Another tankless water heater replacing boiler thread

[2Biz]

It looks like you have cast iron pump flanges with a brass nipple between the two pumps.

Good catch! Wonder how many years I have left?! My system just turned 12yo....The gpm through my heater has remained unchanged at 6.0gpm the entire time, even with the tiny passages in the Takagi Heat Exchanger....I think that reading would be a good value to monitor to see if/when an issue with corrosion is affecting how well the system works. If I remember correctly, the cost of brass or SS flanges and pump housings scared the hell out of me! My pockets wern't very deep then! I can only imagine the price now! I'm hoping the paint Taco uses is an isolator!!! Jk....

There is also a very fine mesh and tiny screen filter in the inlet to the heater. I posted I had issues in the beginning with this filter plugging because I ran a "cleaner" in the system before filling with propylene glycol....I ran a 5 micron filter in line for a day or two to filter the system. Since then, I have never had to take the small filter out to clean it....

Here is a short but good read that CantBreak80 just sent me...Explains a lot and some preventative measures you can take like maintaining propper PH to extend the systme life, even in a system with dissimilar metals.

How water behaves in hydronic systems - HPAC MagazineHPAC Magazine

 

[OurTown]

Good catch! Wonder how many years I have left?! My system just turned 12yo....The gpm through my heater has remained unchanged at 6.0gpm the entire time, even with the tiny passages in the Takagi Heat Exchanger....I think that reading would be a good value to monitor to see if/when an issue with corrosion is affecting how well the system works. If I remember correctly, the cost of brass or SS flanges and pump housings scared the hell out of me! My pockets wern't very deep then! I can only imagine the price now! I'm hoping the paint Taco uses is an isolator!!! Jk....

There is also a very fine mesh and tiny screen filter in the inlet to the heater. I posted I had issues in the beginning with this filter plugging because I ran a "cleaner" in the system before filling with propylene glycol....I ran a 5 micron filter in line for a day or two to filter the system. Since then, I have never had to take the small filter out to clean it....

Here is a short but good read that CantBreak80 just sent me...Explains a lot and some preventative measures you can take like maintaining propper PH to extend the systme life, even in a system with dissimilar metals.

How water behaves in hydronic systems - HPAC MagazineHPAC Magazine

Two sets of sweat brass isolation valve flanges and one set of sweat bronze flanges is $285 plus tax. If I order them between now and tomorrow before end of day they will be here Tuesday. Not ideal because if I don't have this up and running by Wednesday I will have to shut down again because of cold weather.

 

[2Biz]

No pressure here!

 

[Blanco]

Our old DHW circulator had bronze pump flanges. I think the pump was even bronze because it was a painted brown Taco. The floor heat circulator (there was only one pump for the whole system) was cast iron and had cast iron flanges connected directly to copper. Super Wash built about 700 of these washes and our wash was one of their mid-later builds so I would think they would have remedied that by then if it was an issue. It looked and worked fine when I removed it and I think it was the original at 20 years old. It looks like 2Biz has cast iron flanges between his two pumps, and a brass nipple connects them. Most of the companies that sell the premade closed loop systems are using the bronze isolation valve flanges but I did see quite a few that had the regular cast iron flanges directly connected to copper or brass. It must not be a major issue. At least that is what I'm hoping because that is what I have on hand and the bronze flanges are three days out to get. I could order them and swap them out later but my experience is that I may have to fight them to get them to line up.

What size flanges do you need? Menards has them in stock up to 1" for $50. See attached. Dont know if you have one around you. Supply house has tons in stock. https://www.supplyhouse.com/Pump-Flanges-1836000. I prefer to do things once the right way. Nothing pisses me off more then having to do something twice. Super wash may have owned and built 700 washes but im going to guess there were hundreds of differant plumbers. Some washes might have got this while others got that all at the plumbers choice. If you have to use cast because of the tight pinch your in just use them to get up and running but I would change them out later on.

 

[OurTown]

No pressure here!

