Where do I start with Solar heating

[Mike90250]

sorry to post it here as Admin haven't approve for new user like me yet.

my question is: can I connect 2 panel with different voltage in parallel?

Generally, yes, as long as they have Vmp spec within 10% of each other - you only listed one Vmp 30.7v

[monogram]

sorry to post it here as Admin haven't approve for new user like me yet.

my question is: can I connect 2 panel with different voltage in parallel?
Suntech STP250 - 20/Wd Specifications

[TABLE="border: 0, cellpadding: 0, cellspacing: 0"]
[TR]
[TD]STC[/TD]
[TD]STP250-20/Wd[/TD]
[/TR]
[TR]
[TD] [/TD]
[TD] [/TD]
[/TR]
[TR]
[TD]Maximum Power at STC (Pmax)[/TD]
[TD]250 W[/TD]
[/TR]
[TR]
[TD]Optimum Operating Voltage (Vmp)[/TD]
[TD]30.7 V[/TD]
[/TR]
[TR]
[TD]Optimum Operating Current (Imp)[/TD]
[TD]8.15 A[/TD]
[/TR]
[TR]
[TD]Open Circuit Voltage (Voc)[/TD]
[TD]37.4 V[/TD]
[/TR]
[TR]
[TD]Short Circuit Current (Isc)[/TD]
[TD]8.63 A[/TD]
[/TR]
[TR]
[TD]Module Efficiency[/TD]
[TD]15.4%[/TD]
[/TR]
[TR]
[TD]Operating Module Temperature[/TD]
[TD]-40

[NetComrade]

All,

I've followed up with a post on the heating forum on this

https://forum.heatinghelp.com/discussion/165372/sanden-ecocute-instant-heater-as-backup-radiant-design/p1?new=1

After doing some reading, I think I found a solution that will work.. here's a copy and paste of my last post

After reading the following..

https://www.bpa.gov/EE/Technology/EE-emerging-technologies/Projects-Reports-Archives/Pages/Combined-Space-and-Water-CO2-Heat-Pump-System-Performance-Research-.aspx

I decided to flip the Sanden to the DHW side of the heat exchanger.. Sanden really likes the water to be colder. I will need to filter water to minimize impact of well water to equipment.

The long paper basically validated my design (as it has been field tested with backup), and my new design now looks more like the design used in this study.

This will also allow me to pre-heat water for radiant use (but not DHW, although that could be figured out later, IMO), which would have been difficult if Sanden was on the 'heating' side of the plumbing.

Diagram is overly simplified, and will need additional plumbing details by a professional,.

20180319_122415_small.jpg

[NetComrade]

Capex:
Sanden 4K
Taco RMB 1K
Eco 11k $200
Pressure Pal MF200S $600
Heat Exchanger $150
Filter/Expansion tank $200
Manifolds x2 $300
Mixing Valves x2 $300
Misc Plumbing estimated ~1k
-------
Total: ~8K + labor

Solar heat exchangers/sensors/pumps TBD later

[NetComrade]

20180315_124903_smaller.jpg



So here's something I came up with
Disconnect existing tank (T1) from hot water and make it part of my radiant system (looks to be mostly useless though, although its heating elements are capable of producing 15K BTU)
Replace T1 with B1 (Ecosmart Eco11 Instant heater) for hot water.
Setup Sanden as primary heating system for Radiant and Hot Water (prewarm well water via heat exchanger H1)
Use Eco11 as backup for Radiant, as it can generate up to 35K BTU (11kW).
Use Taco RMB Radiant Mixing Block (H2) as radiant circulator, but it will also turn on Eco11 (B1) in case SanDen is not keeping up (e.g. 85F) and add as heat exchanger.
Optionally/later add S1 and S2 heat exchangers to prewarm well water or radiant water by Solar

I know I am missing check valves, expansion tank in this picture, and something that will maintain pressure, water filtering facility (don't plan on using glycol) and probably other details but what are your thoughts?

I am not ignoring heat load calculations, but based on my analysis this will be more than sufficient (and with backup).

I am guessing Sanden would cover 70-90% of heat and DHW use, with a portion of that covered with Solar at some point, and Eco11 picking up some load when it's really cold.

[LucMan]

Here is a simulation for a solar heating job I proposed several years ago, the cost was way over the customers budget so it was never installed as proposed. We installed the radiant floor, and used steel radiators for the second floor sized for 130 degrees at 4 degrees outdoor temp.
The last page with the graph tells the whole story. Your geographic location may be different but the out come will be the same. Equine_Barn_8SKS4_PL750.pdf
The panels proposed were a hybrid panel somewhere between flat plate and evacuated tube, the achievable discharge temps in winter are substantially higher than flate plates as you can see from the graph. The flat plates on my home can only get up to about 90 degrees F in January, not much that can be done in less than 4 hours of sun on a good day.

[NetComrade]

Re: comment about solar not providing enough during the winter.
I think my overall feeling, I need something additional as current system isn't keeping up.
Solar is 'free' and I already have the panels (well, plumbing and support for them won't be free). I don't think solar would be able to provide more than 25% of the load in the winter and maybe 40-50 in fall/spring warmer months... that's where the backup comes in. So backup needs to be able to handle 100% of the load on cold and/or cloudy days.

Re: comment about Slab being a good BTU storage.. I agree, and yet to calculate it's capacity, however, it can only give off so many BTUs while room temp is dropping, and it's not going to 'run out' relatively quickly, so it will help moderate usage of 'backup', but backup is still needed. In addition, I think external storage at higher temperature may still be beneficial, but the cost-benefit analysis may show it's not worth it.

