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Joined on April 17, 2012

Last Post on January 11, 2014

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any way to fix sticky TRV?

@ January 11, 2014 12:05 AM in any way to fix sticky TRV?

One of our Danfoss TRVs sticks in a closed position and will not open to allow hot water flow when the thermostatic controller calls for it (e.g. even if I turn it up beyond 5).

I can take the thermostatic controller off and move the pin in and out a few times, and this will cause water to flow again, but only for a few days. I've lubricated the pin from the outside, but I believe the problem is not that the pin itself sticks, but rather the mechanism inside the valve body where the lubricant does not easily reach.

Is there any fix short of draining the system and replacing the valve? Just to emphasize, the detachable plastic thermostatic thingy works just fine, the sticking is in the metal valve.

Watts 'HAV' automatic radiator bleed valve?

@ December 3, 2013 2:35 PM in Watts 'HAV' automatic radiator bleed valve?

Any actual experience with this valve? They bleed air when dry and shut off when the material in it gets wet and swells. So they can be installed on radiators in any orientation.

Do they work well for years, or do they leak or stop working?

I just installed one on a Runtal baseboard that was slowly collecting air and then becoming noisy. It was almost magical: I opened the shutoff valve in the basement, and by the time I got to the 1st floor the baseboard (previously drained to install bleed valve)  was full of water and yet the bleed valve hadn't spewed any water. But I don't know about the long term.


@ November 27, 2013 1:59 PM in Hydronic Heating in India

I am surprised to hear that there is hydronic heating anywhere in India. You may be misinformed, we Indians hate to say "no" or "I don't know" and prefer to nod and say "Oh yes, we heard something about that somewhere".

Because the heating season is short, it is more economical to have electric heat. In mid-priced hotels and even in some 5-star air-conditioned hotels I have had space heaters delivered to the room on demand, although most nice hotels have heat through the overhead AC vents.

Indian homes (not counting high-rise boxes) are designed to be open to catch the breeze in the long hot seasons. Many homes, even those of the rich, have no heat at all; when it is 45F outside, as it frequently is in Delhi,  it is maybe 50-55F indoors. As a result winters in northern India (for those not staying in heated facilities) can feel more chilly overall than winters in the US.

I can see from your photos of plumbing that you are having a 'real' Indian experience, you're not just staying in a Hilton-Sheraton bubble.

yes, air scoop

@ November 26, 2013 8:38 PM in air collecting in one baseboard only

Yes, we have an air scoop.

Regarding dissolved air in fresh water, I do understand that as the weather gets cold and the water gets warmer (we have outdoor reset), more air will come out of the water since the solubility of gases decreases with increasing temperature (think soda water).

What I don't get is why all of it is collecting at one radiator. I have been going around trying to bleed the other radiators and there is nothing to bleed there.

I also don't get why lowering the surface tension (with surfactants, i.e. dish soap) will affect the solubility of gases in the bulk water. This is something I know a little bit about; really, the two have nothing to do with each other.

pumping away

@ November 26, 2013 12:07 PM in air collecting in one baseboard only

Additional information: the pumps are "pumping away" exactly as they should.

Note also that the problem baseboard is on the 2nd floor; the 3rd floor radiator is not collecting air.

air collecting in one baseboard only

@ November 26, 2013 10:11 AM in air collecting in one baseboard only

Our hydronic heating system is a tangle of copper and galvanized pipes running here and there. There are radiators on three floors. On the 2nd floor there was a Burnham Baseray that was recently replaced during bathroom renovation with a Runtal baseboard. The supply and return lines remain the same.

The Runtal emits low but distinct water flow noises. Every time it does that, I bleed it, and a little air comes out. The noise stops. Two days later it starts again, and I bleed it, and sure enough there is some air....

I don't understand how air can get into a system under pressure, and only in one radiator. I realize that the Runtal is more likely to be noisy, compared to the heavier Burnham Baseray and also the traditional radiators elsewhere in the house. But I have bled the other baseboards and radiators and there is no new air collecting there. This is the only one that keeps getting new air.

