Heating Help

I don't get it...

@ April 4, 2012 8:40 AM in Thinking about a new vehicle for your business

Gasoline vapors don't explode? I'm sure we've all seen how quickly gasoline evaporates... and heard of fuel-air bombs.

It just seems based on knee-jerk reactions rather than solid science. If they were serious about it, they'd prohibit any non-diesel internal combustion vehicles in the tunnels.

Is there really no consideration of size? As in, small container of gasoline/LP/CNG or gasoline/LP/CNG in a vehicle fuel tank, ok; a big tanker of it, not OK?

How much...

@ March 8, 2012 3:06 PM in Aluminum radiators

How much of an issue would you expect this to be in a closed system? Just like iron doesn't like an endless supply of oxygen, but it's ok to deploy it in a closed system because eventually all free oxygen will become bound, it would seem that anything that would corrode aluminum would only corrode a small portion of it before it's all bound, too.

Thermal expansion?

@ March 6, 2012 8:25 AM in The leak detection job from hell....

If the crack was in such a place that it opened up as the piping heated up, could it be that there were inadequate provisions for thermal expansion and that it's only a matter of time before the new elbow cracks as well?

The reason why it would have enough "oomph"

@ March 2, 2012 10:29 AM in Waller House

to circulate through third floor radiators but not the basement one, would be the same reason why, in a monoflo circuit, you need only one diverter tee for radiation above the main, but two for radiation below. Buoyancy. Trying to push lighter water down and heavier water up.

Another stupid question

@ March 2, 2012 7:54 AM in Waller House

Why is he insulating all that pipe only to put a radiator into the space? If he removes all the insulation, chances are he won't need the radiator.

The issue with the flow is likely that there's no means for balancing it across the (now) parallel loops. For one reason or another, the head loss across the original radiators is much less than across the new radiator and there's not enough residual head across the supply and return to overcome the buoyancy and send hot water down to the radiator below the main.

If you were to partially close off the valve on the radiator that IS getting hot, you should eventually get some flow through the basement radiator. If not, you've got bigger problems.

One more thing: you say that the high point vent is on the return line but you don't mention any means of bleeding the radiator itself. You have the means and have used it - right?

Not exactly analogous to cruise control

@ March 2, 2012 7:44 AM in Actual heat loss vs. calculated heat loss....

Cruise control directly monitors the one thing that it is supposed to maintain: vehicle speed. Outdoor reset monitors outdoor air temperature but it is supposed to maintain indoor air temperature (as a proxy for occupant comfort.) What would be analogous to ODR is a cruise control that measures the pitch of the car (slope that it's going up or down) and controls the throttle on the basis of that. Of course, it would not be able to compensate for different numbers of people or luggage in the car and, like ODR, it wouldn't compensate for (head/back)wind either.

Indoor feedback attacks the problem more directly, and is more analogous to a cruise control. Of course, it has its own issues, because the power to mass ratio for a car is much much higher than for a house heating system so the car responds much much more quickly to inputs, allowing for a simple feedback loop. Cruise control can also rely on engine braking - backing off on the throttle will not just cause the car to coast but actually to be actively slowed down - which you don't have with a boiler. Also, there's only one vehicle speed to monitor... but many indoor temperatures. Picking the right (z)one to be the "master" can be tricky.

Yeah, I know... not saying anything new. :-)

Sure they do!

@ February 16, 2012 8:37 AM in Test Holes

The chafing promotes abstinence.

Thanks!

@ February 14, 2012 8:23 AM in Inconspicuous HRV/ERV ceiling inlets/outlets

The diffusers seem to run on the large side of things. I like the high velocity outlets but they're $pendy. Oh, well...

Outdoor reset is better

@ February 14, 2012 8:06 AM in radiant heat loss because of pex placement?

Peter, it's not just a matter of efficiency, but also of comfort. If you've got nothing but a thermostat controlling a high-mass emitter such as the slab, you can expect a lot of under- and over-shooting of the temperature in those zones. By the time the thermostat falls below its setpoint, the slab will have cooled enough that it will take a while for it to warm up to the point where it's once again meeting the setpoint, and by the time that happens (and the thermostat cuts the flow to that zone) the slab will have warmed enough that it will continue to release heat long after the zone is satisfied. It's possible that a very intelligent thermostat (with a PID control, for instance) could anticipate and prevent the temperature variation, but you'd be far better off with near-constant circulation and outdoor reset (where the large mass is kept at or near the optimal temperature so that it keeps up with heat loss.)

Mark, I looked at those...

@ February 13, 2012 10:41 AM in Any anecdotes about transfer plates under uneven T&G?

You'd think that with all the "extensive testing" that they've done that shows their plates outperform extruded aluminum plates (which ones?), that one would be able to find some sort of output graph. If such a graph exists, it must be well hidden because it's not in any of their manuals, specifications or brochures that I have seen. Instead we get a thermograph that's ambiguous at best, and we're supposed to make quantitative commitments on behalf of Watts that Watts is unwilling to make on its own behalf. It rubs me the wrong way.

I'm not sure I understand

@ February 12, 2012 11:11 PM in Any anecdotes about transfer plates under uneven T&G?

UColorado's R value table says that poured concrete is R .08 per inch. So four inches would still be less than half the R value of a 3/4" hardwood floor. I'm using extruded plates at 8" o.c. and there's plenty of room for excellent insulation below. What am I missing?

