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Discussion Starter · #1 ·
We have installed a Munchkin MC120 in a home we are building. It is supplying heat for the radiant heat system as well as heat for an indirect 80 gallon water heater (Superstor Ultra SSU-80). This is the first time I have used one of these systems and so far we are not impressed. The house has a large master bath with large jacuzzi tub and multi valve shower with body sprays. I expected this system to more than supply enough hot water without running out. Wrong. With the shower on and the tub filling the water will last about 10 minutes. Thats garbage for spending this kind of money.
My plumber and I changed some of the settings on the boiler and increased the tank water temp to 130F, it was 120F. But that has only helped by allowing the shower and tub to run 12-15 minutes. The tub does have a large flow (5gpm) but the reason for getting this system was do to the water demand this house was going to have. There are still two other tub/showers upstairs as well as the kitchen and fourth 1/2 bath downstairs.
After reading the manual and it's settings I am thinking the Munchkin is not firing as hot as it should or could. The tank calls for heat after a 7* drop in temp. When it calls for heat the boiler fires and supplies the coil with hot water. From my understanding that boiler should fire as hot as it can so the water tank can recover as quickly as possible. But that does not seem to be the case. I think we should be getting 180F out of the boilers output so it heats the tank quickly. But what we are getting is considerably less. The output temp of the boiler is only 16-17* warmer/hotter than the input temp. So this boiler can only increase the temp by 17*? No way. The hole idea is that it can, I thought, take the input and pump out the pre set temp, in this case 180. But it's not close. Is this $3k boiler seriously only able to increase the water temp by 17*?
From the Munckin website
The "controller utilizes an algorithm to fully adjust the firing rate while maintaining the desired output temperature." In this case the output temp is set at 180. Which again we are not getting.
Now I do like that this system is fully adjustable but I'm not impressed by the domestic hot water supply. I can adjust it to be very efficient or to supply more hot water but right now just getting it to supply as much as I thought it could is proving difficult.
My next test is going to be to increase the tank temp to 140 and then if that does not help much, lower the change in temp to firing. So instead of the tank loosing a full 7* until the boiler fires I will set it to, say 3*.
My plumber is good but he does not know everything about the Munckin and it's system. The biggest concern or question is why will it not put out 180* water when the tank calls for heat? I was thinking maybe it's set to be efficient and thats why it's not fully firing and putting out the 180. I can't seem to find any setting for efficiency for the domestic part of the system. The other thought is that it's sensing the outside temp and noticing it's not crazy cold so it's not firing the boiler to it's full potential. Am I wrong thinking the boiler can and should put out 180* for the domestic?
Anyway sorry for this long post but I am trying to get some answers. If anyone has experience with these things I would be very appreciative to hear your thoughts.
 

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The Grand Wazoo
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I hope that on the next job you consider the end user and do a better job of sizing the equipment to fit the application, because you failed miserably on this one.
 

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The Grand Wazoo
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Great response. Real helpful *******. Thanks.
You're welcome. It's not my fault you lack the skills to hire subs that are capable of supplying equipment sufficient to do the job required, nor is it my fault that you lack the intelligence to grasp the obvious about the equipment you described. It is said that those that have no skills in any trade become GC's, seems like it may be true.
 

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Discussion Starter · #5 ·
You're welcome. It's not my fault you lack the skills to hire subs that are capable of supplying equipment sufficient to do the job required, nor is it my fault that you lack the intelligence to grasp the obvious about the equipment you described. It is said that those that have no skills in any trade become GC's, seems like it may be true.
Wow. I'm truly shocked. Hell of a welcome I'm getting on this site. I feel bad for you and worse for the people around you. You must be a truly miserable person to pounce on someone like this. Does this kind of thing make you feel good about yourself? I come here for some help and advice and you bust my balls. You know nothing about me or my skills yet you make judgments based on one post. I'm really at a loss for words. But I guess there are people like you out there and nothing I can say will change your attitude towards people and life. People come here for help and to share their knowledge. I joined to do both. Why are you here? Please don't bother posting in this post anymore . I will not respond to you anymore and you are doing nothing but belittling someone that came to you for help. Very mature.
I would appreciate any input from anyone else who doesn't come here just to bash people and their intelligence. If this is what this site is all about I'm obviously in the wrong place.
 

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Your boiler is somewhat undersized no doubt to achieve the recovery rate you require. Couple things you should check:

1). Is the pump supplying the Indirect providing adaquate flow??

2). Is the indirect piping loop the appropriate size??

3). Do you have a tempering valve on the domestic hot water supply at the tank?? If so, you might want to run the tank even hotter. While it won't help your recovery time, it will lengthen the amount of water delivered on "First Demand".

