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Cause of Peerless MI-03 Lockouts

D107D107 Posts: 1,616Member
New Peerless MI-03 Boiler installed four months ago. Had two lockouts, one two months ago, the other a week ago. First thought in May was defective damper; not the case. Hitting re-set button solved it in both cases. Opinion then was that some kind of blocked vent switch/downdraft caused it, thunderstorm etc. But this past week air weather was calm.

I have heard that low system pressure can cause such a lockout. Installer says he set expansion tank pressure at 18psi and I see the autofeed prv is set to about 16. Should they be set the same? I measured a system height of 16ft above the expansion tank which the Westank calc said based on that the initial pressure should be set at 17. So those settings seem to be ok. (We have an older house, ceiling heights are a little higher.) On initial install pressure gauge at PRV read about 15-16.

Around the time of the first lockout (not sure if before or after) I noticed pressure gauge was up to about 20-22. (Total system water around 70 gallons, including 48 for Turbomax). I let a little water out of the boiler and it returned to 15 about 6 weeks ago. Right after the most recent lockout, I noticed pressure was back up to about 20. What does this sound like? System controller is Hydrostat 3200+. Set to cold start.

Manual indicates possible causes: defective gas valve, plugged orifice spuds, gas off, flame rollout switch open, limit not working, etc. some of these-- like orifice spuds-- require cleaning.


  • Steve MinnichSteve Minnich Posts: 2,516Member
    By lockout and reset, what exactly are you resetting? If it’s flame recognition, it could be one of the things below.

    Two things I’d check first -
    1. Polarity of hot and neutral
    2. A good ground
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
  • D107D107 Posts: 1,616Member
    edited July 2019
    @Steve Minnich Thanks, no it's the blocked vent switch. Instructions are to Reset switch, locate cause and correct. We have a brand new 5" stainless steel internal chimney liner.
  • HomerJSmithHomerJSmith Posts: 807Member
    edited July 2019
    What do you mean by Lockout?

    If you had a non functioning damper, you would trigger the roll out safety switch, either a chemical fuse or thermodisc. A chemical fuse is non re-settable. How do you reset the boiler so that it works?

    If it is spark ignition the ignition module needs a good solid ground to the spark electrode. Do you have a grounding problem?

    Is the power outlet polarity correct?

    The distance from the top of the boiler to the top of the highest heat emitter is 16'?

    If so, then you divide 16' by 28" and you come up with about 7 psi. 28" equals 1 psi static pressure. Then add 5 psi. That is 12 psi bladder tank pressure. If the tank pressure is higher, does it make a difference? It could. If the tank pressure is close to the pressure relief valve (PRV) setting, cold, then when the water heats up and expands, the the water may push thru the PRV on to the floor. Also, A high tank pressure could limit the acceptance of the tank if the sys pressure is lower than the bladder pressure. To maximize the acceptance value of the tank, the sys pressure should be the same as the bladder pressure.

    The auto feed valve and the bladder pressure should be set at 12 psi to 17 psi. Yes, the same. The boiler gauge should indicate the sys pressure. The pressure gauge will rise when the boiler heats up the water. Can be up to 5 psi higher depending on the water temperature, that's normal.

    If this boiler gives you a fault code that could be a hint to the lockout. If not, I would jump one safety circuit device with alligator clips, one at a time, and observe the results.

    If there are any thermodiscs in the safety circuit wiggle the wire to the connection tab and make sure the tabs a tight to the disc and does not wiggle. A loose tab can cause intermittent lockouts.

    If you have a inducer fan make sure that the exhaust vent isn't partially blocked and properly connected.

    Sys water capacity is 70 gal? Do you have the right size X-tank?

    I don't know. OK I looked it up so some of what I said doesn't apply.

    I read, "The reset control with low water cutoff protects your boiler in the event of dangerous temperatures and drops in the water level." Check out this.

    Is there an elevation problem so that the boiler need to be adjusted for altitude?

    Do you have water circulation?

    Is this propane or NG? I assume it's Spark Ignition.

  • Robert O'BrienRobert O'Brien Posts: 3,163Member
    Does it have an Aquasmart?
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  • D107D107 Posts: 1,616Member
    @Robert O'Brien No, Hydrostat 3200+.
  • HVACNUTHVACNUT Posts: 2,868Member
    First, water pressure has nothing to do with the spill switch tripping.
    The 03 flue is 5" at the hood and there's a new 5" stainless liner but the safety tripped twice in four months. So it's a potential draft issue.
    Not to scare but if you dont have CO detectors, get some.
    The contractor should have a combustion analyzer that can read draft and well as gasses. Has he come back to check?
    Is the crown sealed tight at the top of the chimney? Is there enough combustion air for the boiler to breathe? Any source of negative draft? Attic fan, range hood, ERV?
  • HomerJSmithHomerJSmith Posts: 807Member
    edited July 2019
    OK, I looked at the schematic and you have only two safety switches, rollout switch and a draft blocked vent hood switch (spillage) which is a re-settable thermodisc aside from the micro-switch on the vent damper. Which is what you reset.

