Looking for a thermostat for floor heater

[2Biz]

This is what my old boiler looked like! You can see why it needed replaced. Replacing it is one of the smartest moves I've made with the CW. I'm actually not afraid of turning it on and letting it run. The cost savings in NG is huge...I think I've mentioned it, but last winter in January, the demand heater/boiler ran 25 out of 31 days appr. 12 hrs a day average in January's billing cycle. It cost $125.00 over what my normal NG bill is for heating the ER...Very economical to operate. Another huge savings is the pumps. My old pump was 220v and consumed 12a. The new Taco pumps run on 120v and only use 2a each for a total of 6 amps. That drops down to 2 amps when the boiler pumps kick off. I am extremely happy with the way it turned out.

 

[GoBuckeyes]

2Biz, I know you have 3 bays plus an uncovered truck bay you're heating with your system. If your wash were double the size, obviously that one heater wouldn't be big enough. How would you change your setup if it needed another heater? All of my washes have a minimum of 5 bays plus at least one automatic and aprons so a one heater system wouldn't cut it for me.
Thanks

 

[2Biz]

You can run (2) of the 199 btu heaters in series basically. Plumbed just like mine is per unit only side by side and with (4) Taco 013's, (2) for each heater. You might also have to increase pipe dia., mine is 1". I'm only flowing 16 gpm total through the zones. This is where you have to calculate heat load and how many zones you have for your location.

Since the heaters modulate, you could set the first heater in line to heat the return water/glycol to 105°-110°. It mixes with the return glycol and would be roughly 90°-100°. The 90°-110° glycol is then drawn into the second heater and heats from the 90° to 140°-150°. By doing this you still put out about 7gpm of heated water but at a much higher temperature than my system. If I cranked my heater up to 150° my output decreases to about 3 gpm. When I do that the heater steps up the btu to handle the load/demand which uses more NG. Not as efficient. ***Note*** When you stack two pumps in series, volume stays the same and pressure doubles. When you run two pumps in parallel volume doubles and pressure stays the same.

My zone pump taco 013 puts out a no load 33 gpm. With the head restriction of my zones, I calculated I get about 16 gpm through the pump. I did tons of research on how to calculate head pressure in the plumbing, demographics for weather calculations for heat load, and calculated temperature loss through the system. Every system will be different. From what I remember you want about 3-4 gpm going through each zone, so you'll have to size your zone circulator accordingly. Another key point is the zone circulator has to move glycol faster than the pumps to the heater. Otherwise you create a loop in the heater plumbing which is not a good thing. So my system circulates glycol @ 16 gpm and the heater puts out 7 gpm. So the glycol flows past the primary - secondary plumbing at about a 2-1 ratio.

So to answer your question, I'd install (2) 199k BTU demands and plumb them like I suggested. Primary - secondary plumbing and size the zone circulator for the size system (zones) I have. I think when I did my calculations I needed 130K btu to satisfy my heating load. When my heater runs, it basically heats the glycol from 60°-70° return temps to 105°. You can barely hear the heater run. I'm guessing its modulated down as far as it will go, about 15-30k btu... The Takagi I bought cost $1350. I doubt you could get a modulating 400K BTU boiler for $2700.00 that will work as good as this...

 

[GoBuckeyes]

Thanks 2Biz. I hate hijacking this thread but I'm assuming Slash007 already got all the info he needs.

My systems now are all Raypacks designed by Huron Valley. Where you have only one zone per bay, we have several. In a nutshell, our controls are set up the same. Circulating pump comes on and continuously runs below 35d, Boiler fires according to return glycol temperature, currently set at 60-65degrees. Boiler modulates and basically puts out 90degree glycol.

I was thinking I could cut out the Raypack and in its place add the Tagakis. Most of my systems are running 2" piping and I thought I could keep my circulating pump which is sized for the system unless I wanted to replace it for energy savings with a more efficient one. One difference is that I have a 3/4" bypass that goes between the outgoing and return line which is run fully open. I believe this is done to keep bypassing some warmer glycol back into the colder return glycol to prevent condensing in the boiler and something to do with head pressure and flow? As for the Tagakis in series, if I understand correctly, you're saying the flow actually would go through the two Tacos, through first Tagaki, through the second two Tacos, through the second Tagaki then back into the circulation loop correct? This is definitely a summer install but I'd like to try to engineer it this winter.

