radiator thermostats

g. wilson

I've learned from a heating professional that there are thermostats (in Europe) that can be installed on individual radiators to control the hot water flow. TXV.
Sounds like an excellent problem solver for this 2 family northern house. Cant find info including sources and prices and practicality. Can you help? g. wilson

Brad White_9

Here are a few

Macon Controls (Tunstall Associates in Western MA), Danfoss, Oventrop, Honeywell-Braukmann (larger than the others for some reason).

Personally I have Macon in my house. I like the Allen wrench spud installation feature (short for close quarters) and the general fit and finish. The heads are pretty small and like most, very accurate. Made in Sweden.

TRV's are incredible and sadly under-used.

John Ketterman

This is not a secret, they are freely available in the US as well, but people don't use them because they are not required by law as they are in Europe. They are called thermostatic radiator valves (TRVs). In fact they are wonderful things.

Well, they are wonderful IF the TRV is not the same room as the thermostat for your boiler (no point having two thermostatic devices in the same room), and IF it is hotter than you want in this room. The valve can only reduce flow, it can't increase it.

Danfoss is the most common brand.

As for sources and prices, they are available for purchase over the web (google it), and prices depend greatly on pipe diameter. You need a body and a controller; total may be $30-60 (edit: more like $60-90). Although I am a homeowner and I have put them in, most homeowners are not likely to do the research. That's what professionals are for---they already know how to do it. If you do several valves at a time, you might pay around $200/valve (edit: maybe more).

bob young

trv

do trv work well in a h.w. monoflow system ?

Brad White_9

Beg to differ on $

The valve thermostat (head) alone may go for $30 to $45 with the remote sensor types 50% or more above that. Valve bodies go retail for somewhere in the $50-$75 range depending on size and pattern. Still a bargain!

Brad White_9

Yes absolutely

Because the branches are in parallel, each radiator can have individual control with minimal effect on the others.

The Cv's of TRV's are about 1.8 for the 1/2" size and 2.5 for the 3/4" size, meaning very low pressure drops. A typical 1/2" TRV serving an 8,000 BTU radiator (0.8 GPM) will have a pressure drop of less than half a foot of head. The 3/4" will have a pressure drop at 1.0 GPM (10,000 BTUH in one radiator!) of about 3/8 of a foot of head.

Cool.

John Ketterman

Your right about the operator: https://www.statesupply.com/displayItem.do?sku=DC1020

Valve bodies start at around $25 for 1/2" pipe, though: https://www.statesupply.com/displayItem.do?sku=DC1045

In any case my estimates were indeed too low.

johnnyge

what about steam radiator. is there anything similar for them. I have in my a few Varivalve. to control the steam flow. Is there anything more accurate to control the indivual room temperature.

Mike T., Swampeast MO

Definitely usable on monoflow systems, but two-pipe is preferred.

Check out this document from the "Library" here at Heating Help.

Mike T., Swampeast MO

Yes, TRVs can be used for both one-pipe and two-pipe steam systems.

With one-pipe it replaces the air vent. The TRV body should have an integral vacuum breaker.

With two-pipe it replaces the radiator valve.

Do be aware that TRVs cannot "call" for heat. ALL they can do is THROTTLE heat to maintain your desired setpoint regardless of internal or external gains or losses.

With water, they're best used in a system with true constant circulation of heated water. With steam, a weather-linked, well-adjusted "heat timer" or a "control" space with wall thermostat is needed.

Mike T., Swampeast MO

See why it's not good to mention prices in a public forum?

John_102

Please expand

Hey, Mike -

For the uninitiated (me, anyway), please expand upon

"With steam, a weather-linked, well-adjusted "heat timer" or a "control" space with wall thermostat is needed."

TRV's are in my future, I hope. I'm just trying to understand what you're saying & what my system needs.

Thanks.

Kniggit

missed a brand

I have seen and installed Ammark, they are nice, and they do offer a true one pipe steam radiator valve, if you search you could find it. Looks really promising, but I haven't had a chance to sell one.

K

ALH_4

and

Caleffi also makes them in Europe and last I heard they were considering bringing them over from Italy if there was enough interest.

Radiators with TRV's and modulating condensing boilers are the future of residential hot water heating in my opinion. They're the present in Europe, and for good reason.

-Andrew

Brad White_9

Well....

