First Munchkin failure

Glenn Harrison

Timmie,

The reg. is a Maxitrol RV 48L. 3/4" regulator adjustable from 3.5" to 10". Lennox recomended setting is 4.0". So incoming house pressure is dropped to a steady 4.0" into the unit and then the Honeywell differetial valve drops it to the needed burner pressure based on the vacuum applied to the vent onthe valve by the combustion blower. They also recomend istalling the reg. at about 10 equivalent feet away from the unit to allow a cushion to absorb the stop of gas flow when the unit shuts off.

The idea is not neccesarily to have a set inlet pressure, but to prevent a drop in pressure once the gas valve comes on to prevent rough ignition, which is the primary problem Lennox had with these units for years.

I kind of see what your saying about the regs fighting each other, but if this was a problem, why are we able to do it in commercial high pressure set-ups with step down regs at each unit? It's essentially the same setup, just lower pressures.

Glenn Harrison

Jeff, thanks for the analogy.

That's an excelent way to describe the point of proper pipe sizing, although I don't think I've ever come accross a 4" drop in a line.

Now for my real world question, and before I ask I must admit I haven't put a Munchy in, nor have I serviced one, YET. I have only seen the Peerless twin at the AHR expo, so if I seem a little ignorant on these units, I appologize. I'm also in no way trying to knock the unit, I actually like the looks of the unit, I'm just trying to convey what I see in the real world on a daily basis.

We both know these units are going to be used as replacements. A lot of times these units will be installed on marginal piping, but piping that the old unit ran on just fine for 20 to 30 years, at the same or very close to BTU's capacity. Now the new Munchy is put in and you start having ignition problems. Now the tech/installer has to say "Mr/Mrs customer you have this great, energy efficient unit that I recently installed, but it turns out that the unit is so sensitive to gas flow that I have to replace X amount of gas pipe for X amount of additional dollars". Customer "Well the OLD boiler never had a problem for 30 years, so I have a hard time believing this. I think you just want to take more of my money. I have a contract for a new working boiler that I already payed for, and I'm not paying any more, so you better fix this thing of tear the blankity blank blank unit out of my house" or words to that effect. This of course will start to give the Munchy a bad name in the customers minds and the techs/installers mind, that it is a piece of garbage bla bla bla. Obviously not good for you. What I'm getting at is the unit needs to be a little less sensitive to gas flow and pressure drop or another way needs to be created to smooth these units out in replacement situations like Lennox did with the step down regulator on their Complete Heat units. Otherwise you will have bad mouthing because the units are failing and the excellent reputation that is evolving is ruined, or guys are loosing jobs with the Munchy because they have to ad gas piping to their bids that the other guys are not because they can get away with the existing piping that has worked for 30 years with a .5" to 1" pressure drop, which is much more common.

Now if your still awake after reading my ramblings, feel free to respond. ;-)

hot_rod

As I see it....

we can't have it both ways. I went through this "learning curve" with high efficiency furnaces some 15 to 20 years ago.

They too suffered from decades of complacency on the part of mechanics who were used to just about anything goes. It was the best of times, it was the worst of times!

Now comes hydronics (it's about time!) and we're going through the same growing pangs. Time to tighten up our standards and get on board with the fact that this is a new ball game. The slop is going to disappear, like it or not & marginal installations will not cut it.

My strongest hope is that the US boiler manufacturers have learned from the mistakes of the US furnace manufacturers and give us the information and support we need as we traverse this learning curve. Those that do will have our undying support and loyalty. Those who don't will be relagated to the bone pile.



To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Unknown

Glenn,

> The reg. is a Maxitrol RV 48L. 3/4" regulator

> adjustable from 3.5" to 10". Lennox recomended

> setting is 4.0". So incoming house pressure is

> dropped to a steady 4.0" into the unit and then

> the Honeywell differetial valve drops it to the

> needed burner pressure based on the vacuum

> applied to the vent onthe valve by the combustion

> blower. They also recomend istalling the reg. at

> about 10 equivalent feet away from the unit to

> allow a cushion to absorb the stop of gas flow

> when the unit shuts off.

>

> The idea is not

> neccesarily to have a set inlet pressure, but to

> prevent a drop in pressure once the gas valve

> comes on to prevent rough ignition, which is the

> primary problem Lennox had with these units for

> years.

