Issues with Low heat output

NelsonATC

Hello All,

I'm new here, but need an opinion. A couple years ago, I had a Navien 240 (Thier original combo unit installed, along with a conversion from Steam radiators to baseboards. since then, I have had issues on the coldest days (Im in RI, so we get our share of 0 deg days) not getting the house up past 62* or so without space heaters, especially on the 1st floor. The second will heat fine.

I have noticed that on some days, like today, at 45deg outside, the house still feels cool, so I check the thermostat, and today it read 68 deg. It was set at 72*. So I went down stairs, and the readings in the attached photos is what I found:




So, It shows the unit is pumping plenty of heat, but even though the circulatory pump is running and moving water, the hot water does not seem to be making its way to the 1st floor inlet. To me, it appears to be re-circulating at the manifold right back into the unit. Now, if I close the ball valve on the return side for 30 seconds, then re-open, the hot water begins to flow and the system is fine.

This seems to happen almost daily.

My uneducated opinion is that the Navien unit is not to blame. It seems like the return water may be feeding into the bottom loop of the manifold, this bypassing the Navien unit, and re-circulating into the 1st floor.

Harvey Ramer

Primary secondary piping done incorrectly. I'm not very familiar with Navien but I believe they have a built in pump. However, you have nothing to move the water through the primary loop. You have 2 options, install a pump in the primary loop or cap off the ends of the primary loop at each end just past the last Supply takeoff and last return takeoff.

Zman

That is a strange way to pipe a boiler.
If you were water you would have some tough decisions to make.
On one hand you could go the way the installer had hoped, but it would be kind of tough to get through all those unions, isolation valves, air eliminator and check valve.
It would be way easier to just go around all that through the pipe on the bottom. Granted you would not pick up much heat , but when you are lazy water, that's what you do.

Seriously, you need to get rid of the pipe along the bottom and cap the ends just like the installation manual shows. It will work just fine.

You should also make sure you have checks on the zone pumps or you will have a ghosting problem there.

Steamhead

Bet the steam system worked a lot better than this..............

ratio

A quick fix would be to close the valve on the bottom pipe, the one with the blue handle in the first photo. That should get you through the heating season.

Zman

ratio said:

A quick fix would be to close the valve on the bottom pipe, the one with the blue handle in the first photo. That should get you through the heating season.

That looks like a boiler drain rather than a valve.

Paul48

I thought the same thing, but when I blew it up, it appears to be a long stem valve.

delta T

My money is on a drain, looks like a 1/2 MIP boiler drain threaded into a tapped tee to me.

Wouldn't be to hard to get rid of that loop though. There are isolation valves a plenty, so it shouldn't take too much effort to cut and cap both ends (or really just cut a valve in and shut it off).

NelsonATC

That is a drain.

Ok, seems that my suspicions have been confirmed here.

So, is my best bet to valve off the bottom loop, or just cut it and cap it?

I'm thinking if I cut and cap, I should add a drain on one end?

ratio

Arrrgh, I thought it was a gate valve. Sorry for misleading you.

NelsonATC

Ratio - That would be TOO easy!!!!

Zman

It looks like you have drains on either side of the closely spaced Tee's. If that is the case, I would just cap the ends.

Dave H_2

NelsonATC,

Yes, either cap or valve the "loop" and you'll get the flow you need. This heater does have its own circulator and by your installer using the "Manifold System" he was kinda close.

Take a look at the attached

What you have:


Here is what you need:

And here is the easy fix:

NelsonATC

Sounds like a plan. I'll grab a valve tonight and cut it in.

Thanks to all for you help!