Solar Radiant Monster

The SHEM Solar Radiant Monster package contains four Suntask SR30 evacuated tube collectors, and a complete SHEM 120DB system. The 120DB system includes:

• 1 SHEM 120DB Tank
  
• 1 Wilo Pump
  
• 1 SHEM32 Controller
  
• 1 Black High Temperature Thermistor for Collectors
  
• 2 Grey Low Temperature Thermistors for Tank and Floor
  
• 1 29psi T&P Valve
  
• 1 BlueWhite Flowmeter
  
• 1 Drain/Cleanout Valve
  

*Note: It does not include a circulation pump for the radiant loop.*

The Radiant Monster is configured to produce an amazing amount of energy during the fall and winter months to aid in heat production for an in-floor radiant heating system. With four Suntask 30 Tube evacuated tube collectors, the system overproduces in the summer months. This can be remedied by installing a summer bypass. Below are some example configurations.

No Summer Bypass [PDF]:

This configuration has no bypass. All of the collectors are connected in series. This configuration means that during the summer months, production is incredibly high and produces lots of hot water very quickly. This might not seem like a problem, but it can be a problem due the very high stagnation temperature of the evacuated tube style collector. If the maximum tank temperature is reached early in the day, then the pump ceases operation and all the solar fluid drains back into the tank. This means that during a hot summer month the collector is stagnating on the roof for most of the day. Stagnation temperatures can reach well over 350 degrees. If any hot water is used and the tank temperature drops, then the solar pump is reactivated. When the relatively cool water touches the very high temperature manifold on the evacuated tube collectors, a massive amount of steam is produced. The more hot copper the water has to cool, the more amount of steam produced. If the amount of steam is too much, it has the potential to cause the T&P valve to open causing loss of solar fluid out of the valve.
Reducing the system to only two collectors during the summer months provides two advantages.

1. Allows the production during the summer to be better spaced out through the day to avoid reaching the max tank temperature too early in the day, and therefore shutting off the solar pump, and
   
2. Reduces the amount of mass of copper needed to be cooled so that if the pump is reactivated in the middle of the day much less steam is produced.

Summer Bypass Configuration 1 [PDF]:

In this configuration there are two valves. One valve toggles the flow to the last two collectors, while the second valve opens the bypass to allow the water to return to the tank. Flow rate needs to be adjusted when switching from summer configuration to fall/winter configuration.

Summer Bypass Configuration 2 [PDF]:

This configuration uses two sets of two collectors in parallel. This means that there is only one valve that needs to be actuated to toggle between summer and fall/winter configurations. This configuration also means that the collector tilt for the two sets needs to be configured to allow the system to drainback at all times. In this setup the tilt for two of the collectors flows away from the water feed, which is not ideal, but is necessary to prevent water from pooling near the valve.


Summer Bypass Configuration 3 [PDF]:

This configuration allows the valve to be moved down into the mechanical room to allow switching between summer and winter without having access to the collectors. This might be desirable if the collectors are located on a roof, or any other location that would be hazardous or difficult to access on a bi-yearly basis.
When designing a system using this configuration, you should ensure that the collectors are mounted at the same height, and minimize differences in piping length between the two sets of collectors. Otherwise the flow might not split evenly between the two sets. Exactly even flow is not necessary, but making sure both sets of collectors receive adequate water flow is important. Alternatively, a flow balancing valve can be used to ensure even water distribution, but this might be overkill.

Switching Between Seasons
When switching between different set-ups, care must be taken to prevent water from permanently pooling in a collector or pipe. This is not a huge problem in the summer months, but during fall/winter where freezing temperatures are possible, pooled water can cause permanent collector damage, or pipes to burst. When switching between winter and summer configurations, unplug the controller and let all of the water drain back into the tank. For more info on confirming your tank is drained back, see the post on this forum entitled "How To Tell if your Tank is Drained Back."

If the system shuts off on high tank temp during the day, the system should be locked out if the collector temperature remains above 205F

The observation about the system stopping production after the tank hits high temperature, the pump ceases, and then the collectors reach stagnation temperatures is correct. However, the collector loop can reactivate when the collectors drop below an emergency temperature, as in later in the afternoon.

The controller function for Maximum Tank Temperature is SMX. That function is set on all SHEM controllers to 170 F, based on T2. This function could be set to a higher temperature, but do so with caution. This is a bottom of tank reading. The top of tank temperature could be considerably higher. (See Pg. 20 in manual)

However, also see EMOF, the Emergency turn off temperature of the collector. This is set at the factory at different temperatures depending on the controller! The SHEM 32 has a 195 F setting. The SHEM 32 "E" controller is set at 260 degrees F. The range of settings is 146 - 392 F.

When the T1 temperature drops below the set temperature, the collector loop will reactivate.

Right, I'm just saying that most homeowners don't like to go up to the roof twice a year to change a valve. Therefore the appropriate EMOF setting should be set, then "forget".

So I have two questions.
1) If a set of ET tubes are bypassed (no water flow) durring the summer can they be damaged by excessive and or repeated high pressures inside the inner tube?

2) Do I understand that the SHEM controller will infact lockout if the tank high temp is satisfied and then the EMOF temp on the roof is reached? When I say lockout, ie even if the tank cools back down and needs to be heated ....the pump will NOT start until the ETs cool back down to the point they will not flash? If this is the way it works then couldn't you forgo the bypass valves altogether?

Having a summer bypass is probably unnecessary if your controller has the EMOF function. Matt stated: "If any hot water is used and the tank temperature drops, then the solar pump is reactivated. " That's not true if the EMOF is set.

And don't worry about wasting collectable heat when the pump is off on EMOF. Most of the time you have a fully hot storage tank when the EMOF hi limit is reached.

All the SRCC tested collectors have been exposed to stagnation at full sun. But that's not the same as, say, 5 years of summer stagnation every afternoon after the tank is up to temperature, and I haven't seen any long-term stagnation test reports on ET collectors. Flat plate collectors are fine with it.

Good on the EMOF lockout. That makes sense.
So is that a big selling point for the SHEM32 over other controllers. I mean does most all controllers out there now have EMOF type settings?