Partial TRV's on converted Gravity hot water?

Boilerpro_5

There would still be a thermostat in use, but with full outdoor reset it usually won't do much but prevent overheating during a party.

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=393&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Boilerpro_5

Can it be done

I would like to add some TRV's to a gravity hot water system we are converting to pumped with full outdoor reset and constant circ. The existing rad valves are stuck open so they cannot be adjusted. I was concerned that with the relatively small orifice of a trv that inadequete flow may be an issue with the wide open valves elsewhere.

Any Experiences would be help

Boilerpro

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

Mike T., Swampeast MO

Two homeowners I've corresponded with have installed TRVs only on the upper floor(s) in their gravity conversions and report no problems.

While I'm pretty sure one uses outdoor reset, neither use constant circulation.

How do you plan to stop the flow of heat to the non-TRVd rads when the areas they serve are satisfied?

Paul Pollets

Do em All

Replace the valves on all the rads with TRV's. You'll be easily able to balance the system. They will last another 50-75 years.

The pump will need a pressure bypass differential valve when using TRV's to extend pump life.

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

Boilerpro_5

I've got a couple that way

one using the old rads and a new system with all the convectors in the room with trv's....both owners love em! The one with convectors has radiant in all the baths and central hall under ceramic that just runs straight off outdoor reset. This house also has a large radiant floor under the kitchen and dinette that uses a TRV for control....also works well.

Boilerpro

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

Boilerpro_5

How big have you found for TRV's

Danfoss only makes up to 1 1/4 inch. For those big first floor rads 1 1/2 to 2 inch would be handy for simplifying changout.

Boilerpro

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

Steamhead (in transit)

I did mine that way

a couple of others too- works great!

"Steamhead"

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

[Deleted User]

Or...

a VS pump based on delta something...

Like a Wilo Stratos.

ME

Boilerpro_5

> Danfoss only makes up to 1 1/4 inch. For those

> big first floor rads 1 1/2 to 2 inch would be

> handy for simplifying changout.

> Boilerpro

>


See http://forums.invision.net/Thread.cfm?CFID=3202492&CFTOKEN=31080fe-ebfee900-ab20-4520-a67f-b5dbb3334fb2&CFApp=2&&Message_ID=239591&_#Message238969

Boilerpro_5

The size of the orifice makes very little difference to the heating rate, since

(a) a restriction over a small length (length of the valve body) makes very little difference to the flow rate; to cut the flow you have to have a long length of narrow ID; and

(b) even if there is a reduction in flow rate, this makes only a very little difference to the heating rate. Increase the flow rate by ten times, the heat output will go up only 10-20%.

So using a TRV is not a problem, as long as this is a too-hot room rather than a too-cold room.

Mike T., Swampeast MO

Install restrictor plates in the big plain valves in the common space downstairs. A hole the size of a child's pencil will serve at least 100 sf EDR.

Size the single circulator for 30F delta-t with 6" of head on top of the mod-con's HX. If you need more than 6 gpm it's large, leaky or cold.

Boilerpro_5

> Danfoss only makes up to 1 1/4 inch. For those

> big first floor rads 1 1/2 to 2 inch would be

> handy for simplifying changout.

> Boilerpro

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 393&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Boilerpro_5

Thanks for the info on larger valves

I understand the relationship between flow and heating capacity.....very nonlinear especially at 20 to 40delta tee range and at higher water temps. Cut flow from 20FDelta to 40FDelta with a 180F supply, you get about 90% of output. However, cut flow from 20Fdelta to 60F delta with 130F supply, capacity drops much more quickly because your return is now same temp as your air temp. Of course you are dealing with radiant emmitters, so everything gets greatly skewed at low temps....output remains high. However, when you are dealing with pressure drops measured in Milliches on converted gravity systems and inches in TRV's (CV about 2.8 ), I do pause for a moment and check for experiences. I expect that it will work, and with some of response from those that have tried can now proceed with much greater confidence. Thanks for all your help!

biolerpro