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Author Topic: Flow problem when really cold  (Read 405 times)

Roger2561

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Flow problem when really cold
« on: March 05, 2018, 10:41:09 AM »

Hi all, the attached picture shows the present setup (red line) and proposed change (black line) I was told would help me with my dilemma.  With my current setup (red line), for the most part, when the temps are above zero, the house stays warm and comfy but when it gets below zero, especially at 20 below with a strong wind, my current setup cannot keep up with the demand in the house.  The temp in the house will not get above 65 although the stats are set at 70.  The water coming into the house from the OWB is through 1 inch Thermopex is ~195ish, the return ranging anywhere between 160/170, depending on load.  I have Grundfos 26-99 at the OWB on the number 3 setting.  The feed and return manifolds are 1 1/4 inch copper 3/4 inch zone valves for each zone.  I was told the proposed (black line) will solve my problem.  I cannot wrap my head around how the proposed change (black line) will do this.  Can any of you pros offer some insite?  Roger       
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mlappin

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Re: Flow problem when really cold
« Reply #1 on: March 05, 2018, 11:31:21 AM »

I can see it helping some as the hottest water will be going directly to the zones instead of mixing with cooler water in the boiler. All boilers or water heaters that have a flue for gas or oil lose some heat right up the stack all the time from natural convection.

One issue I see unless I missed something is if all the zones are closed the alpha will be starved of water or will it only run on a call for heat from the oil boiler?

You might have to move your aqua stat as well unless its already after the “new T”
« Last Edit: March 05, 2018, 11:44:02 AM by mlappin »
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E Yoder

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Re: Flow problem when really cold
« Reply #2 on: March 05, 2018, 11:53:53 AM »

The proposed black line on the right sending water to the flat plate will be pulling heated water back through the flat plate which will make the heat transfer lower, not higher. When the Taco/Alpha is running the extra water needed for the zones will be the cool return water which will not get routed through the flat plate. It'll mix at the Tee on the supply manifold and supply lukewarm water to the zones.... I think??
You want to heat the cool return water from the zones. I think the red lines do better at this. With a 26-99 putting cool return water through the flat plate the flow is actually downward through the boiler and I doubt any return water mixes with the hot supply to the zones.
I still think your 1" Thermopex underground is the pinch point, the only way to compensate is more emitters in the zones to run a larger Delta t on the zones and on the Thermopex loop to the wood boiler. This would then equal more total btu's transferred.

If you have a 007 on the zones an alpha might help to get the flow rate up a bit for more even hot temps across all the emitters.  The 007 isn't a real strong pump. But again, more emitters then are needed to use the extra flow.

My thoughts anyway- wonder what you other guys think.
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Roger2561

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Re: Flow problem when really cold
« Reply #3 on: March 05, 2018, 12:06:41 PM »


I can see it helping some as the hottest water will be going directly to the zones instead of mixing with cooler water in the boiler. All boilers or water heaters that have a flue for gas or oil lose some heat right up the stack all the time from natural convection.

**Okay - That makes sense.  Thanks for clarifying.

One issue I see unless I missed something is if all the zones are closed the alpha will be starved of water or will it only run on a call for heat from the oil boiler?

**The alpha will only run when one or more zones call for heat. 

You might have to move your aqua stat as well unless its already after the “new T”

**Not quite sure what you're getting at - I have a strap on, break on rise aqua stat on a piece of copper pipe that's coming into the house from the OWB that's connected to the "TT" on the oil boiler relay.  It's set to 150 so regardless of what the oil boiler water temp is, the oil boiler will only run if the water coming into the house is lower than 150 degrees.  I hope I described that clear enough.  Roger   
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Roger2561

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Re: Flow problem when really cold
« Reply #4 on: March 05, 2018, 12:26:08 PM »

Question - What if I instead took the red line which is now only 1" thermopex and change it all to 1 1/4" copper?  Then instead of entering the 3/4 inch nipple on to of the oil boiler, I connected at the feed manifold just behind the oil boiler thereby by-passing the oil boiler all together?  At the drain, I install 1 1/4" TEE to bring the return water from the zones to Hx?  Essentially getting rid all of the 3/4 inch choke points inside the house and replace everything 1 1/4" copper?  In my simple mind it makes sense but I'm no flow expert (but I did stay at a Holiday Express Hotel last night   :)  )   
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mlappin

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Re: Flow problem when really cold
« Reply #5 on: March 05, 2018, 02:58:12 PM »

I don’t think just changing some of the 1” pex to copper is gonna help much as your supply from the boiler will still be 1” pex. If your heat improves when its really cold, your Delta T is going to rise as well.

