Triangle Tube Prestige Solo 110 Install
Over the summer, I had a TT Solo 110 boiler installed in my home. The boiler uses propane for fuel and replaces an old oil boiler. My home has (3) zones of fin tube baseboard and DHW is produced using an indirect Amtrol BoilerMate. All zones use Grundfos 15-58 circulators on the LO setting. I've attached a photo showing the piping arrangement.
It is very similar to this arrangement except that the TT110 provides a seperate supply for the indirect DHW tank.
The installation was completed in August and everything seemed well with DHW production only. When we started using the heat in October, I noticed 2 issues.
1. The temperature of the DHW tanks drops when the heat zones are running. When the heat is not running, the tank loses 1 or 2 degrees per hour if no DHW is being used. When the heat is running, it can loses 10 degrees in 30 minutes. I've felt the supply and return pipes to the DHW tank while the heat is running and found that they do get warm. I believe that although the DHW circulator is not running, flow is being induced by the heat zones which is cooling the tank.
2. When a single zone of heat is running, the return temperature is within 2 degrees of the supply temperature. This causes the boiler to short cycle. I believe the problem is the flowrate through the zone is much lower than the flowrate through the secondary loop through the boiler. This causes supply water from the boiler to mix with the return at the closely spaced tees. The situation improves when more than 1 zone is running.
My installer recognizes the problem and is willing to make changes to solve the issues. Does anyone have suggestions for correcting these issues?
Last edited by lantaigne; 12-12-2012 at 10:06 AM.
Just found this page and I think it's exactly the problem I'm having.
Here is the heat loss that the installer provided for my home.
The heat loss is 75k BTU for a 0 degree design day and a 70 degree inside temperature. The net IBR rating for TT Solo 110 on propane is 76k BTU, so I don't believe the boiler is oversized. Zone 1 (1st floor) has 7 ft of standard Kompak baseboard and 45 ft of Senior (high output) Kompak baseboard. Zone 2 (2nd floor) has 25 ft of standard and 7 ft of high output baseboard. Zone 3 is the basement only has 8 ft of standard baseboard in one room. We have plans to finish the basement and add to this zone.
It appears to me that I need to combine zones 1 and 2 (and possibly 3) to balance the flow better between the zones and the boiler loop, however, I do not want to loss the ability for each floor to individually call for heat. We keep all the thermostats at 70 degrees 24/7 because I found that recovery from even a 2 degree setback was very long with the outdoor reset.
Would the Grundfos Alpha pumps be another possible solution? Could these pumps be set to balance the flow in the boiler loop to each zone and automatically adjust depending on the number of zones that are operating?
Last edited by lantaigne; 12-12-2012 at 10:09 AM.
Have the heating loop circs switched to med speed.
What is the lowest capacity that the Mod/Con produces verses your lowest heatload would be? Do they match?
If your boiler lowest output is higher than any zone's needed capacity; you would run into problems. I recommend a buffer tank (not to big).
Are there any check valves for the loads?
I would recommend check valves for each load: DHW, zone 1 and zone 2, etc...
X3 flow checks are a must especially with a water maker. Most people don't know what a buffer tank is lol but I think the 110 goes down to 25k.
Originally Posted by arc8
Joehvac25 is correct about the min modulation for the Solo 110 on propane is about 25k BTU. The heat losses for zones 1, 2 and 3 are 32.7 kBTU, 25.4 kBTU and 16.9 kBTU respectively as calculated by the boiler supplier for the installing contractor. These losses are for a 0 degree day though which is a relatively infrequent occurrence. Zone 3 is always less than minimum modulation and Zones 1 & 2 are less most of the time.
There are integrated flow checks in all the Grundfos 15-58s with the exception of the boiler pump. The installing contractor put in Taco 219s in the return line to the boiler and the return line from the indirect hot water tank, however, he left the thumb screws OPEN. I noticed this yesterday and closed both of them all the way. This solved the issue I had with reverse flow through the DHW loop when the CH zones were running.
The flow at the closely spaced tees in the P/S piping is never going to be perfectly balanced since I have multiple zones. The TT manual says the minimum flow through the boiler is 5 GPM at max modulation. If I set 1 zone to operate at 5 GPM (overflowing?) then some of the return water will mix with the supply to the zones when a second zone comes on. If I set it to operate at less than 5 GPM, then some of the supply water from the boiler is mixing with the return from the zone and raising the temperature of the return to the boiler which may or may not take me out of condensing mode depending on the temperature outside (ODR is being used).
It seems to me that a buffer tank is the way to go. I've read that some people use an electric hot water heater with the element removed for this purpose. I will have the installer make this modification, but I'd like to have an idea of the correct way to pipe it. Can anyone point me in the right direction? Perhaps provide a link to a schematic?
Your in luck we put buffer tanks in and I have a pic of one I did. The water heater idea is ok Exept they ports are only 3/4".
Here's a formula for figuring out the tank size.Buffer Tank Size.pdf
Sure, you can use water heater tanks, but it would require you to pull out the elements and put nipples in them.
The 3/4" on top can be use as long as they are not too restrictive (water flow).
Before I invested in a buffer tank. I'd set those circs to med and see if the system worked better.
Beenthere is right a buffer tank is not cheap plus you would have to repipe half of the system. If it would have been done first it would have been more convenient.