Back with circulating pump questions!

[ikessky]

Alright guys, I'm not going to give you a lot of the back story, just where I am at right now. I have a 24' x 40' garage. I have two 300' coils in the floor. I'm going to be heating with a Takagi Jr and it is mounted about 6' high on the wall. Now, the Takagi Jr requires .75GMP to start burning. I tried a Grundfos UP15-42F pump on it and I don't think it's enough flow. The pump kicks on, but the unit will not fire. We pressurized the system with a high pressure pump, and the unit begins firing immediately. However, after a few minutes (maybe 10 or so) it stops firing and will not restart on it's own. The board is supposed to flash diagnostic lights if something is wrong, and nothing is flashing. Then, if you add some flow/pressure via the high output pump, it will begin firing. I'm really suspecting that I need a pump that is much larger in both head and power. And now I see in the manual that for a space heating application, Takagi recommends a high-head 1/12hp pump. The Grundfos I currently have on there is a 0-15 head 1/25hp.

So the question really goes as such: Do you think I'm on the right track with the pump being extremely undersized and not flowing what the Takagi needs to fire?

 

[Sureshot]

Do you have a pressure gauge on the system? Sounds like you are loosing your pressure. Do you have a pressure relief?
Have you let all the air out of the system?
Does the heated water move along in the system?
Did you try running just one loop?
Pics.

 

[ikessky]

I have a plumber coming back today with a pressure gauge and a different pump. I don't think lossing pressure is the issue, but I guess we'll see.

We have tried to purgue air a few different times and have an air separator installed.

We did try to shut one loop off while it was running and it stopped burning almost automatically.

I read somewhere that 300' of 1/2" pex could be have a head of around 9. I really think this all has to do with a pump that is WAY too small. I found some other people's systems that would maybe be somewhat similar and they are running pumps that are 1/8hp or 1/6hp pumps. The one I have on there is 1/25hp! We'll see what happens today after the plumber looks at everything. I'll get some pics tonight as well.

 

[Sureshot]

I would suggest you have a gauge on the system as well as purchasing a temp gun. You can get combination temp/pressure gauges as well. Seems like an impossible to manage setup without a pressure gauge. You do not need a high pressure pump to fill or charge the system. I use a Red Lion effluent pump I bought as a spare for the house. No danger of overpressureing the system. Unless you want plumber bills annually I would get a few tools to work on the system. Oh and the only other time it will quit is Christmas eve or during a blizzard.

 

[ikessky]

I'll get some gauges on it and see what it says. Also, I was just at Takagi's site and they state for a radiant system, Takagi REQUIRES a minimum high-head 1/12hp pump. Otherwise, the system will not flow enough to turn the unit on. I think we have a winner! But I agree with you that I should get some fill pump stuff figured out. I'll have to talk to my in-law's and see what they have already. They are all running OWB's, so I bet they have some tools I can get access to.

 

[CARS]

I'll get some gauges on it and see what it says. Also, I was just at Takagi's site and they state for a radiant system, Takagi REQUIRES a minimum high-head 1/12hp pump. Otherwise, the system will not flow enough to turn the unit on. I think we have a winner! But I agree with you that I should get some fill pump stuff figured out. I'll have to talk to my in-law's and see what they have already. They are all running OWB's, so I bet they have some tools I can get access to.

Didn't you already know that??

Takagi recommends a high-head 1/12hp pump. The Grundfos I currently have on there is a 0-15 head 1/25hp.

I read the first post but was too busy to reply. You weren't trying to get us to talk you out of following the mfg. recommendations were ya??

 

[ikessky]

Didn't you already know that??

Nope. Didn't fully read the directions I guess.

I read the first post but was too busy to reply. You weren't trying to get us to talk you out of following the mfg. recommendations were ya??

I was in no way trying to get around the manufacturer's recommendations. I was simply looking for some verifications that I wasn't running because the pump was too small.

I got home tonight and the plumber was here. He had put on a 1/12HP pump, but the unit still wasn't running. So he called the supply house and I called Takagi. Found out some really interesting info. The supply house stated that I have about 15 feet of head in the floor, but had no idea what was the restriction in the unit itself. He says that the new pump is still too small. Takagi tells me that in need 2-4 GPM for radiant heat. 2GPM is 5 feet of head, 4GPM is 22 feet of head. So I could potentially be looking at 40 feet of head pressure. The supply house says to just piggyback the new pump and the original to get by, and then eventually either go to one large pump or replace the original with another 1/12HP. So that is what we did and I'm up and running. We ran the system for about 30 minutes or more and then it shut down for some reason. The plumber tried everything he did before and could not get it to continue on. So, we pulled the filter cartridge and cleaned it. Put it back in and we were in business again. The plumber left and I went in to eat. Came back out later and the unit is shut off again. So I pulled the cartridge and guess what...... totally plugged. Put it back in, pressurized it again and I'm back in business one more time.

So it looks to me like the Takagi is pretty finicky on system cleanliness and pump power. Also, Takagi is pretty poor on their manual information. The manual states that it fires when it detects 0.75GPM. However, the tech told me that this is only when there is at least 65psi in the system. It would have also been nice to know how much of a restriction was in the heat exchanger itself.

 

[Sureshot]

65 PSI ?? Sounds very high. Does anyone else run this much??

I was always going to add a filter circuit to my fill pump so I could filter my Glycol once a year or so. My system has no filter. Sounds like your system could have used a flush with tap water prior to filling.

 

[ikessky]

I'm humming along at 25 psi right now. I'm thinking the 65 psi was for an install in a domestic hot water situation.

 

[stingry]

I'm humming along at 25 psi right now. I'm thinking the 65 psi was for an install in a domestic hot water situation.

Which pump did you end up with?

 

[ikessky]

Right now, it's a Franken-system. I've got a Wilo 1/12hp (sorry, don't remember the model) with a Grundfos 1/25hp mounted above it. The plumber is coming back with another Wilo today though.