I have it operational but there are some things to tidy up. It seems to cycle quite often considering it is not that cold yet. The return stat is set to kick on the two heater pumps at 55F and off at 75F. The units are set for 105F output. Most of the time I see a 27-29 degree drop from the outgoing temp to the slab vs the return temp. From what I have read that is a good heat loss for a de-icing system. The most flow I have seen on the heater output is 14 GPM total but that was just briefly. Most of the time they are running 12-13. I have the communication cable connected between them. One unit is the "parent" and the other is the "child" with the proper dip switch settings. Based on my calculations, the manual recommended changing the vent length dip switch settings from default. The system is running about 15 PSI and it stays there when all pumps are off. From what I have read, if your system does not stay there when off then you have air in the system. To me, it seemed that the main circulator pump motor was running hot (150F+) but after talking to a Taco tech he said they are supposed to run 140-160. I asked him about the cast iron pump flanges directly connected to copper or brass and he said that is perfectly fine on a closed-loop system. The double pumps are feeding the heaters at 42 PSI which is a 27 PSI rise from system pressure. That would be 62 feet of head pressure. Since I'm using two pumps then I should cut it in half when looking at the flow rate on the chart. It should be about 17 GPM but like I said the most I have seen is 14. If I went with the next size up pump for those (2400-50-3p) theoretically the feed PSI would go up to 46 and the flow rate would be 20 GPM. Since I think I slightly undersized the pumps then maybe I should raise the set temp to compensate. At 55 degree rise it should be 7 GPM each according to the water heater flow chart. At 30 degrees rise, which would be the rise just before they turn off at my current set point, they should be flowing 10 GPM. If I move the set point to 120F then when they first turn on the rise would be 65F and it would have to restrict the flow a little bit which I think means they would be at their max BTU output potential. To me it looks like I'm only using them at 75 or 80% at most. I guess you could argue that they might last longer but I'm thinking about the really cold, overcast, and windy days when I need lots of BTUs.

 

[OurTown]

I have not tallied it up in detail but I'm into this about $8K. Just under 150 sweated copper joints (1 1/2" and 1 1/4") and over 40 threaded connections. I have had to shut it down about 6 times so far to clean the flux out of the heater inlet filter screens.

 

[OurTown]

I just checked the cycle times this morning. Boilers on for 10 minutes, 30 seconds. Off for 42 minutes. 29F outside, 5 MPH winds, full sun on guessing 80% of the heated slabs. In the sun the slabs read mid 40s and in the shade mid 20s. I'm not sure I trust this Klein Tools infrared thermometer because it is reading 14F on the unheated slabs and it only got down to around 19F last night. No ice after a few people have washed this morning though. But, because of the low readings I bumped up the boilers on return temp to 60F and will see how it goes. I'm sure they will cycle on a lot more because it takes a really long time to get down to 55 but not 60. When I had it set to 55 on temp I noticed that just before they come on it's only scrubbing off about 2 degrees from the outgoing temp vs return temp. Is that normal?

 

[2Biz]

What you are seeing makes total sense on the Scrubbing off 2°....You say it stays off for 42 minutes starting at 75°...Then once off, scrubs 2 degrees from outlet v/s return temps till it reaches 55°...Your differential is 20°....So if it takes 42 minutes to circulate the fluid 10 times, which is possible (once every 4 minutes), then it makes sense. 2° drop for each time the glycol circulates...

Your are getting really good cycle times the way you have it set up. Not suprised the swing is 10.5 minutes on 42 minutes off. You have 2 heaters compared to my one and a lot more gpm flow through the heaters. What you will notice, the colder it gets, the closer those 2 numbers will get, like 15 minutes on 37 minutes off. But will always be at a total time of 52 minutes + or - a few...You have a lot of capacity left since your off time starts out at 42 minutes at 32°....I'm guessing when it hits zero out, you'll see about ~25 minutes on and ~25 minutes off. Let me know how far off I am!?

Glad you got it going! Also, ditto on the heater screens...Had the same issue if you remember!

Any pictures?

 

[2Biz]

Curious....Whats the purpose of connecting the heaters if they both run/fire at the same time? Wouldn't they both run exactly the same if not connected? Also what is the vent length dip switch? I don't remember any thing about that. My exhaust vent goes straight up (maybe 12 ft) with a 180° turn down about 3-4 foot above the angled roof. See photo, back side of roof. The white PVC on the right is the floor heater exhaust, and the one on the left is for the HE Hot Water Heater.

 

[OurTown]

Curious....Whats the purpose of connecting the heaters if they both run/fire at the same time? Wouldn't they both run exactly the same if not connected? Also what is the vent length dip switch? I don't remember any thing about that. My exhaust vent goes straight up (maybe 12 ft) with a 180° turn down about 3-4 foot above the angled roof. See photo, back side of roof. The white PVC on the right is the floor heater exhaust, and the one on the left is for the HE Hot Water Heater.

