Some Rads Hot and Some Not (not a air bleed issue)

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Old 11-08-14, 04:53 PM
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Some Rads Hot and Some Not (not a air bleed issue)

I have a Slant Fin Victory (V150EP) hot water boiler. Single zone for a 2 story home. Boiler is in the basement and has about 20 psi water and there is a 30 psi relief valve on the unit. A Grundfos circulating pump is used to circulate the hot water. The unit is serviced each year and each technician states that it's in amazing shape, the gas pressure is fine etc.

There is a wheel valve on the outflow and a wheel valve on the return flow.

All rads are 100% completely bleed of air. This is not the problem.

If I have both hand valves wide open I can only get the water in the system up to approx 104 degrees. All radiators are moderately warm in this condition.

The owners manual states that the unit should run at least 180 degrees. The only way I can get it to 180 degrees is to restrict the water flowing through by manipulating the feed or return valve.

When I do this then the boiler comes up to temperature and most of the radiators get nice and hot, however there are a few on their own run that then get zero heat. The feed line to them is relatively warm however there just does not seem to be enough pressure to push the hot water through them and back through the return.

Once I fully open the valves the water flows to them, however the heat in the boiler drops back down to around 100 degrees.

Any thoughts would be helpful.

Thanks.

Troy.
 
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Old 11-08-14, 05:09 PM
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Hi Troy,

How long have you lived with the unit? Several years? And you are certain that this is something NEW that's going on now?

Pressure gauges lie.

You say the pressure is 20 PSI, do you see it go down when cold and up when hot?

Read this:

http://www.doityourself.com/forum/bo...ure-gauge.html

All rads are 100% completely bleed of air. This is not the problem.
And I say; "Famous Last Words"

there are a few on their own run that then get zero heat.
This is MOST LIKELY an air blockage issue.

manual states that the unit should run at least 180 degrees.
The HIGH LIMIT is set to 180F. That doesn't mean that it will ALWAYS go to 180. This time of the year it would not be at all unusual for the thermostat to satisfy and shut the boiler down long before it gets to 180F.


I need to ask you some questions:

What type of heat emitters do you have? You said 'rads', do you mean standing cast iron radiators? And large steel pipes, like 2" or more?

Or, do you have fin tube baseboards?

Do you possibly have what is called 'Monoflo (tm)' aka 'diverter tee' piping to the rads? You can tell by looking at the piping. Are both the supply and return to and from the rads going back to the same pipe?

Can you take some clear, well lighted pics and post them so we can see what you're working with?
 
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Old 11-08-14, 06:30 PM
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Thanks NJ Trooper. Much appreciated.

Let me know if the attached photos are useful.

Answers to your questions:
How long have you lived with the unit? Several years? And you are certain that this is something NEW that's going on now?
--->We have lived here 6 years and it has been a problem the entire time.


You say the pressure is 20 PSI, do you see it go down when cold and up when hot?
-->the pressure pretty much stays the same regardless of the temperature. It might go up by a couple of PSI max.

All rads are 100% completely bleed of air. This is not the problem. And I say; "Famous Last Words"
--->I trust your insight but these particular rads I attached a funnel to them attached to a hose and a large bucket. Bleed them fully. All I get is cold water.

there are a few on their own run that then get zero heat. This is MOST LIKELY an air blockage issue.
---> I've completely drained the entire system twice and refilled to no avail. When the hand valves are fully open on the boiler the rads get heat, but having the valves fully open causes the boiler to drop heat.

manual states that the unit should run at least 180 degrees. The HIGH LIMIT is set to 180F. That doesn't mean that it will ALWAYS go to 180. This time of the year it would not be at all unusual for the thermostat to satisfy and shut the boiler down long before it gets to 180F.
--> I've adjusted all the settings on the auquastat and it made no difference. Currently set to 220. Photos attached.

I need to ask you some questions:

What type of heat emitters do you have? You said 'rads', do you mean standing cast iron radiators? And large steel pipes, like 2" or more?
---> The house is about 140 years old so all the rads are cast iron and all the piping, with exception of a few feet of copper near the boiler, are all cast iron 2".

