Equipment installed on second floor

ken21510

I have a 2 zone hot water system installed on the second floor of a garage. One zone is radiant tubing in the concrete of the garage and the second is radiant tubing under the second plywood floor. The heating plant is a Tagaki TK- junior propane fired.

There is a primary loop on the TK that uses a NRF-33 circulator to pull the water from the return manifold through the TK. Each zone has a NRF-22 circular that pushes the water through each of the zones and has a check valve installed on each zone at the return manifold in front of the NRF-33. All of this is located on the second floor with the radiator loops below by 5 or 12 feet.

The issue is when either zone calls for heat that zone’s NRF-22 and the NRF-33 turn on but sufficient flow is created to fire the TK. So the pumps run continuously but donot fire the TK. If I close down the input to the NRF-33 at the return manifold and wait a few seconds and then turn it on the the TK fires. Any thoughts as to why the pumps cannot provide enough flow in the system to get the TK to fire? It needs a minimum 0.75 gpm to fire.

Are the NRF-22 strong enough to push the water from the second floor down and back up to return manifold?

GGross

Pictures of the system. Tankless water heaters heat exchangers have a much greater pressure drop than a boiler would since they are supposed to be attached to domestic water systems at 40+ PSI. You could be piped wrong, or not enough flow, or maybe just some air stuck

ken21510

Thanks for the input. Appreciate the commend and the photo posted

GroundUp

It appears to have been working for quite some time, unless it just sat unused for 20 years? I'm having trouble figuring out which pipe goes where but the closed ball valve on the far left probably isn't helping matters. Otherwise given the age and the wrong appliance, there's a good chance that the sediment filter in the Takagi is plugged and/or one of the circulators has given up the ghost. Flow switch may be sticky, especially if glycol is used. The NRF-22 is plenty as long as there is sufficient pressure in the system to do the lifting (6-7 PSI would do 12ft but 12 PSI is ideal).

ken21510

The circulator on top drives the radiate heat in the garage floor. The circulator to the left of the expansion tank supplies the second floor under floor heat. The circulator pump at the bottom pulls from the return manifold when either zone calls for heat. That pump runs whenever either zone is on.

Each zone has a check valve on its return line at the return manifold. There is about 20psi pressure at the input to the heater and 10 psi at the output. There is about ball valve at the left, while closed, simply allows the system to be a one way flow for either zone.

This system is some 15 years old and has worked.

what I do don’t understand is why the heater will not fire up from the start after both zones are satisfied and then one zone calls for heat. The appropriate pumps will turn on and the water is circulating but no fire. Under those conditions if t close the input valve to the lower pump for 3 seconds or so and then open the valve, then the unit fires.

Besides the flow sensor in the heater being satisfies is there any other coniditions that need to be met for trigger the heater on? I’m sort of at my wits end. Any ideas would be appreciated.

Also, someone said this tagaki is not a suitable unit for this application. Why? The manufacture says it is. If not what unit is recommended?

hot_rod

It sure sounds like a flow issue if the switch will not make with just that zone calling.

It is not really a primary secondary piping. Does it work better with the yellow handled ball valve open?

I would remove the 3 way mix valve, disassemble and clean, it may have strainers in it as would that tankless water heater. The Takagi manual would show you how to service any strainers in the unit. Unless it was removed?

We have seen the wire brush in those air purgers plug also, remove the top and inspect it.

PC7060

https://forum.heatinghelp.com/discussion/comment/1828431#Comment_1828431

@ken21510 is correct; found this at the top of the Tagaki TK- junior technical data sheet. First time for everything.

Description / Application: Fully modulating, gas fired, tankless, on demand water heater with sealed combustion (optional) and power-vented flue. Can be installed either indoors or outdoors, and used in either residential or commercial applications. Supplies hot water to: domestic hot water systems (directly or indirectly using water storage tanks), recirculation systems, hydronic heating systems, radiant floor heating systems, and/or combined domestic & heating applications, etc.

I did notice the current generation Series 200 has same broad description but includes this warning:

wonder why combined is allowed but standalone isn’t?

hot_rod

Is it piped like the manual shows for hydronic applications?

EdTheHeaterMan

Another attempt to save money by using the wrong equipment. You should bite the bullet and purchase a space heating boiler. That is the correct thing to do. Trying to diagnose it, clean it , or re-pump it, is just pushing the problem down the road for another day.

EBEBRATT-Ed

Chances are a strainer is plugged or maybe a failed pump, but I doubt it. Those heaters have a high pressure drop.

ken21510

hot-rod: I believe it is piped as shown in the manual but I will check again in the morning.

It does not work better with the ball valve open. As a matter of fact with the valve open and the pumps running the heater will shut down. With that valve open the return manifold gets pressurize higher on the output side of the check valves stopping the flow in the zones. Does explain why the heater shuts off. When the ball valve is closed then the return manifold is at the input water regulator out put 12 psi. The lower circulator then should “pull” the water into the heater and the zone circulators “push” the water through the zones. None of this explains in my heat why the heater doesn’t fire until I close and then open the ball valve on lower circulator.

I’m missing something in all this. Scratching my head

ken21510

all the strainers are clean

ratio

Open the valve on the vertical pipe on the left, see what happens. It looks like the lower pump is supposed to run continuously & keep the water in the boiler moving, then the zone pumps come on & off as needed.

That valve may have been closed in an attempt to get the system working again when something plugged up enough to effect operation.