Add constant circ to existing system

Lou Miller

Hello all, and happy holidays.

I wanted to get my system to run on constant circulation with an outdoor reset and I'm not sure how to go about it. I currently have an oil fired Crown CT-5 boiler. There's 4 heating zones, and one for an indirect WH. There's a Taco ZVC406 and 570 series Taco zone valves that control the zoning. Would I have to scrap the current zoning controls in order to make this work? The house is heated by cast iron baseboard on 3 of the zones and copper fin on the other heating zone.

Constantin

Hmmmm....

If all zones are to be constant circulation, then my guess is that every zone will require it's own mixing system. That is, unless all your zones have the same heat loss all the time for every emitter (which is pretty unlikely, the sun, open doors, etc. will see to that, for example).

Doing this electronically in the basement may be more expense than its worth, given that micro-zoning via TRVs on the radiators, baseboard, etc. is possible. There is the decorators factor (i.e. having a bulb on the end of a radiator) but most homeowners don't even notice them.

I would investigate whether some piping changes would be required for TRVs on your emitters (i.e. that they are piped in parallel as opposed to series, etc.) but unless you have the need to control everything electronically, this is probably the KISS way to go.

With TRVs on the radiators, the OR controller could then be programmed to run with the water at slightly-higher than required temperature to satisfy the emitter with the highest BTU need in the house. Modulating boilers are ideal candidates for these kinds of systems as they can modulate their output to meet the needs as they change.

Lou Miller

TRV's aren't going to work for me. All of my loops are using the radiators as the piping (wanted to conceal the pipes in the basement ceiling for finishing purposes, so everything is in the joist bays). I have two split loops (1" common and 3/4" for the radiators) for the main living area of the house. Both loops go through mutiple rooms and there is about 80 feet of baseboard on each loop (roughly 40 feet of 3/4" on both sides of the loop).

The third loop is continuous copper fin, but that's the basement, and we only installed that to take the edge off, I'm not too concerned with the basement. So if I could avoid doing this on constant circ. that would be fine with me.

The 4th is a laundry area that is right next to the garage and there's a lot of heat loss there. The radiator in this area is too small as well. So we leave the zone valve open on this loop all the time effectively using it as a gravity system (if I'm using the right terms anyway). Within the next couple of years, we're going to build an addition in this area and use this loop for that addition. So constant circ is something I'd want there, but I don't really have to install it now.

I was hoping that I could possibly add a Taco PC700 Add-on Power Control, an outdoor reset, and some I-series mixing valves. I realize the cost would get up there a little, but I wouldn't mind the expense. Everything is really easy to get at to make the changes (everything is neatly tucked into our mechanical room), so the labor end shouldn't be bad at all. It's just figuring out what parts to use and then their cost. I have a decent understanding of basic systems, but constant circ and outdoor resets are something I know little to nothing about. I'll more than likely end up getting a pro to do the work, but want to educate myself first. I don't like doing any project unless I have a really good understanding of how things work beforehand, even if I'm not doing the work. If I'm confident I can do this myself though, I will.

Ted_9

con. circ

As far as I know, American and Canadian controls dont have a true constant circ option.

You can simulate this by adjusting the supply water temp to closely match the heatloss.

I use Tekmar reset controls and T-stats, but Taco may also be a good choice. I do like their I series mixing valves.

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Lou Miller

I'm only saying Taco because I'm hoping that their controls might work better (or be more compatible) with what is already there (Taco). I guess it shouldn't matter though...

clammy

taco i series

I have been given though to constant circ on baseboard jobs and ran into the same sort of promblems you are having .I have looked at the taco i series 3 way valves i believe you could use them for constant circ with variable water temp of course you would have a outdoor and indoor sensor for each zone and the taco valve and depending on you piping arrangement probaly a pump for each zone that's alot of stuff and alot of coin or just usea taco radiant mixing block which is just about everything but that has a little bit of a price tag to .There are alot of differnt things you could do except what type of price tag are you willing to pay .Plus please remenber you might need some boiler return protection also if your constant circ system runs below the boiler condensation temp on the shoulder months .down load the free heat loss calc and run you homes dimension on the program and find out what your homes heat loss is and then check your existing radition from thatmake sure you have the required radition then on the program check your indoor and outdoor temp you will be able to see how low in temp you can go and meet your loss on desing day .If your system is layout correctly that's one plus maybe get rid of the zone valves do a single pump correctly sized to handle all your zones open install throttling valves and balance your flows out and use a tekmar outdoor reset to vary your water temp don't forget about return water temp either .sorry if it's confusing peace good luck clammy

Ted_9

rmb-1

Clammy had a good idea too. The Taco RMB-1 (radiant mixing block) might be a good way to go. The control is made by Tekmar and the body is Taco.

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Lou Miller

Thanks guys. You gave me enough to get me started. I'll call around and get some input from sales people on both the Tekmar units and the Taco units. I'll run the heat loss program too and see what I come up with.

I'm a little concerned about the return temps with my cast iron boiler. All of this might not make sense for me...

Ted_9

boiler protection

Taco I series and RMB-1 and Tekmar controls have boiler protection.

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Constantin

iSeries is interesting indeed...

... I'd like to hear how you did it when you're done and how much you end up liking it.