    Replace the thermodisc as it may be defective and they're cheap. You can probably get one free from the manufacturer. You can check the temperature at the outlet of the boiler and into the draft hood with a thermometer. The flue temperature should be in the boiler output mixed with the draft hood fresh air at about 350 to 450 deg. check that above the vent damper in the flue pipe for this temp. If it is hotter you probably have flue vent problem. A vent damper not fully open. If this temperature is ok? Is the draft hood temp ok?
    What is the rise of the flue off the boiler, it should be 2' vertical rise before running horizontal.

    The flue output is 5", I assume. Corrugated flex pipe has to be one size larger or 6". I assume it is not a common vent in a dedicated chimney?

    I may be that the boiler is overfiring raising the flue temp.

  • D107D107 Posts: 1,616Member
    edited July 2019
    @HVACNUT We have two CO detectors, one low level and one kidde unit. Both show 0. Last printed combustion test mid-April shows draft fluctuating between -.0250 to -.0300. stack temp was 399º O2 8.6% CO2 6.90% CO 1ppm; CO AF 2ppm, 81.4 Gross EFF Excess Air 62%. First lockout happened mid-May, no printout from then but combustion was probably checked. Cement crown should be good--was inspected. In terms of combustion air, since original boiler was firing at 190Kbtu plus there was a 40k btu hwh going into same chimney with no issues, it was felt this 70kbtu firing boiler would be ok w/o FAI. That said our house is fairly well insulated--not super--but that's been for two years. We do have a de-humidifier in the room but it is all within the room so what it pulls it should be putting right back as far as I understand. Gets the boiler room pretty warm plus given all those uninsulated pipes. I'm not sure if dehumidifier was on in Mid-May at last lockout. Chimney is 33ft internal. See photo below:
  • D107D107 Posts: 1,616Member
    edited July 2019
    @HomerJSmith No common vent--we have reverse indirect hwh. To all the respondents, thanks for all the great trouble-shooting tips.

    I wonder about this type of draft set up--no barometric damper, a sudden downdraft could cause this, yes? Doubt it happened though given the weather.
  • This sounds like when Wyatt Earp rode into Deadwood.
    Often wrong, never in doubt.

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  • D107D107 Posts: 1,616Member
    edited July 2019

    No inducer fan; see my photo on prior post to hvacnut.

    Expansion tank size: some have opined that it should be larger for a little extra margin but even during a dhw cycle gauge doesn't read above 22.

    You wrote: I read, "The reset control with low water cutoff protects your boiler in the event of dangerous temperatures and drops in the water level." Check out this.
    Not sure how it would drop the water level, but if it did then presumably autofeed would refill but my water meter shows no sign of any added water.

    No elevation problem, basically sea level.

    We haven't had a problem with circulation--note that we've had heat off since April, so it's DHW only via boiler and reverse indirect. No problem with hot water. In heating season, no noticeable issues with circulation.

    Natural gas and yes, Spark Ignition.

    When I used the online calc, 16ft of system height above boiler came out to 17 psi required for exp tank; perhaps your formula is more precise(?) Years ago -1924 house--the old type expansion tank was in the attic. It was disconnected many years ago, and part of that piping may still exist but at this point I'm quite sure none of it is higher than the top floor radiator.
  • SteamheadSteamhead Posts: 13,576Member
    edited July 2019
    D107 said:

    @Steve Minnich Thanks, no it's the blocked vent switch. Instructions are to Reset switch, locate cause and correct. We have a brand new 5" stainless steel internal chimney liner.

    Check to make sure the burners are not over-fired. Too much exhaust gases can overwhelm the draft hood. Also, make sure the stack damper is opening all the way. Finally, make sure you have enough air for combustion.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • HomerJSmithHomerJSmith Posts: 807Member
    Kind of a nice setup, looks well planned. Personally, I don't like mixing Black Iron pipe with copper, each to their own. Funneling the exhaust vent into a masonry chimney without carrying the vent to the roof can cool the exhaust to the point that the flue gasses lack buoyancy and stagnate raising the draft hood temp. Also, without a B-vent cap that is wind rated, a down draft could acerbate the stagnation and forward movement of gasses up the chimney. Was it windy when it locked out? Where is the chimney located in relation to the prevailing winds?

