Hydronic system not moving antifreeze in garage

jjmik

I have replaced a hot water heater in the garage with a tankless hot water heater. Ran all new plumbing. Added an expansion tank. All new 3/4 copper lines. Refilled the system and purged all air. The pump is running but very little to no water movement. Pressure is at 12 - 15 lbs. I don’t understand what is going on. Using the same pump (but bought a brand new one) bell Gossett nrf 22 , any help would be greatly appreciated!!

PhilDavid

I’m assuming you mean you replaced a hydronic boiler that has a tankless coil for your hot water. And by coolant do you mean your heating system has antifreeze in it?

Gordy

How do you know it’s not miving water?
Did you plumb it as originally configured?
Is pump installed in the right direction?

delta T

What is it pumping to? What size and how long is the tubing in the slab? An on demand water heater has a huge reistance to flow in the heat exchanger, an old tank style water has effectively no resistance in this situation. I suspect that this is the cause of your flow issue.

On demand water heaters are not designed for space heating, and using one for space heating will shorten its life and void the warranty in most cases FYI

jjmik

It is a Richmond tankless water heater. And they are used for closed loop radiant systems. Even gives you directions in the owners manual.

On the manifold each zone has a flow meter. None of them are showing flow. And the water heater is not turning on. Or it will stutter on and off very quickly.

Pump is set up on the inlet side before the expansion tank , and sorry I am using cryotech antifreeze. Not coolant.

jjmik

Not sure on what’s in the concrete for pex. It’s 5/8 line. And the garage is 24 x 36

jjmik

> @delta T said:
> What is it pumping to? What size and how long is the tubing in the slab? An on demand water heater has a huge reistance to flow in the heat exchanger, an old tank style water has effectively no resistance in this situation. I suspect that this is the cause of your flow issue.
I still have the original pump. If I put that on the outlet side would that help push more water or do I need to upgrade my pump?

Gordy

Is the tankless the same as original heat source?
Did original setup use antifreeze?

Gordy

In rereading original post as @delta T said if original was tank style WH your pump just became severely undersized.

Gordy

You would have to run the two same sized pumps in series to increase their head capability. Doubt it will be enough.

jjmik

The original was a regular water heater. Replaces with a tankless. I have 2 bell Gossett pumps. But can anyone tell me what size single pump I would need? 3/4 copper line. About 10’ of line. The pex in the floor is 5/8 and the garage is 24x36. Only took 10 gallons of cryotech antifreeze

Gordy

That’s about 700’ of pex how many loops?

Gordy

Usually a grundfoss 26-99 or similar size

jjmik

There is 3 loops. Can I post pictures on here?

jjmik

The heater calls for 3.9 gpm. The pump I have is 12gpm at 8’ head

the_donut

jjmik said:

It is a Richmond tankless water heater. And they are used for closed loop radiant systems. Even gives you directions in the owners manual.



On the manifold each zone has a flow meter. None of them are showing flow. And the water heater is not turning on. Or it will stutter on and off very quickly.



Pump is set up on the inlet side before the expansion tank , and sorry I am using cryotech antifreeze. Not coolant.

Pumping into the compression tank can cause issues. Pictures of plumbing would help. Any isolation valves? Bypass loop?

Gordy

That’s the problem read the head for that pump on the pump curve chart at 4 gpm it’s not even over coming that.

jjmik

Layout of my setup. (Please be nice!) lol it’s my first time ever plumbing .. lol starting at the water heater hot water outlet, goes straight down to the top side of manifold. Coming out of the manifold through a Y strainer, up to the bell Gossett nrf-22 pump then through the expansion tank and back into the heater. Is there anything I need to change? I did read never put pump before expansion tank. So tomorrow I plan on draining the upper portion and rerouting the pump to the other side of expansion tank ..

The manifold is directly under the heater under the stairs. About 9’ total height

Gordy

What percent glycol mix?

jjmik

> @Gordy said:
> What percent glycol mix?

I used the cryotech-100 straight . 10 gallons I did pump about 3 gallons of water mixed in to get the final top off and recirculate and purge all the air out of the lines

Solid_Fuel_Man

First of all, you should never be above 60% glycol, I'd stay at 40% or less.

Second the circulator needs to be relocated between the expansion tank and the heater, pumping into the heater and away from the expansion tank.