I do think it is OK to state publicly available retail prices (all can be checked and one can see the range). But I do defend keeping contractor labor and total package prices confidential in all but the most generic terms for the "cost of doing business in a given area" reasons.

Mike T., Swampeast MO

I don't work with steam, but have studied it a bit.

If you've used TRVs on all radiators of a steam system you still must be able to tell the boiler to produce steam--the TRVs are incapable of such.

In larger buildings, "heat timers" seem fairly common. They vary the length of and/or length between steam cycles based on outdoor temp. Probably too expensive for residential use, so you use a wall thermostat. The radiator(s) in the space with the wall thermostat [probably] should not have TRVs.

Controlling the boiler in a hot water system with TRVs depends on the boiler and the nature of the system.

Ideally you're using a condensing/modulating boiler with a rather tight reset curve and TRVs on all radiators. Anytime the outside weather is cool enough that the house needs heat, the boiler fires to maintain the reset curve setting and the TRVs do their job of throttling the heat--the circulating pumps(s) run constantly whenever any heat is needed. If daily setback of the entire structure is needed then ideally, the boiler will have a built-in timing program to reduce the reset curve during setback periods.

If the boiler lacks this provision you can use a wall thermostat if whole house setback is wanted without the requirement of manually adjusting all of the TRVs and/or reset curve. For normal operation the thermostat is set higher than any space temp required in the structure. For setback, reduce the thermostat setting to the approximate temp you want to maintain in the house. (Note that the TRVs will NOT be modulating in such a case so make sure that the setting isn't so low that some areas get too cold.)

If you're using a conventional boiler, I still believe it best to use constant circulation, TRVs on all rads and outdoor reset. Of course you do have to concern yourself with condensation due to low system temperatures. (Old original gravity systems with typically oversized cast iron boilers seem nearly immune to condensation problems, but their efficiency plummets in moderate weather.) You can use the same thermostat strategy for whole structure setback if desired and a warm-weather shutdown control is a WONDERFUL and inexpensive addition.

If you have a conventional boiler and are not using outdoor reset with the TRVs, it's probably best to omit the TRV from one radiator and put a wall thermostat in that space. Such space must be chosen carefully--ideally it will be a bit under-radiated compared to the rest of the rooms.

In old multi-floor homes that have been insulated, it's not uncommon to use TRVs only on the top floor as they tend to overheat relative to the lower floor(s). This is particularly acute if the only added insulation is in the attic.

If TRVs are used on ALL radiators a device called a "differential pressure bypass valve" MUST be installed on the system. This prevents the circulator from "dead heading" in the even that all of the TRVs are closed or nearly closed. It can also be used to provide some continual bypass if you adjust it literally "by ear". This can be useful for converted gravity systems with reset as you can find a "sweet spot" where efficiency as measured by total firing time during a period (say an hour) of nearly steady outdoor temp is minimized.

John Ketterman

Exactly. You can't prevent people seeing retail prices on the web, they can do that in a minute or less via Google.

But we need to make sure they don't find out the discounted contractor prices we actually pay the supply house.

John_102

Thanks

Thanks, Mike, for your thoughtful answer. I'll let this simmer in the old brain a bit.

Without hijacking this thread, I'll say my house is a 100-year-old, moderate-to-largish house with a 35-year-old lp-fired boiler limping along. The ground floor is fairly open, while the second floor is mostly compartmentalized. The two-pipe steam system was needlessly complicated (I think) with zone valves & a receiver & pump.

I'm slowly learning enough to be an educated consumer, thanks to the Wall. Thanks again, Mike, and thanks to the many other knowledgeable contributers here.

John_102

Pricing

As a HO, I would HOPE you contractors get discounted pricing not available to me. How else can I expect you to stay in business & provide your expertise? I suppose there are those foolish enough to think all should pay the same price, but be assured that many of us want a good job performed at a reasonable price, and that we know 'reasonable' includes your profit as well as our savings. As the saying goes, the cheapskate pays twice. Maybe a lot more....

[An added edit] My words have been bugging me all day. Obviously there are loads of people who have no conception of the way business works, and a load more who don't think the rules apply to them. There are however a fair number who DO understand you need to pay a few bills yourselves. I have great respect for talented, qualified tradesmen & fair distain for the hacks & crooks. I've dealt with both & the latter group gives me great respect for the former.

Thanks again & peace to you.