Help! Radiator not getting hot

[theskydiveguy]

Hello Folks,

Long time lurker - first time poster.

First - I am not a plumber.

I have added a new rad in my basement and it's not getting hot. My rad system is pretty simple - it's basically a giant loop around my basement in 11\4" blackpipe with 3/4" take off's to each radiator. Some are blackpipe and some have been adapted to copper.

So what I did was - uncap the 2 capped ones and went Black Pipe - Pex AL Pex to the rad. The rad stays cold, if I bleed the rad I can get hot water, but if not it stays cold. All the other rads are hot, so obviously I did something wrong.

Is there are in and out on a rad like this? Did I plumb it backwards? Any help is appreciated.

Picture of a similar rad is attached.

 

[Dana]

Terminology: That's a fin-tube convector, not a radiator. It's not even possible to plumb them backwards.

If it's plumbed in parallel with the hydronic loop piping rather than in series there may be next to zero flow. It's possible that your system is plumbed with "mono-flow tees" to force at least some flow into each heat emitter. If you teed off to this one with standard tees and 3/4" pipe the flow is going to be nearly nil due to the much lower impedance of the 1-1/4" pipe.

 

[Sponsor]

 

[Plumber69]

guaranteed your system is monoflo tees.

 

[theskydiveguy]

Here's a pic of what I did - so those tee's only work one way? So if I switch out the intake and return I should be good ?

Thanks again guys!

 

[Dana]

Most convectors do not have a preferred direction, unless there is a check valve in series with it. Switching the intake & output plumbing would not make a difference. But for clarity, pull the cabinet off the convector and take a pic of it's plumbing connection & internals. If it's a used convector originally set up for steam with a steam-trap under the hood that would impede flow, and need to be yarded out.

It looks like you didn't install a new tee, but use a pre-existing one? Is that true of the other connection too?

What did that/those tees hook up to previously?

Perhaps a schematic sketch of how the system is plumbed to this and other heat emitters would make things clearer.

 

[theskydiveguy]

Most convectors do not have a preferred direction, unless there is a check valve in series with it. Switching the intake & output plumbing would not make a difference. But for clarity, pull the cabinet off the convector and take a pic of it's plumbing connection & internals. If it's a used convector originally set up for steam with a steam-trap under the hood that would impede flow, and need to be yarded out.

Here are a few pics -

There isn't a trap etc - I removed all the plumbing from them and started from scratch. I also flushed it out really well.


It looks like you didn't install a new tee, but use a pre-existing one? Is that true of the other connection too?

Yes you can see both T's in the pictures - I thought I could get away with reusing an old connection. I also noticed that the T's are different - one round one and one hexagonal one per-connection. I have heated the system and the round ones seem to be the supply and the hex the return, just based on which pipe gets hotter first on another loop (to my kitchen) but I am totally guessing here.

What did that/those tees hook up to previously?

I have no idea - they were capped when we moved in.

Perhaps a schematic sketch of how the system is plumbed to this and other heat emitters would make things clearer.

Here are a few pics -

There isn't a trap etc - I removed all the plumbing from them and started from scratch. I also flushed it out really well.


It looks like you didn't install a new tee, but use a pre-existing one? Is that true of the other connection too?

Yes you can see both T's in the pictures - I thought I could get away with reusing an old connection. I also noticed that the T's are different - one round one and one hexagonal one per-connection. I have heated the system and the round ones seem to be the supply and the hex the return, just based on which pipe gets hotter first on another loop (to my kitchen) but I am totally guessing here.

What did that/those tees hook up to previously?

I have no idea - they were capped when we moved in.

Perhaps a schematic sketch of how the system is plumbed to this and other heat emitters would make things clearer.

Yes let me sort out how to get that to you here.

 

[theskydiveguy]

I realize it's not the best diagram ever! It's a very basic system. The only components I didn't add were the automatic fill valves.

 

[Dana]

That's very much a mono-flow tee configuration, and the difference in external appearance may indicate which one is the mono-flow and which is a standard tee. Compare the tees to the pairs that go off to other heat emitters. Normally if it's just a single mono-flow tee the upstream side will be a standard tee, and the downstream side of the radiator will be the mono-flow. If the mono-flow is the upstream side it doesn't create a pressure difference to force flow through the convector.

If the tee types are in the wrong order relative to the loop flow, swapping the tees with one another would fix it, but swapping the pipes to the tees won't. You could force flow with a low volume pump in series with return side of the new plumbing connected to the convector, controlled by a room thermostat & zone relay, along with a ball valve (or globe valve) to adjust the flow downward, since even a very small pump would probably be over-pumping it.

 

[theskydiveguy]

That's very much a mono-flow tee configuration, and the difference in external appearance may indicate which one is the mono-flow and which is a standard tee. Compare the tees to the pairs that go off to other heat emitters. Normally if it's just a single mono-flow tee the upstream side will be a standard tee, and the downstream side of the radiator will be the mono-flow. If the mono-flow is the upstream side it doesn't create a pressure difference to force flow through the convector.

