Oil hot water supplement?

[Reckless]

Hi everyone

So bought a house with an oil fired water heater and am looking for ways to keep the furnance off (I heat mostly with wood stove). Anybody in a similar situation? Ive been looing into on demand or solar supplement. Any other ideas? Is the right section?
The extent of my knowledge on solar is http://www.dummies.com/how-to/content/choosing-a-solar-system-to-supplement-your-water-h.html

Thanks!!

 

[peakbagger]

GIven the upfront cost of solar hot water systems, most recomendations now are to install a heat pump electric hot water heater. If you want go solar, just install net metered PV panels to offset the extra load. If you have an external hot water tank that runs off a zone of the oil system, you could install a gyser heat pump hot water heater on that and save the cost of the tank. Of course unless you have a cold start boiler, a conventional boiler will burn about 1 gallon a day just to keep warm. I just manually shut mine off for the summer, but many start leaking when they cool down.

 

[Slow1]

I've been considering the same as OP for some time now. Just did the annual oil tank fill to the tune of almost $900 and I do believe it was all for hot water.

I have looked at the Geyser heat pumps (many times..) and recently noticed that ASHP with tank may be less expensive - my thought now is to run the heatpump tank inline with the oil heated one and then the water inbound to the oil tank will be hot, thus limiting the oil burn to standby losses. Interested in thoughts from folks on this idea...

 

[Reckless]

you could install a gyser heat pump hot water heater on that and save the cost of the tank. but many start leaking when they cool down.

These two things are correct thanks!!

 

[maple1]

IMO most of the cost in heating DHW with oil comes from standby losses.

 

[Reckless]

and recently noticed that ASHP with tank may be less expensive

Prices I see seem to be double the price of the geyser and how will it help in the winter months? I really have no experience with any of this stuff so any ideas are usefull

IMO most of the cost in heating DHW with oil comes from standby losses.

How is Geyser heat pumps on electric?

 

[maple1]

I don't have one so can't say a whole lot on them. There is quite a bit of reading on them in more than one section of this forum - try a search.

 

[semipro]

If you're a DIYer you may want to check out builditsolar.com.
I think solar preheating still makes sense if you do it yourself or if you're using cold groundwater.

We have a well and a Heat Pump Water Heater (Geospring). I'd love to have a solar unit to pre-heat the 50 degree water coming from my well before it enters the HPWH.

 

[Reckless]

If you're a DIYer you may want to check out builditsolar.com.
I think solar preheating still makes sense if you do it yourself or if you're using cold groundwater.

We have a well and a Heat Pump Water Heater (Geospring). I'd love to have a solar unit to pre-heat the 50 degree water coming from my well before it enters the HPWH.

Preheating the water... this would cut down on time to heat but will it help with keeping the tank up to temp also? Im looking use as little oil as possible.
My friend works for trane and he is looking into this unit for me http://www.trane.com/residential/products/ductless/mini-split/4txk8 . Exploring all my options

 

[woodgeek]

Lots of great comments already. I would say that 'supplement' is not the right word/approach....most of the oil cost is standby loss....preheating the water before it goes in won't save you more than a small percentage. To save, you need to switch to another heater (either HPWH or conventional elec will save you money) and shut down the boiler in the summer. At least in the winter the parasitic losses are heating your house.

Also, a tip....check that your radiators are really cold, not 'warm' in the summer...in a lot of older systems the check valves break and the system thermosiphons (circulates by gravity w/o a pump). This can easily double the standby loss and cost a bundle in summer oil usage and extra AC. Solution...close a cutoff valve off in the spring, reopen in the fall. Save $300.

 

[Reckless]

Lots of great comments already. I would say that 'supplement' is not the right word/approach....most of the oil cost is standby loss....preheating the water before it goes in won't save you more than a small percentage. To save, you need to switch to another heater (either HPWH or conventional elec will save you money) and shut down the boiler in the summer. At least in the winter the parasitic losses are heating your house.

Also, a tip....check that your radiators are really cold, not 'warm' in the summer...in a lot of older systems the check valves break and the system thermosiphons (circulates by gravity w/o a pump). This can easily double the standby loss and cost a bundle in summer oil usage and extra AC. Solution...close a cutoff valve off in the spring, reopen in the fall. Save $300.

My boiler cannot be shut down because it leaks when it is off. How would a Geyser heat pump not save me money by keeping the standby loss of the water heater to a minimum?

 

[woodgeek]

yeah, still seems a kludge. You're still blowing through a lot of BTUs to keep it warm, just paying a little less per BTU. Can you drain it in the summer, or are you afraid it would start leaking when warm? Kinda like leaving your car idling 24/7 because the starter is broken, IMO.

