Zone valves - single pump - indirect water heater

cseevinck

I want to install a ​ Laars mini therm boiler with ​Triangle tube indirect smart 60 with 4 zones for radiators in a basement (1150 sq ft) in Salt Lake City. A friend told me i could do this install using only one GRUNDFOS ALPHA pump and zone valves. Does anyone know how this could be arranged? It seems to me that i need at least one pump for the Smart 60 and one for the zones. I have been scouring the internet looking for possible layout diagrams that would use only one pump with out any results. I would love to see a diagram with this kind of instalation. Any help/input is appreciated.

NY_Rob

The heating coil inside the DHW tank would just be plumbed as an additional zone with an additional zone valve- which would be activated by the zone control unit on a DHW call. If you had 4-zones... now you have 5, one just happens to be the heating coil inside your DHW tank.

It may be tricky with an Alpha pump because if you have a 50K BTU boiler, you need to flow 5gpm to the DHW tank coil, but the Alpha would be set for your spaceheating loops needs... unless you happened to find a DP mode that satisfies both. It may work but perhaps not.

For a few extra $$ over the cost of an additional zone valve, get the 3-speed Grundfos 15-58 and dial it in exactly for your DHW tank and let the Alpha handle the spaceheating loops.

hot_rod

Also beware of the pumping requirement for that boiler, some have fairly high pressure drop.

If it is not a modulating boiler, expect a lot of cycling, those low mass boilers, when multi zoned tend to bounce off and on a lot. Size it close to the load.

HVACNUT

I personally always pipe in a separate circ for an indirect if I come upon a system with zone valves. Then I use a RIB as an isolation relay for DHW priority.

Henry

Not the best boiler choice for the applications and you do need a separate pump for the indirect

hot_rod

NY_Rob said:

The heating coil inside the DHW tank would just be plumbed as an additional zone with an additional zone valve- which would be activated by the zone control unit on a DHW call. If you had 4-zones... now you have 5, one just happens to be the heating coil inside your DHW tank.

It may be tricky with an Alpha pump because if you have a 50K BTU boiler, you need to flow 5gpm to the DHW tank coil, but the Alpha would be set for your spaceheating loops needs... unless you happened to find a DP mode that satisfies both. It may work but perhaps not.

For a few extra $$ over the cost of an additional zone valve, get the 3-speed Grundfos 15-58 and dial it in exactly for your DHW tank and let the Alpha handle the spaceheating loops.

That is a good point. If the indirect had a low pressure drop coil, high Cv zone valve would the Alpha ramp up when that zone called and heating zones closed?
The Alpha certainly has the capacity to move 5 gpm

cseevinck

Thanks for responses. A couple of questions please:
1) Henry: What would be a better choice for boiler?
2) HVACNUT says: RIB as an isolation relay for DHW priority - would a taco Zone 6 Valve Control Module with Priority be ok to control the zones and the Indirect Water Heater pump?

hot_rod

The manual shows a number of piping options. They prefer primary secondary, but direct piping with a bypass and maybe a thermostatic union.

That was a hugely popular boiler in that Salt Lake market, there must be thousands around there. Seems old habits die hard.

cseevinck

hot rod - One of the primary suppliers (Standard Plumbing) recommended only that boiler. Not sure why?

hot_rod

I left Utah over 20 years ago, those copper fin boilers were used before mod cons came to the market. They were promoted as "radiant ready" able to handle low returns. That proved to be not exactly true

Properly applied they are a very efficient little boiler. Great for single zone snowmelts.

Copper is a much better conductor compared to aluminum, stainless or cast. It is a very reliable, no frills boiler.

It may not have the ability to modulate to the changing loads, or an outdoor reset function as most of the new high efficiency mod cons do, but it may be 1/2 or less the cost?

Since they are a low mass, low water content copper they come up to temperature quickly. Unless you use that full 50K output they can cycle off quickly.

It's all about matching the heat generator to the heat emitters and the load to keep them running happily.

Have you done a load calc? A basement that size may have a low heat load, maybe 10- 15,000 BTU. That boiler at your altitude may still have twice the output that you need. But it's hard to find any boiler smaller than 50K.

A buffer tank could be added if cycling causes problems like flue gas condensing, or short cycling. Maybe they are using that Smart tank as a buffer?

Mod con boilers have the ability to modulate down closer to your assumed load, and have weather responsive controls, but more $$.

Do you have a contractor involved? It may be worth paying for a load calc and design. Plenty of good hydronic guys in that area.

cseevinck

Load calc results in 26,000 BTU for the space. My contractor is not very experienced with hydronics. It looks like he will rely on the design recommendations from the supplier. I'm looking at Myson Panel Baseboard Radiators and a Quiet One KS2004 kickspace heater for kitchen.

NY_Rob

Consider cast iron baseboard (Burnham BaseRay or Gov-Board), it's high mass will prevent cycling with your low mass boiler and they will retain the heat much longer than the panel rads.