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Joined on August 20, 2009

Last Post on February 28, 2014

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@ January 15, 2013 2:22 PM in High delta T, how to adjust it?

-purge the long loop and make sure flow through the entire circuit works smoothly and cleanly.

-close the bypass, and see if return temp stabilizes once the rooms heat up. seems unlikely you'd need a bypass here in the end, you probably aren't going to have a 40 degree dt in stable operation.

I wonder if you have a "bullhead" return where both circuits face each other where they reconnect on the return. if so you might be checking flow in one loop with flow in the other. that's a small piping change.

it seems doubtful

@ January 15, 2013 1:47 PM in High delta T, how to adjust it?

that someone ran the system for seven years with a non-heating loop?

regardless, even if it never did, the choice of a 007 is definitely not your problem and you can definitely heat this house with that pump, if it can be heated with this radiation in this piping configuration. as long as the pump isn't bad, of course.


@ January 15, 2013 9:54 AM in High delta T, how to adjust it?

ok, the system worked and then it didn't. the problem is not circ sizing.

basic sanity should also confirm this. while you might not hit a magic 20 degree Dt, this circ is VERY capable of delivering better than 60 degree DT. you have a flow problem. it is not related to circulator SIZING. you could not possibly have an undersized circulator to the point of a 60 degree DT.

you either have a bad circ, bad balancing strategy, clogged valving, or some other flow restriction/balancing problem.

you most definitely do not have an undersized circ to any degree that you should be concerned with.


@ January 14, 2013 11:11 AM in Baseboard, runtal, buderous??? Switching from forced hot air to hydronic!!!

is sure slim. but it's very low output and most homes will need high temps to use it without supplemental emitter capacity.

I would almost always choose something that can operate at lower water temps.

Panel rads are good. but if drywall is coming down, consider radiant ceilings! might be cheaper in the end if low temp is the goal.


@ January 11, 2013 4:47 PM in High delta T, how to adjust it?

but with a 60 degree DT, you'd be pushing 30,000 BTUs per GPM. so with your boiler as the high limit on output, you'd be stuck at about 4 GPM max or you're breaking the laws of physics.

but it's worse. with a 150 average temp in your baseboard, you're down to 380 BTU/ft. or 38,000 BTUs, or about 1.2 GPM max. whatever your pump can or can't do here, it can certainly pump more than 1.2 GPM through 2 circuits of baseboard.

unless it's clogged. or broken. valve it off, pull it out, and try a hose and bucket flow test maybe. if you're pumping toward the boiler, might be able to experiment with short dead head and the pressure gauge to see how hard it's pushing..


@ January 11, 2013 4:02 PM in Misc questions on radiant

I like warmboard too. gypcrete is good but warmboard is more conductive and faster to respond.

if you want to do radiant cooling, however, that generally means you want tile floors, radiant ceilings, or supplemental fancoils in select areas. all depends on solar gain, really. You also need a supertight envelope and an ERV ventilator... still have fresh air ducts. but they are very small. Radiant cooling can be done but load calculations are a must and a designer who understands the limitations is a must.

second time today i've had to post this but we are doing it with a daikin altherma, air to water heat pump. like geo without the dirt work and massive upfront costs. can be very cost effective if it's displacing a boiler as well as a cooling compressor. not sure if there are trained installers in your area though, you'd need to check on that.

not to disagree with other posters

@ January 11, 2013 3:49 PM in Design opinions...

but I'm gonna. we're net zero with PV and even without our additional grant, just the 30% federal payback was less than 15 years. in our case we had a 6 year payback. where are you? local incentives may change it too.

If you're going to go with offsetting with PV heat pumps are a must though unless the load is tiny. We are using air source in a -4 deg F area and it works great. we're Daikin Altherma powering radiant heating/cooling (does have built in 6kw electric element, our heat load is 33kBTU/hr at design).

minisplits are a great option as well for many people. all air source are especially great if they are "away a lot" because cooler water temps/air temps really help COP!

GSHP pretty much only if you can "pump and dump".

100kBTU for a 3000 sq ft house ... either this house is horribly insulated or your numbers are high. with electric installed I doubt that it was horribly insulated... this was energy crunch time, it's probably very well insulated? in any case I would expect 60kBTU or lower in MOST cases.

inadequate heat

@ January 11, 2013 3:42 PM in High delta T, how to adjust it?

and high delta T USUALLY says to me flow problem. even if your current pump is undersized this delta-T is extreme.

I would guess air problem. most especially if the system has been opened for any reason recently. would be solved by a good purging in most cases.

not yet

@ January 2, 2013 2:40 PM in Transfer plates - C vs inverted U


get a sample

@ December 27, 2012 11:13 AM in Transfer plates - C vs inverted U

of any plate you want to buy.