4). Is the DHW on Priority?? In other words, if there is demand for heat as well, will the controls interrupt the demand for heat while there is demand for domestic??


Based on some crude math, the MC 120 will probably take around 26-30 minutes to recover the SS 80 assuming the supply water is about 50 deg and your looking to achieve 115 deg out. Will demands like a jacuzzi and multihead shower, your GPH deamnd is very high, and once the tank is depleted, your boiler isn't large enough to recover.

Couple things you could do if you don't want to scrap the boiler. Go to a reverse indirect like a turbomax:

http://www.thermo2000.com/content/en-US/s2_produits/optimizer.aspx

This type of tank will increase the mass of the heating system because the tank is full of boiler water and just has copper coils that pass through it. The fact that you already have a bunch of boiler water at temp when the demand starts will help stetch the amount of DHW you generate. These are very popular in commercial applications around here.

You could add another tank as well. It not going to help with the recovery time, but you would at least have more hot water on tap before running out.

You really need to sit down and figure out the demands, flows, temp rise, etc. If your unsure, you really need to find someone who can. Today's heating systems are far more sophisticated than the tea kettle systems of the past.
 

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Contractor of the Month
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Great response. Real helpful *******. Thanks.
Good Sir,

I suggest you post your question where you will find more plumbing expertise.

From what I hear the good members of http://www.plumbingzone.com/
will be happy to help you and any other individual with the simplest or most complicated plumbing matters.

Best of luck.
 

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Good Sir,

I suggest you post your question where you will find more plumbing expertise.

From what I hear the good members of http://www.plumbingzone.com/
will be happy to help you and any other individual with the simplest or most complicated plumbing matters.

Best of luck.
Inner why are you stirring up trouble, you know darn well GC's are not allowed to post on PZ, you know the site is for plumber only.
 

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The Grand Wazoo
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Wow. I'm truly shocked. Hell of a welcome I'm getting on this site. I feel bad for you and worse for the people around you. You must be a truly miserable person to pounce on someone like this. Does this kind of thing make you feel good about yourself? I come here for some help and advice and you bust my balls. You know nothing about me or my skills yet you make judgments based on one post. I'm really at a loss for words. But I guess there are people like you out there and nothing I can say will change your attitude towards people and life. People come here for help and to share their knowledge. I joined to do both. Why are you here? Please don't bother posting in this post anymore . I will not respond to you anymore and you are doing nothing but belittling someone that came to you for help. Very mature.
I would appreciate any input from anyone else who doesn't come here just to bash people and their intelligence. If this is what this site is all about I'm obviously in the wrong place.
Hey super genius, you answered your own question in your post, 80 gallons of storage + 5 GPM tub filler + 1 GPM shower head X 10 minutes means you have basically exhausted your storage in that time unless you have exact measurements on the GPM rate for the fixtures in use, the system is undersized. It doesn't take much more than common sense to look at a tub that holds over a hundred gallons and draw the conclusion that 80 gallons of storage just is not going to cut it.

The only A-hole here is the one looking to weasel a way out of paying for his own mistake.
 

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Discussion Starter · #11 ·
Your boiler is somewhat undersized no doubt to achieve the recovery rate you require. Couple things you should check:

1). Is the pump supplying the Indirect providing adaquate flow??

2). Is the indirect piping loop the appropriate size??

3). Do you have a tempering valve on the domestic hot water supply at the tank?? If so, you might want to run the tank even hotter. While it won't help your recovery time, it will lengthen the amount of water delivered on "First Demand".

4). Is the DHW on Priority?? In other words, if there is demand for heat as well, will the controls interrupt the demand for heat while there is demand for domestic??


Based on some crude math, the MC 120 will probably take around 26-30 minutes to recover the SS 80 assuming the supply water is about 50 deg and your looking to achieve 115 deg out. Will demands like a jacuzzi and multihead shower, your GPH deamnd is very high, and once the tank is depleted, your boiler isn't large enough to recover.

Couple things you could do if you don't want to scrap the boiler. Go to a reverse indirect like a turbomax:


This type of tank will increase the mass of the heating system because the tank is full of boiler water and just has copper coils that pass through it. The fact that you already have a bunch of boiler water at temp when the demand starts will help stetch the amount of DHW you generate. These are very popular in commercial applications around here.

You could add another tank as well. It not going to help with the recovery time, but you would at least have more hot water on tap before running out.

