Post edited 8:24 am – January 9, 2012 by ThirdHatt

I will try to get those temps for you ASAP. I did install the soft-starts back in 2010 and they do help alot. Whenever I have both compressors on they both run staged just behind one another by maybe a second or two time wise. They cycle fairly quickly as well, usually running for only a minute or two then shutting off only to come back on a minute or two later. This pattern may suggest that they may not have enough (or any?) temp separation programmed in like you stated.

Another point worth noting, I do not have an automatic chiller control board like newer systems have or even an older control setup like the one for sale in the classifieds section of your website. I have a simple manual control board with a breaker to turn the raw water pump on/off, a breaker to turn the chilled water pump on/off, a breaker for each chiller and a switch to select cool or heat for each chiller. Every time I consider if I would ever want to upgrade to an automatic control board I remember how easy it is to blow breakers on the dock when running both chillers at some marinas and also the significant extra cost of the electric bill when running on both chillers. That combined with the fact that one chiller really does cool (or heat) the boat very well, I just run #1 for about a week, then I run #2 for about a week and so on to keep the running time fairly even between the two. With that being said, for some reason the #2 chiller is not cycling on in heat mode this winter, so on the rare occasions when I use heat I am only using chiller #1.

Yep, I have the factory Dometic soft starts that your link pictures. My chillers were replaced in 2008, confirmed with Marine Air that they were built in 2007. When we installed the soft starts I did see the little red digital display inside the control box so I know where to look for the temp readings. I'll have to find some time to open them up hopefully this week so that I can report back to you what the temps are.

I see your point about the one chiller possibly not keeping the loop cold enough. That sounds quite possible although the air temps are fairly consistant in the 50's even on the weak air handler. It seems to be getting cold enough (as cold as the other air handlers) but it is simply not moving enough air to be effective on that side of the salon, that's all. No matter how low the air temps get, if it is just trickling out of the vents on that side of the room it is just not going to get the job done very effectively.

With respect to the second chiller being set up to run only when the first chiller cannot maintain the temp in the loop, out of curiosity how would that address the difference in run time of the two units, or does it? Seems like th eprimary chiller would have a very high run time compared to the second chiller.

Thanks!

Post edited 1:18 pm – January 9, 2012 by Steve Pooler

Oh…Just so you know…"Soft Starts" are a whole different animal than the "SmartStart" I linked…Two completely different technologies…

I'm also thinking that you may be tripping breakers with two chillers on-line because they are set at the same temp & may try to start at the same time or within a few seconds of each other…

With the DDC board we can adjust the Time Delay to help that too…

Steve~

I took a quick look at one of the control boards and sure enough I do have the new style board with two small buttons just to the left of the display. I did not have time to fire up both compressors and let the loop come to temp so that I could check the inlet and output temps but I will do that ASAP and report back.

Post edited 7:17 pm – January 10, 2012 by ThirdHatt

Well Steve, I opened the control boxes and made sure to power them on at the exact same time so that the displays would cycle from rtr to sup at the same time. #1 seems normal as it cuts in at 50 and cuts out at 42. Here's what threw me: #2 cuts in at 48 and the sup always shows 150! I must have a bad sup temp sensor on #2 I guess? When I run them both, they both cut in and cut out at nearly the exact same time, just as you suspected and as you suggested, that is probably why at come marinas I can blow the dock breaker. This may also explain why #2 will not kick on in heat mode at all. Something is up with #2 without a doubt. Heck, you may even suggest a minor adjustment in #1, but I must say that #1 has always been EXCELLENT at cooling OR heating the boat so I suspect that it is set right or pretty close to right. #2 has done the job mostly, but not nearly as efficient like in mid-summer at mid-day.

I can almost see the wheels turning in your mind! What are your thoughts with this new info?

As always, thank you!