Munchkin lockouts

b young

We had our first winter storm today along with ice, snow, wind, and power outages. I had 4 calls with Munchkin 925 controls with the fault F00. I assumed these are from the power going on and off. Is the 925 a self healing control or will these have to be reset all the time. Also how much power flickering will these take before the lockout.

Paul Cooke

Lockout

For a FOO lockout, here's what the Munchkin manual reads:

"Safety Limit ECO-This code appears if the Safety Limit ECO opens. The ECO will normally open if it senses a temp greater than 225*.

Remedy-Let the unit cool down and push the reset button (S4). Determine if there is water flow through the heater. Manually reset the unit by pushing the S4/reset button. If the lockout continues, replace the switch to correct the problem."

According to their directions, this fault requires a manual reset.

b young

Thanks Paul, I guess if the units are running 180 deg. and the the power goes out for a few seconds the temp will build up and trip the sensor. I guess it would be nice to see the unit try a couple of times every hour to see if it can run rather than shut down completely. What if no one is home to reset it!

Mark Eatherton1

An F00 lockout...

would normally indicate a pump failure, and you don't want to try resetting a dangerous condition automatically.

Probably the best thing you could do would be to provide a small UPS to keep them running if power failures are a regular thing.

There really is not a lot of mass in these boilers, but what is there can cause a substantial thermal stack up if you drop power to it while it's in the full burn position.

I don't know if you've had the opportunity to hear one of these babies fire without circulation, but it's not something you want to happen on a regular basis. It makes your sphincter do the mamba, and makes your feet want to run away, all while your brain is thinking "What the.."

It's set up that way intentionally.

You could wire the TT connections through a N.O. relay powered by a different circuit than the boiler is on. If there is a power failure, the TT call would be interrupted, but the Munchkin would go through its normal post purge shut down process using the UPS thereby allowing the heat to be disipated and avoid thermal stacking the associated nuisance lockout. UPS system start at around 150$.

Just a thought. The same situation has happened to me on non Munchkin types of boilers too.

ME

Boilerpro_3

I was thinking along the same lines

Power goes out, pump shuts off but heat is still traveling through the heat exchanger material. Bang, Bang! OUCH! Just another reason to not use this type of boiler where I'm at.... rural Illinois. Besides, I usually can get 40 to 75 % drop in fuel usage installing plain jane 80%AFUE atmospherics or power venters and good controls in small commercial applications. It appears the old Hydrotherm Multipulse is still the only higher mass condensor out there. If there are any others, I'd like to hear about them.

Boilerpro

Guy_5

Munchkin Lockout

You are on the money as far as that train of thought goes. It may very well be a temperature issue. There is another possibility-The Munchkin 925 control assesses its issues in a numerical manner: If there is an instant electrical problem, it will display F00. Normally this surfaces due to reversed polarity on the TT-end switch wires. The control faults out on the first possible code. If power outages are a common occurence you might want to put a surge suppressor on the line.

Steve Ebels

High mass/low mass

What is the ratio of water content vs. btu input that would be considered the crossover point between high and low mass type boilers. Or is it more a function of heat exchanger material.

My mind is just wandering over the boilers I am familiar with here....... On one hand you have boilers like the Munchie with very low water content per btu input. ( 199,000 with, what, maybe 2-3 gallons of water?) On the other side of the coin you have a boiler like a Vertomat VSB-05 with 191,000 input and 46 gallons of water content. Both are stainless steel construction and operate in a condensing state. Which is which and what's the determining factor?

munchkin-man

199M Munchie only has 4 qts.of water in it

munchkin-man

The ECO goes of at 225* has a 50* diff and will reset its self

munchkin-man

The unit will not fire if it has no delta across the supply and

return. We see the flashing as a result of lack of flow. The thermister feels a delta and allows the gas valve to stay open thus having fire in the hole. The unit flashes the water to steam in the coil only so that the ECO dose not feel it and the unit can run for quite some time in this state. The UPS surge protector can deliver power for up to 45 minutes after a power failure thus easing down the operation of the unit untill TT opens and ends the call for heat.

munchkin-man

There is very little water in them and will thermally disapate

Munchkins surface. This will not cause flashing and will not effect the operation or structure of the unit. Once the pump shuts down the gas valve closes, the sytem goes in to stand by and the water stops moving. Flow check no forced movement no gravity flow.

[Deleted User]

whats a UPS? (nm)

munchkin-man

The step down 24 volt transformer has a built in safety so

that if it is exposed to 48 VA or julted it will shut down to protect it from burning out. The first device in the 24 volt safety limit string is the ECO. The controller knows there is no 24 volts present and the ECO is open so the controller send out a fault code of F00. (High Guy)

Cliff Brady

Could you describe flashing and

its' effects on the boiler and things around it?

Paul Cooke

UPS

Uninterrupted Power System

or

Uninterrupted Power Supply