Hydronic Heating Diagram Help for Novice

KevinCorr

No time to inspect your plan but at first glance I would say you should have a real gas boiler instead of the hot water heaters. There are some threads on using hw heaters as boilers. I have done it but for a temporary set up before I put the 'real' boiler in.

Chris_116

Hydronic Heating Diagram Help for Novice

Hello all,

I am by no means a hydronic expert. I have come up with a design for a hydronic/DHW with a wood boiler, thermal storage, and propane backup heat using a tankless DHW heater. Oh also I have added a small point of use electric hot water heater and a circulatory to provide instant DHW. I got some of the design from a Tarm Solo diagram I found on the internet and I got the other part by looking at the Navien System. I'm interested in getting feedback on the diagram. Please point out any parts of the system that would not work or any improvements. As you can see I also need some help with controls. Oh and please keep the lafter to a minimum

Jamie_5

diagram analysis

I'm no expert, but it doesn't look right to me in a number of ways. First, the loop on the right side of the diagram (feeding the heating circuits) seems to lack a circulator. I can't see what will move water through the heating circuits. The same thing seems to be true of one side of what I guess represents a flat plate heat exchanger in the lower right of the diagram. The circulator off the point of use tank seems to be pumping into a thermostatic valve rather than drawing from it, which should not work well. I don't understand the logic of the boiler loop connection to the loop on the right side. Is C1 acting as an injection pump? If so, why is there a three-way valve on the return?

I think an explanation of the intended logic of the system would also help. Is the storage tank only expected to preheat incoming domestic water? Why not use that heat for space heating as well?

I'm sure others with more knowledge than I have will chime in, but I would be wary about beginning assembly based on that drawing.

Jean-David Beyer

I am no hydronics expert either. I did find reading John Siegenthaler's book "Modern Hydronic Heating For Residential and Light Commercial Buildings -- 2ND Edition" extremely helpful. It does cost a little over $100, so a non-professional might find it difficult to justify buying it. My thought was that if I were going to pay $5000 to $10,000 to replace a lot of my home heating system, $100 was worth it so I would understand what was going on.

I then selected a contractor who, from my experience with several contractors in the area, does very good work. I did think he could have made a bit more effort in calculating the boiler size required, but the actual work performed was very good and the company had no trouble getting everything passed on the very first try.

Once the contractor was selected, we had to choose the boiler. They wanted to know how much I cared about efficiency, how much I cared about cost, etc. When we got through all that, they suggested a Weil-McLain Ultra 3 boiler. I then downloaded their >100-page installation manual and read that. Having read both Siegenthaler's book and that fairly complete installation manual, I thought I understood the issues pretty well.

Those are my only qualifications, so beware of what I say technically. Note that this is all book knowledge. I believe in the value of book knowledge. But that is not enough. I have no practical knowledge other than being the owner of an old GE oil fired boiler for over 30 years (and it was old when I got it). I also was present at the installation of two gas-fired air scorching furnaces at my local place of worship for which I am responsible. There we had several contractors do the maintenance, most of which were replace due to unsatisfactory work (one did not even know to clean the heat exchangers, and one had a couple of passages blocked by soot). One of our members was an architect who knew about building design. He was never a heating contractor, but he knew the issues about contracting for work and making sure we got what we paid for. We called three well-recommended heating contractors for the work. One would not make an appointment to look at the building, expecting us to sit around and wait for him to come. The second looked around and made a quote. Did not ask any questions. The third measured the size of the building (very leaky building, ceilings over two stories high, build almost 200 years ago), looked at the existing furnaces (leaks in the heat exchangers). We selected him.

My first impression of the system you designed is that it was too complicated and I did not wish to study them further, since what I say about it is not backed by any experience. But they may be OK. No matter what others may think of your design, I think it worthwhile to do it. From my point of view, the more a homeowner knows about the systems in his house, the better off he is. But both of us must be aware of the "a little knowledge is a dangerous thing" effect. That is why I did not buy my boiler and indirect hot water heater from some on-line supply house and put it in myself. I can solder 1/2" copper tubing with no trouble, though I am not sure I would do well with 1.25" stuff, and I would have been afraid to pipe the gas. My workmanship is such that it does not leak, but it is not pretty. Professionals can do a better job, and certainly much faster. I guess it would have taken me several weeks to do my job that they did in two days -- and it did not take all of the second day.

hot_rod

This link

shows what I consider to be a better "engineered" method. It can define and predict exactly what is going on hydraulicly.

I scratch my head when I see some of those wood boiler piping drawings. Pumps in series (sometimes) no circ on the heating loops with a P/S crossover. Hard to know what is going on, and when with that piping. Oddly enough they seem to work from what owners of those systems, often DIYers tell me.

In absence of a well thoughtout piping they sometimes throw a big complicated control PLC system on them to "tame" them.

I'd also look into delta T circulators to eliminate a pump and energy robbing thermostatic 3 way valve.

www.hpacmag.sartech.ca/archives/2009/3_April.pdf

hr