thermostatic radiator valves

Eileen Olive

In what way do you mean it runs backwards? I believe my house has a converted gravity system, judging from the large 2" headers feeding up to each radiator on the 1st and 2nd floors--though the supply and return pipes are smaller that go to the 2nd floor--now that seems a tad backwards. Just curious. But I would've figured a smaller supply/return since it's not going all the way to the 2nd floor, 1" pipe to 1st floor 3/4" to 2nd??

flip_3

has anyone had experience using thermostatic radiator valves on a gravity hot water heating system

Unknown

yes

They work GREAT. I used them on a Tarm system with radiators, where the other loops were pumped.

They regulated very well, considering that the pumps running on the other zones made the gravity zone run backwards when any pump was on.

I knew this going into it, and I told the customer that it would work that way.

After a month, his comments? It does run backwards with the pumps running. That's all. His wife said that the control of the room temp was extremely accurate.

I put a 1/2" bypass at the end of the supply and return to keep the loop flowing, when the valves throttled back. I'm not sure that I needed to.

Noel

flip_3

thanks for the reply noel. this is a large system, don't think i would need a loop at the end. have not heard of a tarm system what is that?

World Plumber

thermal radiator valves

The thermal radiator valves work really well. Be sure that your flow is the same direction through all the valves or you may get a banging at the valve where the flow is reversed from the others when it attempts to close. I had that experience on a large system in Europe.

World Plumber

Re: Backwards

The water need to go through all the radiators the same direction. They had another guy move some of my lines to put in a walk in cooler. He got them reversed when he hooked them backup. While I was back here in the states. When I went back and started the system up we had a heavy banging coming from that area. Once I realized the radiator was heating up from the return side and switched the piping everything worked well. Just make sure the water flow is into the valves and you should be OK. The one with the banging the water flow was from the radiator into the valve. All the others were flowing into the valve from the piping. I have over 70 of them at the camp and the all work great. It's hard to use t-stats with 30 inch granite walls. And 18 bedrooms in one building.

Unknown

Why?

What would cause the banging on a gravity system with NO PUMP?

Unless you add a pump to the gravity system, the gravity powered loop shouldn't bang, no matter which way the water flows.

Noel

World Plumber

RE: Banging

Without pumps there won't be anything to make it bang.
The one with the reversed flow was forcing the valve open then the spring would slam it back shut.
Be sure to read the instructions some of the valves must be installed on the horzontal or they won't work right. This might be more critical on a gravety system as there won't be any pressure to move the valve.
Mark

Mike T., Swampeast MO

It seems bizarre, but with gravity systems, given similar sized rads, the higher the radiator served the smaller the pipes leading to and from. The reason is that elevation of a radiator above the boiler is the MAIN driving force of gravity circulation and they had to use smaller pipes on higher radiators to essentially force the water to flow through the lower rads. Some especially "tricky" piping was often used for 3rd floor radiators to keep them from overheating.

This is the complete opposite of forced flow systems where higher radiators are typically further from the circulator thus having more restriction to flow and thus often needing larger pipes.

Paul Pollets

BTW...

TRV's won''t work on a gravity system unless the system is converted to forced circulation by adding a pump and "pumping away".

TRV's can be sized 1/2" to 11/4" and are placed on the supply inlet to the radiator. Larger TRV's are not available in N. America

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Don't tell my customer that.

It's been working since the last century without a pump, on a Tarm wood boiler.

Noel

Paul Pollets

Huh?

are you saying the system has TRV's and is running without a pump?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Yes, by design, from scratch

Noel

flip_3

lots of great info here but still not sure if the investment would pay off for the customer. or if they will work without converting to a pumped system

chris_93

trv and constant circulation

Not too familiar with contant circ setups. I have a customer w/ an old house and cast iron rads. @ story house is all monoflow tees.
They want to separate the first and second floor rads. Am I better to propose a constant circ. setup with trv's. I would assume that the pump will have to run all heating season?
Seems like a waste of energy??
I'm familiar w/ sizing pumps, but how do I would I size the system pump for this setup?
Thanks,
Mike

Mike T., Swampeast MO

TRVs can be used with monoflow (diverter tee) systems, but you have to be careful as they will add some restriction across each rad that previously did not exist. Too much restriction and you won't get sufficient flow.

The most important TRV rating to consider for such a system is Cv. Cv is the amount of water (expressed in GPM) that can flow through the valve producing a pressure drop of 1psi. You want to look for the highest Cv rating. Before proceeding, I'd suggest that you thoroughly examine the system and contact manufacturers or reps. As Dan Holohan says, "If they say, 'Don't worry' [about TRVs in a monoflow system], WORRY and find another manufacturer or rep."

