munchkin boilers

heretic

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tim from Reed Wright

munchkin boiler service history

Have concerns about service history of Munchkins, have installed many different boilers over the years, but when I come to high efficiency boilers I get leary. Have been burned a few times over the new better than ever, most efficient, blah blah boilers that come to market. Would really appreciate a little history of service from the Munchkin installers out there. Thanks in advance, Tim. Ps hardly any here on the west coast.

Bob E

Munchkin or any condensing boiler

I've seen many installations with the Munchkin or also known as the Pinnacle from Peerless. Good boiler, lots of nice features. Why bother? The difference between a boiler condensing and a furnace is day and night. Boiler works on return temperature of the water. Out at 180-200 back at 150-160 best case senario. This is not condensing. They only condense on start up. It will only condense and get the eff. if you have a system designed for the right temp drop. Maybe a good application is all radiant where the return temp is low enough to condense. I would stick with a proven product with good combustion eff. and don't try to add costs of condensing unless the system is designed for it in the first place. There are a lot of low mass gas boilers that have been around longer. Takagi, Monitor, Samsung, Viesman, Biasi, and for non-low mass the Weil Mc CGI's are nice. Good luck.

kevin

well...

you are not right at all Bob about the condensing part.... I have talked with contractors here and at wetstock...they all said that they were having condensate being made during higher heat outputs...ie. running the indirect water heater. Condensing with this unit happends because the stack temps are so low...its vented with PVC. kpc

Troy_3

condensing

I've installed many munchkins and can tell you first hand they seem to condense at higher than 140deg. I can't explain but I had a condensate drain that came loose in the summer and flooded the basement when just making domestic water. I'm talking water over a 20'x 20'area.and I've seen the Monitor boiler also condense at high water temps.

Darin Cook_2

Reality about the Munchkins

I have seen the munchkin condense at higher temps, but let's not forget it is still 92% eff. whether or not it's condensing. When you add a outdoor reset control it will condense much more. Quite frankly for what the munchkin cost's, why would you even bother to sell anything else? A munchkin boiler set up properly will outperform just about anything on the market. There are other condensing boilers out on the market, but for the added expense ,How much bang for the buck are you getting?

Walt

Old Houses are \"Designed\" for Condensing

We have a 100 yr old house. I crunched the numbers on how much output our cast iron radiators will do at a 20 degree temp drop and found that every radiator in the house was WAY oversized. I guess this is because we have insulated the house and put good storms on. To the extent that a heat loss was done when the house was built it certainly would not have factored in modern storms, let alone insulations. They probably just used a rule of thumb that gave them too much output even when the place was first built. Most people seem to have tightened up thier old places in one way or another.

We have an outdoor reset controller that we have set at a minimum of 140 degrees because we currently have an old cast iron boiler. It did not call for a temp above 140 until the temp outside dropped into the mid 30's. We are going to put in a condensing boiler...it should see low temps almost all the time. I am guessing that most retro fits in old houses would work out the same way.

Mark J Strawcutter

may not be a problem

If you crunch the numbers for your house without the storms and insulation you may find you're still over-radiated.

There are several of us here whose older homes are over radiated and over boilered. Mine is typical - current boiler has been running for 30 years or so with temp rarely over 140F and no sign of condensation or thermal shock damage.

It may be a matter of "they don't make 'em like they used to" and a newer cast-iron non-condensing boiler would not survive as well.

Mark

Patrick_3

Munchkin service

I have installed 8 Munchkin boilers and like most new products have had minor problems. One pressure switch had to be replaced. On one boiler the way they route all the wires under the manifold, the ignition wire was pinched and grounding out, nothing major, I now make sure to remove all the wires from the control board and route wires over the top. There is one boiler that is leaking from the condensate trap or connection at bottom of boiler, I do have a replacement trap comming. This might be tough to replace but it is my understanding that they have changed the clamp they where using to correct future problems.
For the price of a high 80% boiler and stainless vent pipe you can't hardly beat the cost of a 92% Munchkin. The performance of this boiler has been very impressive on high temp and low temp systems. Hope this helps, Patrick

Walt

A gambling man

If that is the case, I may back the minimum temp down to see what happens. I plan on replacing it anyway...it has a low water cutoff, so if it cracks open it should shut down. I guess the only thing that I worry about is the gasses in my masonary chimney.

I also need to have someone put a smaller nozzle on the burner. Right now it is short cycling like crazy. The boiler is so oversized it is like a rail dragster in stop and go trafic.

Mark J Strawcutter

you may make matters worse

If it's short cycling and you drop the min temp it may just short cycle even worse.

Mark

Walt

Excellent Point

...I had not thought of that. I may just go the buffer tank route. I will need the buffer tank no matter what I do in the future and I think it will make the problem a little better in the mean time.

Mike T., Swampeast MO

Amen

I'm convinced that radiator oversizing in old homes has a lot to do with things OTHER than insulation/weatherization.

Wood storms were quite common even back then--they're actually more efficient than modern aluminum--if a lot less convenient. Insulation was not unheard of back then--in fact is was the general rule in cold climates--it was just a different form and not generally as effective as modern materials.

I believe that the fuel and controls had much to do with oversizing. Control was quite primitive--usually amounting to how much coal you shoveled and how much you opened the draft damper. Both the boiler grate and the rads had to be large enough to keep a slow fire going all night without letting the place get too cold.

