Boiler set up, Primary Secondary problem (pictures in post)

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Old 12-03-12, 12:59 AM
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Boiler set up, Primary Secondary problem (pictures in post)

Hi to all

I am new and just put this system together, a first for me.

what i have is an 8 zone cast iron baseboard system being fed by 3/4" pex
with a tankless boiler,

problem is water in secondary manifold is about 25 to 30 degrees lower then what it is coming out of the boiler and in the the primary loop, i have this problem even if only one small zone is operating, the delta t is almost 0 once the system warms up.


can someone please tell me if i did something wrong in the piping?

please disregard all the loose wires not done yet.


Thanks
 
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Old 12-03-12, 10:58 AM
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Your piping should be configured with the secondary boiler loop off the bull sides of those tees and the pump should be pumping into the boiler. Thats at a quick glance
 
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Old 12-03-12, 11:20 AM
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RD steam means like this as far as the tees are concerned......This is a combi boiler I did.

What is the make and model of your boiler?



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Old 12-03-12, 11:59 AM
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so you say move the pump right on to the return? i am a bit lost on what you are saying about the secondary loop isn't that what i have coming out of the tees.

the boiler a rinnai c98 237,000 btu LPG i can run a crazy amount of water thru the unit and the water will hold accurately to any temp i set it at, up to 185. its not a 90+ efficiency
 
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Old 12-03-12, 01:22 PM
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The tees are wrong on your set up yanky. Have not looked up manual yet. I do not think the air vent is needed. Should be internal but may be wrong.
 
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Old 12-03-12, 01:44 PM
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Cant find manual on web site.... Can you verify model #??


A bigger issue I see is you gas line is way undersized.... 237k btu?

IMO no way is that 1/2" flex line supplying enough gas. Dont know how long the flex is but 3 ft is normal and they supply only 105k.

Better check that. Should be 3/4 all the way..... You will carbon up that unit and this may be part of your issue.
 
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Old 12-03-12, 04:53 PM
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I know I have to change the flex but I don't think that is an issue, because the unit is running well and heating the water to 185 degrees instantly and no matter what flow rate I put thru it delivered while testing.
The model is rinnai c98.
I still don't understand how what you posted is different then what I have, as for the pump I would have to move it up to th return side of the boiler
 
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Old 12-03-12, 05:18 PM
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Never mind the fact that those pumps are not to be mounted with the motor in a down position like that... read installation instructions.

I still don't understand how what you posted is different then what I have,
Not good at jigsaw puzzles I bet?

It's CLEARLY different. On a tee fitting, the two ends are called the RUN of the tee. The pipe out the side is called the BULL.

The BOILER should be on the BULL, and the SYSTEM on the RUN... can't see the difference?

Look at the red lines Mike drew on the drawing and compare to what you have.

By the way, I've been to Rinnai's website and see no such model as a "c98".

Please read the model number off the dataplate and let us know.
 
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Old 12-03-12, 06:33 PM
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primary loop close tee problem

thanks trooper, as i said i am new at this and i am actually terrible at puzzles, now i got what you guys are saying, so i must switch the tees around to make it work properly? the way the tees are now would cause problem of the full hot temp flow not making it in to the manifold and mixing with the return water?

thanks again,
 
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Old 12-03-12, 07:18 PM
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I didn't say that the tees being wrong was the problem with the temps... not sure if the others did or not, it seemed to me they were pointing out problems rather than analyzing the solution, as I was too... (which you did ask for! be careful asking for constructive criticism around here! you will SURELY get it! )

But you do need to turn that pump!

Let me go back and look at the problem again and think it through.
 
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Old 12-03-12, 07:26 PM
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By the way, there are also requirements for sections of STRAIGHT PIPE upstream AND downstream of your 'closely spaced tees'.

Look at drawing number 6 at this website:

http://comfort-calc.net/primary-seco..._tutorial.html

It spells out the dimensions that you should adhere to. The idea is to minimize the pressure difference between the two side ports and to do this you need what is called 'laminar flow'. Meaning that the flow can NOT be 'turbulent' as it most certainly will be in your setup, coming out of an elbow, and then jammed right back into an elbow.
 
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Old 12-03-12, 07:32 PM
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What is out at the end of the loop with all the zone valves on it? (all the way to the right side) Can't see it too good in the pics... do you have those two supply and return pipes looped together?
 
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Old 12-03-12, 08:08 PM
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IMO we should be more concerned with the gas line before anything else!!!!!!!
 
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Old 12-04-12, 12:53 AM
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i just have boiler drains at the end of the manifold no loop.

do you think if i just add the straight extensions to the runs of the close tees as described in drawing #6 and moved the pump to the the return side of the boiler i would resolve the issue of low flow? or must i change the bull and run as we discussed earlier?

it would require allot more pipe moving to change the tees around and give them the minimum necessary clearance, i am no engineer but i don't see how changing the tees from bull to run would make that big a functional difference.