To be completely honest, I do not know how the addition of TRVs to a monoflow system would affect circulator sizing. I seriously doubt that you would add the pressure drop of ALL the TRVs. Something tells me that you would find the rad with the greatest flow requirement, calculate the additional flow restriction (with TRV) for that rad and add it to the total. Easy to say, but hard to do without completely reverse engineering an existing system. Presuming however that the existing circulator is well suited to the system and that TRVs with the highest possible Cv rating are used, I suspect that there would be no need to change the circulator. This may well be an exceptional application for the new, super efficiency, variable speed circulators operating in constant delta-t mode.

What type of boiler is to be used? Conventional? Mod-con? "Alternative" fuel?

World Plumber

TRV and gravity flow

I just went down and pulled a valve off the shelf read the sheets and went to the Danfoss web sight. I don't think it will work with out adding a pump. They have a chart for figuring the pressure drop through the valve. Min pressure drop is .6 PSI and max recommended pressure drop is 5 PSI. Gravity flow is not going to generate the pressure needed to operate the valve. You would need to put a pump on the system pushing out. The valves are directional so you need to watch you flow direction to them. If you mount the thermostatic controlers on the valves they must be horizontal. I would advise calling tech support at the valve manufacturer you intend to use. Danfoss has a sight at www.na.heating.danfoss.com Their phone number in Baltimore MD. 443-512-2066 You can use the valves but in my opinion you will need to install a pump with them or you WILL NOT GET ANY HEAT. I hope this helps.
Mark

World Plumber

Fixed capacity

You got my curoisity up. Danfoss has a fixed capacity valve for use with gravety system.
High Capacity Valves


Fixed Capacity Valves



Danfoss provides a comprehensive range of radiator valves with fixed capacity.

RA-FN normal flow valves are used in two-pipe heating systems.
Versions: straight and angled with sizes from DN 10 to DN 25 and horizontal angled with sizes from DN 10 to DN 20.

RA-FNE normal flow valves are used in one-pipe heating systems.
Versions: straight, right mounted angle and left mounted angle with the size DN 15.

RA-G (RTD-G) high capacity valves are used in gravity systems or in pumped one-pipe systems.
Versions: straight and angled with sizes from DN 15 to DN 25.

Mike T., Swampeast MO

I VERY seriously doubt that TRVs would work in a gravity system unless you convert to forced circulation. Most likely the boiler would short-cycle terribly at high limit and very little heat making it into the radiators. What's the problem with adding a circulator (or two if primary/secondary is required)? Fully TRVd original gravity systems are ideal for use with a single circulator and a condensing/modulating boiler. Contrary to popular notions, nearly all (or all) mod-cons can be used without primary/secondary--you just have to do some fairly simple math to verify that flow rates will be within the tolerance level of the boiler. With the possible exception of highly conductive radiant floors such systems operate with the highest possible efficiency [with a good reset curve of course ]

Mike T., Swampeast MO

The earliest TRV-like* system I've seen was in a mansion built in 1899. Tour home and it was slow that day and the guide let me wonder around the boiler room. While the house had electricity originally--even wall plugs--I don't believe electric circulating pumps were available. There was a windmill-like device that used flue gasses to circulate water, but if it was ever there, it was long gone.

*Instead of "modern" (and they date to the 1920s) TRVs, it used pneumatic actuators. Everything [appeared] to be sized to gravity standards and I suspect that the valves used had HUGE passages. While the pneumatic actuators seemed to have very little travel, they were quite large and likely packed quite a lot of power. Such systems are still made today, but are generally used only in industrial applications as they require a constant supply of BONE DRY compressed air. The tour guide had no idea how the compressed air was originally produced, but I suspect some sort of liquid was used.

While you could probably replicate such a system today, it would be extremely expensive. The worst problem would be finding an appropriate boiler. Modern conventional boilers lack tapping of sufficient size and you could utterly forget about a mod-con as they are all virtual drinking straws. You could move sufficient water through the piping and radiators under gravity power, but not through the boiler.

Frank Como

Tanless coils for steam boilers

Hi! Does anyone know of a distributor or manufacturer of tankless coils for steam boilers, besides the original manufacturer ( after market ) I would like to replace the tankless coil on my steam boiler. Thank you for your time . Frank at Franklin3@verizon.net