I also (back in the day) 'up insulated' my boiler by stuffing the jacket with FG. Maybe pack the sides in Roxul?

 

[maple1]

Do you have an oil fired water heater, or are you heating your DHW with a boiler?

 

[Reckless]

Do you have an oil fired water heater, or are you heating your DHW with a boiler?

Thats a good question, Im not sure what its called but the water heater has a coil in it thats heated from the furnace that in turn heats the water inside the tank.

 

[GaryGary]

Preheating the water... this would cut down on time to heat but will it help with keeping the tank up to temp also? Im looking use as little oil as possible.
My friend works for trane and he is looking into this unit for me http://www.trane.com/residential/products/ductless/mini-split/4txk8 . Exploring all my options

Hi,
You can build a DIY system that will provide nearly all of your hot water -- it just depends on how you size it. The nice thing about DIY solar water heating systems is that it costs very little to make the collector and storage tank larger than the usual commercial systems -- this gives you some cushion for cloudy days.

This is my system: http://www.builditsolar.com/Projects/SpaceHeating/DHWplusSpace/Main.htm
You can do it with or without the space heating.
We have had a week now of off and on snow, rain, clouds and a bit of sun -- the tank is currently at 116F.
I'm ready for spring -- predicted low for tonight is 14F!

Gary

 

[Reckless]

Hi,
You can build a DIY system that will provide nearly all of your hot water -- it just depends on how you size it. The nice thing about DIY solar water heating systems is that it costs very little to make the collector and storage tank larger than the usual commercial systems -- this gives you some cushion for cloudy days.

This is my system: http://www.builditsolar.com/Projects/SpaceHeating/DHWplusSpace/Main.htm
You can do it with or without the space heating.
We have had a week now of off and on snow, rain, clouds and a bit of sun -- the tank is currently at 116F.
I'm ready for spring -- predicted low for tonight is 14F!

Gary

Pretty cool stuff here hmmmm

 

[semipro]

Lots of great comments already. I would say that 'supplement' is not the right word/approach....most of the oil cost is standby loss....preheating the water before it goes in won't save you more than a small percentage. To save, you need to switch to another heater (either HPWH or conventional elec will save you money) and shut down the boiler in the summer. At least in the winter the parasitic losses are heating your house..

I guess my impression was that reckless was considering getting away from the boiler for DHW entirely which is why I mentioned the preheater/HPWH option.

 

[maple1]

Thats a good question, Im not sure what its called but the water heater has a coil in it thats heated from the furnace that in turn heats the water inside the tank.

OK - sounds like you've got an indirect hot water heater that is heated by your oil boiler. And that you can't turn off the boiler or let it go cold because it will leak (from what you posted). That all means you're kind of up against it on a couple of fronts. Just keeping the oil boiler warm so it won't leak is costing you all kinds of standby losses, before you even get to talking about keeping your hot water heater hot (likely most of your oil is going to standby losses now) - I know, I used to have a boiler like that.

The problem with supplementing or pre-heating your DHW is that you will still need to keep your boiler warm to stop it from leaking. Proverbial rock & hard place. Do you know how cool your boiler can get before it starts to leak? Two angles of thought - either come up with something solar powered (or maybe heat pump powered) and use that to keep your boiler hot (that heat would get transfered to the indirect tank eventually) - or scrap that boiler for a newer cold-start one that you can let go cold, and replace the indirect tank with an electric one. You might be able to recover some costs by selling the boiler & tank (should be no problem selling the indirect if its in decent shape).

Third angle: replace the oil burner with a pellet burning head. Google 'Pellex' for some starter reading on that one - but you'll still be burning way too much fuel just to keep your boiler from leaking.

 

[Reckless]

OK - sounds like you've got an indirect hot water heater that is heated by your oil boiler. And that you can't turn off the boiler or let it go cold because it will leak (from what you posted). That all means you're kind of up against it on a couple of fronts. Just keeping the oil boiler warm so it won't leak is costing you all kinds of standby losses, before you even get to talking about keeping your hot water heater hot (likely most of your oil is going to standby losses now) - I know, I used to have a boiler like that.

The problem with supplementing or pre-heating your DHW is that you will still need to keep your boiler warm to stop it from leaking. Proverbial rock & hard place. Do you know how cool your boiler can get before it starts to leak? Two angles of thought - either come up with something solar powered (or maybe heat pump powered) and use that to keep your boiler hot (that heat would get transfered to the indirect tank eventually) - or scrap that boiler for a newer cold-start one that you can let go cold, and replace the indirect tank with an electric one. You might be able to recover some costs by selling the boiler & tank (should be no problem selling the indirect if its in decent shape).