    Maybe you would want to do a smoke test at the fresh air intake to the draft hood on a windy day to see if you have any spillage.

    I would still replace the thermodisc just to be sure that ain't it.

    Never assume that all the wiring and connection are good and correct.

    By the way are these lockouts happening during the day or nite?

  • HomerJSmithHomerJSmith Posts: 807Member
    edited July 2019
    What is the boiler system SWT set at? What does the gauge temperature on the output of the boiler say at its highest temp during a cycle? How long does it take in minutes after high limit to reach its differential where the boiler fires again?

    Is there any rattling coming from the boiler just before the flame cuts out?

    I ask a lot of questions, but they are important as they tell me about the performance of your sys.

    What the above tells me is, Do you have sufficient flow thru the boiler heat exchanger. Does your pump have enough head at the desired flow.
  • D107D107 Posts: 1,616Member
    edited July 2019
    @HomerJSmith You said 'carrying the vent into a masonry chimney' I'm not sure if I made it clear this is a full 33ft 316L stainless steel chimney liner right up to the top. See attached photos. It's a double flue--adjacent is fireplace. Hoping the vent cap--that covers both--should deter any winds. It's in the center of the house.

    I put the draft readings in a prior post--fluctuating between .0250 and .0300.

    Can't say if it was windy first lockout--was kind of a stormy time so it is possible. 2nd lockout don't think there was any wind, very calm humid night as far as I know. Lockout was noticed in the morning when there was no hot water, but could have happened anytime from sundown to dawn.

    Boiler SWT max at 160, cold start. I tend to look at the boiler temp on the hydrostat which comes from the probe right near the output pipe. Generally it cuts off at 160º boiler temp--VR1816 circ cuts off same time unless rarely aquastat needs more than hydrostat limit in which case circ will continue and eventually re-fire boiler to make dhw temp. in summer boiler temp can continue to rise after shutoff to 170 since with circ off Heat X will continue to transfer heat for a few minutes. Note this is used now for DHW only with Turbomax reverse indirect, so the tank has 48 gallons to be heated.

    If no hot water is being used, in summer it can take 3-4 even 5 hours for the boiler to fire again. I have the Turbomax aquastat set to cut out at 150 cut in at 135. The aquastat element is placed lower than mid-tank, while gauge probe is probably only 5 inches below tank top and seems to read ten degrees higher than probe.

    Can't say I hear rattling before shutoff, though I can make a note to look out for that. Pre-cycle you can hear the damper moving into place.

    The VR1816 is set to fixed speed the second of 5 positions which is the white dot just past the MIN setting. MIN is equivalent to Taco 003, that dot we're set on equals 006.

    The universal hydronics formula would say my 50K net btu boiler divided by (20º∆T x 500) would give me 5gpm flow rate, which is what the Turbomax calls for. If I estimate head with 13ft pipe x 1.5 = 20x.04 = .8 or let's say 1ft head. If I measure every EL, Tee, check valve, etc. I still only get 1.5ft head. Others who have looked at the system photos have said 7 ft head. Don't think that's right since if there was 7 ft head with 006 curve there would be no flow. Negligible loss through boiler and Turbomax. At 1 -1.5 ft head the 006 is giving 8.5-9 gpm, overpumping a bit. Could lower setting slightly to fine tune at some point, but probably not directly related to lock out(?)

  • HomerJSmithHomerJSmith Posts: 807Member
    I would install it with a B-vent cap with a wind designation and with a storm collar. I would have brought the flue up thru a hole on the top of the chimney chase cover and sealed it with DAP 230. A regular B-Vent termination. I have done this kind of install before with ModCon and it works good. Actually venting a gas appliance into a fireplace flue is a no no. Having a chase cap covering both, I think, is exactly that.

    So, your not doing any space heating with this boiler? Just the Turbomax.

    You will have to add up all your head energy losses of everything in the circuit. The 006 at 5 Gpm only gives you 4' head. Only you know if that is enough to maintain 5 Gpm. Flow can be less but performance will be impacted.
  • D107D107 Posts: 1,616Member
    @HomerJSmith We do use boiler for heating but only in heating season.

    My understanding is that if head is really only 1.5' then gpm would be 8.5-9 bit hard to know for sure. As i understand it If head was 4ft then yes gpm would be 5. We get plenty of dhw as is.

