although the upstairs zone with panel rads emit lots of heat i notice a 50-70degree delta t when that zone runs by itself.
anyone care to diagnose? 

there are four rads, each with a TRV.  about 15 feet above the distribution panel. 

Your water temp is too high for the load. the TRV chokes back flow as much as necessary to modulate the heat output.

if you send it 150 degree water and it only needs a 120 average to maintain load, it will modulate to a 60 degree dt to get the average it needs. basically.

thanks rob,

so if i keep the trv's wide open it'll allow more flow to the rads and result in a lower delta t?

yes it would, but then your room temp will overheat because the TRVs can't do its job. alternatively you could, in my example, send it 125 degree water instead of 150 and it would modulate to allow for a 10 degree dt (same average temp).

That said I don't know why you think this Delta-T is important so I don't know how a big a deal this really is. the only concern I can think of is if you weren't piped primary/secondary, and/or you did not have a pressure bypass, you might exceed the max delta-T for your boiler heat exchanger, and/or it may be short cycling.

Or, if this radiator circuit is supposed to be your "high temp" circuit, it's telling you that you can run a lot cooler water. may be time to adjust your reset controller settings.

but if that's not the case, I would be perfectly happy with a 70 degree Dt.

thanks again rob,
it is piped primary secondary allowing pressure bypass (closely spaced t's) but sometimes there does seem to be some short cycling when the radiator zone is the only one calling for heat. b/c the zone is controlled by a t-stat that is not in one of the bedrooms with a rad i thought perhaps the rad trv's are closing but the t-stat still calls for heat-therefore the boiler kicks on, but not for long. sounds like i need to find a happy medium between t-stat and trv setting. or move the t-stat? any suggestions?

if you have a small zone that can call on its own (small meaning small load) then you probably want buffer capacity in the system. or you have to live with some short cycling.

a buffer may indeed be in the offing. there are two more zones (a low temp and another high temp for rads) to be connected so i've got lots more tweaking in my future.

now, regarding the reset controller setting; is that just a matter of reducing the target temperature for the boiler (which is factory set at 186degrees)?
am i right to think that if i target a lower temp that the boiler will happily burn longer and lower b/c the t-stats for the zones will be calling for heat longer as the delivered water will be cooler? thanks for your help.

what is the boiler, and if there are any additional temperature controls installed what are they?

tt solo 110.

it should have an outdoor sensor, and some parameter settings to change to give it an outdoor reset curve. You're wasting a big chunk of the benefit of this boiler if you are not using the outdoor reset feature.

i have it run but not yet connected. i gather that i should let the outdoor sensor do its job..

so rob, is that a correct assumption that i target lower temps to my zones so that the boiler can modulate down? i know i'm not getting condensing unless i run what, 130-140degrees? i wanted to get the kinks out by running higher temps just to make sure heat was getting delivered but now that i know it gets hot i suppose i let the outdoor reset do its job. so do lower temps=longer burns=more efficiency? i know that's a newbie question so excuse my ignorance. ;-)

yes, yes, yes. right now whenever you call for heat the boiler won't modulate until it hits that very high temperature. once you're up there though you have this slow flow situation and you're way outside of condensing.

on a time of year like this I would be shocked if you needed much more than 100-110 degree water to run any system. and it could be significantly less than that.

note this does not mean you will never short cycle again. load is load and minimum output is minimum output. If load is below minimum output, you will cycle, and with small zones you might get short cycles. But you can see what happens. worst case you might cut in a small tank or something.

thanks alot rob. i'm now experimenting with a much lower target temp and will see how that goes. i would be surprised if the load is satisfied quickly at the lower temp as the boiler seemed to cycle for a good long slow while at low fire when it was set at the higher target temp. again, thanks for your patience.