First, I'm in Northern Virginia, currently have a 4.7KW PV system, with 2 eagle sun Solar collectors. I'm currently upgrading to a Daikin Altherma with DHW and Solar assist to replace my existing Solar hot water system. My existing system is currently a closed loop using glycol running from a Steca 0301U Solar Hot water differential controller. I do have a bit of cycling on/off. My question is, while the simple setup I have already works, I'm looking for something to better integrate with the Daikin. It seems my 2 options are a Calefi, or better yet a Taco Variable speed system. My system currently just use's a wilco single speed pump, that the differential controller turns on when a delta t of 7degree F is detected between Bottom Coil of hot water tank, and solar hot water panel output. Any suggestions for a solar pump station?

The only difference you will get is due to the control and probably nothing else. If your current system is balanced correctly, the only thing you can due is use a controller with variable speed. I don't know the pump you are using but if it is a copy of a Grundfos, Wilo or Taco, you will have no problem using the variable speed function of a Resol controller. I think Caleffi controller are re-branded Resol ones.

Cycling on an off is normal in solar systems when the pump speed is too high and there should be a balance valve on the pump station to help with this a bit. The panels need about 3/4-1gpm for the system, WHEN the sun is at full intensity. Anything below that and the variable speed will help.

Can you post a pic of the pump station please

My current system is not all that great. I'm sure I'm missing some pieces/parts. VA had a $2/w solar rebate, and this was the system I got, which a local solar company pieced together, and then I installed it(per there instructions). I pressurized glycol to 20lbs using a 3/4hp pump. I can tell there is airlock when the pump starts, but have no air trap release on roof, only Pressure relief valve.. From the attached pictures you can see my very limited space, and what I came up with. (Looking at install diagrams on internet, it looks like I'm missing stuff, but was in no rush to touch it as, the system was free after rebate & the trouble I had trying to get glycol into the system with non self-priming pump)
I only have about 8' of head, (1 story ranch). I have no idea how to pressure balance.

So since I'm replacing everything except the collectors, I thought maybe about starting fresh with a pump station(with flow meter/temp sensors) to actually work with the Altherma would be the best solution.

So I'm completely open to any and all suggestions.

Thanks!

Well, where do I start. I couldn't see the tank very well but it looks like a Rheem which is OK but it could be better. The pump is a complete unknown to me but it looks like a copy of a 20 year old Armstrong Astro pump. The expansion tanks are upside down. Solar systems should not have auto air vents on the roof unless it is a big system and only with a ball valve below it which is shut off after purging the air out.

If you got a complete Caleffi pump station, it will have the right components and they will be in the right layout, which is important. If you want to draw a diagram of the system components as they are now, I will comment and tell you which ones need changing and which ones don't. If it is then done right, you shouldn't need to change the control or pump. Can you take a close up of the pump si I can see the specs?

One of the weakest links in a system like this is the heat exchanger in the tank. If you can give the details, I will look at it.

Posted By MikeSolar on 27 Sep 2012 08:21 PM
Well, where do I start. I couldn't see the tank very well but it looks like a Rheem which is OK but it could be better. The pump is a complete unknown to me but it looks like a copy of a 20 year old Armstrong Astro pump. The expansion tanks are upside down. Solar systems should not have auto air vents on the roof unless it is a big system and only with a ball valve below it which is shut off after purging the air out.

If you got a complete Caleffi pump station, it will have the right components and they will be in the right layout, which is important. If you want to draw a diagram of the system components as they are now, I will comment and tell you which ones need changing and which ones don't. If it is then done right, you shouldn't need to change the control or pump. Can you take a close up of the pump si I can see the specs?

One of the weakest links in a system like this is the heat exchanger in the tank. If you can give the details, I will look at it.

The installed tank is branded Eagle Sun, 80 Gallon w/bottom coil. But this is being replaced by a Daikin 80gallon water tank. Instead of the glycol going directly into bottom coil, there is a heat exchanger on the exterior that circulates water in the coil via heat exchange when solar is available, otherwise it uses a heatpump to heat the lower coil water. I'm basicaly starting from scratch(on the plumbing side). I have solar already on the roof, and the Daikin tank. I'm open to spend 1k on a good pump station, really just to simplify my reinstall of everything. I think I'm missing parts and other stuff, I just don't think its running as efficiently as it should be right now. The pump only has about 8' of head to the top of the panels(Its plumbed cold into bottom left, hot out top right), about 20' horizontal, then a drop into the Current hot water tank. The controller is connected into the rubber grommit of panel hot exit, and into the top &bottom of the tank. Any recommendations on to how to fix this setup? Thanks,

Posted By tomtoth on 28 Sep 2012 08:53 AM

Posted By MikeSolar on 27 Sep 2012 08:21 PM
Well, where do I start. I couldn't see the tank very well but it looks like a Rheem which is OK but it could be better. The pump is a complete unknown to me but it looks like a copy of a 20 year old Armstrong Astro pump. The expansion tanks are upside down. Solar systems should not have auto air vents on the roof unless it is a big system and only with a ball valve below it which is shut off after purging the air out.

If you got a complete Caleffi pump station, it will have the right components and they will be in the right layout, which is important. If you want to draw a diagram of the system components as they are now, I will comment and tell you which ones need changing and which ones don't. If it is then done right, you shouldn't need to change the control or pump. Can you take a close up of the pump si I can see the specs?

One of the weakest links in a system like this is the heat exchanger in the tank. If you can give the details, I will look at it.

The installed tank is branded Eagle Sun, 80 Gallon w/bottom coil. But this is being replaced by a Daikin 80gallon water tank. Instead of the glycol going directly into bottom coil, there is a heat exchanger on the exterior that circulates water in the coil via heat exchange when solar is available, otherwise it uses a heatpump to heat the lower coil water. I'm basicaly starting from scratch(on the plumbing side). I have solar already on the roof, and the Daikin tank. I'm open to spend 1k on a good pump station, really just to simplify my reinstall of everything. I think I'm missing parts and other stuff, I just don't think its running as efficiently as it should be right now. The pump only has about 8' of head to the top of the panels(Its plumbed cold into bottom left, hot out top right), about 20' horizontal, then a drop into the Current hot water tank. The controller is connected into the rubber grommit of panel hot exit, and into the top &bottom of the tank. Any recommendations on to how to fix this setup? Thanks,

Thats funny. The pump is an Armstong Astro 30.

The one on the first page is a very good pump station,and Caleffi has similar ones. :

http://alphathermalsystems.com/index.php/solar-hot-water.html

 There are a few ways to accomplish what you want. One is to get a double coil tank (I like Viessmann because it has nice big heat exchangers). Hook the solar through the pump station to the lower one and the HP to the upper one.

The other option is a thermosyphon system. Use the Daikin tank with the HP output going to the coil but its sensor should be higher up the tank. Then use the same HX you have in your picture, plumb from the bottom of the tank, through the HX and up to the hot port at the top of the tank, sensor at the cold pipe at the bottom. The solar will cause the column of water in the HX and pipe to rise and start heating THE TOP OF THE TANK FIRST, which is the most usable heat. With luck, the HP will seldom come on.

The double coil tank is the most fool proof but I have done both.