vents for 1-pipe TRVs

jpf321

Is there any theory behind what type of vent to put on a 1-pipe TRV? I'm thinking large vents .. warm the room .. shed the load .. but I'm happy to hear other people's thoughts .. especially those that have had them installed a while. I just added 6 OPS TRV in my bedrooms, kitchen and mudroom (mudroom has an exposed pipe that helps to heat it).

FJL

Treated It Like any other rad

I installed Danfoss TRVs on the radiators in my living room, which is the room that gets the most heat in my apt. I installed Gorton 6 vents. I didn't think to size the vent any differently because it was a TRV. But I can see the sense of putting a large valve to vent the radiator faster and get heat faster, knowing that the TRV should shut down the rad before the room gets overheated. The only caveat to that is that there can be a lag between the time that you get enough heat and the TRV kicks in. Plus, in my apt, I have exposed risers that continue to heat the air even after the TRV shuts down the rad.

David Nadle

I think a little slower is good.

I think a TRV-controlled radiator should vent just fast enough so you don't have a cold room during any kind of heating climate, but not faster. The lag time FJL mentioned is a factor.

jpf321

thanks and FYI ...

they do SHUT it down .. i tested yesterday after install .. inlet floor valves were cold on thos 6 rads even when the other 8 in the house were hot all across. so the TRV certainly kept the steam out of the rad .. I also never broke 2oz./si in pressure. and yes I test, when I cranked them up, the steam flowed in.



I have 4 Macon's and 2 Itsa's .. Macons have an added vacuum breaker, the itsa's have the integrated VB.

jpf321

well this now begs the question ...

better to run on t-stat or heat-timer?



in the t-stat model, some control device senses temperature has dropped below set point in that location and send up heat. but then you get into the problem with t-stat geography, not installing TRV's near the t-stat etc. is that location an accurate measure of the dwelling's overall warmth?



in the heat-timer model, if I understand it correctly, you send heat anytime the end-of-main or wet return falls to a certain temp .. and you send it up for a specific length of time, no longer, no shorter. this way you are basing it more on the system's temp .. bringing TRVs into the mix, they are responsible for their micro-zone .. if you are sending heat for 20mins based on a temperature of the system, the TRVs manage whether to deliver the heat to that space .. if all your TRVs are closed, your pressure control manages the burn. you keep your mains hot at the very least so minimalizes pickup factor. when heat is "needed" in a zone it's delivered much more quickly to the "calling" rad since the mains (and header) are hot.



anyway .. things I've been tossing around in my head since as some have noted, I'm bored :-)

mel rowe

Vents on TRV's

Based on my experience I think there is a benefit to sizing those vents.  Yes, the thermostatic feature will keep the TRV's valve open until the room achieves the desired temp set on the TRV, but only if the boiler also stays on long enough to accomplish that.  If the venting is so unbalanced that the main stat shuts off the boiler before a TRV closes down, how could that particular location possibly achieve the desired temp set on the TRV?   JMHO

Rod

Shutting off the System so air can get in the Vacuum Breaker

Hi jpf- After reading Boiler Pro's article on one pipe steam, I was thinking that if you have long or continuous burn times where the burner doesn't shut off, you won't get air back in the radiator until the thermostat setting is satisfied and the burner shuts off.  With a "regular" boiler this isn't a problem but with an slightly undersized or no pickup factor system it might be. I was thinking of some sort of timeable  break relay on the thermostat circuit? Thoughts?

 -Rod

jpf321

see my post..

above regarding heat timer

jpf321

see post above...

regarding heat timer

Mike Kusiak_2

Heat timer model

The problem with the heat timer model is that there is no feedback from the room temperature to the boiler. So on a warm day such as today, you may only need heat for a few hours in the morning. You don't really want to keep the whole system hot all day long, even if the TRV's prevent the radiators from heating. There is a lot of wasted energy in keeping the boiler and piping hot.



The actual Heat-timer control varies the cycle length based on outdoor temperature and has a warm weather shutdown which disables the boiler when outdoor temp goes above 55F or thereabouts. Even so, the control is imprecise and usually causes under or overheating in mild weather. For example, if the outdoor temp remains constant at 56F, you get no heat regardless of how cold it is inside. Such control may be adequate for a big commercial building, but indoor thermostat control is much more suitable for a normal home.

jpf321

how about...

Running on tstat above a certain outdoor temp and heat timer below? Do you think that may resolve the problems you noted?

Jean-David Beyer

Outdoor reset.

My boiler has outdoor reset built in. THe control monitors the supply temperature and adjusts the firing rate to give the temperatures desired by the reset curve. I cannot believe my boiler is the only one that does this. I assume all modulating boilers can do it.