It's 1x6 decking

@ February 12, 2012 8:08 PM in Any anecdotes about transfer plates under uneven T&G?

laid perpendicular on top of 2x8 joists. The joists are on 16" centers. Frankly, I doubt that the decking is serving any structural purpose presently, but I guess something had to hold up the concrete while it cured. Cutting out every other would accomplish little - I can't imagine laying tubing perpendicular to joist bays, which is how the decking is oriented.

Better yet...

@ February 10, 2012 8:51 AM in Does anyone know of any piping method

It strikes me that it is more important to balance pressure across each mixer to give them best authority, rather than balancing the total pressure drop across circuits. Small difference anyway, given short lengths of plumbing involved.

Here, like this

@ February 10, 2012 8:39 AM in Does anyone know of any piping method

Pardon the crude drawing.

You're cheating... that's two circulators! ;-)

@ February 10, 2012 8:23 AM in Does anyone know of any piping method

I may have to eat my words yet. Only, I don't think that this will work unless you remove the last rung in the ladder - the one right under the expansion tank. And use closely spaced tees in order to hydraulically isolate boiler flow from system flow. Then P1 creates no pressure differential across the mixing valves but merely circulates water through the boiler and the tees, P2 creates pressure differential between both cold (directly) and hot (through closely spaced tees) ports of the mixing valves, and their outlets, and the mixing valves divert that pressure differential between hot and cold legs, creating more or less flow through the closely spaced tees but constant flow through the system. Marvelous! There's even a built in reverse return aspect, balancing pressure drops along the ladder.

Duplicate

@ February 9, 2012 10:19 PM in Any anecdotes about transfer plates under uneven T&G?

post

Yeah, well...

@ February 9, 2012 10:19 PM in Any anecdotes about transfer plates under uneven T&G?

Not so worried about squeaking because there's a 4" slab poured over this subfloor. This is all original construction, in my own 1951 vintage home. What I *do* worry about is what air gaps may have developed between the concrete and the subfloor, where I can't even get at them.

I guess I'll hope for the best. It's a fairly small area, just the entrance hall, so it's not a huge investment in time or materials. Thanks for the pointer, I don't think that a thermal compound would be a good match here but it could definitely come in handy elsewhere.

No

@ February 9, 2012 10:00 PM in Does anyone know of any piping method

There is no way, with a single circulator, to have the water want to go both from A to AB and from B to AB (which is what you need for mixing) unless the circulator is pumping away from the AB port - that is, it's on the mixed circuit. Just think about it. The pressure differential goes the other way.

The only way multiple temperatures could be obtained with a single circulator is to have the valve divert some of the branch return between "direct" back to system, and a heat exchanger where it tempers the branch supply before returning to the system. The reason this would work is that it only requires heat, not hot water, to flow - and for that, you only need a temperature differential and not a pressure differential.

Not suggesting that using heat exchangers makes any sense, mind you. Especially since they're more expensive than circulators. But it would "work."

Any anecdotes about transfer plates under uneven T&G?

@ February 9, 2012 9:13 AM in Any anecdotes about transfer plates under uneven T&G?

I'm talking significant cupping on tongue-and-groove pine running perpendicular to the joists (of course.) Should I just use more screws to force the extruded plate to conform to the subfloor? Any other way to increase contact? Any reports on how well it worked for you, if you've ever done it?

I'm using pex-al-pex, so expansion noise or tubing popping out of the plate if things are not perfectly aligned should not be an issue.

3/4" is probably overkill

@ February 8, 2012 3:22 PM in Cast Iron Radiators and radiant heat manifolds

Not that it'll hurt anything.

One thing to watch with Fostapex is that it is not the same size as "other" PEX-AL-PEX, so you can't use compression fittings. You have to use their prep tool to strip out the outer layers, and use Viega's crimp fittings. Learned this the hard way. Rifeng, MrPex, and even Uponor are all in the same ballpark (bigger than Fostapex); of course, you're best off using the fittings by the same manufacturer as the tubing.

In case there's a leak

@ February 5, 2012 12:12 PM in Uponor manifold positioning

Any leak would drip right on the actuators. Not a problem if you mount the manifolds in the upright orientation - only one 90 degree turn no matter whether the tubing enters from the top or the bottom.

I'm not quite sure I understand why anyone would use fittings (which tend to be restrictive to flow) when the tubing itself can easily be bent.

ANY emitter is capable of constant circulation

@ February 2, 2012 9:52 AM in Turning outdoor reset advice

So, using the parameters I described, you could do something like this: set the min temperature so that the burner is operating constantly at low modulation until the thermostat cuts out. At that temperature, you will be delivering more heat to your living space than you're losing, but you'll still be efficient because 1) you're at minimum modulation, 2) supply temperatures will still be relatively low, and 3) longer burner cycles will result.

Once the thermostat cuts out, the shift parameter will lower the setpoint enough to prevent the burner from firing, and allow the water in the pipes to gradually cool until you drop below your setpoint and the thermostat kicks in again. Your shift should be set to drop you down to a water temperature that's enough to maintain a setback indoor temperature at the mildest outdoor temperature. This should ensure that you get a wider differential, and therefore longer cycles, during mild weather when your heat loss is below minimal boiler modulation.

Your high limit should be set so that it, minus the shift, is enough to maintain your design indoor temperature at the design outdoor temperature. This accomplishes another useful thing: your setbacks will automatically get shallower and shallower as the outdoor temperature (and hence your ability to recover from setbacks) decreases. You also get a little built-in boost capacity in case there's any extra loss due to wind, and what have you.