In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
I just finished installing a Lochinvar WH 55. I piped it direct, because it seemed foolish on such a small system to go prim/sec. I followed a Triangle Tube design. So far, I think I made the right choice, for sure. But there is one thing I want to let anybody doing a similar install to know, forget trying to use a delta t pump. All it seems to do is confuse the whole modulation process. I think the two adjustments, pump speed and boiler firing rate, just chase each other around, until the confusion shuts the boiler down on high limit being satisfied, even though its not even close to that temperature. I don't know how a pump controlled directly by the boiler's computer would work, and I don't plan on spending $400 to find out. My hunch is, might work better, but I think it is totally unnecessary. The modulation process takes care of what I am looking for, delta t seems to be not so critical to good performance.