All suggestions appreciated.

original "mouse turds" thread

@ October 30, 2013 11:25 PM in Knight boiler problems

The original report (and subsequent long thread) was deleted, but I don't know why:

open secret

@ October 30, 2013 11:00 AM in Knight boiler problems

The coffee grounds that collect on these heat exchangers are a big problem that manufacturers won't admit to. Many years ago there was a "mouse turds" thread here that was ultimately deleted. No one knows where these granules come from, but the HX is getting stained and pitted at the same time, and ultimately it will develop pinholes.

People say you need a combustion analysis, but this is inorganic material, it is not carbon and so it is not coming from the gas. It may be leaching out of the stainless steel. I may be wrong, but the fact is, everyone makes up stories; there is no openly available analysis of what the coffee grounds are or an understanding of why they form.


@ October 29, 2013 9:53 PM in does new boiler need combustion analysis?

Thanks for the advice! Boiler was combustion tested and was good out of the box (I have a report with the readings).

HTP Elite FT

@ October 24, 2013 2:40 PM in use 2-stage stat to override outdoor reset?

HTP Elite FT. No boost input. (I didn't realize some boilers had boost inputs...makes a lot of sense..)

Now speaking of boost, what would happen if I wired the 2nd stage signal into the DHW input (not currently used), and tie the DHW circ output and space heating circ output together? There's only one zone. Would that work?

Radiators only, no radiant heat.

use 2-stage stat to override outdoor reset?

@ October 24, 2013 1:55 PM in use 2-stage stat to override outdoor reset?

Is there an easy way to wire a 2-stage stat such that, when the 2nd stage is called for (typically when room temp is more than say 3 degrees away from set point, e.g. during recovery after setback), this overrides outdoor reset and runs the boiler flat out until the 2nd stage is satisfied?

If stats had a 2nd stage output that is NC (normally closed), this would be easy, I could just run the outdoor sensor wire through this switch. In fact the stat output is NO, and switching NO to NC requires an external relay, which I am not eager to do unless I have to.

I'm thinking maybe there is a smarter way to wire it? Or maybe a commercial product that does what is needed?

looked at the gas meter...

@ October 21, 2013 7:46 PM in HTP Elite FT boiler not modulating low enough...problem?

I clocked the gas meter when the boiler is running steadily (and nothing else is), It takes a half foot in 82 sec,, which works out to to 22,000 BTU/hr. For this 110,000 BTU boiler, that is exactly 20% (the minimum fire possible, since it has 5x modulation).  It's not 30% even though the display shows that...

I feel better now. The display is wrong, but I'm not losing energy up the chimney.

Many thanks to everyone for the help.

I'm trying to explain

@ October 21, 2013 6:21 PM in HTP Elite FT boiler not modulating low enough...problem?

Thanks to everyone for the feedback. Clearly I am doing a lousy job explaining the problem. I realize that this is not a calculation that people do normally.

I am NOT complaining that the cycle is too long---that is of course good. It is NOT true that deltaT (difference between boiler supply and boiler return) is too low--- 3 or 4 degrees it is just about what you expect when the water temperature is holding steady at a cool 85F. (DeltaT will go up to ~20 degrees as the water temperature goes up to 180F in cold weather.)

I am saying that the boiler firing level is way too high (at 30%) in relation to the low T (85F) and low deltaT (4F). It should be about half that. I showed my work in earlier posts. I am concerned that the extra heat is going up the chimney for some reason, but probably I am wrong. Where's my mistake?

I am going to monitor the gas meter and see if it is really running at 30%.

not the issue

@ October 21, 2013 4:53 PM in HTP Elite FT boiler not modulating low enough...problem?

I can increase or decrease the primary pump speed (it's a 3-speed pump). If I do, the deltaT at full fire goes down or up (naturally).  The deltaT at 30% fire also goes down or up. Their ratio remains the same, and so the problem I described remains exactly the same. It has nothing to do with the pumping speed.

no radiant loops

@ October 21, 2013 3:02 PM in HTP Elite FT boiler not modulating low enough...problem?

There are no radiant loops, only cast iron radiators. I never treated deltaT as a constant. Also I am only reporting deltaT after things have settled down (become stable).