 

[2Biz]

It can be complex if you haven't studied the concept. But you essentially have (4) tee's in the main trunk. Coming from the return flow, the first Tee supplies 60° return glycol to the heater. Output is 105°. This is input back into the main trunk at Tee number (2). Keep in mind you are flowing glycol bypassing tee 1 and 2 at twice the rate of the output at tee 2. Refering to my system, 16 gpm trunk throughput, 7 gpm flow through the heater. 9 gpm is bypassed. So you'll have mixed return glycol with the 105° temp at tee 2 which will give you appr. 90° glycol at tee 3. Tee 3 supplies heater two with 90° glycol and you raise the temp of the 90° glycol to 140°-150°. This then inputs to Tee 4 and mixes with the 90° temp glycol bypassing through the tee's. The resulting heat to the bays is 130° temp glycol @ 7 gpm. This doubles the heat transfer of my system set at 105° boiler temp and 90° going out to the bays.

Do you know what size circulator you are running now?

My old system was plumbed with 2" I believe. Because it ran at such a low temperature, it self destructed over the years with Acidic Condensation. You have to run a boiler above 140° to keep it from compensating. But the new demands have SS heat exchangers to allow lower than 140° heating. You want them to condensate. That's what makes them so efficient.

I hated to hijack the thread too....But its relative information....We can continue in the thread I started last year if you like...

http://www.autocareforum.com/showthread.php?9409-Tankless-Water-Heater-For-Floor-Heat/page8

 

[GoBuckeyes]

Again, I really appreciate you sharing all this info 2Biz. I know you spent a lot of time working on this and it shows.

I absolutely agree that it is complex. Last year when you were doing this, I read that entire thread several times and went to all those sources you cited and started reading about hydronics and hydraulic separation etc. I need to go back and re-read it all but I feel like I know just enough to get myself in trouble....like most things. Jack of all trades, master of none!

When you said run two Takagis in 'series' I pictured both, what I described and what you described in your last post. This makes more sense. As for my circulator size...I happen to be in my office and was able to find my floorheat schematic for our last wash. There is roughly 3700 sq ft of slab, 4400 ft of 1/2" tubing for 26 zones. The circulator is a Taco 1614 and my schematic notes say: flow rate 52 GPM / Total headloss 26.7 ft. Total system volume is 80 gallons. Boiler is a 627K BTU input.

 

[2Biz]

WOW...I'd want to keep the pump too! $1000... Is a lot to throw away!

Your Raypak...Is it non condensing?

So you've read through my old thread and did some research of your own! I know it was long winded but there was a lot for me to learn and I wanted to share!

26 zones! That's a lot of valves! It looks like you have roughly 1/3 more your heating than me. I don't know if one 199K would be big enough. I wanted to have Wiggle Room in case we have another Blizzard like 78-79....Although I prefer staying at "Young Wippersnapper" status (As IB Washincars called me) and not have to go through that!

So your running 26 zones with 26 gpm. That's 1 gpm per loop. I'm surprised you have return temps of 60° when your outgoing is 90°. The loops must be very close together. But your also running 1/2", I'm running 5/8. I'm sure that is a calculable difference.

My loops are old...About 30 years old. They used 5/8 black water pipe non barrier back then. I wasn't digging it up because it wasn't the right stuff! You really want Oxygen Barrier Pex. It helps keep the oxygen out. Mine seems to work ok. Until my cast iron circulators fail, I won't know how the glycol is affecting them...My total system volume is 25-26 gallons compared to your 80 gallons.

 

[GoBuckeyes]

Yeah I know, pump wasn't cheap. Believe it or not, we built this wash in 2007. The pump and the expansion tank were new and the boiler was a used hot water boiler that we upgraded with modulating gas valve. Last year our $600 expansion tank turned to swiss cheese and was junk. Somehow the ethylene glycol mixture (50/50) went acidic and ate it up. Mid-winter I jury rigged the set up using a 15 gallon soap jug as an 'expansion/holding tank' and some home depot schedule 40 pvc pipe. Just last week I replaced that fix with schedule 80 cpvc and a square removable lid polyethylene tank as a permanent fix. The glycol will have to wait to be flushed and changed until next summer. Why the antifreeze went so bad I'm not sure. We have other systems that are 25 years old with anitfreeze thats not as acidic as this one. Only difference I think of is that our state boiler inspector would not let us run the system closed so we had to run it open air.

To answer your question, the boiler is non condensing. Its probably an early 90's model and 82% efficient at best. Our ground loops are 12" on center. How did you come up with 26gpm? Head pressure is something I don't really understand.
Now as far as my other washes go, I have a few that have the black water pipe as well. I don't really have specs on those, however, based on the condition of the antifreeze (sludgy), the age of the boilers and their inefficiency I'm sure I could save myself some money flushing the lines, and upgrading to an on-demand system.