Lifestyle played a big role as well. All that coal burning spawned by the industrial revolution took its toll on air quality. By around the turn of the 20th century lots of people were getting sick from the air. It was blamed on vitiated (stale) air. "Experts" recommended sleeping with windows slightly open year-round as well as daily "airing" of the home. Many followed the advice. Fuel and servants were cheap and most who could afford hydronics had an abundance of both. While prosperous farmers didn't generally have servants, they had the ever-working farm wife and lots of kids.

I also believe that safety played a role in the sizing. Some early hot water systems operated at enormous pressure and extreme temperatures--they didn't require large rads, but they had a nasty tendency to explode. By the time hot water systems became popular in the US, they were generally safe but the radiation was really large. Since it would be operating at a relatively low temperature most of the time you didn't have to worry too much about carefully watching the fire to ensure that steam wasn't produced.

If all this isn't enough, every formula I've seen for sizing hot water radiation is actually based on steam radiation--additional iron was added since the temperature was lower. Since steam is inherently digital--you've either got it or you don't--I believe steam rads were oversized to begin with so that there was enough mass to keep the space from cooling too greatly between steam cycles. This would also tend to keep steam cycles longer (at the expense of sometimes severe "overshoot" in mild weather).

A coal fired hot water system is however inherently proportional--crudely proportional--but it delivered heat as long as the fire burned and in proportion to its size. Likely the added iron in a water system was unneeded from the start...

To add on last reason they're so large: As radiator design evolved, I'm convinced that their ability to extract heat from water increased as well. Water passages became smaller putting more surface area in direct contact with the water. They thus extracted more heat and the delta t increased. The increase in delta t increased the speed of gravity circulation as well. With the greater delta t, even less supply temp was required. Sizing formulas didn't evolve concurrently and the later rads became even more greatly oversized.

By the time heat loss calculation and formulas for computing flow in a gravity system evolved fully, gravity systems were nearly obsolete.

heretic

Munchkin Condensing

According to HTP, the 92% number is for 180 supply/140 return.
I run 160 supply and typically 130-140 return, and get gallons of condensate.

I recently asked HTP for 'efficiency curve' data for various supply/return temps, but they had no data to offer.
Too bad. Would be a good marketing move on their part. Maybe if they get inundated by requests (hint), this data will become available.

kf_2

Munchkin Efficiencies

Guys,

Please don't get fooled. Heat Transfer lists the Munchkin at 92% AFUE. AFUE is calculated at 140* out and 120* back under CONSTANT load. The manufacturer is not allowed to list efficiencies on a residential BOILER with any other variabled than that.

I don't care what MAGIC stainless steel HTP is using they can't change physics or mother nature. A boiler will not condense ON THE FIRE SIDE unless the return water temps are below the dewpoint of the fuel. For natural gas this temp is 136* degrees. Keep in mind that this is at a 10.5% CO2 (most burners can not achieve this) if not the dewpoint is lowered.

Now, I agree that you will see condensation at higher temps but this is flue gas condensation. The potential of flue gas condensation can occur at just over 85.5% combustion efficiency. Flue gas condensation, while it does lower stack temps, does not transfer any BTU's back into the heat exchanger.

Lastly, if you are measuring efficiency with a combustion analyzer of some sort (I don't care which) none are able to give true readings over 89%. There are some that GUESS but the only way to measure the true efficiency after 89% is to calculate the amount of BTU's per gallon of condensate you are transferring back to the heat exchanger.

kf

heretic

Surprised

This is an exact quote from HTP:

"We test at 180 degree Supply and 140 degree Return for a 92% AFUE to The Test Standards at The Hydronics Institute Boiler Standard ASHRAE 103-93 and May 12, 1997 Federal Register D.O.E. 10 CFR Part 430."

How prevalent is it to run a boiler at 140 degrees supply? Most are not designed to do so. That would be an odd standard.

kf_2

ASHRAE 103-93

Corey,

This is the exact wording straight from ASHRAE Standards 103-93;

"Section 8.4.2.3.2 For condensing hot water boilers the water flow rate shall be adjusted to produce a water temperature rise between 19.5*F and 20.5*F during the steady-state test described in 9.1. During the steady-state and heat-up tests, the condensing boiler shall be supplied with return water having a temperature of 120*F. The maximum permissible variation of the return water temperature from the required value during the steady-state and heat-up tests shall not exceed +,- 2*F, except during the first 30 seconds after start-up, when it shall not exceed +,- 10*F, and between 30 and 60 seconds after start-up, when it shall not exceed +,- 5*F."

This is typed word for word as it appears in the ASHRAE Standards 103-1993 Method of Testing for AFUE of Residential Central Furnaces and Boilers. And by the way, the testing procedure for non-condensing boilers is identical except the temperature rise is 19*F to 24*F.

I agree, these numbers in many cases are unrealistic and that is why people must realize that AFUE doesn't tell the whole story. Oh, and also the testing procedure rewards boilers with less insulation. Go Figure.

kf

Dave_4

increase the deadband to cut down on cycling....

if you're 'over-radiated' (great word Mark J) with cast iron, can you use an deadband control to prevent the burner from firing for 20 minutes.....the rads put out enough heat to keep the temperature reasonably consistent

heretic

Interesting

Thanks for the details.
The more you dig, the more irrelevant AFUE becomes.
Not only is it unrealistic as a measure of efficiency, AFUE doesn't even seem like a good RELATIVE measure for comparing one boiler to another.
I don't suppose there is a competing standard...