VIESSMAN 100-W not Heating house

Gordy

This is a good read on what happens in a separator when flows are =<> between primary, and secondary.

http://goesheatingsystems.com/idronics-hydraulic-separation-new-methods-of-implementing-an-established-concept/

Gordy

In other words when system side flow is greater than boiler flow the return to the boiler should mimic system return temps. How much depends on how much difference there is in the greater flow rate on system side than boiler side.

When boiler side flow is greater than system side flow then the boiler return will be warmer than system return.

So decreasing boiler pump speed so it’s less than system flow will yield cooler return temps with in reason of the boilers max delta to prevent hitting high limit. Or increasing system side flow so it is greater than boiler side flow.

Paul Pollets

without using the LLH, system flow rate needs to be less than 6gpm. If your requirements are for more flow, there will be issues if the correct flow rates can't be delivered or there are "choke points".

Gordy

In reading back through your posts you said the low loss header was originally piped wrong?

Boiler supply, and system supply top ports
Boiler return, and system return bottom ports?

GW

> @Paul Pollets said:
> without using the LLH, system flow rate needs to be less than 6gpm.

Can you explain that Paul? I don’t understand

Gordy

Max flow rate through that boiler is 6.6 gpm.

If the system needs a higher flow rate you need the low loss header, or P/S piping.

Gordy said:

What you gain with a lower gpm, and wider delta at the boiler loop is condensing efficiency more often when Loads allow.
I believe a 35 delta is allowed with that boi
System side flow should always be more than boiler side.

The math is very important.

GW

Yes I may have read that too literally, Paul said LLH. A p/s will suffice

But who sends system water right through the low mass boiler anyway? I don’t think anyone does that

Their 125000 btu boiler is the same max flow right? So either people are ignoring the max flow or the system doesn’t truly need the full btu rating. 35 or so temp drop is virtually impossible with traditional changeout jobs

Gordy

You can pipe direct. Just have to do the math. A converted gravity with ci rads that could use a high delta comes to mind.

Rabbit02

I'll work on getting a pic or two. We've had our fair share of disappointments with these High efficient boilers. In the 1980's it was the GLOWCORE, The 1990's it was the Peerless Pinnacle or Munchkin, then the Peerless Purefire, then the Bosch Greenstar, now the Viessman. I thnk one of the biggest issues is that the older American homes are all built for 180 degree water temp needed, not enough baseboard, cast iron, or they have a toe-kick convection heater in the kitchen set to come on at 140 degree water temp. Like what was said, often times we go back and disconnect the outdoor reset(depending on which manufacture) and run water temp up to 180 which is defeating the purpose of installing the high efficient boiler in the first place. They work great on new construction radiant heat or properly sized emitters for 120 to 140 degrees. Line the whole house with baseboard if its a retrofit on older home. lol. We quit installing the Viessman Combi unit because of too many complaints with the domestic. Americans are not as patient or tolerant to taking cold showers or "any" temperature fluctuations. Thank you all for your comments and suggestions. I will post on the final verdict when it is known. Stay tuned....thanks.

DZoro

Picture is worth more than a thousand words