 

[2Biz]

I got the 26gpm based on pump capacity of 52 gpm minus 26.7 gpm head loss. That means you have a total head loss of 26.7 gpm because of the size pex your using, length, tight turns and fittings all considered. So even though your pump is rated at 52 gpm, it can only push 25.3 gpm through all those lines because of pressure/resistance in the tubing.

I've given what I said earlier about the 4 heater pumps in series some added thought. Maybe this will work better: See pic...This way you would use only 2 pumps to feed both heaters. All your looking for here is pressure. The taco 013 pumps 32 gpm @ 0 head. So it has plenty of volume. You need at least 40 psi to get 7-8 gpm through each heater. If you plumb it the way its pictured, you can set both boilers @ 105° and get 14 gpm of 105° glycol going back into your trunk or loop mixing with return glycol. Make sense...This will give you double my capacity. BTW...I heat roughly 1800 sq ft and have 1800 feet of 5/8 tubing...
Hopefully your not too confused at this point!

BTW...Running your system open allowed oxygen in which in turn lets the glycol turn acidic faster. That's why its very important to keep the oxygen out. Your system will last longer and you can run std cast iron circulators. Otherwise you need bronze or SS...

 

[2Biz]

Let me explain head loss another way. If you attached a 5’ long garden hose to a hydrant, the water will flow freely and lots of it. If you attach a 100’ long hose, the water barely trickles out the other end even at the same inlet pressure. This comparison is exactly the same as the tubing/fittings in each loop…You will have a lot of restriction/friction in 100-200 feet of ½ pex. It takes a big pump to get any volume through those small lines. That's why your only getting 26 gpm from a 52 gpm pump...Its because of the 26.7 gpm of Head Pressure...

You were lucky, Huron Valley did those calculations for you to make it easier to size your next system! Lucky you!

 

[cantbreak80]

So, 2Biz...

Since you're designing, how many Takagis and Tacos will I need for my 7,680 sq ft of heated concrete?

 

[2Biz]

Too many!!!!!

 

[GoBuckeyes]

Wow, 2Biz, I just did a quick speed read of your original project post. I'm going to need to print out that whole thread and do some highlighting!
Here are a couple of questions I didn't see explained or I missed. How did you size your expansion tank? How did you figure or verify your primary pumps flow? I understand the pump has a curve at various head ratings but you didn't know what the head restrictions were on your loops did you? Or did you actually guesstimate the length of the runs and calculate it all using tables for 5/8' tubing etc?

Most importantly, are you sure I could get away with only using two taco 013 pumps? I haven't gotten that far yet but that sure would make it easier.

 

[2Biz]

Here are a couple of questions I didn't see explained or I missed. How did you size your expansion tank?

Look at the bottom of this page.

http://www.pexuniverse.com/how-size-and-select-proper-expansion-tank

It recommended the RX 15 Extrol for my system...5000 feet or less of 5/8 pex. So I got the RX 30...2 times as much is always better, right!

How did you figure or verify your primary pumps flow? I understand the pump has a curve at various head ratings but you didn't know what the head restrictions were on your loops did you? Or did you actually guesstimate the length of the runs and calculate it all using tables for 5/8' tubing etc?

I went to Pexsupply.com and started looking at the various pumps and configurations/documents. I settled on the Taco since all their circulators have a removable cartridge in case of motor failure. You replace the cartridge and leave the pump housing in place. It should make it a piece of cake to swap out cartidges to fix a motor issue.

Each circulator has data on gpm and head pressure ratings/flow charts. If you read through the entire thread, I didn't do so well the first time. I put in too small of pumps because I didn't quite understand head pressure as well as I should and how to read the charts/graphs. Plus I listened to a Takagi Service man who led me astray on pump size.

Your right, I guestimated the tubing length in the bays by measuring the gallons of glycol I took out of the system. This gave me a very close estimate as to how many feet of tubing I had. Then I used one of those calculators I linked to in the thread to calculate the size zone circulator pump needed and size boiler needed. I believe my system was supposed to need 125K btu for our geograghical location. So I went with the 199K BTU. You know, bigger is always better! Right! Based on the tubing length, adjustment for using glycol in the system, (I used 35% glycol to keep this head restriction percentage to a minimum) I was able to calculate head pressure of the whole system. That calculated to about 20 feet of head pressure. I then went to Pexsupply and found the correct pump to give me 16 gpm after feet of head pressure calculateded in. In my case, the taco 013 is rated at 32-33 gpm @ 0 head. At about 20 feet of head, the chart says I would get about 16 gpm with this pump....

