Munchkin F00 fault, sensor okay, but no voltage to it---no heat

Tom Bradd

could go back to your cast iron millivolt gravity piped boiler eh ?

J. Cricket

could use advice

Wow, this Munchkin was fun at first but it's been nothing but trouble. Three failures in three years, two of them on weekends.

Anyway now it's showing F00, which is supposed to mean the temperature has reached 225F, but of course the boiler is quite cold.

I measured the sensor resistance with a multimeter and it's closed (zero resistance). So the sensor is OK. The Munchkin doesn't show a fault if there is no heat call, it only goes F00 if there's a heat call. I measured the voltage at the leads (when not connected to the sensor), it is 28vac (i.e. 24vac unregulated) when there's no heat call, but it drops to zero as soon as there's a heat call and the fan noise starts.

What are my options? Is it a bad transformer? I was doing some plumbing this evening and we have some galvanized pipe...could rust chips in the water somehow cause cause this voltage behavior? The boiler loop pump is running but but I can't tell if it's pulling water.

Can the transformer be changed or is it soldered to the control board? How can I get a control board on Saturday?

Anyway, what I'm looking for are ideas on how to get it back online, I do have a call in to the people who installed it but of course they can't come until late Saturday, Plus I know from past experience that they will not have any specific parts and they will not order anything until after they see the boiler at which time everything will be closed until Monday. Anyway...

[Deleted User]

Check wiring...

You should not be seeing a completely closed circuit. Resistance on a thermostor changes as a function of temperature. If you check the sensor AT the sensor and it shows closed, you indeed have a bad sensor. If its readings in ohms of resistance are correct for the temperature its actually seeing, then the fault is in the wires between the sensor and the board.

ME

Guy_6

FOO

The F00 fault is the first that the control will recognize, so it is sometimes undefined. As ME said above, check the wiring: Disconnect the TT wires from whatever they are attached to and tie them (the ones on the boiler) together. Reset the unit and see what happens. If it runs, there is some issue from your relay/zone valves/etc. that is conflicting with the control. You may end up isolating that end switch.
ALSO- try disconnecting the wires from the water pressure switch (top of left manifold) and jump them. I had seen one switch have an internal water leak that shorted the switch, causing F00. Rare, but easy enough to eliminate.

R. Swatton

If you are still without heat e mail me at

H.T.P.rep@comcast.net

Rich


Authorized Heat Tranfer Products Sevice Agent

J. Cricket

It's not a thermistor. It's a high limit switch (ECO).

J. Cricket

Had a tech here for 1.5 hours. He tried these and other things. He concluded that the control board transformer was bad, but now it is too late to get another one until Monday or later.

I picked the Munchkin and now I am persona non grata in the household. Heat is not like an Ipod or something. A significant failure rate is not acceptable. The condensing furnace in our old house chugged away for years without a failure, but this boiler has had three failures in three years.

J. Cricket

PROBLEM SOLVED...

Called another company and got a tech who was worth twice the king's ransom he charged. He did have a new Munchkin board but it didn't work either. He traced the problem to a deteriorated stat wire (house is very old) that was touching a pipe somewhere and so grounding a Munchkin input that didn't want to be grounded.

So

a) it wasn't actually the Munchkin's fault

b) It WAS the Munchkin's fault. Looking through the other problems people have, the big problem seems to be that the Munchkin is designed for ideal conditions, and when these don't exist it fails with the most unhelpful codes possible. No design effort has gone into saying "What unexpected things could happen and how can we best tell people what has happened?"

Like the mass of wires inside the boiler, the firmware code is disorganized and slapped together. "Stat wire is touching ground...display code F00, exceeded high limit." Makes a lot of sense if you're a munchkin, but not to humans. No one here was able to correctly identify the problem in a post or in private e-mail, although I am sure the disparate possibilities you suggested would all result in the same symptoms. That;s a problem. I am still sorry I bought a Munchkin.

Al Corelli

It wasn't the Munchie

> Called another company and got a tech who was

> worth twice the king's ransom he charged. He did

> have a new Munchkin board but it didn't work

> either. He traced the problem to a deteriorated

> stat wire (house is very old) that was touching a

> pipe somewhere and so grounding a Munchkin input

> that didn't want to be grounded.