    I'll have to look into the b vent idea. The chase cover and fireplace flue damper were put in when old boiler was there with no liner. I guess they could put a smaller chase cover over fireplace flue and then B cap setup on boiler flue.
  • HomerJSmithHomerJSmith Posts: 807Member
    edited July 2019
    The B-vent cap should be higher than the chase cover. When you have more than one circuit, you take the pressure loss of the most resistive circuit at the required gpm in choosing a pump.
  • Steve MinnichSteve Minnich Posts: 2,516Member
    I doubt that flow rates and head loss have anything to do with a tripped flue switch. Firing rate, gas pressure, stack height, stack diameter, stack termination, or a faulty manual reset flue switch is where the problem lies.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
  • D107D107 Posts: 1,616Member
    edited July 2019
    @Steve Minnich Makes sense to me. I timed the gas meter a few times over the past months and found it to be very close to the nominal 70kbtu. But I can get the gas pressure, stack termination, thermodisc-manual reset flue switch checked. And observe the stack damper when it's open.

    @HomerJSmith The dhw circulator is dedicated only to that; therefore as far as I've ever been advised to determine head for DHW circuit I would not consider the lengths of any of the heating circuits. For heating we did measure the most resistive circuit and used that to choose the circ--a separate circ from DHW--which works with three zone valves for the heating circuits. But as has been said I think for the lockouts there are other issues at play here.

    I'm attaching some photos of chimney cap types, including some made for high winds. But the chase cover we have now--even though it's covering two flues--seems much the same as the covers of the others--with holes on the sides and solid on top. We can get a chimney guy to look at it after we check out the other potential causes.

  • HomerJSmithHomerJSmith Posts: 807Member
    Ya, you can cover it with a open chase cover and have a B-vent cap inside, I guess. But use a B-vent cap that will seal where it connect to the pipe. Dura-vent lock to their b-vent pipe on the outside. Some just slip inside the pipe.

    After doing all this and you still have lockouts, further analysis need to be done.
  • D107D107 Posts: 1,616Member
    edited July 2019
    @Steve Minnich @HomerJSmith This is photo of the open stack damper while burner is firing. Seems as open as it could be. I had wondered if it sometimes could get stuck on those penetrating sheet metal screws--I can check it when it's in motion. The damper seems to turn in same direction in 180 degree increments each firing cycle, meaning it shows both damper surfaces every two cycles. Trying to check the low hanging fruit first.

  • Steve MinnichSteve Minnich Posts: 2,516Member
    That’s very possible. A few of those screws look to be 3/4” long. 1/2” is as long as I’d go.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
  • HomerJSmithHomerJSmith Posts: 807Member
    I thought about the screws, too. But if the damper doesn't open all the way the microswitch doesn't close the safety circuit. Besides the screws in your foto look to be above and below the damper travel.
  • clammyclammy Posts: 2,430Member
    I think I would chk the damper motor plug connectors they tend to be a little finicky and seemly a little cheap ,make sure there fully plugged into the damper ,if your still having a issue I would set it to manual and see if any other lock outs occur .has any previsions been made for combustion air I know you have stated that the house is a little tight .you can expect that the new boiler will be a little bit more sensitive to any draft or C A issues then your older boiler . Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • D107D107 Posts: 1,616Member
    Thanks @clammy that's a good tip on the manual (open). Just looking at that plug it appears to be in all the way up to the plastic stops that prevent it going in further. But my guess is the other side would have to be opened to see if in fact the other side is in all the way.

    In general I have wondered if this kind of damper system is as good as a barometric damper which might do better in down or updraft situations. I am glad we don't have the old open draft hood the old boiler had which pulled the heated air out of the basement all winter.

    I wonder if a fan in a can in summer would bring humidity back in that we just took out with our dehumidifier, or would that be minimal since it would only do that while burner is on.

    Yeah I guess the new boiler spill switches would be more sensitive...and of course our old boiler had no spill switch or LWCO, so even though our very sensitive boiler room CO alarm never registered CO at any time even with 40btu hwh, 190kbtu boiler and 22Kbtu drier on all at once, there could have been issues we never knew about. And I know driers can also create issues.

    If it's a draft issue and has only happened twice within a two month interval in the four months since installation, then perhaps certain atmospheric conditions--high humidity?--could bring this on. Anyway, I should get a chimney guy to check everything out before other measures. (33 ft internal chimney)
  • Robert O'BrienRobert O'Brien Posts: 3,163Member
    Something is creating a negative pressure in house. Could just be when a certain appliance is operating with a certain combination of closed doors/windows. Have seen it many times
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