I will be changing the gas flex over to 3/4"

thanks to all of you for all your help, i am pretty sure that with your help i am gonna have this system running right and efficiently
 
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Old 12-04-12, 05:24 AM
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I know I have to change the flex but I don't think that is an issue, because the unit is running well
Mike is right. How do you KNOW it is 'running well'? What are the results of your combustion testing?

From an electrical safety standpoint, what you've got 'jury rigged' there is shameful.

You should not be using ANY plastic covered wire (type NM) in that installation. Every piece of AC wire should be type MC cable, and properly installed, meaning the correct connectors with ANTI-SHORT bushings on the ends of the cable (aka 'red-heads').

Tell me the truth here, don't BS me... did you pull permits? Will this be inspected by code officer?

Is this drawing from the Rinnai manual?



You still haven't given us the full model number so we can find the manual and read it ourselves.

i am no engineer but i don't see how changing the tees from bull to run would make that big a functional difference.
Perhaps an engineering degree might be needed to understand why... but because we don't have those degrees is the reason that we shouldn't try to 'second guess' them. Many times we have to accept things on faith that the engineers and manufacturers know what they are talking about.

OK, let's get back to the problem then... I want to understand what you are seeing, I'm not clear on all the details. You need to tell us ALL the details if we are to help you.

First, it's hard to tell in a pic what size the piping is. You said 3/4" I think in your first post.

Do you mean that you have 3/4" piping in both the primary and secondary loops? That those long manifolds out to all the zones are 3/4" ?

What is the model number of the pump on the boiler loop? Is it the one that came with the boiler?

What is the model number of the pump on the system loop?

Now, you say that when you fire up the boiler, that the boiler loop immediately (almost anyway) goes to a setpoint of 185F ... on BOTH the thermometers on the boiler loop?

I only see a thermometer on the SUPPLY side of the system loops. Is that the one that you are seeing 25-30 less on?

If there is no thermometer on the RETURN side of the system loops, how do you know what the delta T is? How are you measuring that?

Was the cast iron baseboard a pre-existing installation to which you are connecting the new boiler?

If so, did you see the original installation? Do you know it to have functioned? (I'm asking because history is important, those who forget are bound to repeat)

How many feet of baseboard are on each zone?

I know I'll have more... but this is a good start.
 
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Old 12-04-12, 07:28 AM
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Hi

As for the electric, i inherited this mess and pretty much tried to redo the system and it was a complete mess much worse then my mess, as i said in the first post that the electrical wiring is not done i am just testing , everything will be getting MC even the zone valves.

the first loop coming out of the boiler is 1" the manifolds are 1 1/4" and the piping feeding the 50 year old cast iron baseboard is 3/4 pex.

the pumps that are on the system right now are both taco 007, i know i for sure need a bigger pump on the supply manifold because i called taco and with some calculations the biggest zone requires 14.5' of head, they say the loop off the boiler can use a 007, but someone else told me that it requires a high velocity pump.

as for the temperatures, we have 3 gauges the hot side coming out of the boiler has a gauge and it goes immediately to what ever i set the boiler to, also before i crafted this system the supply line always went to 185 when set that way, the return side has a gauge and the supply manifold has a gauge, the water will get hot right up to the close tees and the drops like 30 -35 degrees as it goes into the supply manifold, i guess due to mixing with the return water and my messed up close tees.

once the house warms up, the return and supply gauges have almost zero differential.

the only reason i think the unit is firing fine is because within 20 seconds of the unit coming on, it is pushing out 185 degrees and it will stay that way for the duration, of course i didn't do a flue gas test so i cant be sure.
 
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Old 12-04-12, 07:53 AM
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Page 5 here,

http://s3.pexsupply.com/manuals/1263..._PROD_FILE.pdf

From what code dictates is the gas line can be no more then 36". It seems that your flex line is a home store variety that may be 48".

If so, and even if it is 36" its 1/2" and only supports 125K @ 36" or 106K btu @ 48"

You need 36" in the 3/4 " variety that supports 255,900 btu.


You stating that the unit heats fine, seems to lead me to believe you are not concerned with this issue I pointed out.

I am trying to locate data on implications of starving the unit for gas on a high fire. Possible others can chime in to assist with this concern.
 
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Old 12-04-12, 01:25 PM
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i mentioned before that either way i am going to install a 3/4" flex or i will install rigid pipe that will conform to specs needed.

thanks for pointing it out.
 
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Old 12-04-12, 01:47 PM
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OK, I'm only going to ask once more for you to find and report the model number of the Rinnai. There is no such item on their website...
 
