Existing ground source heating system upgrade to cooling complications

We are at the planning stage of having cooling added to our house which currently is heat only from a water-to-water ground source heat pump and in-floor hydronics. We’ve been renovating the house in stages for over a decade, and only recently decided we need cooling – Portland, Oregon, which, until recently, had very mild summers.

My questions are about our existing system and how it will be modified to accommodate cooling. Unfortunately, we have a very small utility room, so I’m trying to get a handle on what components will be added or taken away and the attached diagrams show our existing and my guess at what might be needed. I’ve looked at system diagrams and descriptions online and most of those are much more complicated than what we have or what I have anticipated would be needed for the cooling upgrade, but those that are complicated probably perform better – some of the most complex looking systems I’ve seen are by John Siegenthaler, P.E., and, as we found out when the heating system was installed, there is a great variety of options/opinions on what’s considered optimal. For our original heating only system, we chose to go with the simplest system in the end that our contractor, a mechanical engineer, recommended.

Can we eliminate the heat exchanger?

Does an additional DHW tank need to be an indirect type like the one we have now?

Any other recommendation or links to a good system diagram/description would be appreciated.

The rest of this post is only indirectly relevant to my query, and just a little more background on our project to explain why we have not contacted the original contractor:

We installed the in-floor pex heating loops as our renovation progressed (tore down our old plaster ceilings then insulated the cavities) ourselves, and, as we replaced our foundation, we ran the ground loops – all done as recommended by the HVAC contractor. However, after the contractor scheduled the installation of the equipment side of the equation, he was many weeks delayed, and, with the 30% tax credit near to expiring and no Congressional renewal, he announced that Water Furnace had raised the heat pump price by $4k due to federal government requirements, and their $14k estimate was now $18k. Then, when we hesitated, he reminded us about the tax incentive expiration and added that he did not need the work. He ended up arriving on the 4th of January, four days after the incentive expired, and reassured us he would back-date the invoices. When they were done with their installation, they had not hooked up the new hot water heater they provided to the domestic water or run electricity to it, saying we would have to hire our own plumber and electrician because that’s not allowed by their licensing.

I could go on with a few more things that were sketchy, but you probably get the picture. Had they charged me $18k for the job to begin with, I would gladly have agreed – I had no idea what the install should cost, and I just wanted professional workmanship and consideration.

The week after they finished their work, Congress extended the tax credit.

I’ve worked in construction all my life, and I’ve seen much, much worse than this, so you learn to take these things in stride. The system has worked flawlessly, even in the weeks when temperatures have reached the low twenties at night (yes, winters are mild here), so we are pleased overall.

For this next stage, I want to be a little more educated before we decide on a system – we’ve already met with a contractor about a DX system before someone pointed out in a subsequent forum discussion that our existing Water Furnace heat pump is reversible – it even has unused ports stating DHW in and out. We contacted the contractor with this news, and he tried to talk us out of the chilled water system – though he never said it directly, we assume this is outside his area of expertise. We realize water chilled systems in residential are not the norm, so we may need to advocate for that system with anyone we talk with further.