I'm not that impressed with the tubing groove in those C plates. not very solid contact from what I've seen so far. but I should be getting a full size plate soon to check out.

contact is king. if the plate needs silicon or whatever it's not a very good plate.


@ December 14, 2012 1:33 PM in help

if the boiler is still warm and injecting heat, delta-T across the radiant loop should be pretty constant. once the loop cools it gives up heat more slowly though and your delta-T will shrink.

no need to change your mix parameters upward unless you were unable to maintain room temperature before. the cycling reduction is from the boiler min change, most likely.

your boiler min should be 140.

there are many delta-T's here

@ December 14, 2012 9:42 AM in help

boiler loop, it's firing differential, injection loop, radiant loop.

please describe which one you're talking about?

what you want

@ December 13, 2012 2:19 PM in help

is low speed injection, lowest speed radiant that works.

you have small zones and a non-modulating boiler. that's a recipe for cycling. might want a buffer tank. however you also have settings on the 356 that can help, such as the boiler minimum setting. If you raise that the boiler will fire longer as long as you haven't satisfied your demand in the meantime.

probably want a small buffer tank though if cycling is a concern.

hold your horses

@ December 13, 2012 2:10 PM in First Winter with TT Solo 110

if you are going to direct pump this boiler to the zones, you better be sure your smallest zone will take at least 2 GPM, which is the bare minimum TT wants to see going through this boiler to avoid rampant short cycling. 30 dt on minimum fire.

usually you need a bypass. modulating pumps, not a good idea in this case, unless you are primary/secondary OR very sure your smallest zone has adequate minimum flow.

I have no idea

@ December 13, 2012 2:04 PM in First Winter with TT Solo 110

what chris is on about here. those are closely spaced tees. they do not have to hit the pipe from the same axis. the elbow a few inches away reduces their effectiveness, but the pressure drop between the two tees is practically zero. You are basically hydraulically separated and you do not have any piping problems i can see here.

even the expansion tank is not a problem. as long as you do not have a significant pressure drop between the suction of the pump and the expansion tank you are "pumping away". Such as in this case.

you are overpumped. this is why zone by pump systems are not as efficient as zone valve systems. end of story.


@ December 12, 2012 2:07 PM in Bobcat boiler/Rad/Radiant System mixing valve issues

I'd cross your fingers that the valve is backwards. that's a one time fix.

really nasty water is a bigger issue for your boiler and all the other valves and such as well. then you want to consider dirt separation and maybe cleaning/treatment of the system.

you can

@ December 12, 2012 11:37 AM in Bobcat boiler/Rad/Radiant System mixing valve issues

try purging through it with cold water and see if flow occurs.

or disconnect and see if you can see through it, blow through it, flush through it, etc.

they don't stick often IN CLOSED SYSTEMS, unless again you have really nasty water with gunk in it, typically from standing cast iron radiators or other "high particulate" sources.


@ December 12, 2012 10:56 AM in Bobcat boiler/Rad/Radiant System mixing valve issues

if you want to kill your boiler.


@ December 12, 2012 10:53 AM in Bobcat boiler/Rad/Radiant System mixing valve issues

have H and C reversed, it would cause the kinds of problems you're talking about. you'd basically have a closed leg at that point. these valves DO have very significant pressure drops, so your behaviour when the valve is open is completely predictable (and is what I said was probably going to happen earlier in this thread, self pat heh)... but when that valve is closed if you are NOT pulling water through the valve at all, it's either busted, clogged, or backwards. Especially if you do get flow through that zone when the end of the header valve is open.

it's pretty unlikely that the valve is busted on a closed system. so that leaves clogged or backwards. Clogged would only be likely if this is a really scrungy system... existing cast iron radiators with really nasty water, maybe?


@ December 12, 2012 10:30 AM in Bobcat boiler/Rad/Radiant System mixing valve issues

you have installed the valve backwards. you would not be the first to do that.


@ December 10, 2012 3:40 PM in Bobcat boiler/Rad/Radiant System mixing valve issues

I don't think you should remove the mixing valve: you almost definitely need it here.

the only question is whether it should be on all radiant or just the slab zones.

the chances that those radiators will run at temps good for your slab are pretty small.

foil is foil

@ December 10, 2012 2:35 PM in Bobcat boiler/Rad/Radiant System mixing valve issues

it's not really insulation. not very good insulation anyway, even though it has "radiant" in its name it's generally not adequate by itself. If you have access, add real insulation under it: R15 between heated spaces, 25 over tempered space, 35 over unheated space.

the point I'm making is you don't really know what your situation is. you can move stuff around and then find you are still in a problem zone, because you aren't planning this out with real information. real information in this case is a room by room heat load and analysis of the emitters. as long as you're fine with moving things around on that control panel "until it's right", so be it. but that's the price you pay.
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