Reverse Return Loop versus 4-Way Mixing Value

Crissie

Putting a new base board heat boiler system in home. Planning on Weil McCann GV90, cast iron boiler with secondary heat exchanger. I was exploring using a panel radiator in a couple of areas. The rep at Panel radiator company was helpful and suggested using a 4-way mixing value to protect the boiler and control supply temperatures. Spoke to my contractor and he said that is not necessary because he was designed the system to have a Reverse Return. Does this sound correct?

STEVEusaPA

No offense, reading all your threads, you seem to be getting a lot of info from your contractor(s), from bad to flat out wrong. I actually wonder if this isn't a DIY project, which is fine, and you're asking questions based on what you read on line and are trying to formulate a plan-which is also fine.
-or-
You're using a plumber who doesn't understand hydronics.

My advice to you is to get the system properly designed first-Room by room heat loss will tell you the amount of baseboard you need in each room and at what temperature at design day.
Properly sized & properly piped, properly controlled...period. It's the only way to properly do it for maximum comfort, energy savings & maximum longevity of the equipment.
Every boiler manufacturer includes instructions on if & how they want their boiler protected.

Crissie

STEVEusaPA said:

No offense, reading all your threads, you seem to be getting a lot of info from your contractor(s), from bad to flat out wrong. I actually wonder if this isn't a DIY project, which is fine, and you're asking questions based on what you read on line and are trying to formulate a plan-which is also fine.
-or-
You're using a plumber who doesn't understand hydronics.

My advice to you is to get the system properly designed first-Room by room heat loss will tell you the amount of baseboard you need in each room and at what temperature at design day.
Properly sized & properly piped, properly controlled...period. It's the only way to properly do it for maximum comfort, energy savings & maximum longevity of the equipment.
Every boiler manufacturer includes instructions on if & how they want their boiler protected.

This is not at all a DYI. I have a major problem with ductwork, a tri-level house and have been trying to explore options find a solution since April. I have only contacted top-rated companies and over a dozen come in. The feedback I get from each is like night and day. 80% of the HVAC companies in this area do furnace and boiler replacement, perhaps some ERV type work, and that is it. They may do some piping or ductwork, but it is limited. The few that I have found that can take on a whole house system are booked 5-6 months out, or - I am working with the feedback I am sharing.

dopey27177

no matter what system you install you need to make sure that the return water is at least 140 degrees F.
This can be done two ways. A diverting valve from the header to the return before any zone valves. or using an outdoor reset thermostat set for a return temperature of 140 degrees.

Jake

GroundUp

Reverse vs direct return has absolutely nothing to do with water temp. Nothing whatsoever. If someone actually told you that, just block their number and forget about them because they haven't a clue what they're talking about. Both BB and panel rads are high temp, and the GV90 is built to run with condensing temps if necessary- boiler protection is 1000% unnecessary. Unless your BB and rads require different water temps (doubtful), no mixing valve of any sort should be used.

Crissie

dopey27177 said:

no matter what system you install you need to make sure that the return water is at least 140 degrees F.
This can be done two ways. A diverting valve from the header to the return before any zone valves. or using an outdoor reset thermostat set for a return temperature of 140 degrees.

Jake

The contractor said that if the boiler starts with temp that is 90 degrees, it doesn't need return temps that are higher than 140. Honestly was not following him. Sounds like perhaps he was dancing because of my question. Is it unusual for a homeowner to have a mechanical engineer design a boiler system for a contractor to work off of? Thanks

Crissie

GroundUp said:

Reverse vs direct return has absolutely nothing to do with water temp. Nothing whatsoever. If someone actually told you that, just block their number and forget about them because they haven't a clue what they're talking about. Both BB and panel rads are high temp, and the GV90 is built to run with condensing temps if necessary- boiler protection is 1000% unnecessary. Unless your BB and rads require different water temps (doubtful), no mixing valve of any sort should be used.

LOL. This is concerning. He was designing a BB water temp of 160. I think it might be too low because it requires a lot of baseboard.

HomerJSmith

I have used a Taco I-Series set point mixing valve with a sensor in a bypass arrangement and it worked very well. The sensor kept the return water to the boiler at about 135 deg, minimizing start up and sustained gas condensation.

There is always some condensation at start up. What you don't want is sustained condensation in a cast iron boiler.

I have seen panel radiators running at 180 deg. I think you need to determine your supply water temperature. I didn't look at that boiler specs, but being cast iron, I wouldn't think it is modulating. Whether it can handle flue gas condensation, I don't know.

Ya, know, a hydronic specialist is a highly trained guy in the plumbing trade. I find so many mistakes in the sys that I have been called in on and this site is replete with problems caused by bad installations.

I would be asking a lot of questions about how many boilers, what kind of boiler he has installed, and the systems that they were installed in. Why he want to do what he wants to do. His training. His answers should be precise and clear.

Crissie

HomerJSmith said:

I have used a Taco I-Series set point mixing valve with a sensor in a bypass arrangement and it worked very well. The sensor kept the return water to the boiler at about 135 deg, minimizing start up and sustained gas condensation.

There is always some condensation at start up. What you don't want is sustained condensation in a cast iron boiler.

I have seen panel radiators running at 180 deg. I think you need to determine your supply water temperature. I didn't look at that boiler specs, but being cast iron, I wouldn't think it is modulating. Whether it can handle flue gas condensation, I don't know.

Ya, know, a hydronic specialist is a highly trained guy in the plumbing trade. I find so many mistakes in the sys that I have been called in on and this site is replete with problems caused by bad installations.

I would be asking a lot of questions about how many boilers, what kind of boiler he has installed, and the systems that they were installed in. Why he want to do what he wants to do. His training. His answers should be precise and clear.

I started out by working with the owner of the company, who seemed straightforward and objective, not trying to sell me any one particular solution. He hired this 'expert' who supposedly has 25 yrs of experience in boiler installs and support. This expert was trying to persuade me to go with a Navien high condensing Boiler. I've seen too many bad reviews on it. He was pretty aggressive on it, so I finally said if you all want to guarantee me that I would have service issues and be without heat in the winter, I will consider it. The boiler expert said he would, the owner pulled him back and said no. I asked for references from client for whom he installed it, the boiler expert said he would have to contact his customers from his prior experience. Seems very odd, there is definitely something off with him. But I like the owner. The problem I have is other companies all have the 'own' brand of boiler they want installed, and if I don't want to you that brand, they don't want the job. I don't want a condensing boiler because pretty much everyone, even the manufacturer's admit they require high service and have more possibilities of breaking down, requiring 24-48 hrs to get a part. I am in Chicago, going 24 hours without heat is a nightmare.

hot_rod

With low mass distribution, panel rads, fin tube, low mass "dry" radiant, etc boiler return is not so critical. That boiler is a small water content and fairly low mass for cast iron. I think some of the GV have return protection built in?

If it were a radiant, low temperature system with a large "hungry" concrete slab... then return protection is a must.
From a cold start you want the return to a cast boiler above 130°F within 10 minutes. Again, if the boiler has return temperature protection build in, you are safe regardless of the distribution or return temperature.