>

> So

>

> a) it

> wasn't actually the Munchkin's fault

>

> b) It WAS

> the Munchkin's fault. Looking through the other

> problems people have, the big problem seems to be

> that the Munchkin is designed for ideal

> conditions, and when these don't exist it fails

> with the most unhelpful codes possible. No design

> effort has gone into saying "What unexpected

> things could happen and how can we best tell

> people what has happened?"

>

> Like the mass of

> wires inside the boiler, the firmware code is

> disorganized and slapped together. "Stat wire is

> touching ground...display code F00, exceeded high

> limit." Makes a lot of sense if you're a

> munchkin, but not to humans. No one here was able

> to correctly identify the problem in a post or in

> private e-mail, although I am sure the disparate

> possibilities you suggested would all result in

> the same symptoms. That;s a problem. I am still

> sorry I bought a Munchkin.

Al Corelli

It wasn't the Munchie

> Called another company and got a tech who was

> worth twice the king's ransom he charged. He did

> have a new Munchkin board but it didn't work

> either. He traced the problem to a deteriorated

> stat wire (house is very old) that was touching a

> pipe somewhere and so grounding a Munchkin input

> that didn't want to be grounded.

>

> So

>

> a) it

> wasn't actually the Munchkin's fault

>

> b) It WAS

> the Munchkin's fault. Looking through the other

> problems people have, the big problem seems to be

> that the Munchkin is designed for ideal

> conditions, and when these don't exist it fails

> with the most unhelpful codes possible. No design

> effort has gone into saying "What unexpected

> things could happen and how can we best tell

> people what has happened?"

>

> Like the mass of

> wires inside the boiler, the firmware code is

> disorganized and slapped together. "Stat wire is

> touching ground...display code F00, exceeded high

> limit." Makes a lot of sense if you're a

> munchkin, but not to humans. No one here was able

> to correctly identify the problem in a post or in

> private e-mail, although I am sure the disparate

> possibilities you suggested would all result in

> the same symptoms. That;s a problem. I am still

> sorry I bought a Munchkin.

Al Corelli

It wasn't the Munchie's fault

The diagnostic codes are there for what is INSIDE the case.

Worn thermostat wires are, and have been causing weird problems for years, with all kinds of boilers.

There is no logical reason to expect the firmware to "figure out" anything outside its realm. Thermostat wires running through the house are definitely out of this realm.

Please don't bash a product because an outside device failed.

ALL of the Munchies in my care are operating quite well. Sure, early on there were difficulties, but they were MY difficulties, not HTPs.

hr

Looks to me like Guy

hit the nail on the head around 11:00 as far as likely suspects. Very good service from a former HTP employee, I'd say

hot rod

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gerry gill

i agree hot rod!

if he'd of done what Guy said he would have had heat sooner..

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Jeff Lawrence_25

You know

I've done similar things all the time. When I get a complaint about something not working right, one of the first things I do is disconnect the Tstat (red wire on a heat/cool unit) and jump it out. It takes one problem, maybe two, right out of the circuit.

Thinking more about it, most of the locals here have run 20 gauge tstat wire for years and now the tech support people are saying that everything needs to be 18 gauge. Hmmmm.

J. Cricket

You're right, Guy did say that. I don't know what the first tech was trying then, because I showed him these suggestions.

But why should this problem happen, though? Stat wire faults could cause no heat call or constant heat call or intermittent heat call, sure. But it takes about a $1.75 electronic component to isolate the stat input so that while it may not work right, it won't pull down the 24v supply and spit out spurious fault codes.

If "Worn thermostat wires are, and have been causing weird problems for years, with all kinds of boilers", then there is an industry-wide problem.

brucewo1b

If "Worn thermostat wires are, and have been causing weird problems for years, with all kinds of boilers", then there is an industry-wide problem.

Just because a Tstat wire gets hit by a nail screw or staple, gets yanked on too hard and the insulation comes off and shorted by said staple doesn't make it an industry wide problem, it may be a problem for a tech to decypher and correct but not one that needs to be addressed by Equipment manufactuers as that is outside their perview. Same can be said for broken tstat wires sometimes a nightmare to find but my problem not the equipment manufactuer, they may have a thought as they have been called on all sorts of troubles that I have never seen but then again I have found a couple that they couldn't decypher.

radmix

munchkins

Lately I am hearing a lot of munchkin bashing on the wall. I personaly have about 125 munchkin installs withen the last 4 years and only went back on two calls. one pressure switch and one bad outdoor senser.

