Basement radiator no heat (Navien NCB240)

[Matt13]

In October 2017 I had an NCB240 installed replacing an oil fired boiler. The lone basement radiator never worked last winter. 2017/18 was my first winter in the house. We are updating the finished side of the basement so would like to get it working.

At the time of the boiler installation the installer bled the radiator and tried to get it working but could not. He was supposed to come back and fix it but never did. Fast forward to today and I had the installer return to diagnose the problem. He was unsuccessful in bleeding the radiator again. He believes my 1 1/2 inch monoflow tee is blocked and needs to be replaced. He says this is common of monoflow tees. He is charging me $875 to drain the system and replace this tee which seems very high for what I would guess to be 2 hours of work.

Is this price reasonable?

Is there anything else I can try to get this radiator working? I never witnessed the radiator working but the previous owner who I am still friendly with assures me it did. One search online suggests shutting off all radiators except the basement one and then attempting to bleed the radiator. Could this potentially work?

I will attach some pictures shortly but my understanding is that I have 2 pipe hot water system. There are two monoflow tees that are both coming from the supply pipe and connect to the basement radiator. They are spaced about 6 inches apart.

 

[Dana]

Did the contractor use an infra-red camera or IR thermometer in making this diagnosis? It's probably worth investing $50 for a pistol-grip IR thermometer and making some observations. A monoflow tee that is installed backward or has become eroded would lower but not prevent flow through the radiator. Even very low flow would be detectable with a IR themometer.

On a monoflow tee system shutting off the other radiators won't help for bleeding air- the flow is still going through the loop pipe. The system is under pressure from both tees. It should be possible to bleed air from the radiator even if the monoflow tee is blocked. Does air or water come out when bleeding the radiator?

Wrenching out & replacing a mono-flow tee is not 2 hours of work, but $875 seems a bit on the steep side. That quote may be that high to cover the down-side risk- getting that tee off is likely to break a few things that would also take time & money to replace.

Basements have very different heat loss characteristics than first floors, and it may not be worth fixing this. The heat loads of basements are also quite low, and can be made lower by air sealing and insulating the basement walls.

 

[Sponsor]

 

[Matt13]

A little bit of water drips out but that's about it. I don't hear much if any air coming out.

Attached are the photos.

 

[Dana]

Since it's under pressure from both tees, both would have to be blocked for only a tiny dribble to come out of the air bleeder valve. Even with the monoflow tee corroded up it should be peeing pretty robustly, not barely dribbling, like a geezer with prostate issues.

It's possible that he gate valve at the radiator is blocked (or not capable of opening)?

If the tee side of the monoflow is blocked you should be able to disassemble the 3/4" side and ream it out with a drill (carefully avoiding damaging any threads, or drilling through the flow deflector inside the tee. )

What happens when you crack open the drain valve on the tee next to the radiator a bit? (Put a bucket under it first.)

How brave are you about DIY stuff?

How cold does the basement get without the radiator functioning?

Basement loads are smaller, but steadier than above grade floor loads. If it's all on the same zone it'll usually overheat the basement when it's cold outside, underheat it during milder weather. Making it a separate zone with it's own small pump running off the boiler or a water heater would make the basement less likely to over/under heat.

It also may be possible that for not a whole lot more than the quoted repair a half-ton to 1-ton point terminal heat pump (PTHP) could be installed to heat the basement as it's own zone.

 

[Plumber69]

Its even possible your bleeder is messed up. changing that is cheap and easy

 

[Plumber69]

looks like copper lines feeding the rad. I drain the system and put ball valves in. Then you could do a test loop with out the rad.

 

[Plumber69]

Amd what is that fitting above the boiler drain

 

[Matt13]

I was able to tinker with the bleeder a bit and now its flowing strong. I bled about a gallon (no idea if this was too much or not enough) of water out of it and both the supply and return copper pipes got hot but the radiator remained cold. The supply line was hot right up to where it connected to the radiator. The return was hot for about 80% of the pipe but seemed to get less warm as it got about 2 feet from the radiator.

When I opened the drain valve on the copper pipe water flows out pretty strong.

Is it possible that the monoflows are really blocked if both the copper lines were getting hot?

 

[Dana]

If the pipes to the radiator are getting hot, you're getting flow and the monoflows are not blocked. If no air came out of the bleeder it was not vapor-locked (which would have been rare for a basement radiator anyway.)

The photos aren't completely clear on the radiator plumbing. It appears there may be be a tee in the pipe to one side of the radiator (the stub off the valve with the white paint on it- is that an ell or a tee?) Is it possible that it's a radiator bypass so that flow through the radiator can be adjusted by a valve?

 

[Matt13]

Here are some additional photos. I've tried putting the valve in every possible position to make sure it's open.

 

[Dana]

The valves with handles get cranked all the way counter-clockwise.

This thing looks like a simpler version of a flow balancing valve. Is there a name or number cast into the bronze anywhere?

If something is clogged with gunk or out of adjustment that would be a prime suspect.

See (without stripping it) if you can turn the slotted screwdriver part in the middle counterclockwise. If it seems stuck I suspect if you crank the hex nut 1/8 of a turn counterclockwise it will unlock the slotted screwdriver thing in the middle that can be used for adjustment. I would expect a turn or two counter clockwise would be enough to tell if it's doing the trick.

There are more sophisticated versions, including thermostatic types, and the internal details vary. But since it's designed to be a flow restrictor it's far more likely to become clogged than a monoflow tee, which is designed to be a flow diverter, something that shares flow rather than throttling flow.

The balancing valve was probably installed to be able to deal with the under/overheating problems related to being on the same zone as a fully above grade floor with dramatically different heat loss characteristics. At some point you may want to swap it for a thermostatic version with a wall mounted temperature sensor, or a regular hydronic zone valve operating off a standard wall thermostat.

The internals of your balancing valve might be similar to this Honeywell radiator valve or it could be quite different, but with most of them the center screw is what adjusts the flow:

 

[Matt13]

I did not see any numbers or markings on the balancing valve. I turned the screw 2-3 rotations and bled the radiator again but the radiator stays cold. I noticed the copper pipes leading to the radiator only seem to get hot a few feet after the monoflow tees. After I start bleeding the radiator I am able to get them hot all the way to the connection with radiator.

 

[Dana]

Do both pipes get hot when bleeding down the radiator, or is it just one side?

If both get hot it means the monoflow tee is not plugged, since there is flow toward the radiator on both connections.

If just one of the pipes gets hot, or gets hot a lot faster than the other, there is a restriction on that side. If it's the side with the balancing valve, the balancing valve is probably closed down too much or stuck or gunked up .

Since there is flow on both sides it means it's possible to force flow through the radiator with a pump. A small pump and a zone relay controlled by a wall thermostat in the basement is a FAR preferable solution than replacing an eroded mono-flow tee, due to the room to room balancing issue that can never be resolved when a basement is on the same zone as the floor above.

Even a Taco 003 is overkill, but they're more expensive than the Taco 005, which is even more overkill. An 005 in series with the balancing valve (for throttling back the flow to lower-noise, lower velocity flow) would be pretty cheap, ~$110 for the pump, at internet pricing). A single zone SR501-4 zone relay would add another ~$55 at internet pricing. Throw in another $50 for thermostat & wire and some fittings for cutting in the pump and it would be ~$250 in parts as a DIY, assuming you're comfortable with draining and refilling at least that part of the system. I'm not sure how much of the system could be isolated.