pump speed w/ Viessmann 200

TAG

What Alpha II setting should one use for the primary side pump of a Viessman 200. It's the smallest 200 model -- 60k or so output.

My new house -- that should have been done last summer has the above 200 boiler and the same small Alpha II pump for both primary and secondary. The house has 4 manifolds and about 33 loops of Pex -- all working very nicely off the Secondary Alpha on "Auto" . Initially, I put them both on "Auto" . After a while I was thinking that really the primary should be static -- settled on speed II. It has worked fine heating about 4500sf for two winters now.

Today when I went over for the first time in a month the primary pump was showing 3gpm and 18 watts --- temp of boiler was 106. It was 37 outside. I played with some other pump settings -- bumping it up to speed III the pump was showing 5gmp and 43 watts .... boiler was now down to and running at 96 degrees.

Is there a reason to use one or another ... ? There was a bit more flow sound at the higher speed ...

Alan (California Radiant) Forbes

I'd go with Constant Pressure III since the pressure drop never changes. The recommended maximum flow through the boiler is 6.2 gpm.

sunlight33

If you have a low loss header you would want the secondary side to have equal or greater flow than the primary side.

TAG

Is the goal to try and push as much water through the boiler as possible?

Obviously one needs to have enough flow to take the heat off the boiler's exchanger and with more flow through the boiler at a given BTU output the exchanger temp will drop. With the Viessmann using a sensor on the LLH I'm wondering how that is changing as the flow goes up and the temp of the boiler water is dropping.

Alan: Viessmann's manuals are large and maybe I'm just missing some simple line where it has a recommended range vs a possible or recommended max. It would seem that running the pumps on the lowest setting that works would be the goal as far as electrical use ... It does seem with the Alpha II there is higher flow/head potential in Pressure mode .... I'm just trying to understand the use of this type of pump on the Primary side. It does seems like it's features are overkill for the aplication ... I bought it for the lower electrical usage.

The boiler has been working well and last year when we had a very cold week (low teens) -- I was there more often and the boiler was running in the 127 range ... never saw it above 130 although I was never there at night

Alan (California Radiant) Forbes

I'm just trying to understand the use of this type of pump on the Primary side. It does seems like it's features are overkill for the aplication ...

If you are using a LLH, the job of the boiler and boiler pump is to load the LLH with target temperature water that will get picked up on the secondary side. You want this to happen quickly and a fixed speed pump will do this at low or high demand times. A ΔP pump is overkill.............in my opinion.

Paul Pollets

I use a 15-58 3 speed (Edited) for the primary and Alpha's for the system pump(s). The primary pump is set at "2" and the Alpha's set at "Auto Adapt" after all air is purged.

TAG

Paul Pollets said:

I use a 15-55 3 speed for the primary and Alpha's for the system pump(s). The primary pump is set at "2" and the Alpha's set at "Auto Adapt" after all air is purged.

15-55 or 15-58 ? That's what I have in place for the indirect tank loading. 15-58. Was going to order for the primary as well -- just ordered the two Alpha's. Could switch them out as I have a new spare 15-58.

I did not do the install -- but, had supplied all the parts.

sunlight33

I use speed 2 on my 15-58.

TAG

Alan (California Radiant) Forbes said:

I'm just trying to understand the use of this type of pump on the Primary side. It does seems like it's features are overkill for the aplication ...

If you are using a LLH, the job of the boiler and boiler pump is to load the LLH with target temperature water that will get picked up on the secondary side. You want this to happen quickly and a fixed speed pump will do this at low or high demand times. A ΔP pump is overkill.............in my opinion.

I sort of figured it was overkill .. but, it got me thinking. What's the best flow since you can control it --- if both speeds get the job down but at different temps .. is one using more propane? The higher flow is using 25 more watts.

My 200 is from around 2015 even though it was installed two years ago -- I can't find any display on the unit showing the actual fire rate -- it just has if the burner is on. The later ones have an actual fire rate showing.