I was just wandering where your aqua stat was is all, where its at now it won’t matter how you change the indoor boiler loop.
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Re: Flow problem when really cold
« Reply #6 on: March 05, 2018, 04:52:13 PM »

I don’t think just changing some of the 1” pex to copper is gonna help much as your supply from the boiler will still be 1” pex. If your heat improves when its really cold, your Delta T is going to rise as well.


I agree, the choke point isn't the loop from the oil boiler to the flat plate.
Roger- is there any way to add emitters in the house? I don't want to be dogmatic but I think that might be your best bang for the buck.
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Re: Flow problem when really cold
« Reply #7 on: March 05, 2018, 06:06:50 PM »

Marty - If this helps, the aqua stat that operates everything is a triple aqua stat on the oil boiler. 

Yoder - We were going to do that very thing anyway, we're a couple of weeks away from starting a renovation project of the master bath and we will be tackling the emitters at the same time.  The main part of the house will be pretty easy to do but the apartment will be difficult due to the layout. 

On an unrelated question;  My master bath presently has an 8ft section of a baseboard emitter.  Because of the renovation, we cannot use it the bathroom (it'll be relocated to elsewhere in the system) there will be no room for it.  How well do those toe-kick hydronic heaters work?  I'm thinking of installing one under the vanity I'll be installing. 
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coolidge

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Re: Flow problem when really cold
« Reply #8 on: March 05, 2018, 06:14:02 PM »

Keep in mind those toe kicks need a good cleaning every year.
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mlappin

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Re: Flow problem when really cold
« Reply #9 on: March 05, 2018, 06:21:05 PM »

Keep in mind those toe kicks need a good cleaning every year.

That and a common complaint is they are noisy. I was looking into them as you can get kits to make em wall mount, thought it might be nice for the upstairs bedrooms. Between the yearly cleanings and possible noise have ruled that out.
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Re: Flow problem when really cold
« Reply #10 on: March 05, 2018, 06:25:38 PM »

https://www.supplyhouse.com/Beacon-Morris-K42-K42-Kick-Space-Heater-4770000-p
This one would be a fairly close match in btu's to 8ft of baseboard. Next size up would allow for running on low speed fan. Noise is mentioned.
« Last Edit: March 05, 2018, 06:28:14 PM by E Yoder »
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Re: Flow problem when really cold
« Reply #11 on: March 05, 2018, 06:59:42 PM »

What if you only change the black line in the left but leave the other line the way it is?

How long is the 1" pex between the flat plate and the oil boiler?
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Re: Flow problem when really cold
« Reply #12 on: March 06, 2018, 03:23:39 AM »

I think I'll leave everything alone with exception of changing out the Taco for the Alpha and adding emitters.       

RSI - The length from the Hx to the top of the oil boiler is about 4 feet.  The length from the drain to the Hx is about 8 feet.   

Thanks for the heads up on the toe-kick heaters, I did not know about the annual cleanings but I kind of suspected there would be noise.
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Re: Flow problem when really cold
« Reply #13 on: March 06, 2018, 12:11:49 PM »

One thing I've been reading about on various heating sites is running 1/2" pex in the walls to do radiant wall heat. Sounds like it's a very comfortable heat and you can get more surface area than just floors.
I've threatened to fish a roll of pex up through the hole where the drain comes through under my tub to make it toasty warm... when I get time.
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Re: Flow problem when really cold
« Reply #14 on: April 27, 2018, 05:35:00 AM »

Hi all - It's been a while since we last discussed this problem.  I have added approximately 30 feet of Slant Fin baseboard emitters to the longest zone I have.  I hope it helps.  I've also added a couple of primitive drawings using "paint".  One of the drawings shows my current zone configuration, the 2nd drawing shows something I have in mind but not sure if it will help my situation.  I look forward to your comments and suggestions. 
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