DHW from hydronic heating boiler - Jeff (Hammer)Kokoskie

Bill NTSG

I do not like to see cold start controls on cast iron sectional boilers. Cold start is when the boiler is allowed to cool to room temperature between cycles. Condensation and soot combine to cause corrosive acid that destroys metal and boilers faster than running the boiler during the summer as you stated. Warm start, maintaining a minimum temp. [i.e. 120°], will help keep things from rusting and help with recovery when you have a demand for hot water. It is much easier to keep up than to catch up. If you have a tankless coil you most likely have the control with a low limit setting. If piped and wired correctly your set up should serve you well. Working for an oil company we see cold start or boilers that are shut off when no hot water is being used. It is not always pretty. Gaskets cool off and contract causing water leaks. The worst thing is the annual cleaning when the big old iron monster has been off all summer and you have to run it for an hour just to dry it out enough to brush it out. Keeping it warm or keeping a pilot burning in a gas fired boiler does more good than the small amount of fuel consumed to keep things warm. JMO

Hammer

DHW from hydonic boiler

Because of our expanding family, my wife and I have been searching for a new house for some time. The typical newer house in our area (central PA) consists of an air-to-air heat pump or gas-fired furnace w/ A/C.........both bad choices as far as I am concerned. A few weeks ago, we happened on to a beautiful, newer home that met our space requirements. As luck would have it, the home is heated by a base board hot water system and cooled by a ducted A/C unit......not radiant heat, but damn near the best of both worlds regarding winter/summer comfort!

The heating system consists of 5 zones (which includes one in the garage!) and gets it heat via an oil-fired (gas is not available) Weil McLain cast iron section boiler (I don't recall which model). The 5 zones are fed from individual B&G zone pumps. The boiler contains a DHW coil, circulator and small (30 gal) storage tank. I didn't get the specs on the coil, but it must be a fairly high recovery unit for such a small storage tank. Incidentally, the storage tank is simply an electric water heater w/o the elements connected to the elec service.

Finally, my question........I'm concerned about summer time operation of the boiler. Since the only heating load on the unit will be DHW, I'm worried about pre-mature failure of the boiler due to condensation and cycling. I figurred I would install a larger electric hot water heater and interconnect it w/ the system. In the summer I would valve off the boiler loop and use the electric unit for DHW purposes. Electricity is relatively cheap around here so I'm not as concerned about a few months of electric-based DHW as I am about tearing up the boiler. What advice can you heating pros give me? Are my concerns valid? Thanks.

Mark Hunt

The boiler Mark H

should have a High/low operating limit which will cause it to maintain a minimum temperature year round.

I think you'll be just fine the way it is.

When the time comes to replace the boiler, I'd recommend an indirect fired water heater as a seperate zone. I have no love for tankless coils whether they are piped to a storage tank or not. Although the piping method you have there will allow better control of the water temps at the tap.

Hope this helps!!

Mark H

www.comforthometech.com

eleft_4

right on Bill

Hey Bill are you doing OK?
AL

kevin

How would you go about wiring up something like that? what controls? kevin C.

Bill NTSG

Kevin

Do you mean wiring a booster [storage] tank and circulator? Pretty simple really. Many times when we do electric heat conversions the customer has a new or nearly new electric water heater. Some of the better ones are well insulated and make good storage tanks. We often use the electric water heater thermostat that is already in place. In can be used to simply activate the circulator pump. Or a little more complex, operate a switching relay to start the pump and activate the burner. This will allow lower stand-by temps at the boiler. Any multi zone relay or a honeywell 845A. Or like mentioned before the t-stat on the water heater and a small bronze pummp like a 005 or 006 taco or similar. I would post a pic but misplaced the file

Hammer

storage tank

Bill/Kevin:
Although I haven't checked directly, I believe there is a low limit on the t-stat. the couple times I've been in the house, the boiler is warm (not hot) even though the house is empty (so the DHW load is zero). The existing tank that is being used a storage vessel is actually a 30 gal electric heater that does not have the elements connected. Theoretically, I could just connect the electric up and use it for the summer operation. I figurred I would install a manual valve and piping around the existing circulator (to bypass the boiler coil) and use the system pressure for circulation. The problem is that 30 gal will never satisfy the household needs between my wife, 2 daughters and all of the laundry, shower and dishwashing needs. So, I thought I would just install a larger, electric DHW tank and interconnect the piping to the existing system. I would still bypass the boiler circulator/coil. The controls wouldn't have to be complicated........just use the new tank's t-stat and manualy open/close valves at the beginning/end of the heating season. What do you think?

Bill NTSG

I Think

I am a bit confused. Sounds like a lot of work. I would use the oil. I had a 40 gal electric for four months while my house was undergoing construction and major remodeling. My electric bill incresed by more than $50 a month. Two adults no kids. With oil hot water I averaged 5 gallons a week. Less than $20 a month. With electic , a load of wash and a couple of showers = no hot water. With oil I have Never run out in the 15 years I have lived here. JMO I would keep the oil boiler. Every one has an idea on stuff . Mine is partial to oil and boilers

Kevin Coppinger

Bill

> Do you mean wiring a booster [storage] tank and

> circulator? Pretty simple really. Many times when

> we do electric heat conversions the customer has

> a new or nearly new electric water heater. Some

> of the better ones are well insulated and make

> good storage tanks. We often use the electric

> water heater thermostat that is already in place.

> In can be used to simply activate the circulator

> pump. Or a little more complex, operate a

> switching relay to start the pump and activate

> the burner. This will allow lower stand-by temps

> at the boiler. Any multi zone relay or a

> honeywell 845A. Or like mentioned before the

> t-stat on the water heater and a small bronze

> pummp like a 005 or 006 taco or similar. I would

> post a pic but misplaced the file

Kevin Coppinger

Bill

No, I meant what control would you use ,how do you set it and is the wiring simple enough for a plumber to do on the boiler side to keep the boiler a warm start as opposed to a cold start.

Floyd

Hey Jeff!!!

Your getting all worked up about nothing!!! Your gona end up spending money that will get you nowhere!!!
Leave it alone and you will be fine!!

Floyd

Bill NTSG

Oh Yeah

Kevin , most cold starts have HW 8148 aquastat. Replace it with a HW 8124. All of the wires are the same for burner, circ. , t-stat , L1 - L2 , etc. Like any thing with electricity if your not real comfortable.......... but yes , should be fairly easy. I set the minimum about 120° [low limit] and the high limit at what ever is required to heat the house on a cold day , say from 150-190° depending on radiation and other factors.

kevin

Bill

Thanks, I had heard about doing this a whileback. I didn't realize that so many guys have had problems w/ cold starts. The guys on the installation side should talk more w/ the guys on the service side of boilers more..... kevin c.