Do you possibly have what is called 'Monoflo (tm)' aka 'diverter tee' piping to the rads? You can tell by looking at the piping. Are both the supply and return to and from the rads going back to the same pipe?
----> Supply and return are two separate cast iron pipes.
 
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Last edited by NJT; 11-08-14 at 06:49 PM.
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Old 11-08-14, 06:38 PM
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Added a link to some more photos.


https://plus.google.com/photos/11556...13306069031425
 
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Old 11-08-14, 07:04 PM
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I believe the problem is that the boiler has no bypass of any kind. The massive volume of water in the system is simply not allowing the boiler to heat it all up at once.

Read this:

http://www.slantfin.com/images/stori...sation_fgc.pdf

I have to ask: How many times in the past 6 years have you had to replace the flue pipe?

I don't see the 'condensate drain' that the Slant-Fin installation manual calls for. See figure 6a on page 7

http://www.slantfin.com/images/stori...ctory_v_40.pdf

Has your technician looked inside the flue passages of the boiler? I know he said it's in great shape, but....... My guess is that the flue gas has been condensing forever. Flue gas condensate is acidic and will EAT the boiler from the inside out, along with the aforementioned flue pipe AND the masonry in the chimney.

Has the chimney had a LINER installed in it? If that chimney has not been inspected, top to bottom with a CAMERA (not just Joe Schmoe looking down with a flashlight), I would strongly advise you have that done.

How many square feet is the home?

I believe that boiler is 150K BTUH, is that correct?
 

Last edited by NJT; 11-08-14 at 07:29 PM.
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Old 11-08-14, 07:19 PM
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I've not yet had to replace the flue pipe and it looks original from the day the boiler was installed. Not sure if the tech looked inside the flue passages. I've watched them scrub with brushes and then vacuum but that is likely not going into the passages.

They do check for CO2 in the flu pipe by inserting a probe and measure in the room around the unit. The flue had 13ppm when the inspection was done Sept 25th 2014.

The liner in the chimney is a clay so I should likely have someone inspect it. Thanks for the suggestion on that.

The home is around 2900 sq feet.

The unit is 150,000 BTU.

Aside from the potential damage that could have already likely occurred, any thoughts on how to add a bypass? Is it a DYI or should a pro come in. I find it difficult to find knowledgeable tradepeople for this stuff. Fewer and fewer homes have boilers.

Thanks.
 
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Old 11-08-14, 08:14 PM
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Not sure if the tech looked inside the flue passages. I've watched them scrub with brushes and then vacuum but that is likely not going into the passages.
That's good that they brush it... yes, those are the internal flue passages.

They do check for CO2... had 13ppm ...
The CO2 would be expressed as a percentage. The 13 ppm was probably CO (monoxide, not dioxide)

The CO number is OK.

Aside from the potential damage that could have already likely occurred, any thoughts on how to add a bypass? Is it a DYI or should a pro come in. I find it difficult to find knowledgeable tradepeople for this stuff.
A BOILER bypass is probably not going to help much, since you will still have cold water coming back to the boiler. Yes, the boiler will get hotter on the supply side with less flow through it, but there is still massive amounts of cool water returning.

A SYSTEM bypass isn't advised for your installation either. You don't want to divert flow away from the radiators. You need to move a lot of water through the system.

I think for your system a PRIMARY/SECONDARY setup with a THERMOSTATIC 3-way valve is probably the best solution.

I don't know your skill set, the physical part of cutting and soldering pipe is easy enough to learn with some practice, but the work also needs to be engineered.

The diagram below is what I would consider. Your SYSTEM pump (the one on the horizontal) should be sized for a good flow through the system. The pipe connecting the supply and return should probably be at least 1-1/4", but IMHO 1-1/2" would be better.

For 150K BTUH, you should also use 1-1/4" on the boiler loop as well.

The pump you have for the boiler now is fine for the boiler loop.