But I should have made clear that I was talking about the boiler deltaT (deltaT in the primary), not the deltaT from the radiators (secondary). So the nature of the radiation (and whether the load is being throttled)  is not relevant.

Water comes into the boiler at T1 and goes out at T2. (Both these numbers can be read at the boiler front panel.) The difference deltaT =T2-T1 depends on the BTU being delivered to the water as it goes through the boiler, and nothing else. It is not a constant, but it depends only on the modulation of the boiler.

When the boiler is running at 100%, I see that deltaT is 23F (reasonable). When the water temperature is set at 85F, deltaT is 4F (reasonable), but boiler is running at 30%. It should in fact be running at (4/23)*100% = 17%. (Roughly---of course it can't modulate below 20%.)

Another way to see the problem is that if it really requires 30% fire to heat the water from 70F (room temperature) to 85F, then at 100% fire it will only manage to heat it to 70+(85-70)*100/30 =120. That's not true, it actually gets to 180F without a problem; so why is it running at 30% when the water output is 85F and the input is 81F?

HTP Elite FT boiler not modulating low enough...problem?

@ October 21, 2013 11:38 AM in HTP Elite FT boiler not modulating low enough...problem?

We got a new HTP Elite FT.  The control is pretty much the same as our late unlamented Munchkin, with a few small improvements. Among other things I can now see the modulation level (%) on the status screen.

The unit is supposed to have a 5x turndown, i.e. lowest level should be 20%. However, the displayed modulation level never goes below 30%. As a test, I set the water temperature really low, 85. The return temperature is 81. Delta-T at full fire is 23, so (85-81)/23 = 17%.  But the burner never goes below 30%. It doesn't go on or off as far as I can tell from the display; it just sits at 30-31%. This makes no sense to me.

Is it losing the extra heat somewhere?

There's no one from HTP on these forums, is that right?

how to replace backflow valve in B&G Chek-trol?

@ October 19, 2013 12:25 PM in how to replace backflow valve in B&G Chek-trol?

The flow check valve (I hope this is the right term...the valve that only allows water to flow one way) built into this pump isolation valve has become increasingly noisy. I couldn't find any way to remove it in a non-damaging fashion.

I am able to turn it but it doesn't unscrew, it just turns in place. I was finally able to irreversibly pull out the ball and spring, so now there's no noise, but the rest of the plastic body is still in there. I'd like to remove and replace it so I have a backflow preventer again. Is there a trick to it?

Many thanks! 

of course

@ October 19, 2013 12:19 PM in why use primary/secondary if not needed?

Primary pump runs when boiler runs, and boiler runs when thermostat calls for heat.

In system with outdoor reset, the boiler runs most of the time, and so the extra pump in a P/S system runs most of the time too.


@ October 18, 2013 12:31 PM in why use primary/secondary if not needed?

Sure, but summer gas usage gives you a baseline to subtract.

It's not as if this needs to be precisely accurate; you want the boiler to be slightly oversized, but not as much as heat calcs oversize it.


@ October 18, 2013 12:02 PM in why use primary/secondary if not needed?

"Extrapolation" means you take the gas usage (actual, not estimated) in ANY winter (mild or not) and use that to CALCULATE what will be needed on a design day (since BTUs used are roughly proportional to the degree-days).

The Taco Bumble Bee is an interesting device, I didn't know about it. I have to think about how well it works when there is outdoor reset. If the water is 90F, as it is for my system in October or April, running the pump at dT=20 means the pump is not really running at all.


@ October 18, 2013 11:31 AM in what is replaced when replacing boiler?

Yes, we should not have made assumptions. Most customers are not technically savvy enough to get into details; I know more than some, but I guess we were in a hurry (unexpected HX failure) and I didn't do due diligence.

PS The previous boiler died because it was a POS (Munchkin).

PPS This post was edited by me, not an administrator.


@ October 18, 2013 11:29 AM in what is replaced when replacing boiler?

What you say is very reasonable.

Unfortunately our contractor (the premium-priced HVAC company in our town)didn't discuss any details, and I didn't know enough to ask. Now they're only doing a "quick change artist" job and we have no leverage.
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