My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

"Mikepier" wrote in message
...
My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

The coil could be coated with mineral deposits, insulating it, or you could
have a bad mixing valve .

On May 4, 9:49*am, "RBM" wrote:
"Mikepier" wrote in message

...

My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. *Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

The coil could be coated with mineral deposits, insulating it, or you could
have a bad mixing valve .

What mixing valve are you referring to, the one on the boiler? I see a
mixing valve, but it is shut off, which means I'm assuming 100% hot
water out of the coil.
If you are referring to the shower mixing valve, I should point out
the same problem happens when washing clothes,dishes etc.

Is this a problem in the summer as well (when the boiler is not also used to
heat the house)?
--
Peace,
BobJ

"RBM" wrote in message
...

"Mikepier" wrote in message
...
My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

The coil could be coated with mineral deposits, insulating it, or you
could have a bad mixing valve .

"Mike rock" wrote in message
...
On May 4, 9:49 am, "RBM" wrote:
"Mikepier" wrote in message

...

My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

The coil could be coated with mineral deposits, insulating it, or you
could
have a bad mixing valve .

What mixing valve are you referring to, the one on the boiler? I see a
mixing valve, but it is shut off, which means I'm assuming 100% hot
water out of the coil.
If you are referring to the shower mixing valve, I should point out
the same problem happens when washing clothes,dishes etc.

You have a cold water pipe feeding into the coil on the boiler, and a hot
water pipe exiting the coil. Somewhere at that location should be some type
of mixing valve, so you don't get 180 degree water flowing through your
domestic pipes. If it is off and not allowing any cold water to mix, the
problem is with the coil.

You have a cold water pipe feeding into the coil on the boiler, and a hot
water pipe exiting the coil. Somewhere at that location should be some type
of mixing valve, so you don't get 180 degree water flowing through your
domestic pipes. If it is off and not allowing any cold water to mix, the
problem is with the coil.-

There is a tie valve between the cold input and hot output of the
coil, I am assuming this is the mixing valve to mix in the cold water.
This valve right now is off, why I don't know, but in any event why
would the coil be the problem if the valve is off? Are you saying
maybe the oil company turned off the mixing valve to compensate for
the coil being dirty?
Regardless, if I'm getting "full strength" hot water out ( mixing
valve off) theoretically I should have more HW than if the valve was
on, so that's why I suspect a bad coil.

"Mike rock" wrote in message
...
You have a cold water pipe feeding into the coil on the boiler, and a hot
water pipe exiting the coil. Somewhere at that location should be some
type
of mixing valve, so you don't get 180 degree water flowing through your
domestic pipes. If it is off and not allowing any cold water to mix, the
problem is with the coil.-

There is a tie valve between the cold input and hot output of the
coil, I am assuming this is the mixing valve to mix in the cold water.
This valve right now is off, why I don't know, but in any event why
would the coil be the problem if the valve is off? Are you saying
maybe the oil company turned off the mixing valve to compensate for
the coil being dirty?
Regardless, if I'm getting "full strength" hot water out ( mixing
valve off) theoretically I should have more HW than if the valve was
on, so that's why I suspect a bad coil.

I suspect the valve was turned off when the coil stopped producing hot
water. You should be getting full temperature hot water, unless the coil is
dirty

"Mikepier" wrote in message
...
My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

Good chance it is the coil clogged or nearly so.

If the boiler is more than 15 years old, before dropping hundreds to replace
the coil, consider replacing the boiler it with a more efficient boiler and
a water tank that is indirect fired. I changed mine last December to a
System 2000 and my oil use so far is down 32%. I don'[t have summer use
yet, but I expect hat to be dramatic also. Ask the in-laws how often that
boiler kicks in during the summer just to maintain the hot water at
temperature. Quite often from my experience. With no heat on, I don't hear
mine go on at all because the 40 gallon tank holds it at temperature for
days if not used. Mine is from www.energykinetics.com

If they opt for a new boiler, be sure to check out state funded rebates and
0% financing available through the state.

Before buying a whole new system just because the coil is failing, I would
suggest buying a separate water heater. Install the water heater in series
with the output of the tankless coil so that hot (or at least tempered)
water goes to the heater and thus requires much less energy to bring the
water in the heater to the necessary temperature. This also has the added
benefit of letting one turn off the boiler during the months that it is not
needed to supply heat to the baseboard radiators since, when not heating the
house, a boiler is a very inefficient way to produce domestic hot water.
--
Peace,
BobJ

"Ed Pawlowski" wrote in message
...

"Mikepier" wrote in message
...
My in-laws have an oil fired hot water baseboard system with a
tankless HW heater coil rated at 5 GPM. Presently the aquastat is set
for the boiler to come on when the water temp drops to 165 deg and
shuts off when it hits about 185-190 deg.
When someone takes a shower, the water temp initially is very hot, but
then after about 5 minutes the HW starts to run out. Any ideas what
could be causing this? Could the coil be dirty such that it impedes
the heat transfer?
The boiler heats the house with no problem, its just the HW part that
has an issue.

Good chance it is the coil clogged or nearly so.

If the boiler is more than 15 years old, before dropping hundreds to
replace the coil, consider replacing the boiler it with a more efficient
boiler and a water tank that is indirect fired. I changed mine last
December to a System 2000 and my oil use so far is down 32%. I don'[t
have summer use yet, but I expect hat to be dramatic also. Ask the
in-laws how often that boiler kicks in during the summer just to maintain
the hot water at temperature. Quite often from my experience. With no
heat on, I don't hear mine go on at all because the 40 gallon tank holds
it at temperature for days if not used. Mine is from
www.energykinetics.com

If they opt for a new boiler, be sure to check out state funded rebates
and 0% financing available through the state.

"Marilyn & Bob" wrote in message
...
Before buying a whole new system just because the coil is failing, I would
suggest buying a separate water heater. Install the water heater in
series with the output of the tankless coil so that hot (or at least
tempered) water goes to the heater and thus requires much less energy to
bring the water in the heater to the necessary temperature.

Separate heater may be a good idea, but not in series with a clogged coil
that can restrict flow.

As for replacing the entire system, that depends on payback and present
efficiency. In the right conditions, the systems is free of cash outlay.
My interest free loan is $67 a month, but my savings in oil is bout $70.