Monoflo sytem

Wayco Wayne_2

Looked at a job yesterday that had an old monoflow system all in black pipe. I am looking to change the boiler, but the circ is an old B & G 100. How do I upgrade the circ without creating problems with the system.

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Perry_2

Wayne

This matched my house to a T (in more than one way).

My replacment system has a TACO 007 pump.

I have noticed some differences; and if I had to do it over again....

First the differences: People on this board and I batted about about how much flow the Series 100 pump was putting out (this affected how well a Vitodens 200 would match). It all came down to how much head was in the system.... Based on maximum reasonable heat load on the house and the fact that I got about 20 F drop across the system it seemed that the Series 100 had to be operating at no more that 10 GPM - which rates to 8 Ft head on the pump curve.

Because of that I installed a Low Loss Header with the Vitodens 200 and a secondary circulating pump.

My heating contractor does not like non-TACO pumps and would not consider installing a 3 speed pump from another company.

With the new system the temperature drop is about 5 F on cold days - and it is really obvious that the TACO 007 is moving a lot more water (and if you look at the pump curve vs the Series 100 -it can).

The Vitodens 200 operates at a maximum temperature rise of 10 F (and actually is oversized for my house as minimum firing rate is still to much heat at 10 F outside temperature for continuous operation: We need smaller mod/cons).

However, carefull study on what the Vitodens 6-24 pump can do, and the actual heat load in the house indicates that the Vitodens appears to have been able to handle my system without a LLH (i.e. it could put out about 4 GPM at 8 ft head - which would have matched my heat load with a reasonable temperature drop). That would have saved me $1000 or more on parts and installation.

So, my suggestion: Can you get a differential pressure gauge (say 0-20 Ft H2O) and figure out a way to measure the actual head loss of the system you are looking at? That and a good heat loss analysis will give you an idea of exactly how much pump capacity you need - and which pump curve works.

It might be that the Vitodens 200 6-24 or 8-32 built in pump will handle the system all by itself (how much parts and labor savings in not having to install a separate pump - along with other considerations).

An alternate stratagy is the Grundfos (spelling?) 3 speed pump.

I wish you well on this.

Perry

[Deleted User]

The NRF 33 is

our pump of choice when replacing a 100 on monoflo systems.

Uni R_2

Pretty simple...

Wayne, a monoflo system actually has fairly low head (unless a lot of the monoflo branches are closed) but they do require a certain velocity, otherwise the water won't want to leave the main circuit. A small 3 speed pump like a Grundfos 15-58 would be a safe bet on the medium speed. You could see if it can run on the lowest speed and still heat the house evenly or if there are lots of flow obstructions set it on high.

If you are running the circ 7/24 200 days a year, it (or any small $100 circ) will be pay for itself in 2 years because it only uses around 0.75 amps verses the B&G which uses 1.75 amps. The 15-58 is adjustable, quieter and cheaper to run. You and your customer can't lose on that.

The built-in flow check can be left in or easily removed for this application because it's not needed.