hot water solar questions

[Ralph]

Hi,
I just joined. I have a solar hot water system for domestic hot water that dates back to President Carter. The system works great. The insulation on exposed 3/4" copper on roof has deteriated.
My question is: Is this insulation necessary? The system heats the glycol solution very adequately and I need to know how much the black foam insulation contributes to the efficiency if at all?
Thanks in advance for any help.
Regards,
Ralph

[inetdog]

Hi,
I just joined. I have a solar hot water system for domestic hot water that dates back to President Carter. The system works great. The insulation on exposed 3/4" copper on roof has deteriated.
My question is: Is this insulation necessary? The system heats the glycol solution very adequately and I need to know how much the black foam insulation contributes to the efficiency if at all?
Thanks in advance for any help.
Regards,
Ralph

How much heat loss the insulation is preventing will depend on the outside temperature and the length of the exposed line. Think of what the heat loss would be if you had the same length of exposed hot water pipe between your tank and all of the water uses and then multiply by the length of time that the glycol is circulating.

One way to check this would be to use a very accurate thermometer to measure the temperature difference between the glycol at one end of the exposed pipe compared to the other.

The conservative thing to do is replace the insulation.

[Ralph]

Thanks for reply

How much heat loss the insulation is preventing will depend on the outside temperature and the length of the exposed line. Think of what the heat loss would be if you had the same length of exposed hot water pipe between your tank and all of the water uses and then multiply by the length of time that the glycol is circulating.

One way to check this would be to use a very accurate thermometer to measure the temperature difference between the glycol at one end of the exposed pipe compared to the other.

The conservative thing to do is replace the insulation.

Thanks, Do you have a recommendation for the insulation for the tubing?

[inetdog]

Thanks, Do you have a recommendation for the insulation for the tubing?

As insulation goes, good and easy to apply is the split cylinder foam pieces that are used for insulating hot and cold water pipes. Use tape to close the split and make an air circulation-reducing seal.

I am not sure whether the standard stuff is rated for UV exposure, so you may have to use some sort of UV protective wrap around it too. Cloth, UV resistant plastic film, aluminized mylar with the aluminized side out? Not sure what would be best.

[russ]

What I used is called armaflex and it needs protection - tape or other

[LucMan]

Depends on how much piping is exposed on the roof. One or two of feet without insulation won't make much difference in overall efficiency.
Do not use the split foam insulation that they sell at home depot it will melt onto the pipe at around 150 degrees.
Use 1" wall thickness Armaflex or equivalent Rubatex insulation with an aluminum or PVC jacket added to protect the insulation from UV light.
Fiberglass pipe insulation may also be used.

[SteveC]

As it happens, I am currently building a solar water heating system--almost done. Homemade thing. Anyhow, in researching the pipe insulation, I found that there are two types made by Armaflex. Both types are sold around where I live by both HD and Lowe's. Which are about the only options for buying this sort of thing here. At least, without ordering online.

One type is an open-celled foam and is quite inexpensive, I think it was a couple bucks a six-foot length. The other type is closed-cell foam and is referred to on the Armaflex web site as "rubber." It is also sold in six-foot lengths and is about three times as expensive as the open cell, about $6 a length here. According to the charts on the web site, and also the postings on various forums and etc. regarding setting up a heating system, the closed-cell insulation is superior in insulating and worth the price difference. I suppose it depends, ultimately, on where you live and your ambient temp's outdoors. Here, it can get below zero F. so the best insulation is...best.

Both types need UV protection. There is a paint sold by various companies, including Armaflex, for this, but I have only found it in the gallon size for well over a hundred bucks. I need about a cup or two. So, I am, instead, trying a foil/butyl rubber tape I also ran across in one of the big-box hardware stores. Supposed to be "weather proof." I won't know how well it works out as I am just going to use it today, be a while before I can tell. Fortunately, the way I have my collector box set, I only have about four feet of two copper pipe runs to protect outdoors.

Hope this helps....

By the way, Armaflex also sells a contact-type cement for use on its pipe insulation. Also sold in small cans at HD, etc., for about $8. The insulation has a self-sealing tape or something in the split, but there are places one must cut the insulation and configure it around valves, unions, etc., and I figured the adhesive was worth a few more bucks to get it all sealed up. The stuff is called Armaflex 520 Adhesive. Don't know whether any other brands/types would work as well. If you already have something around, you could test it on a small scrap of insulation, might well work just fine. Someone else on the forum here probably knows.

[Ralph]

Armaflex ut solaflex info

By the way SteveC, I just found out about Armacell UT Solaflex. It is the new name for Armaflex HT I believe. You may want to look it up. It withstands 300 F and has good UV protection so it does not need a cover although painting or covering was mentioned to extend it's life.. It is somewhat pricey but it may be appropriate for your project. Hope this is helpful.

[Mike90250]

Avoid open cell (and fiberglass) insulations and wraps, unless you can be absolutely sure they will not soak up any water from wind driven rain. Add water, and they become thermal conductors.
Indoors, they are OK.

[MikeSolar]

Open cell will melt.....period

closed cell or fibreglas clamshell are the only two ways to do it. Armaflex, rubatex and a bunch of others are closed cell and are there for higher temps. Use the glue and cover it it is UV "resistant" not stable so covering it is advised. Fibreglas needs to be covered with a PVC jacket and tape or glue. It is more commercial so stick with the rubber.

[wsofteners]

hot water tank

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