If the tee types are in the wrong order relative to the loop flow, swapping the tees with one another would fix it, but swapping the pipes to the tees won't. You could force flow with a low volume pump in series with return side of the new plumbing connected to the convector, controlled by a room thermostat & zone relay, along with a ball valve (or globe valve) to adjust the flow downward, since even a very small pump would probably be over-pumping it.

Ok - since I cant plumb the convector backwards. I charged the system - got it heated and the pex al pex gets hot to the touch (warm) but doesn’t seem to get warm all the way along near the rad just until about the first elbow. If I bleed the rad I can eventually get hot water, but it takes time.

I assume there is water flow because the pex gets hot.

I’m not changing Tees because that’s a huge job and I assume once I touch that old pipe I’ll be in for more than I want to handle!

 

[Dana]

I agree- putting a wrench on the old stuff is likely to turn out to be more trouble than it's worth, which is why I suggested a thermostat & pump solution as an alternative method of forcing flow.

That may be a "better" solution anyway, since the heat loss characteristics of basements are so different from fully above grade floors. It almost never works well to combine a basement zone with an above-grade zone. If operated as a single zone the basement is typically too hot during some seasons, not warm enough during others. By controlling the convector's water flow with local pump on a thermostat it avoids overheating the basement.

 

[Plumber69]

I had to move some pipes and put monoflo tees in. It was so hard to unthread the pipes. They were so tight the pipe was collapsing

 

[theskydiveguy]

Yea, that's my concern - I don't want to touch the old stuff if I don't have to - I think what I will do is add a pump and manifold for the basement zone. Any chance anyone can recommend a pump as well tell me if I can just take it off the ring?

So - Ring - Monoflo Tee - Pump - Manifold? Would that work for 5 convectors (thanks Dana) - in the basement - I don't need it super warm like the main part of the house.

Thanks

 

[Dana]

Five convectors that size could probably roast you out of the basement! At an entering water temperature of 180F a 2' x 2' x 5" deep fin tube convector puts out better than 2500 BTU/hr or better.

Run a load calculation on the basement. Hot2000 or Loadcalc would be good enough for this- these are not super accurate, it would at least put an upper bound on it. If none of your basement walls are insulated, it's probably worthwhile to air seal and insulate the walls to at least 3-4' below grade (which you'd be able to determine using those tools). It appears to be a rubble wall/stone foundation in good condition, no obvious water leaks in the glimpse shown in the pictures so far. A couple inches of closed cell polyurethane foam from the subfloor all the way down to 4' below grade (or the slab) does a great job of moisture & sealing it, but there are cheaper ways to get there too. Even if you let the basement idle along at 10C in winter an uninsulated basement is still a major chunk of the heating energy use for most houses.

 

[theskydiveguy]

Five convectors that size could probably roast you out of the basement! At an entering water temperature of 180F a 2' x 2' x 5" deep fin tube convector puts out better than 2500 BTU/hr or better.

Run a load calculation on the basement. Hot2000 or Loadcalc would be good enough for this- these are not super accurate, it would at least put an upper bound on it. If none of your basement walls are insulated, it's probably worthwhile to air seal and insulate the walls to at least 3-4' below grade (which you'd be able to determine using those tools). It appears to be a rubble wall/stone foundation in good condition, no obvious water leaks in the glimpse shown in the pictures so far. A couple inches of closed cell polyurethane foam from the subfloor all the way down to 4' below grade (or the slab) does a great job of moisture & sealing it, but there are cheaper ways to get there too. Even if you let the basement idle along at 10C in winter an uninsulated basement is still a major chunk of the heating energy use for most houses.

Thanks Dana

Here is what I got - (No idea if this is correct)

Heating BTU
269,588

 

[Dana]

That would be correct on if there four or five basement windows devoid of glass. (Seriously- it's an order of magnitude too high if this is a normal sized residence.)

About how many square feet of floor area, how many windows & exterior doors, and how much of the foundation walls are above grade, and what is your postal code (for outside design temp purposes)?

 

[theskydiveguy]

That would be correct on if there four or five basement windows devoid of glass. (Seriously- it's an order of magnitude too high if this is a normal sized residence.)

About how many square feet of floor area, how many windows & exterior doors, and how much of the foundation walls are above grade, and what is your postal code (for outside design temp purposes)?

That's what I thought!

Building built in 1885 - Double brick walls - no insulation
3 storey - Attic is not heated by this system it also was spray foamed and is heated by electric if we turn it on.
Each floor is 1500 sq ft (4500 ft plus 1500 sq foot basement)
Basement has the entire perimeter spray foamed in the joist bays this past summer to seal it up.