>

> I kind of see what your saying about

> the regs fighting each other, but if this was a

> problem, why are we able to do it in commercial

> high pressure set-ups with step down regs at each

> unit? It's essentially the same setup, just lower

> pressures.

Unknown

Glenn,

> The reg. is a Maxitrol RV 48L. 3/4" regulator

> adjustable from 3.5" to 10". Lennox recomended

> setting is 4.0". So incoming house pressure is

> dropped to a steady 4.0" into the unit and then

> the Honeywell differetial valve drops it to the

> needed burner pressure based on the vacuum

> applied to the vent onthe valve by the combustion

> blower. They also recomend istalling the reg. at

> about 10 equivalent feet away from the unit to

> allow a cushion to absorb the stop of gas flow

> when the unit shuts off.

>

> The idea is not

> neccesarily to have a set inlet pressure, but to

> prevent a drop in pressure once the gas valve

> comes on to prevent rough ignition, which is the

> primary problem Lennox had with these units for

> years.

>

> I kind of see what your saying about

> the regs fighting each other, but if this was a

> problem, why are we able to do it in commercial

> high pressure set-ups with step down regs at each

> unit? It's essentially the same setup, just lower

> pressures.

Unknown

Glenn

If I am not mistaken that was a negative pressure valve on those Lennox units using the suction from the combustion air blower to establish gas flow based on pressure difference in the combustion chamber. Negative pressure valves have a tendency to react differently than a standard servo pressure regulator type gas valve. The fact that Lennox wanted that regulator 10' away from the gas valve is becasue of what I am talking about that happens when two low pressure regulators are installed to close to one another on the manifold. They will react off of one another causing pressure bounce. The desire to stabilize pressure is so that the negative pressure system is able to provide sufficient gas when called for. This is not however a typical solution to these kind of problems. Sizing piping to these units with a minimum 1" pipe size is the best solution.

On commercial high pressure set ups you usually have pounds pressure on the inlet side of those regulators with rather large piping and adequate sized manifolds to allow the regulators to work in conjunction with one another for the high demand at ignition. Many of those also come on at low pressure then increase to high pressure to take care of that problem. Pounds to inches regulators work differently than inches to inches regulators. We required a minimum 2" pipe size to most commercial applications such as you are talking about.

I recently was talking with some folks at Maxitrol about CSST applications that use a pounds to inches regulators. They were very clear that even then they want some distance from the regulators to the gas valve. They have had problems with set ups that do not space them apart.

You also have to be very careful on many gas valves that have an allowable pressure loss thru the gas valve of 1" water column. That typically comes into play on the high end of the capacity of the gas valve. This is why the specs on most valves want a minimum 5" WC at the inlet.

Unknown

It behoves us all

to first follow the basics and do the fundamentals. Sizing the piping is one of the first things that should be considered. Especially on a retrofit.

If the piping is sized correctly there will be NO PRESSURE DROP when the equipment comes on 7" WC static pressure - equipment comes on pressure should be 7" WC with the unit running. If it is not something is wrong!!! The charts and tables in the code allow the use of different allowable pressure drops .3" WC or .5" WC etc. Those are factors that should be used so that there will be no drop in pressure.

As far as the Hydronics industry going thru a learning curve, how long will it take? I have seen in the last 20 years boilers, wall hung units, foreign units units which promised to be the answer to everything. Most of them are now sitting at the curb waiting for the trash man. Or someone is servicing them so often that it is ridicolous.

I am not so sure that the Warm Air people have learned all the lessons that need to be learned. That is a subject for another time.

It amazes me that things us old timers learned years ago that you should not do. Along comes some new product that repeats the mistakes of many years ago. History repeats itself.

A British engineer named Thomas Green experimented with Pulse Combustion before World War II, his final analysis was that it was not feasible for internal combustion systems. The Germans stole it made the "Buzz Bomb" and dropped it on London. Along comes Pulse Combustion here in America many years later and we found out the only thing it is good for is "Bombs". Maybe that is what the Mother of All Bombs is about. Oh well it is past my bedtime.

munchkin-man

Sorry gentalmen

I am extremly buzzy today and will have to repond on monday all have a great weekend.

Unknown

HELP!!!

I can not wait till Monday.