Connecting them allows the parent unit to control the child unit. I think under low demand situations it allows one unit to run and then the next time it switches to the other unit. I doubt it does anything in my situation though but I thought I would try it. IIRC any vent over 20 feet needs the dip switches changed. Every 90 degree elbow adds 5 feet and every 45 degree elbow adds 2.5 feet.

 

[OurTown]

What you are seeing makes total sense on the Scrubbing off 2°....You say it stays off for 42 minutes starting at 75°...Then once off, scrubs 2 degrees from outlet v/s return temps till it reaches 55°...Your differential is 20°....So if it takes 42 minutes to circulate the fluid 10 times, which is possible (once every 4 minutes), then it makes sense. 2° drop for each time the glycol circulates...

Your are getting really good cycle times the way you have it set up. Not suprised the swing is 10.5 minutes on 42 minutes off. You have 2 heaters compared to my one and a lot more gpm flow through the heaters. What you will notice, the colder it gets, the closer those 2 numbers will get, like 15 minutes on 37 minutes off. But will always be at a total time of 52 minutes + or - a few...You have a lot of capacity left since your off time starts out at 42 minutes at 32°....I'm guessing when it hits zero out, you'll see about ~25 minutes on and ~25 minutes off. Let me know how far off I am!?

Glad you got it going! Also, ditto on the heater screens...Had the same issue if you remember!

Any pictures?

Do you ever change your settings throughout the winter as the outside temps change? When it is colder out, maybe below 20F the original settings were too low to keep up. Lately, I set the heaters set at 115F and the return stat at 65F On, 80F Off. Yesterday evening the slabs did not stay ice free after someone washed so I shut down all SS bays. If there is sun and not much wind it seems to keep up fine. Also, our tubing is ran in a way that we can't shut off a bay or two. With our old boiler setup we would also have to crank up its slab stat to compensate for the cold.

 

[2Biz]

Do you ever change your settings throughout the winter as the outside temps change? When it is colder out, maybe below 20F the original settings were too low to keep up. Lately, I set the heaters set at 115F and the return stat at 65F On, 80F Off. Yesterday evening the slabs did not stay ice free after someone washed so I shut down all SS bays. If there is sun and not much wind it seems to keep up fine. Also, our tubing is ran in a way that we can't shut off a bay or two. With our old boiler setup we would also have to crank up its slab stat to compensate for the cold.

I don't have to make any changes... But I would imagine tubing depth might make a difference? But not sure. Yea, I'm still at 105° heater setting, return stat on at 55° off at 70°....This winter and last winter I just started shutting down when it gets this cold. But I still leave the floor heat on so I don't have to deal with any frozen lines or anything. I do have them freeze protected to below zero, burst -50°, but for the little extra it costs per month its not worth the risk to me to turn it off while closed down. Also don't shut floor heat off to a bay or two if they are shut down and 2 are open. I don't mess with the zone valves once I got them set.

 

[Overachiever]

Mine are ice free. and I have the crappy 8" of concrete with floor heat on the bottom of that, its -11 outside. Return temp says 68 and I have the takagi's set to 100 degrees (i also use the cable between them). I guess I'm curious if maybe too much flow is going through your trough loop? I had to throttle that so it wouldn't hog all the antifreeze.

 

[2Biz]

Mine are ice free. and I have the crappy 8" of concrete with floor heat on the bottom of that, its -11 outside. Return temp says 68 and I have the takagi's set to 100 degrees (i also use the cable between them). I guess I'm curious if maybe too much flow is going through your trough loop? I had to throttle that so it wouldn't hog all the antifreeze.

For my trough heat loop....I lose very little heat (only a few degrees) between supply and return since its insulated so well. So maybe a non issue for Ourtown??

 

[OurTown]

Mine are ice free. and I have the crappy 8" of concrete with floor heat on the bottom of that, its -11 outside. Return temp says 68 and I have the takagi's set to 100 degrees (i also use the cable between them). I guess I'm curious if maybe too much flow is going through your trough loop? I had to throttle that so it wouldn't hog all the antifreeze.

No trough loop. When it got cold enough to operate it was losing about 30 degrees which I think is about ideal. Today I noticed it was only scrubbing off about 15 which is not ideal. I'm not sure what is going on there. What do you have your ON and OFF set on your thermostat? My units are running at 120F (it won't let me raise it higher) and the stat is set at 65F ON and 80F OFF. Today the units ran for 6 minutes and then off for about 6 minutes, 30 seconds.

 

[OurTown]

For my trough heat loop....I lose very little heat (only a few degrees) between supply and return since its insulated so well. So maybe a non issue for Ourtown??

No trough loop. Just electric for that.