TRV sizing for old HW system with big pipes

Al Roethlisberger

Thanks Paul,

Yes, I realize(and dread) trying to retrofit the smaller valve into the space the old 2 inch manual valve formerly occupied.

So it would be ideal to find a true 1 to 2 inch TRV.

You mentioned finding some European TRV valves that will fit this larger size. Do you recall the manufacturer and/or models so I can research?

Thanks
Al

Al Roethlisberger

TRV sizing for old HW system with big pipes

I've posted a variety of questions about increasing efficiency of my old ca1929 overhead gravity system that was converted to a sealed circulated system in 1991.

One of the many recommended approaches to manage the efficiency of the system was the strategic use of TRVs.

Well, I've been researching this for a while, and one of the challenges I have is that in most cases my radiator supply/return piping(and hence the radiator valve) starts at 1 inch and goes up to 2 inch.

After calling around to manufacturers like Myson, Danfoss, and Honeywell, it appears that the largest high flow TRVs are the Honeywell V100 series that goes up to a 1.25 inch size.

So my question, given that my system is now forced HW versus purely convective/gravity fed, would it be a problem to install and step down to the 1.25 inch TRV units on some of my radiators that currently have 1.5 or 2 inch return pipes?

Honestly, most of my "problem"(over heating) areas have smaller pipes that I think the Honeywell will fit exactly, but a handful are of the larger 2 inch variety. I wanted to see if fitting the smaller valve would likely cause big problems with the radiator heating properly.

Thanks,
Al

Paul Pollets

It would be nice...

to change all the valves to TRV's for optimimum performance. You could re-pipe the 2" valves to 1" and still heat the radiator, however you'll find the valve rough-in size changes everything. It is impossible to install a new 1" TRV valve body where a 2" angle valve existed without serious modifications of the risers and laterals. It simply won't fit, unless you do.

I've ordered metric valves from Europe in 11/2 and 2" size for remodeling historic homes...they work and will fit on US pipe threads if you know what you're doing.

The radiator has a certain BTU load, depending upon its size. A 10,000BTU radiator can be fed by a 1/2" valve. A 30K BTU radiator can be fed by a 3/4" valve, and so on. In a gravity conversion, the small radiator valves may not look "right", but work.

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Mike T., Swampeast MO

Absolutely no problem using a smaller TRV body. The 3/4" - 1 1/4" TRV bodies typically have identical flow ratings and are more than adequate for the largest rads.

Al Roethlisberger

Thanks Mike.


Thanks

Mike T., Swampeast MO

Nearly all TRV manufacturers make bodies in 1/2", 3/4", 1" and 1 1/4". To my knowledge none make anything larger than 1 1/4".

Tunstall does however make conversion kits for your existing hand valves of any size. While more expensive than a standard TRV body, they can prevent some serious piping headaches.

If you do convert your larger existing valves, make certain that the appropriate TRV operator is used! The TRV operator will be vertical and most if not all TRV operators need to be horizontal in order to sense room temperature properly. By using a remote sensing TRV operator (the room temp sensor is attached with a tiny capilliary tube), you can orient the operator in any direction.

Al Roethlisberger

Very very cool...


Thanks so much, this may be exactly what I am looking for.

I'd love to keep the old valve bodies, for aesthetics and the aforementioned piping challenges.

I'll definitely give them a call.

According to their website: http://www.maconcontrols.com/about.html

"Tunstall E-Z Fit conversions can be engineered for all manual radiator valves. Sample may be required. "


If accurate, you just can't beat that!

Thanks again!
Al

Mike T., Swampeast MO

From reports hear here, that statement is accurate. Cost however is likely to be several times that of an off-the-shelf TRV body.