Third angle: replace the oil burner with a pellet burning head. Google 'Pellex' for some starter reading on that one - but you'll still be burning way too much fuel just to keep your boiler from leaking.

Alot of good points there, I was more worried about keeping the tank warm rather than keeping the furance warm. What is the easiest way to determine the temp that the boiler will leak? And will running the supplement directly to the boiler first keep it warm enough to stop it from leaking AND also keep the DWH temps up? Those are my main objectives now, thank you!! As for pellets... no thanks I have 4 acres of free heat, maybe a oil/wood boiler that will run base board down the road somewhere but I just bought this house and have other things to spend money on.

 

[maple1]

You could turn the aquastats down a bit at a time until you notice it leaking, then note the boiler temperature - if you know how to do that. Or just turn it off for a while & watch it periodically until you see a leak then note the temperature. The higher the temperature that the leak appears at, the more up against it you are. I had my boiler turned down to around 140° for summer DHW. It had coils in it rather than an indirect tank, but I think you'd still want the boiler at least that temp for DHW production - depending on usage. My boiler used to leak just below 140 so I was right on the edge with mine.

How old is your boiler? What model? Where exactly does the water come from when it leaks? If it's fittings you might be able to get the leaks stopped. Mine liked to drip from around the coils - I had to take the shell/skins off to see the source of the leak. What temperature is your boiler maintaining? If on the hot side (180?), you could try turning it down to around 140-150 for the non-heating months. That's what I would check out first & right now. The higher the maintained boiler temperature, the more your standby losses will be - at the expense of reduced DHW recovery time.

If you could get your boiler so it wouldn't leak when it goes cold, I'd replace the indirect tank with an electric one & shut the boiler off for the non-heating months. You might be able to sell the indirect for more money than it would cost for a new electric one, depending on model, age & condition - and your monthly operating costs would be significantly lower.

 

[Circus]

I agree with everyone else. Your hemorrhaging money feeding the boiler just for a little hot water. For now, shut down the boiler and buy a conventional water heater. Natural gas price is at a ten year low and you'll be using less than half the fuel than now. You can always add solar later.
Guess it all depends on where and how bad the boiler leaks, whether parts are available and if you have natural gas.
An electric heater would also save fuel if you don't use much hot water. Besides, they're not vented and they make good solar storage if you change the anode every six years or so.

 

[Reckless]

It had coils in it rather than an indirect tank

Bought the house 3 months ago and Im a first time home owner so forgive me in advance.....
My hot water tank has a coil in it also, Im not sure if it makes a difference or not. Boiler is a weil-mclain built/installed in 87 and its a really shallow fire bow. When I went to check the temp on the boiler it was at 140 and boiler kicked on and went up to 190. The hot water tank is set for 125ish (was at 150 and was scalding). I cannot tell where the leak is and the only time I noticed it is when my FIL shut the boiler off over night by accident (In the middle of january :| ) and there was a small puddle of water coming from the bottom, but it hasnt leaked since.

For now, shut down the boiler

Like I said it leaks when shut off and I have a ton of other projects to do rather then take apart the boiler and find the leak. It does need a cleaning soon so maybe I can work with the oil guy and he can help me locate the source.

 

[maple1]

I would adjust the aquastat so it only heats to 160 rather than 190 - that should reduce some heat loss, although you'll still be losing it. The 190 is needed more for keeping up with space heating demands.

Maybe insulate what you can (is your piping insulated?).

That's for starters - you'll have to fit further action around your schedule & priorities. But it shouldn't take a whole lot of work to at least see where/how it's leaking - or if the oil guy is coming for a service soon you could shut it off for a while before he comes so it'll be leaking when he gets there so he can tell you where it's leaking from. It could be something as simple as bad flange gaskets somewhere or a valve stem. Those old boilers generally weren't designed to be let go full cold (they like to be kept hot all the time), but if it was done gradually & infrequently (twice a year?), I'd try it. Don't know what you're spending on oil for DHW in the summer months, but I'm at around $30/mo (at 0.16/kwh) using a new 80 gallon electric hot water heater for a family of 5.

 

[velvetfoot]

Isn't it already operating as a cold start boiler? I mean, if it's summertime and the indirect tank is up to temperature, it could be hours before the boiler starts up again.

 

[maple1]

No - the boiler maintains set temperature even with no call for heat. From above that sounds like 140-190.