[NetComrade]

had struggle pasting this info out of documentation:
Applications Combination Heating and DHW
It is permitted to use the SANCO2 system to provide some limited capacity
heating (radiant, fan coil, etc.) in certain areas of North America, when combined
with a minimum of 25 gallons per day usage of DHW.
It is NOT permitted to use the SANCO2 system to provide heating as its only
function.
Sizing
Maximum heating capacity must be less than 8,000 BTU/h.
Minimum design ambient temperature must be above 27

[NetComrade]

You can connect as many Sanden units as you want.. They support it for apartment production. Although they prefer you do it for hot water production, not radiant heating.
Using it for heating primarily would definitely be a hack from their perspective. But when I spoke to someone on the phone they didn't seem to frown upon it as much as their documentation would imply (would still probably be out of warranty)

While gas is cheap, i don't have any as this is a rural location, and propane is a hassle (nor cheap). Each unit is 2200USD.
Very efficient unit.

[LucMan]

	space	differene with outside	R		btu's to maintain
old wall	900	80	9		8,000		80F inside 0F outside
old foor	900	30	15		1,800		80F top of floor, 50F bottom of floor
new wall	540	80	2		21,600		80F inside 0F outside
new floor	800	30	15		1,600		80F top of floor, 50F bottom of floor
windows			2
room upstairs	320	80	20		1,280
					34,280

This would be my BTU calculation with current setup (as is).. If I get the walls to R20 or about, my requirement becomes about 10000 BTU (ignoring windows for now).

This is within range of the Sanden (15000BTU, although officially they claim no more than 8000BTU load to support radiant heating).. Since my current Fujitsu still has 2 ports available and we still want radiant heating, that's what I will need to pursue (Fujitsu mostly for cooling, as it may not keep up with heating.. but technically it has 13000BTU unutilized as well (current two ports are 14K and 9K BTU units)

Not even sure I need to fiddle with solar at this point although I probably still will.

You can still run a loop directly off the drainback tank to your slab no storage tank required or recommended. The slab will be your storage if you can pump enough BTU'S into it during sunny days.
Daikin used to sell the Altherma air to water heat pump here in the US but it was not a good seller so they removed it from the US market. Maybe you can pick one up in Canada or one of the other major brands (Panasonic, Mitsubishi, etc). They are good sellers in Europe but gas and oil are way to cheap in the US for these units to be popular.
The Sanden units are a little small unless you can twin them. Have you contacted Sanden about a twinning kit?

[J.P.M.]

	space	differene with outside	R		btu's to maintain
old wall	900	80	9		8,000		80F inside 0F outside
old foor	900	30	15		1,800		80F top of floor, 50F bottom of floor
new wall	540	80	2		21,600		80F inside 0F outside
new floor	800	30	15		1,600		80F top of floor, 50F bottom of floor
windows			2
room upstairs	320	80	20		1,280
					34,280

This would be my BTU calculation with current setup (as is).. If I get the walls to R20 or about, my requirement becomes about 10000 BTU (ignoring windows for now).

This is within range of the Sanden (15000BTU, although officially they claim no more than 8000BTU load to support radiant heating).. Since my current Fujitsu still has 2 ports available and we still want radiant heating, that's what I will need to pursue (Fujitsu mostly for cooling, as it may not keep up with heating.. but technically it has 13000BTU unutilized as well (current two ports are 14K and 9K BTU units)

Not even sure I need to fiddle with solar at this point although I probably still will.

Get some information about how to calculate building HVAC loads. You're missing a lot, starting with the idea of design temps. Also, know that infiltration losses/gains can often add ~ 25 - 75 % or more to the simple conduction loss, or that R20 insulation will not give you an R20 wall.

[NetComrade]

	space	differene with outside	R		btu's to maintain
old wall	900	80	9		8,000		80F inside 0F outside
old foor	900	30	15		1,800		80F top of floor, 50F bottom of floor
new wall	540	80	2		21,600		80F inside 0F outside
new floor	800	30	15		1,600		80F top of floor, 50F bottom of floor
windows			2
room upstairs	320	80	20		1,280
					34,280

This would be my BTU calculation with current setup (as is).. If I get the walls to R20 or about, my requirement becomes about 10000 BTU (ignoring windows for now).

This is within range of the Sanden (15000BTU, although officially they claim no more than 8000BTU load to support radiant heating).. Since my current Fujitsu still has 2 ports available and we still want radiant heating, that's what I will need to pursue (Fujitsu mostly for cooling, as it may not keep up with heating.. but technically it has 13000BTU unutilized as well (current two ports are 14K and 9K BTU units)

Not even sure I need to fiddle with solar at this point although I probably still will.

[bcroe]

The problem with a drain back system in cold cloudy climates, is it works the least well when
you need it the most. Thermal storage is not going to carry through bad weeks. The big
advantage to net metering, is being able to use summer energy in the winter. I see the
ways to do that are the latest high efficiency low temp mini splits combined with great
insulation. Bruce Roe

[LucMan]

First step is always to calculate heat loss for your structure. This will tell you exactly what your BTU requirements will be for heating at any given outdoor temperature.
Software is available, just enter all the info and the software will spit out the BTU loss' s. You can then play around with changing insulation values to find the sweet spot for your application.
Your above post indicates that you have excellent understanding of what you want to accomplish.
Good luck
ps HVAC CALC works well and it used to be available for purchase for one time use.

http://www.hvaccomputer.com

[DanS26]

You might want to consider how you want to heat your spaces. Is it important to heat your entire house (ie every sq. ft.) to a comfortable level or do you want to heat the space you are in to a comfortable level?

The answer to that question will determine how and what your heating strategy will be.