Unknown

Codes are not the

absolute answer to all things that can go wrong on equipment. I always tell my students,"you still have to be able to use a multimeter as the fault codes only relate to the immediate and local problem". Sometimes there can be two problems on a unit, the fault code will only show the first failure. DON'T GET RID OF YOUR METER YET!!!

John McArthur_2

Tim makes an excellent point. I recently helped a friend with a GB142 that would only lock out at night. The fault code was "loss of flame ionization" but the problem was too much moisture in the LPG and the regulator was freezing. I have a Munchkin that I posted about a week ago that locks out on F9, but only at night. I believe the problem is the same. It is also an LPG install.

My point is, the code may only indicate a symptom of the real problem. There's a reason a good tech can charge a "kings ransom".

S Ebels

Not here

I'm not bashing Munchkin. They are a good product built to a price point where a lot of folks can afford a condensing boiler. They, like ANY manufacturer, have some bugs and idiosincracies that need to be identified and worked out. The ones that I have out in the field have not been overly problematic. They simply are what they are and HTP doesn't make any wild claims regarding faultless operation. HTP also does an admirable job of backing their product with technical service. No complaints here.

Guy_6

troubleshooting

Higher tech equipment is different than the old school stuff that we all were used to dealing with, and every manufacturer is going to have some high tech fault issues that defy straight line logic. The best service advice that I can give in any situation like this is to disconnect everything back to the boiler (indirect, TT, outdoor sensor),and work your way out from there.
As for trusting the last guy's work....we will have to leave that for another set of posts.

EBEBRATT-Ed

Fault codes and microprossor read outs will only get you so far and will sometimes lead you down the wrong trail.

You still need to be able to use a meter ,troubleshoot and get away from the boiler and check things.



ed

brucewo1b

That would be ok with me Tom

[Deleted User]

And waste a minimum of 30% of your energy...

Get used to it guys. It's going to become a standard.

ME

brucewo1b

Mark I now that but

I also love heat when the lights are out without all the extra stuf you have to do to make it happen with mordern boilers

mikep7777

Hi Bruce,
I think the point is that if a thermostat wire is a commonly damaged system component, the boiler should be designed with that in mind, and it should not be displaying useless fault codes. Yes, the thermostat is outside of the boiler jacket, but that doesn't mean the system shouldn't be able to recognize the fault (or, as appropriately, not identify the fault incorrectly.)

This isn't a low-tech hunk of iron; it's a computerized product that has some intelligence built in to it. It's not too much to ask that the intelligence actually be intelligent.

And regardless of whether the problem truly was in the boiler, that's what the customer sees - a boiler that's to smart for its own good, shutting down because it thinks it has a failure when the real cause is external. Just because the system is more complicated than an older boiler doesn't mean that we should expect poorer reliability.

Guy is dead on with his assessment; if the tech had isolated the boiler, he would have figured out the problem pretty quickly. However, since the boiler diagnosed it's own health (incorrectly), the tech didn't think to do the right analysis of the problem.

brucewo1b

Mike

If the t-stat is part of circuit A the computer only knows it did not get a signal across curcuit A, not what went wrong in circuit A. This is where the tech comes in. I will say that I do think that some manufactuers could have better diagnostic or trouble shooting diagrams for such occurances.

J. Cricket

But the computer did not say that something was wrong with the stat circuit. It said F00, which means temp high limit exceeded.

I understand now that this is because all the high limits and the stat use the same 24vac supply, and if any of them is shorted to ground it pulls the 24vac line down, and the temp high limit happens to be the first limit checked by the computer. But that would fail Design 101.

Let's take a software example. You are filling out a web form to get life insurance. It asks for your age. Instead of entering a number, you mistakenly enter your first initial. The software then tells you that your claim has been denied and you've been reported to the authorities for fraud (in fact you don't even have the insurance yet so you can't have made any claim). The programmer can explain in great detail why this happened, based on the way the software was designed. Would you accept that explanation?

brucewo1b

Let's take a software example. You are filling out a web

Lets say I went into the insurance co and the first attendant make a mistake typing up my claim. I go back and see a new attendant and they discover the mistake and correct it. Then it was lack of experiance or understanding on he part of the first attendant, that I would accept not blame the system for the mistake of the first attencant. Now if you are willing to pay NASA prices for your boiler I can somewhat understand your displeasure but I don't think you paid NASA price for your system. And even at that NASA has to step back once in a while to figure out what went wrong.