Looking for some input on distribution

[jeffesonm]

Now that storage design is solidified, the next phase of my boiler planning is sorting out the heat distribution.

Current setup is two zones which seem grossly out of balance and an oil boiler with a pump of unknown size. I figure it its strong enough to circulate through zone 1, it's got to be blasting water through zone 2, which is supported by the extremely loud creaking and popping I hear from the radiators when zone 2 valve opens.




For my new setup I was inspired by the simplicity of Noah's constant circulation with ODR setup. While I don't have radiant emitters (yet) I do have way more baseboard than needed which I'm hoping will allow me to run lower water temps and get more out of my storage. I'd like to split the big zone in two so I end up with three roughly equal zones. I'll ditch the zone valves, go to constant circulation and use a 3-way Taco iSeries mixing valve with ODR to vary water temp to match demand.








In the little spreadsheet, calculations are based on 180 water. In the big spreadsheet, the flow/head calculations are based on the BTU/hr needed to match heat loss but if I understand the Taco circulator selection PDF, that is really just the minimums required to move that amount of heat... targeting 2-4 gpm flow in all zones at all temps seems like it would work. Also min supply temp is really min average supply temp.

In terms of balancing the system, rooms with more baseboard/sq ft will be warmer than those with less... same with those at the beginning of the zone vs the end. I'm figuring I can plumb the rooms with less to get heat first and maybe it will all work out. If not, I can pick the next highest ODR curve and wrap some foil around the fins of the hot room. If whole zones are too warm, maybe I can throttle down flow with a ball valve?

For the oil boiler backup I will keep the thermostats and bypass the mixing valve, straight to zones. Heat loss calcs are some estimation, some experience. Over time I hope to improve insulation to reduce load and add radiant in different parts of the house.

I've crunched lots of numbers and on paper at least this seems like it might work, however I also read this article and just math doesn't cut it. Also apart from the published output charts (which I used in these calculations) I couldn't find much practical experience running low temp baseboards.

Looking for some input from the more experienced on potential pitfalls.

 

[willworkforwood]

First I'll give you an answer on running low temp baseboard, from my own 6 year experience with standard hi-temp baseboard distribution and a wood boiler. I run without storage, but have become very familiar with, and am highly aware of water temps. I have a number of thermometers on various pipes, and have come to "think" in terms of BB water temp. On many less cold days we run the boiler more like a wood stove, and frequently have a small fire going which produces water temps of 150-170. Having been through every possible variation of weather condidtions, I can tell you for certain that if the BB water temps are matched appropriate to the heat requirement, these lower temps will heat the house just as effectively as 180-190 temps will on a cold day. And the heat requirement varies constantly. As I write this, it's 14F outside but with full solar gain. The the BB water temp is currently 155, and the house is at the typical 73F that it almost always is. With full sun today, I'll shut the boiler off for a few hours, and then later relight the fire and produce water temps of 170F or so for a short period of time. But tonight the boiler will have a good fire and send the 180+ temps that will be needed througout the upcoming cold night.

Next, I'm wondering why you are planning on making extensive changes to your distribution system, before having any experience with your new wood system. It's hard to determine from what you wrote exactly what the current problems are (if any). You wrote: "Current setup is two zones which seem grossly out of balance". But what is the actual heating situation? Are some areas of the house too warm, and others too cool right now? I suggest that if you have no major problems (other than paying for oil), why not leave your currently distribution system intact, and get a year's experience running with wood heat. Your learning curve will be mainly when to recharge storage, and what temp to bring it up to. And this will be determined by how low the storage can go and still heat the house adequately. Every day is different, and there's lots of trial and error before you completely get the hang of it.

I'm not questioning that your proposed change wouldn't be better, but will it really be necessary? And again with radient; based on near universal opinion, is superior to BB. But the question is will your actually need it? Now if you simply want the better comfort of radient, and have the $$ to get it done, then that's a different story. But that consideration aside, I'm thinking that perhaps your current system may do just fine, once you no longer have to constantly keep the temps turned down in order to burn less oil. Your heating pattern is likely to change (for the better), once you are burning wood. Not trying to be critical of your plan - just giving you a perspective of what changing to wood heat can mean to you.

 

[jeffesonm]

Good to hear your experiences with baseboard. I am looking forward to greater comfort with this setup, along with making fires less frequently (vs current wood stove).

As for the zones, I started by using the Taco circulator selection PDF to calculate the head loss and flow requirements for the two zones as they exist today. It seemed difficult to find a pump that would satisfy 6 gpm @ 21' head without being way oversized for 3.5 gpm @ 3' head. All piping is easily accessible in the unfinished basement, so for the one time cost of $50 in copper and the minor inconvenience of sweating a few more pipes, I can get by with one smaller pump and run it at low speed. All the zones start/end at about the same place, so reversing flow is just a matter of deciding which end to connect to supply and which to return.

I also like the simplicity of controls in this setup. Distribution: circulator always runs and ODR adjusts water temp according to demand. Supply: EKO controller runs boiler circulator, charging storage until the fire's out. Me: build fires when needed with as much wood as needed to keep storage charged.

I plan to add radiant under tile floors when I remodel the bathrooms and kitchen in the future. Supplemental heating would nice but it's really for warm feet.

 

[willworkforwood]

Have you considered replacing with an Alpha, or other ECM pump? The auto detect setting is usually the best of all worlds.

 

[jeffesonm]

Yes I have been looking at the Alpha and Bumble Bee. I do intend to use them in the new setup... should pay back relatively soon, especially with constant circulation.