or 170 degrees. If the house is cold during the coldest weather, turn the "Hi" up a notch.You can shut the burner off at the end of the heating season. Get it cleaned before you turn it back on. That is the best time to clean them. The soot just falls off and often, you can clean them to "new" conditions.
  • Tim McElwain
    Tim McElwain Member Posts: 4,554
    Get in touch with

    George Lanthier at www.firedragonent.com and ask him about "cold start" oil systems.

    The truth is that since we have gone to Intermittent Pilot on gas (no more pilot) keeping the water at least warm it has added maintenance problems to gas boilers. It is always good to maintain some kind of temperature in the boiler.
  • shadowdoc2
    shadowdoc2 Member Posts: 5
    edited April 2011

  • meplumber
    meplumber Member Posts: 678
    Ice, I thought we had adopted the official name of "Crumbles?"

    The ice man is right.

    Those of us that have spent more than our fair share of days sucking soot from boilers absolutely hates to see a cold start boiler that hasn't been touched in over a year.  The little bit that you save on oil will be re-spent with the service technician.

    Turn the low limit down to 140 and see what the actual dollar amount difference is between the cold start and triple aqua boilers.  You will be surprised.
  • Fortunat
    Fortunat Member Posts: 103

    Of course maintaining a boiler at 140 degrees unnecessarily is a waste of oil.

    I'm not an oil tech and don't clean boilers for a living so I can't tell you if cold starting a boiler makes that job harder, but I can tell you that it saves a substantial amount of oil, especially when the boiler doesn't have a HW load on it at all. The standby load (stack and jacket losses) on a typical oil boiler is on the order of .5 to .7 G of oil per day during the non heating season.

    Yes you can modify the triple aquastat so that it works like a high limit (just one wire to snip), but it is not recommended (and I'm pretty sure it is a code violation in most places). I'd suggest you buy your brother a 6 pack and have him come over and swap in a high limit control for your boiler.

    This is 2011. There are all kinds of reasons we can no longer afford to be wasting oil and $ is only one of them.

  • Mac_R
    Mac_R Member Posts: 117
    Cold Start

    I have used cold start on many new systems I have installed.  The trick to cold start is using a boiler that can handle cold start and make sure the unit has enough air so it is not going to soot.  Running outside air on your systems is a good way to ensure you have proper air for combustion.  With that combo I have never had to get out the soot saw.  Most of the time there is nothing there  and what is there is easily removed with a small brush and dust pan.  No more lugging the vacuum up and down.  I install the Buderus G115WS with the Beckett NX burner.  The Logamatic 2107 is cold start in the summer time. 
  • Jason_13
    Jason_13 Member Posts: 301
    Old habits are hard to break

    I have been installing boiler for over 30 years. I also have been installing cold start boiler for about 20 years when I determined that DHW coils must have been introduced by the devil himself. Too expensive to operate and in my area many water quality issues.

    One thing I learned real quick when I started installing cold start boilers was the importance of proper sizing, combustion testing and importance of near boiler piping and boiler flow.

    When you do your homework you have no problems with cold start even in boilers not serviced every year. Like anything else you need to spend the time to do it right. Better oil filtration I found to be essential.

    It also got me to think about other problems encountered with boilers such as nipple leaks, condensation, short cycling, fuel consumption etc. Sizing is critical for boiler cleanliness fuel savings. Over sized boilers cause faster and more frequent expansion/contraction of the iron. This will result in more stress and nipple wear. Cast iron boilers should expand slowly and raise temp slowly.
  • Greg Maxwell
    Greg Maxwell Member Posts: 212
    Cold Start

    We have been selling cold start boilers starting with the Crown Freeport back in 1985, and it just keeps getting better. We dont see any condensing issues to speak of, unless you have an exceptionally large volume system, and none of the service issues regarding kibbles and bits, unless not serviced properly, or using the old "set up by eye" method. In all fairness, the cold start boilers we use, were designed for cold start, so they actually have tighter flue passages than pin boilers. In a standard residential setting cold start is the way to go. Actually, the more correct classification would be on demand. The only thing you have to watch, is boiler water volume. If you are looking at a fairly small, under 20 gal boiler, than cold start will be good. If you want to try it, get the new Honeywell L7124U universal control. It can do either, so if you dont like cold start, you can set it at a reasonable low limit setting.
  • Jason_13
    Jason_13 Member Posts: 301
    Cold Start

    Actually every boiler today is designed for cold start both commercial and residential. There is not a problem when properly sized, set up and piped. Most of the kibbles and bits come from no boiler protection when required and improper setup.
  • Mac_R
    Mac_R Member Posts: 117
    cold start

    watch it.  not every boiler made today is cold start.  I will say read the manual that came with the boiler.  That will tell you what the manufactures recommendations are for low temp settings.  I know the new yorker FR122 requires a minimum temp of 120.  Wile the FR-HGS1 and 2 come with cold start controls.  just read the manual and you will be fine.  Set up is very important.  where you test is just as important.  to many times I go out to new customers homes and find the test hole in the wrong place or no hole at all.  In this day and age with digital combustion testers  there are people out there who are still to lazy to do a run time test.  No excuse.  one place the test hole was on the other side of the draft regulator.  there was 2 feet of smoke pipe before it.  why?  I am chalking it up to ignorance.  I hope it is not stupidity. 
This discussion has been closed.