193B1701 - Danfoss 193B1701 - ESBE Series 1-1/4" 3-Way Thermic Valve (Body Only)

193B1704 - Danfoss 193B1704 - ESBE Series Thermostatic Element, 140F Opening Temperature

The way this setup would work is this:

When there is a heat call and everything is cold, both pumps would start and the boiler would fire.

There would be full flow in the system, and full flow through the boiler, but because it's cold, the thermic valve would recirculate the boiler water until it got up to about 130, at which point that valve would start to divert flow from the bypass to the system, letting some water return from the system and start injecting the hot water into the system.

The thermic valve would 'modulate' for a while, recirculating some of the hot boiler water and mixing with some of the cool return water, until the water returning from the system was up to 140, at which point it would be 'all in'... no bypass flow ... all the boiler flow going through the system.

Makes sense?
 

Last edited by NJT; 11-08-14 at 08:53 PM.
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Old 11-08-14, 08:19 PM
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By the way, you could theoretically leave your air scoop and expansion tanks where they are, but you would have MUCH better air removal capability moving them to the supply side of the boiler and PUMPING AWAY from the tank with the system pump.

Google the term 'pumping away' for more information than you want to know about that.
 
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Old 11-08-14, 08:28 PM
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Awesome! Thank you so much. This makes sense of a problem I have been stumped with for some time.

Although a bit beyond my DIY skills, at least I can talk this through with the trades when I get them to do the work.

Thanks again NJ Trooper. Totally owe you one!

Troy.
 
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Old 11-08-14, 09:05 PM
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You're quite welcome Troy.

I modified the drawing a bit, if you refresh the page you'll see the changes.

There certainly could be some 'details' missing, the drawing is for general concept only.

In case your installer needs a little more help, here's a drawing showing the critical dimensions of the closely spaced tees.



It's most important that the tees be as close as possible to each other. You don't need the elbows on each end, those are shown to indicate that there should be at least 8XD upstream and 4XD downstream before any other fittings, valves, etc.
 
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Old 06-02-15, 03:52 AM
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Recommendation on Circ Pump

NJT:

Now that the heating season is over I'm ready to tackle this project.

Any recommendations on the system pump or should I just get the exact same one as the boiler loop?

Thanks again for your valued advice!

Troy
 
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Old 06-03-15, 05:25 PM
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Hi Troy,

I don't think you want the same one for the system loop.

You MIGHT be able to get by with something like the Taco 007, and since they sell millions of them, they are quite a bit cheaper than the next step up:

007-F5 - Taco 007-F5 - 007 Cast Iron Circulator, 1/25 HP

But I think I would personally consider the next step up, an 0010.

0010-F3-1IFC - Taco 0010-F3-1IFC - 0010 Cast Iron Circulator with Integral Flow Check, 1/8 HP

BUT, considering the difference in price, and that the 007 will most likely move enough water in your system, I would be tempted to try it first and see how it goes. The odds are in your favor that it would do just fine.
 
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Old 12-01-15, 04:20 PM
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Problem Solved! Another small nuisance introduced

Hi NJT:

Firstly, I want to thank you for your help on this issue. I did all the work myself and can report to you that all my rads are nice and hot! I could not be happier. Thank you.

There is one small problem introduced with my new configuration. Noise. I'm finding that there is an intermittent 'gushing' and popping sound that travels from rad to rad. The sound is similar to grease in a frying pan.

I've drained and refilled the system and boiler loop multiple times and all rads are 100% bled of any air.

Any thoughts?

Thanks again!

Troy.
 
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Old 12-01-15, 05:55 PM
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I've drained and refilled the system and boiler loop multiple times and all rads are 100% bled of any air.
Any thoughts.... yes... STOP draining the system. Every time you do you reintroduce more air.

I friend of mine has a system like yours and it's a bugger to get the air out. I had it all worked out and I had to replace a defective pump.

I had to raise the boiler pressure to get all the air out of the second floor and then dump some water back out.
 
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