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I am finding out that flat plate HX is somehow not completely reliable in isolating a dual purpose HWH system serving Domestic HW/Radiant panels.
Are the concerns of using a Flat plate HX realistic.
What other types of HX are available and lend themselves to this application?
I like the Superstor HWH, which has a true isolation HX built in,
however my local wholesaler lists it at $5000.
I understand the flat plate is the most efficient transfer of heat
and water, however if it is not the safest choice can anyone inform me of any better ones
Thanks.
BTW I have city water and will have only plain water in the heating system.
Replies
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I really don't have any concerns regarding cross-contamination when considering using stanless-steel flat plate heat exchangers.
If using an anti-freeze in the RFH portion, you may want something more bulletproof. The way to avoid that is to not use anti-freeze.
Sure, they can fail...everything can fail...but I think they're pretty reliable.
There are code compliance issues...check with your local inspector to see if your code even allows them. Some areas don't.
*Mongo,thanks for supplying what I am looking for, an informed opinion as I am a novice in this area.Since both sides of the HX are potable water (although the heating side will be a closed system), and since I don't plan on consuming Domestic HW, I'm probably looking to deep at this.
*Other kinds of heat exchangers? Spiral, tube-in-tube, U-tube in tube, "hot rocks", etc. Flat plate is widespread because it is simple and effective enough. If it needs to be tiny, cleaned often, sees huge temperature gradients, or super efficient (90%+ transfer), then you end up with one of choices listed above.Why worry about something non-toxic (water or propylene gycol) leaking through a future hole in the stainless steel from the low pressure side (RFH at about 15 psi) to the high pressure side (HWH at 40-60 psi)? Non-toxic means non-toxic. SS doesn't corrode. Leaks go from high pressure to low pressure. You are looking at this too deeply. Go flat-plate and save $1000. Or skip the HX and save another $700, but you've already said you want one. -David
*David, Mongo, aj, and others,thanks for all the advice, it is going a long way to helping me make an informed decision.
*David... met a guy in a Big Box last night with a question about water heaters. Told him to come here and ask then pay really close attention to a guy named David Thomas because he teaches me a lot. Just wanted you to know that and thanks.
*WHW: Thanks. Just got back from my annual mental-health, winter road trip. WI to FL, round trip, driving over roads I hadn't taken before. Then flew back to Alaska.