controls with trv

singh

Thanks for your reply.

I have two upcoming systems that are all panel rads.
One will be two GB 142s, and Buderus panel rads.
The other will be two TT prestige.
Two make things more interesting , the buderus job may have home automation also.
The TT job has fireplaces in each room. Not really a good location to place stat anyway. Panel rads will be on 1st and 2nd floors, TRVs on all rads, never liked them without them , never found a cover for the end, just those little red caps.

I am considering a 508 with an ODR . Disable air sensor, place in boiler room and connect to a sr501 to turn on circ.

With the buderus considering all tekmar,265 and em10s for GB , 335 for zone mangement with 480 user switch for remote automation control, have end switch from 480 to go into 335, to turn on circ zone with panel rads.

It just seems that even though these are "european" boiler systems , controls for such seem less than straight foward.
I do like the the idea of putting a stat in the least radiated room. What about disable air , use a slab sensor knowing that it wont be satisfied unless some solar gain hits the sensor. I'm pretty sure I'm over thinking it,

Thanks.

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WV EGBERT_2

without

the common thermostat on the wall. Best ways to control rads with trv's. Cost and simplicity of controls important.


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Unknown

TRV & controls

Individual TRV's replace room thermostats, since they are self contained with a sensor and actuator built in. The additon of a basic outdoor air reset system is a great way to maximize their effectiveness. Honeywell has the AQ2000, Tekmar and others have similar systems. Some boilers have a built in reset. Think of it as "cruise control for your house". The system looks at the outside air temperature, and varies the water temperature to match. The colder it gets outside, the hotter the water is, and vice versa. All automatic. The combination of TRV's, panel radiators, constant circulation and outdoor reset is very common in Europe.

WV EGBERT_2

Looking for specifics, a way to actually turn the circ on, not sure if I want constant circ 24/7 with warm weather shut down.
Indoor reset control would be ideal.



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Mike T., Swampeast MO

The simplest way to control a fully TRVd system is to run the circulator anytime that the outside temp is low enough that the structure requires heat. In other words your warm-weather shutdown locks out circulation (and the boiler--if possible) when the outside temp is above say 55F - 60F.

An extremely crude form of indoor reset can be introduced by omitting the TRV in one room that contains a conventional thermostat. Such room is ideally the least radiated (with regards to the room's heat loss) in the structure. This ensures that a heat call continues long enough for all of the TRVs (when untouched) to be satisfied.

Could you be more specific about your intended application? What sort of radiators? Conventional boiler or modulating/condensing? TRVs on all radiators or just some? If a mod-con boiler, which brand and model? (This matters are the built-in control philosophies can be VERY different.) Some are designed with TRVs assumed, others aren't.

Mike T., Swampeast MO

For the Buderus GB job (and assuming TRVs on all radiators), I would suggest using what used to be the only form of reset available when it was introduced in the U.S. -- indoor via the dedicated, protrietary Buderus RC-1 control. Such does however require a bit different way of thinking both on yours and the occupants parts.

Such resistance to change is--I believe--why outdoor reset for the GB is now standard issue in the U.S. (BTW, small--say no more than 10,000 btu design heat loss radiant zones can use FHVs in lieu of TRVs. Those with no more than about 100 sf--think bath--can use a floor temp modulating version of FHVs instead of air temp modulating.)

Placement of the RC-1 is CRITICAL! For general North American climates, construction and lifestyles I personally believe that the best location for such is an interior hallway without any radiator--in other words it's heated by the areas around it.

To understand why I find this placement of the RC-1 to be best you have to understand something of the control theory. The purpose of the RC-1 is to provide the lowest possible supply temperature suited to maintain space temperature. It is a reset curve adjuster--NOT a conventional wall thermostat!

Buderus would likely suggest that the RC-1 be installed in common space heated by TRVd radiator(s). Such turns this area into the master of all master zones. While great for solid masonry, exterior insulated structures in a comparatively stable climate, it's LOUSY for typical North America.

Put the RC-1 in an interior space WITHOUT a radiator and it becomes a heating curve/efficiency control--NOT a thermostat! Seriously--I would cover ANYTHING that indicates either actual room temperature or desired room temperature setting with such covers to be removed ONLY after the homeowners understand--by direct experience--what is happening.

Set the thing too low and you won't even be able to maintain your desired TRV settings in the rest of the house. Set the thing too high and you'll be able to raise temperature quite rapidly by cranking a TRV with the caveat that fuel bills may well increase. Somewhere in between, any but those who could care less about how much energy they pay for will find the happy medium between economy and versatility that best suits not only their lifestyle but their climate and construction of the home.

Design the GB system well using TRVs and FHVs (if required for radiant floor/ceiling/walls), intially set the RC-1, placed as suggested, for about 65F, covering any indication of setting and room temp and tell the homeowners to make increasingly fine adjustments--if necessary--to suit their lifestyle. Also suggest that the find AND KEEP the minimum TRV setting that gives the desired room temp suited for its use. If they want bedrooms cool--KEEP them cool. If they want bathrooms warm--KEEP them warm. If they want the ENTIRE house to cool down at night tell them to use the automatic setback provisions of the RC-1 in moderation. The more energy efficient the shell, the less setback.