insulating a boiler

Ron Schroeder

Hi Constantin,

Are you talking about

http://www.butlersunsolutions.com/index.html

I couldn't find any dual coil tanks on their site. I am looking for more affordable dual coil tanks.

mark schofield

In recently installed a Weil Mclain WTGO 3, which will provide DHW durring the summer months thru the tankless coil. A solar storage tank will feed preheated water to the inlet of the coil. The boiler will probably loose a little heat thru the jacket durring the day. Would it be safe to add a few inches of rigid foam (like Thermax) to the outside sides and top of the boiler to minimize heat loss durring the day when no one is home and the only demand will be for hot water durring the evenings? Thanks, Mark S

Brad White_51

I would not do that...

The proximity of combustibles (potentially toxic combustibles at that) to the boiler and flue surfaces speaks loudly to me. Also your building code probably requires a fire barrier (gyp board of some type or thickness or equivalent) over the foam.

The boiler already has about an inch of fiberglass board or blanket already which is designed for much higher standby temperatures so I see little benefit.

Might you consider not feeding through the coil when you charge the tank? I do not have a good picture in my mind about your set-up, but am asking why flow through the tankless all the time there is flow especially when you are charging the tank.

My $0.02

Brad

Constantin

I would use a different material...

... I concur with Brad re: not using the plastic insulation. Our neighbors steam boiler went into thermal runaway one night and the exterior of the boiler became hot enough to melt a plastic bucket 6" away. The floor was too hot to walk on. Keeping combustibles away is important even if the boiler does not feel warm when it's operating normally!

What you could consider doing is insulating the boiler with appliance-rated fiberglass like mcmaster carr sells. That stuff is hard to burn, but you will have to pay very careful attention to ensuring that all openings that are supposed to be open (i.e. air intake and the like) remain that way. Securing fiberglass well can also be more trouble than one would think...

I would look at the system as a whole... where are the standby losses occuring? If your heat is escaping up the flue, then wrapping the boiler in more blankies will only increase the amount of standby heat lost up the flue vs. into the house.

Lastly, if you really want to reduce standby losses, I suggest putting in an indirect water heater and getting rid of the tankless coil that will force your boiler to run at very high temperatures. If you go to Butler Solar, they have relatively inexpensive dual coil tanks that can be heated via solar and your boiler. You can pre-heat the water going into the indirect with a GFX heat exchanger pulling heat out of the wastewater leaving your home.

Ron Schroeder

I don't know if the WTGO can be used as a cold start boiler, but if it can, one configuration would be to use Solar as primary to heat your DHW tank and only have the boiler come on if the DHW tank gets below about 120 degrees. Then the DHW tank water could be circulated thru the tankless coil to "recharge" the DHW tank. With a properly sized system and controls, the boiler may only have to come on a few times each summer.

hr

What sort of DHW load do you have?

From about May- late August on I get 100% of my DHW from solar. About 200 days of sunshine around here.

You might consider a solar tank with a back up electric element. The cost of intermitent electric use may offfset firing the boiler for tankless use?

Do some math. Generally 1- 4X8 panel will drive a 65 gallon tank. If you can install two panels figure about an 80 gallon solar tank.

I like the Vaughn tank for solar with electric element back up. I have a 65 in my shop and an 80 at the house, both over 15 years old!

Those cement lined (Hydrastone actually) schuckers, or suckers, will hold heat for 3 days or more without sunshine. About 325 lbs for the 80 gallon. EMPTY!

They may also offer a dual coil model?

www.vaughncorp.com

hot rod

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Constantin

Ah, that drives me crazy...

... I could swear they sold dual coil stainless tanks at one point. Perhaps their solar wand made that business obsolete... the internet archive machine shows no entries for the past so this memory may be a false one.

A quick research online shows a couple of companies, with DHT and their ST Pro being a potentially interesting source. Have you priced them out already?

Unknown

What about

using some other material in place of the fiberglass they wrap the boiler with ? Is there such a material that'll hold the heat in longer with the same thickness as what is on there now ? But I believe it probably aint worth doing - the Gold holds its heat in very well as-is .

Kevin_in_Denver_2

Solar domestic recirculation

Ron,
This is the exact approach we used in the 80's. We had many customers complaining about the backup heat source firing in order to fight standby losses. A differential controller mounted directly to a tiny pump can be accomplished for under $300. Because of the abundance of summer sun, this will keep the boiler off all the time.

If you start using fancy solar tanks, replacement cost becomes an issue.

Leo

When you walk

When you walk into a basement and it isn't 75 degrees because of the stand by losses of the boiler there is no reason to insulate. Most of the newer boilers are insulated very well the Gold included. I have found the gold to be one of the boilers that stays much cleaner in the heat exchanger when kept warm. If it is allowed to be cold start be disciplined about the annual service.

Leo

Ron Schroeder

Not all of the losses are out the jacket. In many boilers, most of the loss is up the stack. That is why I much prefer cold start and wide differential DHW aquastats in the non-heating season for DHW either with or without solar. The idea is to never have the boiler hot unless it absolutely has to be.