Unknown

Research on my own

I finally found spec sheets from Honeywell in the Netherlands on VK 8115V valves used on Munchkin. They were lost in the pile of stuff I have on Munchkin. ( I am still trying to learn)

I am not sure exactly which models they are using
These controls are gas controls with an integrated 1:1 Gas/Air regulator

VK 8115V 1028

VK 8115V 1093

The specs on those valves for minimum inlet pressure is 0.22 psi which is roughly 6.8" WC.

This causes me some concern as these valves have been seen on some other equipment recently in my travels.

I got these spec sheets back in 1999 maybe they have been upgraded.

I am going to e-mail Bill from Honeywell and see what he knows about them.

Some info on them is as follows:

The VK8115 1028/1093 gas controls with 1:1 gas/air regulator have been developed for use in 12 Vrac domestic heating appliances with premix (fan control) burners for direct burner ignition (DBI).

Vrac is rectified AC voltage.

There is also a VK 8115V 1077 and 1085 series using 24 Vrac

Suffix "V" standard opening with integrated gas/air pressure regulator.

Outlet pressure range is .6 to 7.9" WC

Minimum operating pressure 4.5" WC

Maximum air pressure

3" WC without outlet gas pressure (before ignition)

7.9" WC with outlet gas pressure present (after ignition)

Unknown

For your information

the valve that is on the MunchKin unit in my training center is the VK 8115V-1077 which according to the spec sheet can operate with 4.5" WC inlet pressure.

bill clinton_3

Gee, this thread kinda reminds me

of Voyager.

Bill

tim from Reed Wright

munchkin failure

Wayco wayne, We have had more than 20 years of the problem of low gas pressure mains causing unreliable starts on any thing from standing pilots to direct ignition. Here in seattle they have finally got most of the mains installed for 2# pressure +. Now the old days of telling clients to wait for the cold to subside so pressure goes up is gone. This although makes me feel better to be able to decipher what is going on with the system.I just hope the one munchkin I have installed does not give me any other hiccups.

Glenn Harrison

Timmie, you are correct,

The valve in the Complete Heat is a negative pressure valve balanced by the combustion blower. It is the same valve as i the Munchkin, execpt it is 24VAC. The regulator was originallly supposed to be installed right by the uits, but recently they changed it to 10 equiv feet away, probaly because of what you said. The reason they came up with the regulator is that in many cases, the 1/2" pipe they originally speced as o.k.'ed could not be changed to the now mandatory 3/4" pipe, including a condo building we did in Downtown Chicago that all the gas piping except for 5 feet at the units is buries in the walls/ceiling and cannot be changed.

The commercial application I was thinking of is like several small commercial buildings I have seen where the service is 2 pounds at the meter, and then dropped to a constant 6" to 7" at each unit, and then the gas valve reg drops it to 3.5" to 4" manifold. This is vertually the same thing as I am describing with the Complete Heat units.

I'm also well aware of the one inch drop thru most valves, and have had arguments with local gas personell that did not want to change a reg. that was running at 5" inlet for a 4" manifold appliance.

Should be able to talk to the Muchkin men more at Wetstock tommorow. Should be interesting.

Unknown

Now that everyone is back Munchkin time

Can I get my questions and the questions of many others answered?

Unknown

Munchkin Answers!!!

What say ye!!!

Bill Barrett

Where's Jeff ?

Bill Barrett

Where's Jeff ?

What say ye? Where's Jeff?

AL_6

Back pressure

Real fast i have not read the responses you got but they have had problemas with the pressure switch when not vented to specs. You may be getting back pressure on the exhaust. If you are venting straight out the boiler with no distance to the outside this problem does happen. I beleive the instruction tells you to vent something like 10 feet min. Something i don't like. In later models the pressure switch will no longer exist as so i was told because of this problem. Hope you get it fixed cool little boiler. Most likely done by now.

Floyd

The answer is simple......

This problem is NOT........ a Munchkin problem!!!!!!!


It IS...... a PIPING problem!!!!!!

Unknown

Read Further up for the questions

in the process of talking about this problem other issue have come up as to pressure and procedures for setting up the system. I feel these are important questions that need to be answered. I have many more questions on Munchkin I would like to get answered, should I post all of them here?

Floyd

I'll tell you a secret.....

You're more likely to get a response from Jeff, if you start a new thread and let this one die.
He's not real thrilled about the title!!!!