Getting Closer

Rodney Summers

Meant non-condensing boilers

Rodney Summers

Getting Closer

to finalizing the system I'm getting installed.

I've got two floors of baseboard and one of radiant.
I've got solar DHW that will need a boiler loop for backup.
4 zones (one for each floor one for DHW) now and maybe two more needed later.
I've got future plans for more panels and a separate 750Gallon storage tank to assist the radiant.
Location is Cape Cod.

I'm between two quotes. One is Viessmann(VR2-27) and the other Buderus(G115). Both have the fancy OEM controller.

I'm assuming both of these are condensing boilers so using the outdoor reset and mixing valves for the radiant are not an issue, right?

When time comes to integrate the 750 gallons solar heated water, does either of these manufacturer/boiler choices have any advantage over the other?

The Viessmann quote actually comes in about $1000 lower than the Buderus. That supply house is giving better price on Pex and using Radiant Side Track plates vs Joist Trak.

So, what should I go with?

Constantin

Condensing?

My recollection is that the G115 is a non-condensing boiler. Do you mean the GB142 perhaps? I'm also unlcear on the Viessmann unit you're referencing, as it does not seem to be a Vitodens either.

Mixing valves may be a necessity if you want to heat DHW and the home heating system at the same time, though mixing valves can limit the temp spikes for a much lower price, I suppose.

Even if you turn off the radiant circs during DHW, chances are that the water temperatures inside the boiler after a DHW call has been satisfied will be much higher than what you'd want to hit the radiant circuits with, though the little hot water the condensing boilers store would be quickly diluted. Either boiler should be fine controlling a mixing system.

As to which boiler will be better for the later add-on of a solar system, that is a good question. I don't know what systems the Buderus people have, but I seem to recall that the latest set of solar controllers from Viessmann allow the usage of the solar storage tank as a heat source for home heating systems. Perhaps Joe and someone from Viessmann can elaborate on the OEM-preferred ways of hooking up a solar home heating system.

Given a choice between a Vitodens and a GB142, my favor would tip towards the Vitodens due to the material choices of the HX and the proximity to the US HQ you enjoy.

Rodney Summers

Those are the models

It is the G115 Buderus and the VR2-27 Viessmann.

For the eventual addition of solar panels for the radiant, I think what I want is a motorized valve that some controller can signal to take solar tank water or boiler water, right? Can either of the OEM controllers mentioned control this as well or will I need something additional?

Constantin

Aha, a very different ballpark then

The Vitorond and the G115 are very versatile boilers, I assume you're looking at using them with oil? With the Vitotronic 200 and the Vitosolic controls, you should be able to heat the place and make DHW at the same time.

joe_66

SOLAR

check out the vb2-22 it really isnt that much more expensive than a vitorond.It will be easier to pipe with a nice divicon station mounted right on one side it also can handle lower temps than the vitorond and has a better HX. Who is designing the solar equip Imean I dont think Viessmann will even sell you equipment if they dont design the system.What will you do with all that solar energy in the summer?What I know of solar in new england is that you can get about 60% of your DHW and thats really it besides a pool

Constantin

Depends also on the configuration..

Bob Gagnon has a very happy solar system up in NH. If space heating is in the cards (and that's a big if considering how much of the house you have to plaster with solar water heaters in MA to cover your heating needs), then putting in vertically mounted collectors can work quite well... very little uptake in the summer, a lot more in the winter.

Make it a drainback system, let it stagnate in the summer when you don't need it.

To make solar really work in MA, I think the house will have to be very well insulated and incorporate passive solar uptake as well. R8 windows with high IR transmission and a large overhang to keep the summer sun out and things like that.

I agree on the Vitola... it can handle lower water temps in case your radiant system can run at low ones as well. However, with staple-up + plates as it would appear, what percentage of the season will that be?

Rodney Summers

I'm doing the solar

I've already got three panels up that are providing all of the DHW in the summer, except for poor weather spells over 2 days, for the two of us. That's with a 25 year old tank and heat exchanger. In the winter on a sunny day, I'm getting 150-160 off the panels.

I've got a 15K load for the radiant floor based on 0F. I'm not designing the solar portion for that temp and instead looking at how much use I can get out of it at 20F which is still below the avg for the winter temps here. That load is 12K. I've inspected similar systems nearby that are new and sized similarly. The required water temp for the radiant floor is 95F. I'm designing the solar array to be able to conservatively take 750 gallons of water from 95F to 125F at an outside temp of 20F on a sunny day. That mass will provide me 750 x 8.33 x 30 = 187425 / 12000 ~ 15 hours of required water temp for radiant floor. Looking at using evacuated tube collectors so I might be able to get the temps up a bit.

Overheat in the summer is an issue. I'm thinking of going drainback but not sure if I want the added complexity. There's a void in the basement concrete that's 8x8'. The previous owner had a hot tub there. My plan is to dig this out and use it for the storage tank location. I plan to oversize the tank by a certain amount so that in the summer I can simply increase the water level to prevent the higher summer temps. I'm also going to use this system for heating the hot tub.

This is all going in steps. I need to make sure the oil system is in place before next winter. Sick of burning wood and coal and the electric BB bill is brutal. Hope to get that portion completed by the summer time. I'll then move ontot the solar portion.

Need to figure out the plumbing and controls for integrating the solar water with the boiler water for the radiant loop. I've a background in controls and enough plumbing/electrical experience to be dangerous. Should be fun.