2 exterior doors that go outside - one has a window one is solid
2 doors that go to the garage which is not insulated

Main floor - 10 windows
Second Floor - 12 windows
Third Floor - 2 small windows
Basement - 4 windows

Foundation walls are less than 2' above grade. They are stone.

Postal - K9H2M7

Thanks again Dana

 

[Dana]

I was asking about just the basement, not the whole house, since that's where you're adding the convectors.

Assuming the an 8" wall thickness the R-value of the brick is about R1.5, the interior + exterior air films add another ~R1 for R2.5 "whole wall", or a U-factor of about U0.4 (= 0.4 BTU/hr per degree-F difference per square foot of brick wall area.) If it's a 15" thick rubble foundation it'll be about U0.3.

To put a none-too accurate (but better than a WAG) number on the losses of the below grade wall & basement floor I'll run the numbers as if it were 4' above above-grade and no losses to the ground. I'll also assume 1' of brick wall exposed by open floor joists, and a rectangular 30' x 50' footprint (=160 foot perimeter.)

Basement windows are typically 3-4 square feet. I'll also assume no exterior doors to the basement. and 16 square feet of window.

The 99% outside design temp for Peterborough ON is -23C/-9F and I'll assume a basement temperature of +15C/+59F, for a temperature difference of 28C/68F.

Brick wall basement losses:

U0.4 x (1' x 160') x 68F= 4352 BTU/hr

Foundation wall area (with fudge factor for the rest) is 4' x 160' , less 16' of window area = 624 square feet.

Foundation wall (+ fudge) is then:

U0.3 x 624' x 68F= 12,730 BTU/hr

Assuming the basement windows are single-pane (no storm window) they run about U1. Basement windows are typically 3-4 square feet.

Window losses:

U1 x 16' x 69F= 1104 BTU/hr (If double-paned or storm windows that drops to about 500 BTU/hr)

Add it up and you're at 18,366 BTU/hr (ignoring infiltration for now.)

That's a heluva a lot less than 269,588 BTU/hr, eh? (Does your boiler even have 270K of burner output?)

If you installed " of closed cell foam on the foundation wall & brick right up to the subfloor the U-factor of the U-factor of both the brick & rubble wall falls to ~U0.077. The combined brick & wall area is 784', and the losses would then be:

U0.077 x 784' x 68F = 4105 BTU/hr + window losses of 1104 BTU/hr comes to 5208 BTU/hr + infiltration losses.

Assuming 9' from the slab to the subfloor and 1500 square feet you're looking at 1350 cubic feet. Assuming reasonbly tight window & wall it's reasonable to assume there is no more than 0.25 air exchanges per hour of outdoor air infiltration, so that's (1350/4=) 338 cubic feet per hour. The specific heat of air by volume is about 0.018 BTU per cubic foot per degree F, so your infiltration losses would be about:

0.018 x 338 cubic feet/hr x 68F = 414 BTU/hr....

... bringing the total up to 5622 BTU/hr for an insulated basement. If your windows leak tons of air the infiltration losses could be 5x or more higher than that, especially if your top floor ceiling is leaky too (since the air leaks at the bottom & top of the house add up to the greatest amount of stack-effect drive.)

It would only take 0-1 convectors that size to keep the basement above 15C if it's insulated, since you have the distribution losses of the fat loop pipe with ~R2 insulation on them, and the standby / jacket losses of what's probably a beastly sized boiler in the basement.

Uninsulated it could conceivably add up to 3-5 of those 2' x 2' x 5" convectors. To get a better handle on their output, measure the actual depth & height of the fins, and the total width of the cabinet, as well as the high-limit temperature of your boiler, and your actual targeted indoor temperature for the basement.

 

[theskydiveguy]

So, I thought I would update you all. I realize that I dropped the ball and never got back to you. I hate finding threads online that the OP never completed.

After a solid winter as low as -35C we saved over $300 in gas compared to the winter before which weather wise was comparable.

The basement was warm, not hot. This was due to both the insulation and the convectors I imagine.

I had to add a pump to the new manifold which solved my flow problem.

This summer I replaced the last 2 basement windows with modern windows that hopefully will further with the energy savings.

I wanted to thank you all for your advice and help sorting this all out.

Cheers

 

[Dana]

So, I thought I would update you all. I realize that I dropped the ball and never got back to you. I hate finding threads online that the OP never completed.

After a solid winter as low as -35C we saved over $300 in gas compared to the winter before which weather wise was comparable.

The basement was warm, not hot. This was due to both the insulation and the convectors I imagine.

I had to add a pump to the new manifold which solved my flow problem.

This summer I replaced the last 2 basement windows with modern windows that hopefully will further with the energy savings.

I wanted to thank you all for your advice and help sorting this all out.

Cheers

There's nothing quite like ruminating about a heating system issue on a day when it's north of 30C outside (in my area), eh?

Glad to year it's all working out!