Third, your circulator may not be up to the job. I'm not familiar with B&G off the top of my head, but you need a high head low flow circ to flow through a tankless.

Gordy

Antifreeze is more viscous than water the more concentrated the more viscous . So you are fighting the head of the tankless he, the viscous fluid.

jjmik

Ok. I can dilute it some. But the -100 cryotech shows it can be used undiluted. Diluted it drops the freeze point dramatically

jjmik

Cryotech chart

Solid_Fuel_Man

Do you plan on not having this garage heated all the time?

the_donut

Pump curve.

Gordy

If you have no flow, and are not air bound the chart would indicate you are trying to overcome over15’ of head between the Hx, viscous fluid, and pex loops.which is 0 flow for the nrf22

jjmik

> @Solid_Fuel_Man said:
> Do you plan on not having this garage heated all the time?

I live in Illinois and use it all winter long around 65 degrees. But if it were to ever quit I’m afraid of it freezing and bursting the lines

Solid_Fuel_Man

From personal expierence (I have a lot with radiant slabs) freezing won't be an issue for at least 32 hours unless you have tubing very close to the overhead doors. Antifreeze adds too many problems.

In My own home in northern maine, ive left the garage unheated for several days with no antifreeze in the system. Tubing is 20" away from overhead doors though.

Gordy

50 % glycol is more than plenty for a full time operational system.

jjmik

> @Gordy said:
> If you have no flow, and are not air bound the chart would indicate you are trying to overcome over15’ of head between the Hx, viscous fluid, and pex loops.which is 0 flow for the nrf22

I have a hard understanding of the flow charts could you recommend the proper pump? Or would a second bell pump work?

Gordy

Having the expansion tank on the inlet side of the pump is preferred, but will do nothing for flow.

Gordy

You could try both pumps you have in series since you already have them see what happens

Gordy

In series the nrf 22 would overcome 24’ of head at 5gpm. Should get the tankless going. If that’s all the head you have if not bigger pump.

Gordy

Whether that’s enough flow for 4 loops hard to say with out a heat loss.

Gordy

Those calculations are based on 100% water.

jjmik

It’s only 3 loops. 4th is plugged.. I don’t really want to run into problems. So I will get a higher rate pump. Would the Grundfos 26-99 work then? Or what would be the best recommendation?

Gordy

There is a lot of variables to answer definitively.

You must understand glycol adds to head loss, and changes specific heat of the fluid. In other words a glycol mix Carries less heat. This requires more flow. Increasing flow increases head.

To make matters more complicated is how your system is implemented. If used intermittently, and a cold start from say 45 degrees or less is possible the fluid becomes more viscous yet so now you need a pump to overcome that calculated head loss to get things going until the fluid is in operating temperature range.

We have no idea what the load is for the system to begin to calculate what temperature, and flow rates the loops require. You are also down a loop so now the remaining three have more load.

To top it off most charts only go to 55% concentrations. So that's all the variables to precisely calculate the proper sized circulator.

I'm quite sure you don't want to buy multiple pumps to throw at it to see what works.

So as you can see I nor anyone else could suggest a pump size correctly with the information at hand. I'm sure the system worked before, but you made some significant changes with the new tankless, and the glycol.

Gordy

Technically the tankless should be piped primary secondary. One pump for the system(loops) the other for the tankless. Usually that works best, and keeps pump sizes more reasonable.

Technically I wouldn't recommend using a tankless. As they complicate things. It's probably way oversized for the load. What size is the tankless?

jjmik

Thank you! The system only has 3 loops. The new manifold has 4. So I just blocked what I didn’t use. The old stystem was actually ran with radiator fluid. With the nrf-22. The water hearer was going out every winter so I decided to try and upgrade. I purchased the house 3 years ago and this is the 3rd winter I’ve had to replace or repair the water heater. So I decided to go tankless. Nothing has really changed besides engine coolant to cryotech. And added a few more elbows and an expansion tank. Luckily I purchased quick connect fittings. I will try and add the second pump tomorrow.. is there an additional flow meter I could use or are the metered on the manifold pretty accurate?

Gordy

Another thought is the filter screen on the tankless may not like the glycol solution. What model tankless? 4 gpm seems high for minimum flow for a tankless to operate. Most faucets don't run that high in a domestic hot water use scenario.