You really need to sit down and figure out the demands, flows, temp rise, etc. If your unsure, you really need to find someone who can. Today's heating systems are far more sophisticated than the tea kettle systems of the past.
Thanks tc. My plumber has done many of these and I have done a good amount of reading on this system, so I know he plumbed it correctly. The plumbing supply house also did the calculations before we purchased the unit. However the homeowner added the 5gpm tub spout after the fact. So that is what is hurting us. My plumber is meeting with the experts at the supply house today to see what can and should be done. It's probably not as bad as I am making it out to be. It's just that tub spout that hurts.
As for the flow rate he is checking on that today. The indirect piping loop is the correct size according to specs (1"). We are running the tank at 130 now vs. the 120. Like you said it does not help the recovery but supplies "more" hot water. It has already made a difference. The DHW is on priority. The radiant shuts down completly as soon as the tank calls for heat. So the boiler puts all it's power to recovering the tank. Thats why I don't (plumber is working on this) understand why the boiler can only up the incoming loop temp by 17 degrees. My impression from my reading of both the Munckin and UltraStor was the Munckin would provide 180 degrees of water to recover the UltraStor as quick as possible. I'm meeting with my plumber this afternoon so we should have some answers.
Your recomendation of a reverse indirect is the exact system I have thought about for years. When I met with my plumber pre-project I asked him about that and he said that the UltraStor was what everyone was using and it would be fine. But logically it seemed to make more sense to have a coil running through hot boiler water to heat the domesting vs. having what we have now where the boiler water runs through the coil providing the heat to the DHW in the tank. Just seems to me the reverse way is more efficient and would provide almolst endless hot water. Thanks again for your input.
 

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I'm not that familiar with the newer vision controls, but with a DHW call, the boiler should go straight into high fire and bypass and sort of reset control. When you say you only see a 17 deg difference, is that while the tap is continuously open?? If you stop using hot water does the loop temp of the munchkin DHW loop eventually see 180 deg?? If not then you have a control problem.

The coil in a SSU80 is capable of alot of heat transfer. With the flow rate you describe, it wouldn't surprise me that the coil is quickly being immersed in 45-50 deg water and the boiler is dumping heat into the tank faster than it can initally make it. Download the SSU manual and look at the first hour ratings, you need a large boiler to hit those numbers of output, so with continuous demand, its not surprising that the boiler is struggling.
 

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Discussion Starter · #13 ·
I'm not that familiar with the newer vision controls, but with a DHW call, the boiler should go straight into high fire and bypass and sort of reset control. When you say you only see a 17 deg difference, is that while the tap is continuously open?? If you stop using hot water does the loop temp of the munchkin DHW loop eventually see 180 deg?? If not then you have a control problem.

The coil in a SSU80 is capable of alot of heat transfer. With the flow rate you describe, it wouldn't surprise me that the coil is quickly being immersed in 45-50 deg water and the boiler is dumping heat into the tank faster than it can initally make it. Download the SSU manual and look at the first hour ratings, you need a large boiler to hit those numbers of output, so with continuous demand, its not surprising that the boiler is struggling.
No word from the supply house and plumber yet. The supply house only deals with plumbers, so even as a contractor they won't talk to me about it. My plumber says hopefully today or tomorrow.
Meanwhile. As you said the boiler should go straight to high fire. But, unless I completly misunderstood how these boilers work, I dont' think it is. The 17 degree increase is from the input to the boiler to the output (closed loop). So if the boiler is firing at say 140 and pumping it through the coil, it loses 17 degrees and comes back to the input of the boiler at 123. The only way that initial 140 will increase is when the tank water increases. So if the tank is at say 100 and the boiler is firing the loop at 140, the boiler will only increase that 140 as the tank increases. So when the tank reaches it's set temp of 130 the boiler will have an output of 170. So to answer your question. If there is no DHW being used in the house the boiler will still never get to 180.
Thats my initial question or concern. I thought it was suposed to take whatever input temp of the water and, within reason, increase it so the output is at 180 thus giving the fastest possible recovery. Maybe I'm wrong on that. That is what my plumber is suposed to ask the supplier. You seem to agree with me that that is what should be happening and you think it may be a control problem.
I hate wasting water but I'm going to play with it again today and see what kind of temps we get at various points.
Thanks again for your help and input.
 

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Why not call HTP direct?? I know the vision control will tell you the fan speed and I belive, but am not 100% sure,that the fan speed is directly related to the firing rate.
 

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Discussion Starter · #15 ·
Thanks again TC for your help and advice. After some calculations, troubleshooting and talking with HTP, the boiler is firing properly and at it's highest capable output. I looked into the Reverse indirect but it has lower ratings than the Superstor so we are sticking with the Superstor. The issue, as mentioned by everyone is simply the boiler being undersized for the application and/or the indirect should be bumped up to a 120 gal. So we have turned the tank temp up to 140 and lowered the firing differential so it calls for heat after a 4 degree drop vs a 7. So far so good. Not perfect but not as bad. We will see how it goes over the winter months and decide if upgrading to the 120 gal is worth it.
Thanks again for everyones help.
 
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