Look at this link:

http://s3.pexsupply.com/manuals/1350984290609/84479_PROD_FILE.pdf

There is a lot of info there. When you click on any Taco pump on the Pexsupply site, there will be a manuals tab to D/L or view the manual for the pump. Most of them will be listed on the gragh, so you simply have to choose the right one...Yea...Simple right! Now you know why I didn't get it perfect first time out of the gate...

 

[2Biz]

Most importantly, are you sure I could get away with only using two taco 013 pumps? I haven't gotten that far yet but that sure would make it easier.

So your REALLY wanting me to put my head on the chop block eh! This is taxing me trying to remember all the calculations I went through...

So lets look at it...First I calculated temperature rise needed in the system. Mine is 30-40°. Then I looked at the boiler chart to see how many gallons of throughput I get at 40° temp rise through the boiler. That figure was 7-8 gpm...Then I looked at the boiler chart to see what PSI it takes to shove 7-8 gpm through the boiler. That figure (On the chart of the boiler) was 50 feet of head at 8 gpm or 40 psi...The calculation to convert PSI to feet of head is 1 psi =2.31 feet of head...Thats just a calculation you'll need to know.

So basically I needed a pump that has a head pressure rating of 50 @ 7-8 gpm. The Taco 013 has a pressure rating of 28 feet of head at 7-8 gpm. Not enough for the 50 feet of head needed to overcome pressure through the boiler to get 7-8 gpm. So I stacked two of the 013s in series to double the psi or head pressure to get the needed flow rate. The results of stacking two of these in series gave me 40 psi. Should have been closer to 48, but I got 40! Still good enough to get me 7 gpm. It was close enough.

Forgive me...I'm out of brain cells at the moment. I don't know how adding another Takagi to the mix changes output pressure of the two pumps. I'm sure there has to be a decrease in pressure since you are feeding two heaters. Give me a little bit, maybe it will come to me at 3:00 am when I'm wide awake thinking about it!

Maybe the direction to go on the feed pump to the heaters is a bypassing procon. I looked into this but didn't get anywhere. With the procon you could dial in the pressure needed...You're only pumping 70°-80° max return temp glycol... Just a thought...

 

[2Biz]

Most importantly, are you sure I could get away with only using two taco 013 pumps? I haven't gotten that far yet but that sure would make it easier.

Cold feet! Have you looked at other Demand Heaters to see if they have lower internal head pressures?

 

[slash007]

I haven't responded in a few days as I keep forgetting to take pics everytime I go to the wash, but I finally remembered Here are a couple pictures of my setup. One is of the boiler, other is of the thermostats. I did move them to a covered location so the temp seems accurate. I see that most are attaching the thermostat of the boiler to the return, but mine are plastic. There are some iron fittings, but I don't know if those would work? What is my best bet in regards to setting up when the boiler itself fires?

View attachment 532 View attachment 533

View attachment 534

 

[2Biz]

I don't know how that's going to work correctly with both sensors outside. I would think you would only want the circulator sensor outside. It should power the whole system on, then the boiler t-stat would cycle on/off based on return glycol temps. I would also think that taping the boiler sensor/probe to the return plumbing would suffice as mentioned earlier in the thread. Just wrap it with insulation and duct tape. The return temps will be below 70-80°.

You're only about an hour away. If your ever close, give me a call and stop by. I'll show you what I've done. PM sent...

 

[mjwalsh]

I don't know how that's going to work correctly with both sensors outside. I would think you would only want the circulator sensor outside. It should power the whole system on, then the boiler t-stat would cycle on/off based on return glycol temps. I would also think that taping the boiler sensor/probe to the return plumbing would suffice as mentioned earlier in the thread. Just wrap it with insulation and duct tape. The return temps will be below 70-80°.

You're only about an hour away. If your ever close, give me a call and stop by. I'll show you what I've done. PM sent...

2Biz & others,

The only thing I would add to the attaching the sensor to the plumbing (on the pipe surface) is that some HVAC experts assisted me with some heat sink compound designed for that very purpose. Not sure on the exact gain in accuracy ... but I would think it would be helpful.

mike walsh king koin usa

 

[2Biz]

The most accurate would be to cut into the plumbing and install a well. But I probably wouldn't do that either. Using the Heat transfer compound and insulation/duct tape should work fine. Once you get it dialed in, it should be consistent. Thanks Mike....