High limit keeps tripping on Weil McLain WTGO 7 series 3

TheLeakyTub

I have a forced air on the primary loop then a tee with a Taco hydraulic separator then a pair of baseboard radiators for a cold basement. The boiler was leaking between the sections and was treated with stop leak (bad idea I know now). After that it overshot and tripped the high limit and wouldn't call for heat on the domestic hot water resulting in cold showers, this causing mad wife syndrome, this in turn causing suffering. Had it serviced again, he changed the triple aquastat setting pretty low. Still trips occasionally still cold water sometimes.

So after some research I drained the boiler but not the radiator or baseboard loops, I pulled the DHW coil, descaled it with a CLR and a submersible pump and scrubbed the black Shmoo off the outside and inside of the coils and the well. I refilled it, it leaked, wrapped the o ring in ptfe tape and put ptfe paste on the outside of the face by the studs, no leaks. Didn't break a stud (I used up a lucky from what I've read.)

Now DHW is good but still trips high limit switch. That switch is new BTW. I have started on 180 high 160 low 20 diff, tripped. Went down to 150 high 130 low 10 diff so far so good in person I leave for 5 minutes and it trips. I have only seen it trip one time in person. Before cleaning the DHW it hit 170 on the thermostat turned off and then ran to 220 and started hissing out of the air releases. That time the low temp happened just as the house reached the target temp so there was no load on the system when it fired. Since cleaning it is sitting at high temp limit most of the time. I haven't seen a spike in person but every morning when I wake up it is tripped it if I leave for a few hours it is tripped.

Questions:
Should I drain everything and clean again?
What else can cause the over shoot? I haven't cleaned the flue but it was serviced in Fall.
Should I clean the analogue temp and pressure well?
Could it have too powerful a nozzle or something? 210 MBH on 3000 sq. ft chalet in the snow zone with decent insulation. With no heat overnight 10° it was down from 64° to the 50° in the morning. Manual says 2.0 gpm.

Second Questions:
Should I replace it with the same thing this summer?
One contractor recommended a HTP Phenix or AO Smith Vertex if I switch to propane.

I have calls out to control specialist but they're not here this weekend and it's 10° any help would be appreciated.

SuperTech

I'm not understanding what high limit you are talking about that is "tripping". An oil fired boiler shouldn't have a high limit that trips like a high limit on a gas furnace that trips and locks out operation. The boiler high limit just shuts off the burner, at 160 degrees or 180 you should have no problem getting DHW. Some over shooting is normal, but it sounds like you were actually boiling the water and that's not good.

The analog gauge doesn't affect operation of anything.

Are you referring to the burner primary control being tripped and it needs to be reset to operate the burner? If so then that has nothing to do with temperature settings or aquastat operation.

I'm sorry to break it to you but if you have a boiler that's leaking from the sections it's time to look at replacement options. Propane will give you the ability to get a higher AFUE efficiency, but AFUE has nothing to do with how much it will cost you to heat your house and make DHW. You could probably get a Energy Kinetics oil boiler or a three pass with an indirect tank and save at least 10-15% in fuel costs over the Weil McLain with the tankless coil.

STEVEusaPA

Keep in mind if it's been very cold for a long time (you mention 10°). The cold water entering the boiler for domestic hot water production is very cold, and therefore output will be reduced.
You're working with 1960's technology and it's time for an upgrade-better controls, better boilers, indirect or EK with/without an indirect as @SuperTech mentioned.

You don't need a 'controls specialist' whatever that is/means. Just a good tech with knowledge of hydronics.

I also wouldn't switch to propane, but that's just me. Like mentioned above, there are some good boilers and good technology with oil that will get you up to 87-90+ efficiency.

the_donut

Stop leak has the ability to seal up all kinds of things, including things that shouldn’t be sealed up.

I’d replace boiler when you can. You’ll be money ahead with lower fuel cost if you find a good installer.

HVACNUT

I also don't know what you mean by tripped. Is there a manual reset high limit other than the triple that's set to about 20 to 30 degrees above the 180 limit on the high side of the triple?
What elevation is the house at and what pressure is the boiler set to?

TheLeakyTub

The high limit switch is a Honeywell L4006E.
It is set at 220°
House is at 4400'
24 psi.
Cold water is probably low 40s it is snow melt and bone chilling.
Made it through last night at 140 low 150 high 20 diff. Sitting at 170 on the dial.

HVACNUT

You'll have to check actual temps, not using the tridicator gauge at the boiler and supply. Either the 8124 or 4006E is faulty.
Take the 4006E out the circuit. Set the 8124 to 200-180 with no heat zones running.and cycle the boiler to limit (the burner circuit should open at 180). Have someone turn on one heat zone and check actual supply temp. If it exceeds 200 at the start of a heat demand, the 8124 is faulty and the 4006E is doing its job.

TheLeakyTub

Will do. The 4600E is new by the way.

SuperTech

I would definitely get rid of the 8124. Get yourself a L7224U. In my experience it is much more accurate and reliable. I replace broken and malfunctioning 8124s with the digital L7224U all the time.

But I'm concerned about your use of stop leak. The auxiliary high limit installed on your boiler is unusual. I've never seen a Weil McLain with one. Someone installed that for a reason....

HVACNUT

> @SuperTech said:
> The auxiliary high limit installed on your boiler is unusual. I've never seen a Weil McLain with one. Someone installed that for a reason....

He mentioned it was a chalet. Maybe it's some kind of code in the community. I thought it was weird too.

@TheLeakyTub, you can also look into the Hydrostat 3250 Plus. It offers low water cutoff protection if the system doesn't already have it as well as triple acting. You'll have to use their insertion well.

TheLeakyTub

Opened (shutting down burner) at 180 1st time and ran to 200 on analogue thermometer and held at 200 no load. Tried again opened at 185 and ran to 203 and held. 4600E tripped so, I turned it up to 240 and tried again. Works. I guess the 4600E isn't calibrated correctly? I manually calibrated it both the old one and the new one in boiling water (204° at this altitude.) Seems to be spot on at 204° at least. Bulb is seated in the well based on the spare well.

Re-read the manual again. You're right no mention of anything like a L4006e in there except a mention of "additional temperature control (when used)" on the B1 B2 red wires coming off the "combination high limit low limit relay and transformer" aka L1824a. ****? It was on there from original install for sure. The first fitting on top of the boiler is a cross with a McDonnell level control on one side and the L4600e on the other.

Fired again after I resembled it. Opened at 175° rose to 200° stopped on the button. Slowly turned the L4600e dial down. Tripped at 227° so it's reading 27° higher than the thermometer and the L1824a.

TheLeakyTub

I'm not sure how good the installers were. There is galvanized steel between the copper DWH coil and the copper tempering valve. Seems like a double no no with oxygenated water moving through it all the time.

TheLeakyTub

Even at 240 on the high limit it still tripped when I walked away. Lowered triplestat to 170 150 20. Waiting. I am sorely tempted to cold short the red wires on The L4600 and trust in the aquastat. What's the worst that could happen? Overshoots to ? and boils if some gas? Better than being shut off entirely when I leave right? What's the lowest high temp you would run on a forced air hydronic given the situation?

HVACNUT

Typically you want to see about 140 at the hydro coil. What brings on the fan at the A/H? Aquastat, time delay or thermostat?

TheLeakyTub

Fan is on the thermostat. My neighbor came in when it was off and said the fan was running in a cold boiler.