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Old 12-04-12, 02:39 PM
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Hi

look at the picture the model # is printed right on it there is no other info on it I was not the one who purchased it, I inherited this mess
 
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Old 12-04-12, 03:14 PM
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Open up the cover or look for the name plate on the unit. You can get the full model # from there. We can only guide you with basics unless we can find the manual to give proper instruction so we can help you better.

Thanks for the confirm of the gas line.
 
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Old 12-04-12, 04:01 PM
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I dunno, maybe it's a RC98i ... and here's something funny I found in that install booklet. Seems to apply to ALL their products, kinda generic statement:

Iron Components

Do not use Rinnai water heaters directly for space heating applications involving iron radiators or applications with any iron components.

Iron components may oxidize creating rust that will clog the inlet filter of the Rinnai water heater.
Rut Row Reorge!
 
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Old 12-04-12, 04:20 PM
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Hmmm troop...It would seem possibly its a HWH model?????

Geez...!!!!
 
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Old 12-06-12, 12:11 AM
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hi guys

here is the link on the rinnai site to my unit its the c98 commercial unit and says that it can be used for space heating but does not offer much info on it.

please let me know what you guys think.

thanks

http://www.rinnai.us/documentation/d...s/U273-430.pdf
 
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Old 12-06-12, 08:38 AM
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Page 28 of manual: Installers Installation Copnsiderations
2) This water heater is suitable for residential water (potable) heating ONLY. DO NOT use this water heater for space heating, combination space heating/
domestic water heating, or commercial water heating applications. Doing so will
void the warranty
 
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Old 12-06-12, 09:07 AM
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I inherited this mess
Is it too late to DIS-inherit it? Can you walk away?
 
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Old 12-06-12, 03:46 PM
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Troop that is for the residential unit, I have the commercial unit that clearly states that I can use for space heating, it's somewhere in the manual right after where it mentions what you posted, I am not ready to give up yet......

Thanks for your help
 
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Old 12-06-12, 04:02 PM
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While you are checking, here are some thoughts. The manual refers to both ASME- and non-ASME approved units. Water heaters are not usually ASME stamped; is yours? Hot-water heating boilers are typically built under ASME codes.
 
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Old 12-06-12, 04:22 PM
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I like to see the name plate on the unit. I suggest finding it and taking a pic. This way we can all be on the same page..
 
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Old 12-06-12, 05:03 PM
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A little late here but this is the explanation.
i am no engineer but i don't see how changing the tees from bull to run would make that big a functional difference.
The whole idea of p/s and hydronic separation which allows two pumps to not interfere with each others flow. This is done by low pressure drop between the tees which is the reason for them to be very close.
The second reason this works is due to the same resistance created by entering and exiting the branch of the tee's. Let's assume the tees are 1-1/4" copper tees. If the run of the tee's are mounted on the primary loop and the branch of both tees are connected to the boiler (secondary pipe).
Everything having to do with flow is all about equivalent feet of pipe which than becomes resistance. The run of a 1-1/4" copper tee is equal to about .6 ft. of pipe per tee. When entering the tee and turning to exit the tee is equal to 5.5 ft. of pipe. So if installed properly the return tee where the water enters the return side of the boiler is 5.5 ft. and the supply pipe entering the branch of the supply tee is 5.5 ft. They are equal.
Let's rotate one of the tee's. Now we do not have p/s we have bypass piping, we have lost hydronic separation so now the flow of one pump can affect the flow of the other pump. The one tee is equal to 5.5 ft of pipe and the other one is equal to 0.6 ft of pipe. We also do not have the distance before and after the tee's required.
There should never be anything between the closely spaced tee's.
See chart.
Equivalent Feet Pipe Chart
Also check this out
Primary/Secondary Piping Common Problems
 
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Old 12-06-12, 05:41 PM
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I am not ready to give up yet......
I know yer not, I can tell you are determined to make it work right, so I'm gonna stop beating around and ask you a straight-forward question:

Are you prepared to start over from the beginning?

Do you own a SawzAll ?

I'm not trying to be funny, because that is the only way I personally would approach that system if I were called upon to 'make it work'.

You might be able to save the supply and return manifolds...

You said:

the piping feeding the 50 year old cast iron baseboard
Rinnai said:

Iron Components

Do not use Rinnai water heaters directly for space heating applications involving iron radiators or applications with any iron components.

Iron components may oxidize creating rust that will clog the inlet filter of the Rinnai water heater.
If you persist in attempting to use that water heater as a space heater, you had better incorporate some sort of easily cleanable WYE STRAINERS to keep the rust out of the heater.

There are so many other defects that have been mentioned that the only sensible thing to do is start over.
 
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