Adding DHW and rebuild of hot water system

jabbott

I live in a one hundred year old house in Wisconsin. It is a big old house, the main part of the house is about 4500 sq ft. It has seventy six single pane windows. There is a 1700 sq ft third floor that is currently unheated. I might want to do something about that some day. The house has a new (1997) addition about 800 sq ft, we use as a home office. I added some slantfin to the office, otherwise it is heated with a gas fireplace insert. The kitchen is good sized and is heated by a freestanding gas stove. It has a poured concrete floor that is about a foot thick over a garage. I would really like to put radiant floor heat in the kitchen some day.



So I guess that is the lay of the land. In past years I have heated the house with bio fuel. But this year the bio fuel boiler sprung a leak. We tried to switch to gas, but the gas boiler had not run much in the past few years. When we tried to fire it up it didn't run consistently. We decided to take advantage of the rebates this year. We bought a new Munchkin 140,000 but boiler.



When we got the boiler, I pretty much just plumbed it in. It was about -10 and even with the gas and wood fireplaces running the house was dropping about two degrees every hour we were offline. So it was sawzall time and then I just plumbed it. We limped through the winter getting some convection into the main house zone when we ran the office zone. I am sure it wasn't the most energy efficient setup. But we made it to spring. Now I would like to re-plumb the whole thing.



I am just about to buy a HTP SuperStor DHW that I would like to tie in. I have been picking up zone valves on Ebay and got a good deal on a Taco ZVC406-EXP zone control the other night. I am thinking of building the zones with the zone valves even though they might not be hooked to something right away. And, from what I understand, I can add a second zone controller for those zones in the distant future.



I would like to start with four active zones. The main house, which is going to be a huge zone. Zone two, the office. Zone three, the garage under the office that I would like to put some slant fin into and keep it above freezing. And, zone 4 the garage under the kitchen that I would like to keep about 50 …because my Harley likes to be nice and warm. :-) Makes it more comfortable to go down and sit on it and dream about the summer too. Now that zone will only have one large cast iron radiator so I am a little worried about short cycling.



So I think I have a fair handle on what I am doing. I have three pumps in the current system and I think I can do the new setup with three pumps. Are there things I should be considering? I made an initial design that included a differential pressure bypass valve, but talked to a guy who knows a lot about this stuff and he felt they are expensive, trouble, and not needed on a well done design. …But, was a little sketchy on what constitutes a better design.



From the picture, think about if I added one more pump in front of the DHW which I forgot to put into my design. What are your opinions?



--ja

Gordan

A better design

The Munchkin can control a separate DHW circulator, right? If so, the better way to pipe in the indirect would be directly from the boiler loop, with its own circulator. When DHW calls, the Munchkin gives it priority and runs the DHW circulator but not the boiler circulator.



Depending on the details, there might be two reasons why piping in the radiant floor the way you have it illustrated could be an issue (without further refinement.) Firstly, radiant panel loops tend to have a considerably higher pressure drop than baseboard or radiator circuits, so balancing them may be an issue. Secondly, radiant panels tend to require considerably lower water temperatures.



As far as the DPBV is concerned, it is required with a constant duty circulator to prevent velocity noise and erosion when only a low flow zone is calling. If you replace your system circulator with a differential pressure ECM circulator such as a Wilo Stratos or a Grundfos Alpha, you shed the requirement for the DPBV and gain a lot of electrical efficiency in the bargain.

Roland_18

DHW

Just a comment on your choice of SS ultra. I have one on my home system and have had no problems save one. If your water has iron/rust/minerals in it, these will depost inside the tank and possibly on the coil, reducing it's effectivness. Flushing out the s.s.u. is not so handy as there is no access from the outside. If you have not yet purchased the s.s.u., investigate tanks that have ports large enough get a garden hose into for flushing/inspection.